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The effect of ’rc’ mutation on the performance of chickens under different densities and flock sizes Ali, Ahmed 1983

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THE EFFECT OF ' r e '  MUTATION ON THE PERFORMANCE  DIFFERENT  OF CHICKENS UNDER  DENSITIES AND FLOCK SIZES BY AHMED ALI  M.Sc,  Bangladesh A g r i c u l t u r a l  A THESIS SUBMITTED IN PARTIAL THE REQUIREMENTS  U n i v e r s i t y , 1970 FULFILLMENT OF  FOR THE DEGREE OF  MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department o f P o u l t r y  Science)  We a c c e p t t h i s t h e s i s as conforming to the r e q u i r e d standard  THE UNIVERSITY OF BRITISH COLUMBIA October 1983 (C) Ahmed A l i , 1983  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t  the L i b r a r y s h a l l make  it  and study.  f r e e l y a v a i l a b l e f o r reference  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by t h e head o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s .  It i s  understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l n o t be allowed without my  permission.  Ahmed A l i  Department  o f , P o u l t r y Science  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date  7Q^  October  12, 1983  Columbia  written  ii  ABSTRACT The impact o f v i s u a l investigated  c o n t a c t o r the l a c k o f i t  by u t i l i z i n g g e n e t i c a l l y  ment i n v o l v i n g two genotypes b i r d vs 2000cm  2  replications.  per b i r d ) , Parameters  (blind  on egg p r o d u c t i o n was  b l i n d chickens  vs s i g h t e d ) ,  two f l o c k s i z e s measured were:  two d e n s i t i e s  (1$4#  level  r  gland  eggs w h i l e r e q u i r i n g 4 4 . l g l e s s There was no s i g n i f i c a n t  gain, f e r t i l i t y c o u n t , plasma  period,  difference  in  body weight gained between the  Significant  genotype x f l o c k s i z e and genotype x d e n s i t y  feed e f f i c i e n c y  and f l o c k s i z e s compared with normal  Other parameters measured provided evidence and had b e t t e r  These parameters  Results  had l e s s  interactions  may have some commercial  value.  also  sensitive  coverage d u r i n g the  energy requirement  It  to  evidence is  experimental t h a t the  therefore  for a c t i v i t i e s  experiment i n d i c a t e  b l i n d c h i c k e n not o n l y has good p o t e n t i a l  hens.  t h a t the b l i n d c h i c k e n s were  than normal o n e s .  from t h i s  two  chickens.  a l s o provided c i r c u m s t a n t i a l  c h i c k e n s were under l e s s s t r e s s  egg p r o d u c t i o n .  feather  hens.  compared to normal  i n d i c a t e d t h a t the performance o f the b l i n d c h i c k e n s was l e s s  t h a t the b l i n d c h i c k e n s  corticosterone  feed per b i r d per day compared to normal  Thus b l i n d hens had b e t t e r  period.  o f eggs,  b l i n d hens produced 12.7% more  genotypes.  less active s o c i a l l y ,  and two  weight.  During the two-month experimental  densities  per  2  number o f eggs c o l l e c t e d , egg w e i g h t ,  pecking and comb damage s c o r e s , l e u k o c y t e  and adrenal  experi-  (1000cm  vs 4SS 1 6 $ ) ,  amount o f feed taken from feed t r o u g h , body weight feather  in a factorial  t h a t the  as an experimental  blind  concluded other  than  genetically  animal  but  also  iii  TABLE OF CONTENTS Page ABSTRACT  ii  TABLE OF CONTENTS  iii  LIST OF TABLES LIST OF FIGURES  v  ACKNOWLEDGEMENTS  i  v  i  i  i  i  x  INTRODUCTION  1  REVIEW OF LITERATURE  5  I.  II.  Productivity  5  1.  Egg p r o d u c t i o n  2.  Egg weight  3.  Feed consumption  4.  Body weight  5.  Fertility  Parameters  5 ,  12 ••••••  II. III.  15 18  measuring s t r e s s  21  1.  Feather  pecking  21  2.  Adrenal weight  23  3.  Corticosterone  25  4.  Leukocytes  28  METHODS I.  9  31 Experimental  animals  31  Rearing c o n d i t i o n s o f b i r d s before s t a r t Management o f experimental  birds  o f experiment  31 32  iv  TABLE OF CONTENTS  (Continued) Page  IV. V.  VI.  Experimental Parameters  design  32  measured  33  1.  Number o f eggs c o l l e c t e d and egg weight  33  2.  Amount o f feed taken from feed trough  34  3.  Body weight  34  4.  Fertility  5.  Feather  pecking and comb damage s c o r e s  35  6.  Leukocyte count and plasma c o r t i c o s t e r o n e l e v e l  37  7.  Adrenal  38  gain  o f eggs  34  gland weight  Data a n a l y s e s  38  RESULTS I. II. III. IV. V. VI. VII.  4  Number o f eggs c o l l e c t e d Egg weight Amount o f feed taken from feed trough  50  Body weight gain Fertility  pecking and comb damage s c o r e s  55 and adrenal  gland  57 59 68  Performance o f b l i n d c h i c k e n s 1.  53  o f eggs  Leukocyte c o u n t , plasma c o r t i c o s t e r o n e l e v e l weight Feather  41 48  DISCUSSIONS I.  .  1  Statement  number 1  68 68  V  TABLE OF CONTENTS  (Continued) Page  II.  2.  Statement  number 2  71  3.  Statement  number 3  73  4.  Statement  number 4  77  5.  Other c o n s i d e r a t i o n s  Aditional observations  78  1.  Fertility  78  2.  Flock s i z e and d e n s i t y  80  SUMMARY REFERENCES APPENDIX  from experiment  78  8  4  8  6  101  vi  LIST OF TABLES Table 1  Page S c o r i n g method to assess the degree o f pecking damage to back and rump  36  2  S c o r i n g method to a s s e s s the degree o f pecking damage to the comb .  36  3  Effects  o f genotype on parameters measured  42  4  Effects  o f d e n s i t y on parameters measured  43  5  Effects  o f f l o c k s i z e on parameters measured  44  6  E f f e c t o f time on egg p r o d u c t i o n and egg weight o f the experimental birds  45  7  Effects  47  8  Significant  9  S i g n i f i c a n t GXF i n t e r a c t i o n f o r feed taken from feed troughs by experimental b i r d s  51  10  S i g n i f i c a n t DXF i n t e r a c t i o n f o r feed taken from feed troughs by experimental b i r d s  52  11  Significant  o f r e p l i c a t i o n (hatch) on parameters measured DXF i n t e r a c t i o n f o r egg weight o f experimental b i r d s  ..  49  DXF i n t e r a c t i o n f o r body weight gain o f experimental  hens  54  12  Mean body weight g a i n , adrenal weight and l e u k o c y t e count o f experimental r o o s t e r s  56  13  Significant  GXF i n t e r a c t i o n f o r l e u k o c y t e count o f experimental  hens  58  14  Mean f e a t h e r l o s s and comb damage s c o r e s o f the experimental  birds  15  Significant birds  GXD i n t e r a c t i o n f o r comb damage s c o r e s o f experimental  16  Significant birds  GXF i n t e r a c t i o n f o r comb damage s c o r e s o f experimental  17  A n a l y s i s o f V a r i a n c e f o r percent hen-day egg p r o d u c t i o n o f experimental b i r d s  60 61 62 102  vii  LIST OF TABLES  (Continued)  Table 18  Page A n a l y s i s o f V a r i a n c e f o r p e r c e n t hen-day egg p r o d u c t i o n o f experimental b i r d s with adjustment f o r age d i f f e r e n c e s between replications  103  Mean p e r c e n t hen-day egg p r o d u c t i o n , egg weight (g) and feed requirements (g) o f b i r d s with adjustment f o r age d i f f e r e n c e s o f b i r d s between r e p l i c a t i o n s  104  20  A n a l y s i s o f V a r i a n c e f o r egg weight o f experimental  105  21  A n a l y s i s o f V a r i a n c e f o r egg weight o f experimental b i r d s with adjustment f o r age d i f f e r e n c e between r e p l i c a t i o n s  22  A n a l y s i s o f V a r i a n c e f o r amount o f feed taken from feed troughs  19  by experimental 23  birds  106  birds  107  A n a l y s i s o f V a r i a n c e f o r amount o f feed taken from feed troughs by experimental b i r d s with adjustment f o r age d i f f e r e n c e s between replications  24  A n a l y s i s o f Covariance f o r body weight gain o f experimental  25  Analysis o f Variance for i n i t i a l  26  Analysis of Variance f o r percent f e r t i l i t y  27  A n a l y s i s o f V a r i a n c e f o r l e u k o c y t e count o f experimental hens  112  28  A n a l y s i s o f V a r i a n c e f o r adrenal weight o f experimental hens  113  29  A n a l y s i s o f V a r i a n c e f o r plasma c o n c e n t r a t i o n o f c o r t i c o s t e r o n e o f experimental  birds  hens  108  body weight o f experimental hens o f experimental b i r d s  ..  109  .  110  ..  Ill  114  viii  LIST OF FIGURES Figure 1  Page A comparison o f weekly  egg p r o d u c t i o n between s i g h t e d and  b l i n d chickens 2  3  46  A comparison o f i n i t i a l back and rump f e a t h e r s i g h t e d and b l i n d c h i c k e n s A comparison o f f i n a l  back and rump f e a t h e r  damages  damages  between  64  between  s i g h t e d and b l i n d c h i c k e n s 4  A comparison o f wing and t a i l  65 feather  damages between  sighted  and b l i n d c h i c k e n s 5  A comparison o f comb damages between s i g h t e d and b l i n d c h i c k e n s  66 ..  67  ix  ACKNOWLEDGEMENTS I  am i n d e b t e d to Dr. K.M. Cheng f o r the o p p o r t u n i t y to l e a r n  and p r a c t i c a l  aspects o f a g r i c u l t u r a l  Cheng's c o n s i s t e n t a d v i c e , this  study are g r a t e f u l l y  r e s e a r c h under h i s s u p e r v i s i o n .  and Dr. J . F .  acknowledged.  Richards  March, Dr. D.B.  are g r a t e f u l l y  Etches and h i s  Bragg,  acknowledged.  c o r t i c o s t e r o n e samples were analysed at the U n i v e r s i t y c o u r t e s y o f Dr. R.J.  technical  o f G u e l p h , through the  associates.  assistance,  Roland K.C.  i n the p r e p a r a t i o n o f t h i s  p a t i e n c e i n the t y p i n g o f t h i s Very s p e c i a l  thesis  Low f o r h i s  am g r a t e f u l  her  thesis.  to the Bangladesh A g r i c u l t u r a l of British  their  study.  Research C o u n c i l f o r making  Columbia p o s s i b l e under IDA C r e d i t Fund  T h i s r e s e a r c h study was supported by A g r i c u l t u r e Canada O p e r a t i n g  Grant #1027 and a l s o by Natural of  care  suggestions  thanks must be g i v e n to my w i f e and c h i l d r e n f o r  my s t a y at The U n i v e r s i t y #828BD.  i n the  and Kamily Cheung f o r  p a t i e n c e and understanding d u r i n g the course o f t h i s I  CR.  b i r d s , Cathleen N i c h o l s , Dean C r i c k , Y o u s i f Y o u s i f and Andy  Hickman f o r t h e i r and a s s i s t a n c e  Dr.  Plasma  I wish to thank Mel Hudson and Bob Chan f o r t h e i r a s s i s t a n c e o f experimental  Dr.  guidance and encouragement d u r i n g the c o u r s e o f  V a l u a b l e s u g g e s t i o n s from P r o f e s s o r B.E. Krishnamurti  theoretical  Canada Grant #A-8062.  Sciences  and E n g i n e e r i n g Research  Bangladesh A g r i c u l t u r a l  study l e a v e so t h a t I can perform t h i s  r e s e a r c h at  University  Council  granted me a  UBC.  Ahmed A l i  1  INTRODUCTION The gene  'rc , 1  an autosomal r e c e s s i v e m u t a t i o n , causes b l i n d n e s s i n chickens  when i n the homozygous s t a t e . cannot p e r c e i v e l i g h t  (Cheng et al_.» 1980).  ground o f t h i s mutant , to i n d i c a t e  The b i r d s l a c k rods and cones i n the r e t i n a  Cheng e t a]_. (1978)  A f t e r a n a l y s i n g the g e n e t i c have d e s i g n a t e d t h i s  the absence o f rods and cones i n the r e t i n a .  r e p o r t e d a case o f h e r e d i t a r y i n behavior and e x t e r n a l of hereditary  Hutt  Very l i t t l e  information is a v a i l a b l e  from the works o f Hutt (1935)  also 'rc'  and Cheng e t aj_.,  on the behavior and  (1980)  It  i s apparent,  how-  that blind chicks readily  feed and water i n an e n c l o s e d b a t t e r y o r pen.  Under normal r e a r i n g c o n d i t i o n s , s u r v i v a l  r a t e o f a f f e c t e d b i r d s has not y e t  been determined but performances i n terms o f egg p r o d u c t i o n , body weight fertility  mutation  ( C l a y t o n , 1975;  l e a r n to eat and d r i n k as well as normal ones when they are exposed to available  'rc'  S e v e r a l o t h e r forms o f r e p o r t e d cases  r e p r o d u c t i v e performance o f b i r d s having v i s i o n a n o m a l i e s . ever,  (1935)  b l i n d n e s s i n c h i c k e n s are e v i d e n t i n the l i t e r a t u r e  Smith e t aj_., 1977).  back-  gene as  b l i n d n e s s which seems to be s i m i l a r to  eye morphology.  and  and h a t c h a b i l i t y  gain,  are thought to be i n the normal range (Cheng e t  a!.,  1980). Many environmental density  (floor  area  factors  per b i r d )  i n f l u e n c e l a y i n g hens'  and f l o c k s i z e (number o f b i r d s per f l o c k )  received considerable attention Hill,  1977  ment, l a y e r s  (Adams and J a c k s o n ,  and Cunningham and O s t r a n d e r , 1982). are k e p t , as a general  out l o w e r i n g p r o d u c t i v i t y .  performance, o f which  rule,  have  1970; Adams e t al_.» 1978;  In modern p o u l t r y manage-  i n a p l a c e as small as p o s s i b l e w i t h -  This has o c c u r r e d to keep a balance with i n c r e a s i n g  2  c o s t s o f b u i l d i n g , equipment and l a b o u r w h i c h , as a consequence, has brought about a s i g n i f i c a n t change i n l a y i n g hens'  environment.  In a r e s t r i c t e d environment such as i n an i n t e n s i v e animals become dependent (Kilgour,  1972).  on  tations  each o t h e r and on the s u r r o u n d i n g environment  This a f f e c t s  is also a part of intensive  p r o d u c t i o n system,  normal  animal  behavior o f a n i m a l s .  husbandry and i t  by the animals concerned ( A r b i ,  and n o n - a d a p t a b i l i t y emerges  1978).  I n t e n s i v e housing  demands b e h a v i o r a l  The q u e s t i o n o f  under those c o n d i t i o n s .  adap-  adaptability  N o n - a d a p t a b i l i t y may  impose s t r e s s which may appear to be g r e a t e r with h i g h e r d e n s i t i e s and l a r g e f l o c k s i z e s than with lower d e n s i t i e s and small Such s t r e s s w i l l Studies  result  i n poor p r o d u c t i v i t y  i n c r e a s i n g i n number.  to manipulate o t h e r environmental  bird.  among b i r d s i n a f l o c k .  There i s a l s o an i n c r e a s i n g  For example, i n t e n s i t y o f l i g h t interactions  Hughes and Black (1974) observed t h a t b r i g h t l i g h t (17 to 22 l u x )  increased a c t i v i t y  (Shaver 288) reared e i t h e r  layers  interest  c o n d i t i o n s to reduce the l e v e l o f s o c i a l  houses c o u l d be manipulated to reduce s o c i a l  dim l i g h t  1980).  c o n c e r n i n g b i r d d e n s i t y and f l o c k s i z e on the performances o f  are p r o g r e s s i v e l y  teractions  per  flock sizes ( H i l l ,  poultry  among the f l o c k mates.  (55 to 80 l u x )  highly s i g n i f i c a n t l y  i n cages o r pens.  in  in-  compared to in  birds  They a l s o found a d i r e c t  re-  l a t i o n s h i p between a c t i v i t y and pecking damages. T h e r e f o r e , under low i n t e n s i t y  of l i g h t  (dim l i g h t ) ,  p r o b a b l y , the b i r d s  see each o t h e r w e l l , t h u s , r e d u c i n g a g o n i s t i c encounters among them.  Some S c i e n t i s t s  are a l s o attempting to r e s t r i c t  b i r d s by u s i n g s p e c t a c l e s to reduce s o c i a l 'specs'  (social  stress.  cannot  interactions)  the v i s i o n o f  the  In A u s t r a l i a , the use o f  (specs are a n t i - p e c k i n g d e v i c e s made o f a c o l o u r e d f l e x i b l e  polyethylene  3  material.  When f i t t e d on the nares o f the hens, they a l l o w them to l o o k to  the s i d e o r down but not d i r e c t l y ahead) i n c r e a s i n g (Cumming and E p p s , 1976). literature  d e s c r i b i n g the e f f e c t s  i n commercial l a y i n g f l o c k s has been  S e v e r a l r e p o r t s are a v a i l a b l e  c o n t a c t and a g o n i s t i c b e h a v i o r ,  and i n c r e a s e s  productivity.  in reducing s o c i a l  stress  social  More r e c e n t l y ,  hierarchy.  1978).  pecking by  save energy from reduced s o c i a l  The use o f specs a l s o has  by l i m i t i n g v i s u a l  hens  1977; A r b i ,  These works suggest t h a t f i t t i n g specs to hens c o n t r o l s f e a t h e r  interactions  the  o f specs on the performance o f l a y i n g  (Cooper and B a r n e t , 1966; Cumming and Epps, 1976; Karunjeewa,  reducing visual  in  advantage  c o n t a c t and b r e a k i n g down the  c o l o u r e d c o n t a c t l e n s e s f o r l a y i n g hens  have been i n t r o d u c e d i n the United S t a t e s f o r r e d u c t i o n o f c a n n i b a l i s m i n c h i c k e n s ; hens f i t t e d with red l e n s e s  (rosy glasses)  appeared to be the  least  s t r e s s e d (Time magazine, December 2 9 , 1980, page 1 4 ) . Despite many advantages  o f using mechanical  l a y i n g h e n s , t h e r e are some d i s a d v a n t a g e s a l s o . devices  need to adapt to them.  l a b o u r and c a p i t a l to the b i r d s disease.  (if  investments.  not f i t t e d  The g e n e t i c a l l y  advantages.  However,  until  in  of  Furthermore, they c o u l d be a h e a l t h hazard-  properly)  i n v i t i n g b a c t e r i a and p a r a s i t e s  the o p p o r t u n i t y to conduct i n v e s t i g a t i o n s blind birds in this  to cause  such d i s -  i n t o the  use-  c o n t e x t has not  now. undertaken to determine i f  the l a c k o f  the performances o f c h i c k e n s ( u t i l i z i n g the g e n e t i c a l l y  and t h e i r  vision  The hens f i t t e d with such  b l i n d b i r d s are o b v i o u s l y f r e e from a l l  T h i s study was t h e r e f o r e affects  to c o n t r o l  In a d d i t i o n , they i n c r e a s e c o s t s i n terms  f u l n e s s or disadvantages o f g e n e t i c a l l y presented i t s e l f  device  sighted counterparts)  under d i f f e r e n t ' d e n s i t y  sight  blind birds  and f l o c k  size  4  conditions.  5  REVIEW OF LITERATURE  I.  Productivity 1.  Egg p r o d u c t i o n Egg p r o d u c t i o n i s  laying strains  by f a r the most important t r a i t  and accounts f o r about 90% o f the t o t a l  commercial egg p r o d u c t i o n (Oluyemi of intensive  and R o b e r t s ,  husbandry p r a c t i c e s , l a y i n g hens'  1979).  farm income from In the modern system  g e n e t i c back-ground and  environment have been changed i n many ways ( C r a i g , The numerous breeds o f y e s t e r d a y  i n commercial egg-  its  1982).  have been r e p l a c e d e n t i r e l y  by the  White Leghorn f o r white egg p r o d u c t i o n and by the Rhode I s l a n d Red and New Hampshire breeds f o r brown egg p r o d u c t i o n . many s t r a i n s strains  f o r commercial egg p r o d u c t i o n have been d e v e l o p e d .  are not expected to be e q u a l l y w e l l adapted to i n t e n s i v e  ditions.  Genetically  p r o b a b l y bear on t h e i r (Craig,  W i t h i n the White Leghorn b r e e d ,  influenced behavioral  These  various  housing c o n -  d i f f e r e n c e s e x i s t i n g among s t o c k s  r e l a t i v e adaptatedness to high d e n s i t y  environment  1982). The response o f d i f f e r e n t l a y i n g s t r a i n s  under i n t e n s i v e  d i t i o n s has been the s u b j e c t o f many i n v e s t i g a t i o n s . conducted two experiments over two years i n v o l v i n g  rearing  Adams and Jackson 6  con(1970)  commercial l a y i n g  strains.  They observed h i g h l y s i g n i f i c a n t s t r a i n e f f e c t on hen-housed egg p r o d u c t i o n i n one experiment but not i n the o t h e r . hen-day p r o d u c t i o n , the d i f f e r e n c e either  experiment.  However, when p r o d u c t i o n was expressed as  between s t r a i n s  became n o n - s i g n i f i c a n t  This r e s u l t indicated that s t r a i n d i f f e r e n c e  d u c t i o n was due to d i f f e r e n c e s  in  i n egg p r o -  i n sexual m a t u r i t y o f the p u l l e t s as w e l l  as  6  differences  in mortality  of laying birds.  was conducted by Marks et a]_. s t o c k s and r e c o r d e d t h e i r  (1970).  Another experiment on egg p r o d u c t i o n  They a l s o used  egg p r o d u c t i o n over a f u l l  was repeated i n the f o l l o w i n g y e a r .  6  commercial egg l a y i n g  year.  In both o f t h e i r  The same experiment  trials,  they observed  h i g h l y s i g n i f i c a n t d i f f e r e n c e s among s t o c k s i n percent hen-day egg p r o d u c t i o n . The number o f c h i c k e n s housed i n the same cage a l s o a f f e c t s Emmans (1971) in  6  surveyed  strains  11  different  strains  of layers  egg p r o d u c t i o n .  kept i n c a g e s .  showed a r e d u c t i o n i n egg p r o d u c t i o n when they were housed at 4  per cage r a t h e r than 3, but the egg number o f the remaining 7 s t r a i n s show any s i g n i f i c a n t d e c l i n e .  d i d not  In another study (Anon, 1974), 4 b i r d s at  per b i r d were compared with 5 b i r d s a t 418cm . 2  8  Birds  523cm  2  Nine d i f f e r e n t s t r a i n s were u s e d ,  o f those showed a r e d u c t i o n i n egg p r o d u c t i o n under the most crowded c o n -  d i t i o n s w h i l e one d i d not change. 0.7 to 1 0 . 4 % .  The r e d u c t i o n i n egg p r o d u c t i o n v a r i e d  That egg p r o d u c t i o n i s  s i g n i f i c a n t l y affected  r e p o r t e d by Feldkamp and Adams ( 1 9 7 3 ) ; A i t k e n e t al_. (1973)  from  by s t r a i n s was and H i l l  also  (1977).  In a r e c e n t study u s i n g two s t r a i n s o f White Leghorn p u l l e t s , Cunningham and Ostrander (1982)  reported s i g n i f i c a n t s t r a i n differences  housed egg p r o d u c t i o n . In t h e i r s t u d y ,  1  s t r a i n averaged 4% more eggs per  hen on a hen-day and hen-housed b a s i s than the o t h e r Studies  f o r hen-day and hen-  strain.  on genotypes i n v o l v i n g s i n g l e l o c u s on the v a r i a b i l i t y  p r o d u c t i o n are not common.  In one s t u d y , Bullerman  (1981)  o f egg  observed a r e d u c t i o n  o f 17% i n egg p r o d u c t i o n o f dwarf genotype (dw/dw) compared to non dwarfs under i d e n t i c a l  conditions.  not f i n d any v a r i a t i o n s  Merat and Bordas  (Dw-)  ( 1 9 7 9 ) , on the o t h e r hand, d i d  i n pea comb genotype (Pp)  compared to s i n g l e comb  (pp).  The e f f e c t o f f l o o r s p a c e , s o m e t i m e s . r e f e r r e d to as b i r d d e n s i t y on egg  7  p r o d u c t i o n o f l a y i n g hens has been w i d e l y (1945)  investigated.  Hoffman and Tomhave  observed the e f f e c t o f d e n s i t y on the egg p r o d u c t i o n o f New Hampshire  p u l l e t s a t d e n s i t i e s o f 2564, 3437 and 4320cm per b i r d .  The high d e n s i t y  2  group (2564cm two g r o u p s . per b i r d )  2  per b i r d )  Siegel  l a i d about 18 eggs l e s s  (1959)  i n f l o o r pens.  a year)  compared two extreme d e n s i t i e s  than the  and Fox and C l a y t o n (1960)  other  (3716 vs 1239cm  The egg p r o d u c t i o n r a t e s were 48% f o r  and o n l y 38% f o r h i g h - d e n s i t y g r o u p s .  decreasing f l o o r space.  (in  2  low-density  On the o t h e r hand, Nordskog (1959)>  r e p o r t e d o n l y small d e c l i n e s  i n p r o d u c t i o n from  From t h e e a r l y s i x t i e s onward, most d e n s i t y  related  s t u d i e s were made i n cages and have demonstrated a r e d u c t i o n o f egg p r o d u c t i o n as the cage d e n s i t y i n c r e a s e d (Lowe and Haywang, 1964; Moore e t a l . , 1965; Cook and Dembnicki, 1966; B e l l  and L i t t l e ,  1966; Owing e t a l . , 1 9 6 7 ; Wilson  e t al_.1967; Champion and Z i n d e l , 1968; Adams and J a c k s o n ,  1970; Grover e t  al.,  1972; Foss and Carew, 1974; H i l l , 1977 and Cunningham and O s t r a n d e r , 1982). Group s i z e o r c o l o n y s i z e a l s o seem to s i g n i f i c a n t l y c o n t r i b u t e egg p r o d u c t i o n o f l a y i n g s t o c k s . difficult density  to e v a l u a t e  its  (Hughes, 1975).  effect  In most o f the e a r l i e r s t u d i e s , i t  A i t k e n e t a]_. (1973)  observed t h a t compared to  u s i n g 3 o r 5 b i r d s i n small  (78%)  cages (41cm x 41cm) and 9 o r 18 b i r d s  was from the small cage-low d e n s i t y and lowest  from the l a r g e cage-high d e n s i t y . responses.  birds  Feldkamp  i n l a r g e cages (72cm x 82cm) found s i g n i f i c a n t e f f e c t o f c o l o n y s i z e . rate of lay  has been  because g r o u p - s i z e has been confounded with  housed two per cage those housed one per cage l a i d 9% more e g g s . ejt al_. (1973)  to  Adams and Jackon (1970)  rate  Highest (70%)  a l s o observed  similar  The e f f e c t o f i n c r e a s e d c o l o n y s i z e on the hen-day r a t e o f l a y  s t u d i e d by Wilson e_t al_. (1977).  was  Increased colony s i z e depressed egg p r o d u c t i o n .  8  Mean r a t e o f l a y was s i g n i f i c a n t l y  h i g h e r f o r i n d i v i d u a l l y caged b i r d s  than f o r b i r d s housed e i t h e r  (67.39%)  per c a g e .  3  A review o f l i t e r a t u r e  or  (1968)  (67.39%)  indicated that a l l  area per b i r d d i d not respond i n a l i n e a r o r d e r . Zindel  5  or  5  group s i z e s i n  (75.59%)  (63.54%) constant  As f o r example, Champion and  found t h a t 3 b i r d s per cage had b e t t e r egg p r o d u c t i o n compared  to 2, 4 o r 6 b i r d s per c a g e .  In another s t u d y , Tower e t a]_.  (1967)  had shown  t h a t 10 b i r d s per cage was more p r o d u c t i v e than 2, 5 o r 20 b i r d s per c a g e . The egg p r o d u c t i o n o f l a y i n g hens i s a l s o i n f l u e n c e d by the and s o c i a l (Tindel  rank ( a c c o r d i n g to peck o r d e r )  and C r a i g ,  dominance a b i l i t y , (1972)  1959).  In s t u d i e s  o f the i n d i v i d u a l s w i t h i n  involving strains  Biswas and C r a i g ( 1 9 7 0 ) ,  observed t h a t ,  compared to t h e i r  l y , : s o c i a l l y dominant s t r a i n s  C r a i g (1970)  These workers  I n d i r e c t evidence o f the w i t h i n  (1971)  cages.  On the o t h e r hand, t h e i r  flock  and by Biswas and  g r e a t i n crowding s i t u a t i o n s .  Fitting  ranks f o r egg p r o d u c t i o n  c o n t a c t among hens  Cumming and Epps (1976)  hens found i n c r e a s e d egg p r o d u c t i o n and feed e f f i c i e n c y . 11% more eggs than the c o n t r o l  is  ' s p e c s ' to the hens may r e d u c e , to some  c o n t a c t and thus reduce the s o c i a l  1978) and improve p r o d u c t i v i t y .  White Leghorn  i n f l o o r pens.  r e p o r t e d t h a t the impact o f v i s u a l  e x t e n d , the chance o f v i s u a l  to  r e p o r t e d t h a t a s t r a i n o f h i g h l y a g g r e s s i v e White  were r e v e r s e d when those s t r a i n s were kept s e p a r a t e l y McBride  separate-  o f egg p r o d u c t i o n r e l a t i v e  Leghorn had h i g h e r egg p r o d u c t i o n than a s t r a i n o f more peaceful when kept i n i n d i v i d u a l  social  and Lowry and A b p l a n l p  a g g r e s s i v e n e s s on egg p r o d u c t i o n was p r o v i d e d by C r a i g (1970) Craig (1970).  a flock  r e l a t i v e performance when kept  had h i g h e r l e v e l s  s u b o r d i n a t e s t o c k s when kept t o g e t h e r .  d i f f e r i n g in  behavior  stress  (Arbi,  i n s t u d i e s with specThe spec-hens produced  hens over 11-month l a y i n g p e r i o d .  Other  reported  9  studies using spec on hens showed considerable improvement in egg production of spec-hens (Karunajeewa, 1977 and Arbi, 1978). Among many other factors which can affect egg production of laying hens, the most important are dietary composition (Lebbie et ajk 1981; Vargas and Edward, 1982), light (Odom and Harrison, 1979; Nys and Morgin, 1981) and temperature (Arad et a]_. 1981). 2.  Egg weight Egg size is very important in the production and marketing of eggs  (Christmas et al_. 1979).  Romanoff and Romanoff (1949) stated that egg size  could be expressed in terms of egg weight, because weight provides a basis of comparison which is more convenient than dimensions or volume.  The egg weight  of laying hens is influenced by numerous hereditory, environmental and physiological factors. Earlier reports (Romanoff and Romanoff, 1949) on the egg weight of different avian species Indicated large variations between species.  Ostrich  for example lays eggs which are on the average 1400g, Swan 285g, Canada Goose 135g, Pea Fowl 90g, Turkey 85g, Duck 80g, Leghorn Fowl 58g, Pigeon 17g and Humming Bird 0.5g. The effect of heredity on egg weight of chickens has been investigated. Warren (1953) reported that egg weight is a highly heritable character. fieritability estimates were reported for this t r a i t .  Numerous  King and Handerson (1954)  found that the heritability of egg weight on the basis of full-sib correlation and regression of daughter on dam were 0.48 and 0.60 respectively.  Hogsett and  Nordskog (1958) reported heritability estimates to be 0.36, 0.45 and 0.41 in light breeds and 1.15, 0.55 and 0.85 in heavy breeds on the basis of paternal  10  half-sib, maternal half-sib and full-sib correlations respectively.  Kinney (1969)  summarised the reported heritabilities of light and heavy breeds for early egg weight and mature egg weight.  For early egg weight light breeds averaged 0.45,  0.53, 0.45 and 0.52; heavy breeds 0.57, 0.65, 0.67 and 0.63; for mature weight, light breeds 0.36, 0.45, 0.50 and 0.44; heavy breeds 0.58, 0.54, 0.58 and 0.46 respectively according to s i r e , dam, full-sib and regression methods.  Recent  reviews on the heritability estimates of egg weight are not evident in the literature. The effect of strains on the egg weight of laying hens has been the subject of several investigations. Cunningham and Ostrander (1982) reported significant strain effects for average egg weight in two White Leghorn egg laying strains. (62g vs 58g).  Egg weight for one strain averaged 4g more than the other one They also found that the strain which had the heaviest egg weight  had also produced the most eggs.  Akber et a]_. (1983) had also demonstrated  differences in egg size of 7 genetic stocks of White Leghorn type chickens. On the other hand, Hill (1977) did not find such variations in two other commercial strains of White Leghorns. Several authors reported that they found no significant influence of bird density on egg weight.  Cuinningham and Ostrander (1982) observed that birds  housed 4 per cage compared to those housed 5 birds per cage had the same egg weight.  Hill (1977) conducted two experiments with Babcock 300 and Shaver, 288  stocks.  This author demonstrated that birds housed 310, 387 or 464cm per bird, 2  or 3, 6, or 12 birds per group did not have significantly different egg weights in either of the experiments.  Similar results were also reported by other workers  (eg. Aitken et al_., 1973; Adams and Jackson, 1970).  11  Egg weight i s r e p o r t e d to be s i g n i f i c a n t l y a f f e c t e d by cage s i z e , the r e s u l t s layers  are i n c o n c l u s i v e .  Cunningham (1982)  r e p o r t e d t h a t White Leghorn  housed i n s h a l l o w cages l a i d s i g n i f i c a n t l y h e a v i e r  the deep cages ( 6 0 . l g vs 5 8 . 9 g ) .  Significantly  but  heavier  eggs than b i r d s  average annual  in  egg  weight f o r b i r d s i n s h a l l o w cages compared to b i r d s i n deep cages were a l s o r e p o r t e d by H i l l (1976)  and Hunt (1978).  Contrary to the above f i n d i n g s , L e e and B o l t o n  r e p o r t e d t h a t White Leghorn l a y e r s  housed i n deep cages l a i d  l y h e a v i e r eggs than those housed i n s h a l l o w c a g e s . and Cunningham and Ostrander (1982)  significant-  Adams and Jackson  (1970),  d i d not f i n d such d i f f e r e n c e between  shallow  and deep cages with v a r y i n g p o p u l a t i o n s i z e s . The r e l a t i o n s h i p o f l a y i n g h e n ' s body weight and egg weight was vestigated  by s e v e r a l  authors.  a t 28 weeks o f age i n t o l i g h t  Harms e t al_. (1982) (L),  medium (M)  in-  d i v i d e d Dekalb XL p u l l e t s  and heavy (H)  body weight g r o u p s .  The b i r d s were housed i n 20.3 x 45.7cm w i r e cages f o r a p e r i o d o f 16 weeks. They found egg weight to be r e l a t e d ences were found between a l l 1 and 2g d i f f e r e n c e s  three  body weight g r o u p s .  i n egg weight between  a n o t h e r s t u d y B e l l e t al_. (1981) two weight c l a s s e s  to h e n ' s body w e i g h t .  smaller eggs.  into  18 weeks o f a g e .  Light pullets  f o r the 1 day groups and 2.8g f o r the 18 week g r o u p s .  segregated  T h i s amounted to  McClung and Jones  s t a t e d t h a t egg weight  i s a f u n c t i o n o f age o f the hens  at  2.4g (1973)  results.  Age o f the hen i s a l s o a c o n t r i b u t i n g f a c t o r to egg w e i g h t . e t al_. (1978)  In  o f SCWL p u l l e t s segregated  Performance r e c o r d s were kept to 68 weeks o f a g e .  a l s o reported s i m i l a r  There were a p p r o x i m a t e l y  at 1 day o f age versus  1 day and 18 weeks produced s i g n i f i c a n t l y  differ-  the L to M and M to H g r o u p s .  used 3 s t r a i n s  (heavy and l i g h t )  Significant  Gilbert rather  12  than the p e r i o d o f l a y . Saeki e t a]_.,  Reports  by p r e v i o u s workers  1967; Weatherup and F o s t e r ,  (eg.  Cowen e t a l _ . , 1964;  1980) i n d i c a t e d t h a t egg weight  in-  c r e a s e s m o n o t o n i c a l l y with age and approaches an asymptote. Many o t h e r f a c t o r s nutrition  (Lebbie  (Arad e t a]_., 3.  also affect  egg w e i g h t .  Some important ones  e t a l _ . , 1981; McDeniel e t a l _ . , 1981), ambient  temperature  1981) and l i g h t schedule (Nys and M o r g i n , 1981).  Feed consumption Feed c o s t accounts f o r at l e a s t  t w o - t h i r d o f the t o t a l  ducing eggs (Wing and Nordskog, 1982) or 70% o f t o t a l (Pym and N i c h o l l s , 1979).  cost of  pro-  cost f o r producing b r o i l e r s  Any improvement i n the e f f i c i e n c y o f feed  would be o f economic b e n e f i t . to i t s  are  utilization  The amount o f feed t h a t a b i r d consumes i s  related  energy requirements which i n t u r n i s a f f e c t e d by g e n e t i c s and environment.  One way o f comparing feed consumption i s feed component' (Bordas and M e r a t ,  by means o f a n a l y s i n g the  1981).  The r e s i d u a l  the amount o f feed consumption remaining a f t e r weight and egg mass.  'residual  component was d e f i n e d as  statistical  adjustments  f o r body  Expected feed consumption was e s t i m a t e d from a m u l t i p l e  r e g r e s s i o n e q u a t i o n u s i n g independent v a r i a b l e s weight change d u r i n g the t e s t  such as mean body w e i g h t ,  p e r i o d , and egg mass produced.  body  The r e s i d u a l  was  then c a l c u l a t e d as observed feed consumption minus expected feed consumption. Using t h i s measurement, Merat and Bordas  (1979)  demonstrated t h a t pea comb  hens consumed about 2% l e s s feed than s i n g l e comb (pp)  hens.  (Pp)  They suggested  t h a t with the s m a l l e r s i z e o f comb and w a t t l e s f o r Pp h e n s , heat l o s s e s and hence energy requirements are l e s s .  In another study (Merat et a J L ,  was a l s o found t h a t white hens (I/I,  I/i)  consumed s i g n i f i c a n t l y  feed than c o l o u r e d hens i n a 28-day p e r i o d .  less  They c o u l d n o t , however,  1979)  it  (140.8g) assign  13  any p l a u s i b l e e x p l a n a t i o n . Significant  variations  were found by Bordas and Merat C o n v e r s e l y Arboleda (1971) variation  in residual  feed consumption w i t h i n  ( 1 9 7 4 ) , Watenabee e t al_. (1975)  and Lee and Nordskog (1975)  i n the White Leghorn l i n e s  Bordas and Merat  (1981),  observed h i g h l y s i g n i f i c a n t d i f f e r e n c e s Wing and Nordskog (1982)  comparing  that individual  2  feed consumption  brown egg s t r a i n s ,  between s i r e f a m i l i e s  i n two p o p u l a t i o n s o f White Leghorns c o n s i s t e d o f  indicates  (1977).  f a i l e d to f i n d such  in residual  e s t i m a t e d the h e r i t a b i l i t y  and 0.15 ± 0.06 r e s p e c t i v e l y .  and Hagger  lines  t h a t they were s t u d y i n g .  On the o t h e r hand, between l i n e d i f f e r e n c e s exist in chickens.  genetic  i n both s t r a i n s .  of residual  feed consumption  4909 b i r d s to be 0.29 ± 0.07  These moderately high h e r i t a b i l i t y  estimates  feed consumption r e c o r d s should be c o n s i d e r e d i n  re-  l a t i o n to s e l e c t i o n f o r e f f i c i e n c y o f egg p r o d u c t i o n . Quite a number o f s t u d i e s have so f a r measured feed consumption i n chickens in r e l a t i o n (eg.  to such environmental  f a c t o r s as group s i z e and d e n s i t y  Feldkamp and Adams, 1973; Jensen e t a l _ . , 1976).  In these s t u d i e s group  s i z e ranged from 1 to 5 b i r d s and d e n s i t i e s were between 350 and 1400cm bird.  Jensen e t al_. (1976)  o f three  level  per  r e p o r t e d t h a t hens housed a l o n e a t e more than groups  kept i n the same a r e a .  to compare the e f f e c t s  2  Ouart and Adams (1982)  conducted two experiments  o f cage s h a p e , f e e d e r s p a c e , cage d e s i g n , b i r d  density,  o f f e e d i n g , and f e e d i n g p e r i o d on f e e d i n g behavior and b i r d movements.  They found t h a t feed consumption was s i g n i f i c a n t l y a f f e c t e d by b i r d  density.  Hens housed 2 per cage consumed 10.5g more feed per b i r d d a i l y than those housed 3 per c a g e .  Furthermore, they a l s o concluded t h a t i n c r e a s e d feeder space  important i n r e d u c i n g f e e d e r c o m p e t i t i o n d u r i n g f e e d i n g t i m e .  is  14  Social  rank and f e e d i n g behavior may have c o n s i d e r a b l e i n f l u e n c e on  the amount o f feed consumed and feed s p i l t . f e e d i n g was i n v e s t i g a t e d  The s o c i a l  by Candland e t al_. (1968).  rank and p r i o r i t y  in  Within a r e s t r i c t e d  en-  vironment t h e r e e x i s t s a s t r o n g c o r r e l a t i o n between the two v a r i a b l e s .  In  t h e i r s t u d y they used p a i r e d  comparison t e c h n i q u e , a l i m i t e d f e e d i n g p e r i o d and  food d e p r i v e d c h i c k e n s ,  found t h a t i n d i v i d u a l s  and  having high s o c i a l  spent a l o n g e r time i n f e e d i n g than low ranked b i r d s . more energy e x p e n d i t u r e .  Longer f e e d i n g  rank requires  On the o t h e r hand Syme and Syme (1974) observed whole  group c o m p e t i t i o n f o r feed i n a pen environment having 7 to 8 b i r d s per pen and o b t a i n e d a poor c o r r e l a t i o n between the peck o r d e r and time spent i n command o f the feed box. When animals feed i n g r o u p s , another k i n d o f s o c i a l operative:  social  facilitation  (Craig,  1981).  t i t i o n o f an a c t performed by one i n d i v i d u a l Thus, the two kinds o f s o c i a l facilitation  influence  Social  influence is  facilitation  by o t h e r i n d i v i d u a l s  is  also  the r e p e -  (Arbi,  influences act in opposite d i r e c t i o n s ,  1978).  social  f e e d i n g a c t i v i t y , whereas a g o n i s t i c b e h a v i o r i s  likely  to reduce f e e d i n g by s u b o r d i n a t e s . Social  interactions  can be d r a s t i c a l l y  s p e c t a c l e s on l a y i n g hens and b l o c k i n g t h e i r  a f f e c t e d by p u t t i n g opaque  frontal  vision.  Cumming and Epps  (1976) r e p o r t e d the e f f e c t o f s p e c t a c l e s on the feed consumption o f 4000 Leghorn-Australorp cross l a y i n g hens. consumed 6% l e s s  total  They found t h a t hens wearing  feed than c o n t r o l  'specs'  hens and t h e r e was a l s o an improvement  i n feed e f f i c i e n c y as measured by g o f egg per kg o f feed consumed.  Arbi  (1978)  s t u d i e d the f e e d i n g behavior o f hens wearing specs and r e p o r t e d t h a t c o n t r o l spent much time i n p l a y i n g with the f e e d , f l i c k i n g i t  around, f i l i n g i t  up or  hens  15  pecking a t the feed t r o u g h . the f e e d .  Spec hens tended to eat r a t h e r  than p l a y with  They ate q u i c k l y , reduced time spent i n f e e d i n g a c t i v i t y ,  wasted l e s s  feed than c o n t r o l  hens.  and  He concluded t h a t because o f the  d u c t i o n i n f e e d i n g time spent by spec h e n s , energy e x p e n d i t u r e due to activities  feeding  was a l s o r e d u c e d .  Another advantage o f specs i s loss.  re-  Emmans and C h a r l e s  (1976)  to reduce f e a t h e r  i n d i c a t e d t h a t maintenance ME  Energy) requirement by hens with e x t e n s i v e f e a t h e r with a l a r g e amount o f f e a t h e r exposed s u r f a c e than f u l l y  p e c k i n g and  feather  (Metabolizable  l o s s i s much h i g h e r .  Hens  l o s s may l o s e up to 40% more heat from t h e i r  f e a t h e r e d hens.  Karunjeewa  (1977)  reported  that  the use o f specs s i g n i f i c a n t l y reduced f e a t h e r l o s s i n p u l l e t s and r e s u l t e d a 6.6% r e d u c t i o n i n t o t a l  ME i n t a k e .  A study o f feed consumption by p u l l e t s was conducted by Stappers than p u l l e t s  in  (1969).  Pullets  under cage o r f l o o r  situations  i n cages consumed 5.6% l e s s  energy  i n f l o o r pens.  The feed consumption o f l a y i n g hens i s a l s o a f f e c t e d by a h o s t o f other factors  such as i n t e n s i t y o f egg p r o d u c t i o n , body w e i g h t ,  schedule (Bordas and M e r a t , 4.  Body  1981; McDonald, 1978 and Nys and M o r g i n , 1981)  weight  Commercial  p o u l t r y breeders s t r i v e  o f c h i c k e n s (White Leghorn s t r a i n s ) Briggs,  1968).  maintenance. layers  and l i g h t  by 454g ( l i b )  varieties  t h a t l a y a t a high r a t e (Nordskog and  The purpose o f doing t h i s Nordskog (1960)  to develop small bodied  is  to reduce feed requirement  for  demonstrated t h a t an i n c r e a s e o f body weight  of  above the mean decreased income, but s i m i l a r i n c r e a s e  in  body weight i n b i r d s below the mean was b e n e f i c i a l  economically.  These  results  16  lead to the c o n c l u s i o n t h a t a s a t i s f a c t o r y important f o r economic g a i n .  body weight i n l a y i n g hens  is  Nordskog and Briggs a l s o emphasized the i m -  portance o f an optimum body weight i n l a y e r  strains.  l o w e r i n g body weight by lOOg per b i r d from over a l l  They showed t h a t mean o f 1500g decreased  hen-housed egg p r o d u c t i o n by 18 eggs i n a p r o d u c t i o n p e r i o d o f 332 d a y s . It  has been r e p o r t e d t h a t  body weight or gain i n body weight  are  normally d i s t r i b u t e d and are a f f e c t e d by many genes each with a small and a l s o by many environmental  factors  (McCarthy,  1977).  A d u l t body weight o f c h i c k e n i s a h i g h l y h e r i t a b l e t r a i t and R o b e r t s o n , 1966). tabilities  Kinney (1969)  effect  (Clayton .  summarised most o f the p u b l i s h e d h e r i -  o f mature body weight o b t a i n e d by p a t e r n a l  half-sib correlation  method.  The v a l u e s o b t a i n e d averaged 0.52 f o r l i g h t breeds and 0.49 f o r  breeds.  These h e r i t a b i l i t y  nature o f t h i s  trait.  e s t i m a t e s a r e i n d i c a t i v e o f the h i g h l y  For t h i s  reason body weight responded well  and has been one o f the important f a c t o r s  in selective  heavy  heritable to  selection  breeding (McCarthy,  Body weights o f c h i c k e n s vary a c c o r d i n g to b r e e d .  1977).  Standard weight  of  Rhode I s l a n d Red a d u l t s and t h a t o f White Leghorn a d u l t s are r e p o r t e d to be 3856g vs 2722g r e s p e c t i v e l y (Nesheim et a l _ . , 1979). gain between s t r a i n s  f o r males and 2948g vs 2041g r e s p e c t i v e l y  for  females  On the o t h e r hand, r e p o r t s on d i f f e r e n c e s i n body weight  o f White Leghorns are c o n f l i c t i n g .  Significant  variations  i n weight gain o f commercial l a y e r s t r a i n s were r e p o r t e d by A i t k e n et a}_. (1973), Lee and B o l t o n  (1976)  Ostrander (1982)  and a l s o by H i l l  (1977).  found no such v a r i a t i o n  C o n v e r s e l y , Cunningham and  i n body weight gain o f  2  strains  of  White Leghorn l a y e r s . G e n e t i c s t u d i e s r e g a r d i n g the e f f e c t o f a s i n g l e gene on body weight o f  17  c h i c k e n s were conducted by s e v e r a l (1981)  compared the body weight o f dwarf hens (caused  linked recessive parts  authors u s i n g d i f f e r e n t  gene, dw, H u t t ,  i n two temperatures  1953) with t h e i r  (normal  gene l o c i .  by the e f f e c t  normal non-dwarf  1 8 ° C - 2 0 ° C and high  32°C).  o f a sex(Dw ) +  temperatures  respectively,  body weight a t  vs 1958 and 1523g f o r n o r m a l s . was 30% o f t h a t o f the normal  e t al_. (1980)  age o f f i r s t  normal c o u n t e r p a r t s . causing v a r i a t i o n  c o n d i t i o n was 24%.  and the c o r r e s p o n -  In another study o f  layers  b i r d s from 20 week o f age to  Touchburn e t al_. (1980)  Other gene l o c i  i n body weight  the  a l s o r e p o r t e d 27% r e their  do not seem to have as much i n f l u e n c e  gain o f c h i c k e n s . authors  e t aj_.,  l o c u s and body weight  Studies  in  For example, the pea comb  (Kan e t a l _ . , 1959; S m i t h , 1961; S i e g e l  1977) but no r e l a t i o n s h i p was found be-  in chickens.  c o n c e r n i n g b i r d d e n s i t y on body weight o f egg l a y i n g s t r a i n s  and the r e s u l t s  are i n c o n c l u s i v e .  and area per b i r d were confounded. gain as b i r d d e n s i t y  In  In most o f the s t u d i e s  are  group s i z e  those s t u d i e s some have observed reduced  increased  (Grover e t a l _ . , 1972; Wilson e t  1967; Foss and Carew, 1974; Dorminey and A r s c o t t , Hill,  hens  gain o f dwarf c h i c k s at 5 week o f age compared with  and Dudley, 1963; and W i l l i u m s  body weight  two  91 week o f age averaged 1356 and 1131g  demonstrated t h a t dwarf  gene was s t u d i e d by s e v e r a l  variable  at  egg (176 days) gained on an average o f 13.33g per b i r d per day com-  d u c t i o n i n body weight  tween t h i s  For dwarf hens at the  hens i n the moderate temperature  pared to 16.93g f o r normal hens.  (Pp)  cages  The r e d u c t i o n i n body weight o f the dwarf  d i n g value i n the high temperature Koroleva  counter-  From 17 week o f  a g e , h a l f o f 74 dwarf and 80 normal s i z e d hens were kept i n i n d i v i d u a l 18-20 °C and the o t h e r s a l s o i n cages but at 3 2 ° C .  Bullerman  al.,  1971; Jensen e t a l _ . , 1976,  1977 and Cunningham and O s t r a n d e r , 1982), o t h e r s observed i n c r e a s e d  body  18  weight gain i n m u l t i p l e caged b i r d s compared to i n d i v i d u a l l y caged b i r d s (Lowe and Haywang, 1964; Tower e t a K » found no e f f e c t  per b i r d were v a r i e d i n space a l l o w a n c e ,  Besides,  systematically  i n one study i n which group s i z e and area  and i n d e p e n d e n t l y ( W e l l s , 1973), a r e d u c t i o n  a t a given group s i z e ,  The group s i z e s used i n t h i s  no e f f e c t on weight  gain.  r e s u l t e d i n a lower weight  group s i z e , at a given space a l l o w a n c e ,  The space p r o v i d e d was 387, 465 and 581cm  i n the general  to become p a r e n t s . r e p o r t e d to a f f e c t  meaning o f the term i s  the a b i l i t y  Many f a c t o r s , both g e n e t i c and environmental fertility  i n domestic  The evidence t h a t f e r t i l i t y  per  bird.  i n chickens i s a h e r e d i t a r y  o f dams with t h e i r d a u g h t e r s .  findings. tability  Hampshire) tability  of f e r t i l i t y  of this  Blow e t al . ,  to be as high as  r e p o r t ( A b p l a n a l p and K o s i n , 1953) a l s o confirmed  to be very low ( 0 . 0 2 ) .  as C r i t t e n d e n e t a K  full-sib correlations variance  of f e r t i l i t y  In New Hampshire c h i c k e n s C r i t t e n d e n et_ a]_. of f e r t i l i t y  correlation  i n Standard Bronze turkey was i n f l u e n c e d by  These authors e s t i m a t e d h e r i t a b i l i t y  Another l a t e r  are  t r a i t was not  o f 0.19 ± 0.05 between f e r t i l i t y  heredity.  individuals  fowls.  ( 1 9 3 5 ) , who r e p o r t e d a s i g n i f i c a n t  reported that f e r t i l i t y  of  in o r i g i n  r e a l i z e d before the work o f J u l l  0.81.  2  had  Fertility Fertility  (1951)  gain.  p a r t i c u l a r experiment were 3, 4 , 5 o r 6 b i r d s per  On the o t h e r hand, v a r y i n g  5.  others  o f b i r d d e n s i t y on body weight g a i n (Cook and Domnicki, 1966;  Champion and Zindel , 1968).  cage.  1967; A i t k e n e t a l _ . , 1973) and s t i l l  used ,  (1957)  reported  Using the same breed  G i l b r e a t h et a]_. (1962)  their heri-  (New  obtained  heri-  to be 0 . 0 2 , 0.21 and 0.14 a c c o r d i n g to s i r e , dam and respectively.  Buckland (1971)  t r a i t and o b t a i n e d h e r i t a b i l i t y  e s t i m a t e d the  of f e r t i l i t y  genetic  to be 0 . 2 1 ,  0.31  19  and 0.22 f o r t h r e e measures o f f e r t i l i t y fertility  and percent hens f e r t i l e .  such as d u r a t i o n o f f e r t i l i t y ,  In one more study ( S a l o n i a  percent  and Shushu,  1972) r e p o r t e d h e r i t a b i l i t y v a l u e s o f 0.25 and 0.44 f o r f e r t i l i t y  i n two  lines  of chickens. The above r e p o r t s i n d i c a t e d t h a t fertility 0.40) is  estimates  v a r i e d from low (0.02) to high (0.81) with i n t e r m e d i a t e values  being more f r e q u e n t .  partly  in chickens h e r i t a b i l i t y  These r e s u l t s  suggest t h a t  fertility  under h e r e d i t a r y c o n t r o l and s e l e c t i o n f o r i t s  of  (0.20-  i n avian  species  improvement c o u l d be  effective. Breed d i f f e r e n c e s i n male f e r t i l i t y ( P a r k e r , .1961; Sol 1 er e t a l _ . , 1965). fertility  have been r e p o r t e d i n the  literature  These authors o b t a i n e d s i g n i f i c a n t l y  lower  i n C o r n i s h males than i n Delware, New Hampshire and White Rock m a l e s .  They a t t r i b u t e d t h i s  to the f a i l u r e o f C o r n i s h males to mate n a t u r a l l y ,  t h e r e was no s i g n i f i c a n t d i f f e r e n c e s i n f e r t i l i t y i n s e m i n a t i o n was u s e d .  Fertility  I s l a n d Reds was compared by Hutt  (1940).  He found lower f e r t i l i t y  fertility.  (Dunn, 1927) have been r e p o r t e d  The presence o f a c e r t a i n gene may  Buckland and Haws (1968)  and rose comb (RR)  Adams e t al_ (1978) flock s i z e .  strains  1975), between i n d i v i d u a l s ( S o l l e r e t a l _ . , 1965) and whether  to have s i g n i f i c a n t e f f e c t s on f e r t i l i t y .  pea comb (Pp)  i n White  F u r t h e r m o r e , d i f f e r e n c e s between  o r not the males and the females were r e l a t e d  also affect  artificial  o f White Wyandotte, White Leghorn and Rhode  Wyandotte than i n the o t h e r two b r e e d s . (Bhagwat and C r a i g ,  between breeds when  since  r e p o r t e d lowered f e r t i l i t y  in  c h i c k e n s compared to b i r d s with s i n g l e combs.  found t h a t f e r t i l i t y  was s i g n i f i c a n t l y a f f e c t e d by  They t e s t e d two experimental s t r a i n s o f White Leghorn c h i c k e n s  housed i n cages a t a c o n s t a n t d e n s i t y o f 534cm per b i r d e i t h e r 2  i n small  flocks  20  (l«t:10??) or i n l a r g e f l o c k ( 2 J $ : 2 0 ? ? ) . fertility  From 20-44 week o f age the mean  o f the b i r d s was 39.4% f o r small  f l o c k vs 55.5% f o r l a r g e f l o c k .  t h i s study they f u r t h e r r e p o r t e d t h a t f e r t i l i t y from 0 to 100%.  of individual  flocks  In another study i n v o l v i n g b i r d s i n l a r g e r f l o c k s  Hughes and Holleman (1976)  reported f e r t i l i t y  o f 94%.  It  In  varied  (8$i:80$|),  is evident,  therefore,  t h a t the l a r g e r the s i z e o f the f l o c k (with a c o n s t a n t male-female r a t i o ) , h i g h e r the f e r t i l i t y within  the  rate.  This may be due to male-male c o m p e t i t i o n f o r mating  flock.  There  1s  some evidence t h a t f e r t i l i t y  rank or peck o r d e r o f the b i r d s . social  the  Guhl  i n chickens i s a f f e c t e d by s o c i a l  and Warren (1946)  suggested t h a t  rank or peck o r d e r o f the hens to which males are i n t r o d u c e d  t h e i r mating b e h a v i o r . are i n t e r m e d i a t e  the  affects  Males tend to mate more f r e q u e n t l y with the hens which  in social  rank but not with the h i g h e s t or lowest ranking hens.  The same authors a l s o s t a t e d t h a t when three o r more males are put t o g e t h e r a p e n , both the frequency o f mating and f e r t i l i t y ranking males.  are h i g h e s t f o r the top-  The lowest r a n k i n g males mate l e s s f r e q u e n t l y w i t h few f e m a l e s ,  because o f i n t e r f e r e n c e It  in  from the h i g h e s t r a n k i n g m a l e s .  was r e p o r t e d i n s e v e r a l  e f f e c t on the f e r t i l i t y  s t u d i e s t h a t the age o f a p u l l e t has an  o f eggs produced.  Sunde and B i r d  (1959)  reported  that  eggs l a i d by p u l l e t s which had j u s t reached sexual m a t u r i t y d i d not hatch as well as l a t e r  eggs presumably due to i n f e r t i l i t y .  greater v a r i a t i o n  i n percentage o f f e r t i l e  and l a t e m a t u r i t y  groups.  the f i r s t  first  a l s o found  eggs from p u l l e t s o f e a r l y  Garwood and Lowe (1982)  m a t u r i t y group ( 1 s t egg on 159 days)  Tomhave (1958)  fertile  maturity  r e p o r t e d t h a t i n the  early  egg was found two days  egg but i n . the l a t e m a t u r i t y group ( 1 s t egg on 174 days)  one day  after after.  21  T h i s d i f f e r e n c e was not Other f a c t o r s health II.  are s e a s o n , s t a t e o f n u t r i t i o n and  measuring s t r e s s  Feather  pecking  Feather  pecking i n G a l l i n a c e o u s b i r d s i s a b e h a v i o r a l  1873), more o f t e n t h i s with c a n n i b a l i s m . ferent  affecting f e r t i l i t y  ( L a k e , 1974; L o r e n z , 1959).  Parameters 1.  significant.  (Ottel,  term i s confused with a g g r e s s i v e p e c k i n g and sometimes  Generally,  feather  pecking and c a n n i b a l i s m are q u i t e  from a g g r e s s i v e behavior (Wennrich,  of feathers  phenomena  1974).  Feather pecking i s  dif-  the  loss  due to pecking by o t h e r b i r d s sometimes a s s o c i a t e d with hemorrhaging  o f s k i n (Hughes and Duncan, 1972). pecking a c t i v i t y  Aggressive pecking i s  the v i g o r o u s and quick  o f a b i r d a t the head o f another b i r d (Wennrich,  the o t h e r hand, f e a t h e r and c a n n i b a l i s t i c  1974).  On  pecks are performed much l e s s  v i g o r o u s l y and q u i c k l y and g e n e r a l l y not d i r e c t e d towards the need o f the mates.  Feather  pen-  pecking i n most o f the cases does not r e s u l t i n bloody wounds,  but the bloody wounds caused by c a n n i b a l i s m are u s u a l l y due to f e a t h e r p e c k i n g . A l l e n and P e r r y (1975) by f e a t h e r  also reported that cannibalism in birds i s  pecking and they are independent phenomena with a d d i t i v e  Various causative  factors  t h a t can i n f l u e n c e f e a t h e r  have been c l a s s i f i e d by Hughes and Duncan ( 1 9 7 2 ) . are d i e t a r y feather  influenced effects.  pecking i n  birds  The main f a c t o r s  involved  c o m p o s i t i o n , environment, hormones and p s y c h i c f a c t o r s .  Whether  pecking i s  under g e n e t i c c o n t r o l  is  still  controversial.  The i n f l u e n c e o f i n h e r i t a n c e o r h e r e d i t y on the occurance o f p e c k i n g has been i n v e s t i g a t e d by s e v e r a l  authors.  Ritcher  (1954)  feather  found  22  considerable strain differences cluded t h a t , f e a t h e r (1972)  and Charles  i n the i n c i d e n c e o f f e a t h e r  eating is a hereditary (1976)  characteristic.  a l s o observed d i f f e r e n c e s  that,  f a c t o r s and g e n e t i c b a s i s o f t h i s irrespective  o f the c a u s e ,  m o d i f y i n g the i n d i v i d u a l (1980)  'trait'.  certain  susceptibility  He c o n -  Hughes and Duncan  between s t r a i n s  l o s s due to p e c k i n g , wear, o r b o t h , i n l a y i n g hens. causal  pecking.  for  feather  They d i d not a n a l y s e However,  the  they suggested  g e n e t i c f a c t o r s may be i n v o l v e d  to these c a u s e s .  Similarly  in  Cuthbertson  s t a t e d t h a t f e a t h e r pecking behavior when i d e n t i f i e d i n a s u i t a b l e  has an i n h e r i t e d component and t h a t s e l e c t i o n to reduce i t s  way,  occurance should  be f e a s i b l e . A l l e n and P e r r y (1975) i n b i r d s by the end o f the during laying period i s  reported that in chicken feather  rearing  period,  pecking occurs  but c o n t i n u a t i o n o f i t s  occurance  i n f l u e n c e d by group s i z e and d e n s i t y per b i r d .  Adams  e t aj_. (1978)  demonstrated t h a t b i r d s housed 22  significantly  poorer f e a t h e r i n g than those housed 11 (1 & and 10$%) per group.  Hughes and Duncan (1972)  and 20$$) per group had  a l s o found a s i g n i f i c a n t group s i z e e f f e c t  damage with more severe damages i n groups o f 8 growing p u l l e t s than i n groups o f 4 . battery (1969) feather  A c c o r d i n g to Kivimae (1976)  cages had a n e g a t i v e  effect  on f e a t h e r  housed i n cages  high d e n s i t y o f l a y e r s  on the plumage.  Similarly,  Hoffmeyer  observed t h a t high d e n s i t y and f l o c k s i z e i n combination i n c r e a s e d pecking i n  pheasants.  Type o f housing or d e s i g n o f cages may a l s o i n f l u e n c e f e a t h e r in b i r d s .  Simenson e t al_. (1980)  r e p o r t e d t h a t b i r d s housed i n wire  had s i g n i f i c a n t l y h i g h e r f e a t h e r damage than those housed i n l i t t e r Similar  in  r e s u l t s were a l s o observed by Duncan and Hughes (1973)  pecking floor  floor.  and Touson (1977).  23  Both found t h a t housing system i n f l u e n c e d the infegument o f the The use o f specs i n l a y i n g hens pecking and c a n n i b a l i s m ( A r b i , 1978). control  hens vs 1.2  f o r spec-hens.  Cumming and Epps (1976) after  11 months o f l a y  2.  Adrenal  1971).  effective  in c o n t r o l l i n g  Pecking damage s c o r e s were 3.3  T h i s d i f f e r e n c e was h i g h l y  hens, but no q u a n t i t a t i v e  glands p l a y a c e n t r a l  r o l e i n the f o w l ' s  cortical  usually r e f l e c t  tissue  feathered  data were p r e s e n t e d .  response to  In mature b i r d s , i n c r e a s e s and decreases i n adrenal  f r e q u e n t l y occur i n response to seasonal and environmental variations  for  significant.  a l s o r e p o r t e d t h a t spec-hens were b e t t e r than c o n t r o l  feather  weight  The a d r e n a l (Siegel,  was  birds.  weight  changes, and these  f o r the most p a r t growth and atrophy o f the a d r e n o -  (Holmes and Cronshaw, 1980).  On the o t h e r hand, a number o f  s t u d i e s have r e p o r t e d the s i g n i f i c a n c e o f g e n e t i c i n f l u e n c e and s o c i a l on the response o f adrenal Siegel  and S i e g e l  gland i n domestic (1969)  In  weight.  In one t r i a l  adrenal  Adrenal  in six  different  glands were e x c i s e d at 57 they observed  significant  weight expressed as mg per lOOg body  weight f o r males and females ranged from 7.63-  10.30mg and 6.87-8.81mg r e s p e c t i v e l y .  In the o t h e r t r i a l ,  from 6.74-8.95 i n males and 6.82-8.20 i n f e m a l e s . Ali  weights  both o f t h e i r t r i a l s  d i f f e r e n c e s among s t o c k s f o r adrenal  density  fowl.  compared adrenal  g e n e t i c s t o c k s o f c h i c k e n s i n two t r i a l s . days o f age o f the c h i c k s .  stress  the same  varied  In a more r e c e n t experiment,  and March ( u n p u b l i s h e d data) s t u d i e d two commercial egg l a y i n g s t r a i n s  one b r o i l e r s t r a i n f i v e days.  f o r adrenal weights o f c h i c k s a t ages from one day to  The glands were monitored at day 1, 14, 21 and 35.  and h i g h l y s i g n i f i c a n t s t r a i n  d i f f e r e n c e was e v i d e n t i n a l l  and thirty  A consistent  days o f measurements  24  (expressed as mg per g o f body weight) with an e x c e p t i o n f o r day 1 where was found not to be s i g n i f i c a n t l y d i f f e r e n t . broiler strain.  Bareham (1972)  f e r e n c e i n adrenal  2  layer  strains  reared e i t h e r  demonstrated the e f f e c t s  o f crowding on the adrenal  Leghorn c o c k e r e l s aging from 7-17 weeks. 743.0 557.0 and 3 7 1 . 6 c m  2  per b i r d .  were observed up to 11 weeks. t h i s age.  Birds  battery  adrenals.  The d e n s i t i e s  density.  Siegel  weight o f White  p r o v i d e d were 9 2 9 . 0 ,  No c o n s i s t e n t e f f e c t s  o f housing d e n s i t y  Whereas h e a v i e r a d r e n a l s were found beyond  housed 3 7 1 . 6 c m  s i g n i f i c a n t l y heavier  in  dif-  pens.  Adrenal gland s i z e may a l s o be i n f l u e n c e d by s o c i a l (1960)  weight was from  on the o t h e r hand, found no s i g n i f i c a n t  response o f  cages or i n deep l i t t e r  Lowest adrenal  it  2  per b i r d compared with 929cm  2  per b i r d had  From these r e s u l t s , the author s t a t e d  that  i n h i g h e r p o p u l a t i o n d e n s i t i e s such as 3 7 1 . 6 c m per b i r d , symptoms o f a d a p t a t i o n , 2  a s s o c i a t e d with p h y s i o l o g i c a l s t r e s s were produced. Siegel,  1969) i n v o l v i n g  464.5 and 929cm adrenal this  weights.  2  6  Another study ( S i e g e l  g e n e t i c s t o c k s , housed at two b i r d d e n s i t i e s  per b i r d r e s u l t e d i n no s i g n i f i c a n t e f f e c t s Three o t h e r s t u d i e s a l s o r e p o r t e d no e f f e c t  gland (Bareham,  o f d e n s i t y on  These n o n - s i g n i f i c a n t r e s u l t s were o b t a i n e d presumably because, the  general  below the p h y s i o l o g i c a l l i m i t  1983).  densities  imposed by the  birds  well-being. Social  interaction  between i n d i v i d u a l s w i t h i n  a s s o c i a t e d with crowding may a l s o i n f l u e n c e adrenal (1961)  of  o f d e n s i t y on  1972; B o l t o n e t a l _ . , 1972; and P e s t i and Howarth,  used were not c r i t i c a l l y  and  a f l o c k not  necessarily  gland w e i g h t .  Flickinger  r e p o r t e d t h a t c o c k e r e l s i n uncrowded c o l o n i e s e s t a b l i s h dominance  hierarchies  as sexual m a t u r i t y a p p r o a c h e s .  The adrenal  gland weight  then  25  becomes c o r r e l a t e d r e c i p r o c a l l y with the s o c i a l It 1971).  i s well  Arbi  (1978)  known t h a t adrenal  rank o f each i n d i v i d u a l .  gland weight response to s t r e s s  demonstrated t h a t wearing specs (see  (Freeman,  pages 2 & 3 f o r  description)  i n l a y i n g hens reduced s t r e s s a s s o c i a t e d with a g o n i s t i c a c t s and f e a t h e r T h i s was a l s o r e f l e c t e d  by a r e d u c t i o n i n adrenal  had been on f o r t h i r t e e n  and a h a l f months, the adrenal  spec-hens were s i g n i f i c a n t l y l i g h t e r without s p e c s ) .  gland w e i g h t s .  This r e s u l t  eating.  When specs  gland weight o f  i n comparison with c o n t r o l  the  hens (hens  i n d i c a t e s t h a t c o n t r o l l i n g v i s i o n i n l a y e r s may  be a s s o c i a t e d with a r e d u c t i o n i n s t r e s s due to l e s s a g o n i s t i c and f e a t h e r  pecking  activities. 3.  Corticosterone The major s e c r e t i o n o f the adrenal  corticosterone  (Assenmacher, 1973).  t i v e measures o f s t r e s s  (Eskeland,  It  gland o f most a v i a n s p e c i e s  had been used as one o f s e v e r a l  1978).  Stressors  are t y p i c a l l y  v i a ACTH s e c r e t i o n by the hypothalamus ( C h e s t e r ,  1957) and r e s u l t s  corticosterone l e v e l .  a rise  As s t a t e d by S e l y e (1976)  very constant c h a r a c t e r i s t i c  of  objec-  mediated i n an  elevated  in corticosterone i s a  stress.  The consequences o f i n c r e a s e d l e v e l  o f c o r t i c o s t e r o n e are m a n i f o l d s .  B i r d s which are more s t r e s s e d are s u s c e p t i b l e to v a r i o u s  types o f d i s e a s e s  (Gross and Colmano, 1971; G r o s s , 1972; and Brown and N e s t o r , 1973). c o r t i c o s t e r o n e induces o s t e o p o r o s i s i n a d u l t b i r d s ( S i e g e l Although i n c r e a s e d c o r t i c o s t e r o n e l e v e l survival  is  increases  Increased  and L a t i m e r ,  the p o t e n t i a l  1970).  for short  term  under acute s t r e s s , growth and development o f young b i r d s are d e p r e s s e d ,  i f such high l e v e l  i s maintained over extended p e r i o d o f t i m e .  l o s s e s i n body weight and reduced r e p r o d u c t i v e c a p a c i t y  There are  also  (Bartov e t a l _ . , 1980).  26  Brown and Nestor (1973) secretory a c t i v i t y It  found t h a t t u r k e y s  has been r e p o r t e d t h a t  Siegel,  1975).  more s e n s i t i v e (1966)  the plasma c o n c e n t r a t i o n o f of lines  or s t r a i n s  o f c o r t i c o s t e r o n e are not very d i f f e r e n t  apparent o n l y i f  cortical  improved egg p r o d u c t i o n , growth r a t e and reduced m o r t a l i t y .  in unstressed birds i r r e s p e c t i v e levels  s e l e c t e d f o r low adrenal  corticosterone  s e l e c t e d f o r high or low  and t h a t the d i f f e r e n c e s  become  the b i r d s were s t r e s s e d (Brown and N e s t o r , 1973 and Edens and Freeman and Manning (1975)  r e p o r t e d Rhode I s l a n d Reds to be  to s t r e s s than L i g h t S u s s e x .  found n o n - s i g n i f i c a n t d i f f e r e n c e s  On the o t h e r hand, S i e g e l  and S i e g e l  i n the r e s p o n s i v e n e s s o f 4 s t r a i n s  of  c h i c k e n s they s t u d i e d to ACTH. The r e p o r t e d e s t i m a t e s o f normal c o n c e n t r a t i o n o f plasma c o r t i c o s t e r o n e i n a v i a n s p e c i e s vary a c c o r d i n g to the method o f q u a n t i t a t i o n  (Etches,  1976).  Three methods - F l u o r o m e t r i c , C o m p e t i t i v e P r o t e i n B i n d i n g , and Radioimmunoassay were commonly used ( B e u v i n g , methods and t h e i r and by Beuving  relative  (1980).  A d e t a i l e d d i s c u s s i o n o f the use o f  effectiveness  have been p r o v i d e d by Etches  who found values  An a s t o n i s h i n g high v a l u e  was r e p o r t e d by N i r e t a]_.  (1975),  these  (1976)  Normal plasma c o r t i c o s t e r o n e i n l a y i n g hens was  by C u l b e r t and W e l l s (1975) o f plasma.  1980).  assayed  i n the range o f 7 to 20ng per ml  (about  lOOng per ml)  i n 21-day-old c h i c k s  but Buckland and Blagrave  (1973)  obtained  a value o f o n l y 5ng per ml i n 39 day-old c h i c k s . The evidence t h a t  plasma c o n c e n t r a t i o n o f c o r t i c o s t e r o n e i n l a y i n g  f o l l o w s a d a i l y rhythm was p r o v i d e d by Beuving and Vonder ( 1 9 7 7 ) . White Leghorn l a y e r s  (25-30 weeks o l d )  in individual  They housed  cages and examined the  plasma c o r t i c o s t e r o n e e v e r y 3 hours f o r 24 hours and found c o n s i d e r a b l e dividual  variations  and a l s o a c l e a r d a i l y  rhythm.  hens  in-  A maximum (2.3ng per ml)  27  was found at the end o f the n i g h t (5:30) and a minimum (0.5ng per ml) a t beginning o f the n i g h t ( 2 0 : 3 0 ) . i n c o r t i c o s t e r o n e occurs j u s t It  T h e i r f i n d i n g s a l s o confirmed t h a t a r i s e  p r i o r to o v i p o s i t i o n .  has been observed t h a t c o r t i c o s t e r o n e l e v e l s  i n c r e a s e d by i n t e n s i v e  husbandry p r a c t i c e s  the work o f Mashaly et a]_. (1982) s t u d i e d the response o f adrenal densities  the  it  (Gross  was not f u l l y  o f l a y i n g hens are  and S i e g e l ,  1973).  realized.  But  until  These workers  glands o f l a y i n g hens under d i f f e r e n t  cage  by radioimmunoassay f o r c o s t i c o s t e r o n e from serum o f s a m p l e s .  The  b i r d s were housed 3, 4 or 5 b i r d s per cage a t 19 weeks o f age i n 12' x 20' cages.  A f t e r 48 hours subsequent to housing average c o r t i c o s t e r o n e c o n c e n -  trations  f o r 3, 4 or 5 b i r d s per cage were 1.038, 1.599 and 2.058ng per ml  respectively.  This r e s u l t  i s an i n d i c a t o r o f a p o s i t i v e c o r r e l a t i o n  number o f b i r d s per cage and the i n i t i a l  response o f the adrenal  between  glands.  another more r e c e n t study with b r o i l e r c h i c k s to determine the e f f e c t s  In  of  p o p u l a t i o n d e n s i t y on the growth, feed e f f i c i e n c y and plasma c o r t i c o s t e r o n e , P e s t i and Hawarth (1983) per b i r d .  brooded c h i c k s i n b a t t e r i e s  They observed s i g n i f i c a n t l y  at 116, 232, 348 and 697cm  h i g h e r plasma c o r t i c o s t e r o n e f o r  kept a t 697 (14.5ng per ml) and 348 (12.2ng per ml) c m (4.9ng per ml)  or 116 (5.4ng per ml)  cm  2  2  chicks  per c h i c k than a t 232  per c h i c k at 3 weeks.  The r e s u l t s  o b t a i n e d by P e s t i and Hawarth were o p p o s i t e to t h a t o f Mashaly e t al_.  It  could  be a t t r i b u t e d  in  bird  densities  to d i f f e r e n c e s  used by these  i n age o f the b i r d s and/or to d i f f e r e n c e s  authors.  Furthermore, i n one e x p e r i m e n t , B a r n e t t and B a r t l e t t the e f f e c t s  of spectacles  (polypeepers)  c o r t i c o s t e r o n e i n White Leghorn (WL)  (1981)  studied  on the c o n c e n t r a t i o n o f plasma  and c r o s s b r e d (XB)  hens.  WL was housed  28  either  i n cages o r on l i t t e r ,  experiment up to 14-day a l l  b i r d s were without  experiment specs were f i t t e d ed from a l l  but XB o n l y i n c a g e s .  From day 1 o f  spectacles.  to h a l f o f the b i r d s .  On day 15 o f  h a l f and on days  1 5 , 1 7 , 2 1 , 25 and 28 f o r the second h a l f o f the e x p e r i m e n t .  in cages.  o f specs on plasma l e v e l  of  They  corticosterone.  Leukocytes Leukocytes a r e agents i n the  and are a b l e to remove p a r t i c l e s It  is  known t h a t ,  age o f the b i r d s and s e x . contains  defence  o f the body a g a i n s t  infection  and micro-organisms f o r e i g n to the body (Hodges,  l e u k o c y t e count i n b i r d s v a r i e s Barger e t al_. (1958)  from 15000 to 30000 white blood c e l l s  a c c o r d i n g to b r e e d ,  reported that fowl's per ml o f b l o o d .  blood  Schermer  has summarised v a l u e s o b t a i n e d by d i f f e r e n t authors and showed t h a t the is  mean  (P<0.01) h i g h e r than WL  were 0.88 ± 0.08 and 1.32 ± O.lOng per ml r e s p e c t i v e l y .  d i d not f i n d any s i g n i f i c a n t e f f e c t  1974).  The o v e r a l l  The mean c o r t i c o s t e r o i d c o n c e n t r a t i o n on day 1-14 f o r WL i n cages  and on l i t t e r  4.  the  Blood samples were c o l l e c t -  b i r d s on days 1, 3, 7, 11 and 14 f o r the f i r s t  c o r t i c o s t e r o i d c o n c e n t r a t i o n i n XB was s i g n i f i c a n t l y  the  from 9300 to 32000 with an average o f 20000.  g r e a t deal o f v a r i a t i o n s  range  These f i g u r e s demonstrate a  i n the e s t i m a t i o n o f l e u k o c y t e numbers i n c h i c k e n s .  In p a r t , these d i s c r e p e n c i e s may be a t t r i b u t e d  to the method o f making the c o u n t ,  and i n many cases', t o the small number o f b i r d s used ( S t u r k i e ,  1976).  A detailed  d e s c r i p t i o n o f d i f f e r e n t c o u n t i n g methods f o r l e u k o c y t e can be found i n and Jamroz ( 1 9 6 1 ) ,  and Schermer  S t u d i e s with e f f e c t s counts are not numerous.  (1967)  Lucas  (1967).  o f b r e e d , sex and age o f the b i r d s on t o t a l  Most estimates o f l e u k o c y t e counts i n c h i c k e n s  from White Leghorn breed (Fenstermacher,  1932; B i e l y and Palmer,  leukocyte are  1935; Twisselmann,  29  1939 and Lucas and Jamroz, 1961). blood c e l l s figures  (per ml)  Lucas and Jamroz  (1961)  to be 35787 i n Rhode I s l a n d Red f e m a l e s ;  f o r males were not g i v e n .  l e u k o c y t e s to be 18630 i n dominique c h i c k e n s . appeared to be h i g h e r than what i s found t o t a l  difference  Total  l e u k o c y t e counts i n McGuire and  to be 38700 i n t u r k e y  Cook (1937)  r e p o r t e d no s i g n i f i c a n t v a r i a t i o n  to sex i n c h i c k e n s aging from 26 to 183 d a y s .  q u a i l s u s u a l l y have s l i g h t l y lower counts than a d u l t s and H a r r i s o n (1969)  turkeys'  Cavett  blood.  Sex  a g e , the c e l l  ( S t u r k i e , 1976).  Freeman (1971)  that leukocyte  the a d u l t  indicators  in chickens.  response were p a r t i c u l a r l y  Wolford and Ringer sensitive  f o r the f o w l .  index o f a d r e n o c o r t i c a l  are found to be very s e n s i t i v e  By 3 weeks o f level.  (1962)  Leukocyte count may a l s o be a  hyperactivity  (Newcomer,  1958).  to s t r e s s o r s such a c o r t i c o t r o p h i n  1955; Newcomer, 1958).  concluded  to s t r e s s and perhaps was  Leukocytes (Siegel,  g e n e r a l l y agreed t h a t t h e r e i s a l e u k o c y t o s i s f o l l o w i n g  o f ACTH ( H u b l e ,  low  s t a t e d t h a t changes i n l e u k o c y t e count c o u l d p o s s i b l y  the best i n d i c a t o r o f s t r e s s  is  Barton  demonstrated t h a t the blood o f the neonate c h i c k s i s  numbers i n c r e a s e and reach e s s e n t i a l l y  be used as s t r e s s  i n the count  Young c h i c k s and  i n l e u k o c y t e s and changes r a p i d l y d u r i n g the growing p e r i o d .  It  reported  i n l e u k o c y t e counts i n a d u l t c h i c k e n s was observed by Olson (1937)  attributable  1968).  comparative  B l e i n (1928)  reported for chickens.  l e u k o c y t e counts (per ml)  but not i n c h i c k s .  reliable  white  They a l s o r e p o r t e d t h a t White Leghorn male  c o n t a i n s 16615 l e u k o c y t e s compared t o 29397 i n f e m a l e s .  (1952)  reported total  injection  An i n c r e a s e i n l e u k o c y t e number due to  s t r e s s may p r o b a b l y be a s s o c i a t e d with i n c r e a s e d demand f o r immune response o f the s t r e s s e d animal 's body system so t h a t i t 1963).  c o u l d cope with the s t r e s s  (Selye,  30  The response o f l e u k o c y t e s a f t e r Davison and F l a c k  (1981)  u s i n g 3-week o l d Rhode I s l a n d Red c h i c k e n s .  o f l e u k o c y t e s were counted a t v a r i o u s 32 hours a f t e r  an i n j e c t i o n o f ACTH was s t u d i e d by  the i n j e c t i o n .  intervals  over an extended p e r i o d o f  They observed a b i p h a s i c response o f  There was an 18% decrease i n the number o f l e u k o c y t e s one hour a f t e r j e c t i o n and 40 to 50% i n c r e a s e between 4 and 8 hours a f t e r s i g n i f i c a n t l e u k o c y t o s i s was s t i l l r e t u r n e d to normal 24 hours a f t e r Environmental  factors  i n evidence a f t e r the  Number  leukocytes. the  in-  the i n j e c t i o n .  A  12 hours but the counts  injection.  such as r e s t r a i n t ,  h a n d l i n g , c o l d and  starvation  cause a change i n l e u k o c y t e numbers s i m i l a r to treatment with ACTH ( H u b l e , 1955; Newcomer, 1958; Wolford and R i n g e r ,  1962 and S t u r k i e ,  showed t h a t a d u l t b i r d s r a i s e d i n b a t t e r i e s compared to 23600 f o r those r a i s e d o u t s i d e .  1976).  Olson  (1937)  w i t h i n a b u i l d i n g had 17000 l e u k o c y t e s However, very  l i t t l e is  c e r n i n g the e f f e c t o f b i r d d e n s i t y on the change o f l e u k o c y t e c o u n t .  known c o n One r e c e n t  study ( P e s t i and Howarth, 1983) with 3-week o l d female b r o i l e r c h i c k s d e m o n s t r a t ed no s i g n i f i c a n t d i f f e r e n c e s  i n l e u k o c y t e counts as d e n s i t y i n c r e a s e d from  697cm  bird.  2  per b i r d to 116cm per 2  Other f a c t o r s  such as d i e t  ( G o f f e t a l _ . , 1953), drugs (Hunt and Hunt,  1959) and exposure to X-rays (Lucas and Demington, 1957) a l s o p l a y a s i g n i f i c a n t r o l e i n changing l e u k o c y t e s .  31  METHODS  I.  Experimental  animals  Data were o b t a i n e d from two g e n o t y p i c c l a s s e s o f c h i c k e n s maintained the Avian Genetics  L a b o r a t o r y , The U n i v e r s i t y  heterozygous f o r the autosomal r e c e s s i v e The o t h e r genotype i s  homozygous f o r  o f the genotypes was o u t l i n e d by II.  'rc'  of British  gene ' r c ' and i s  Cheng e t al_.  Rearing c o n d i t i o n s o f b i r d s b e f o r e s t a r t The c h i c k s f o r t h i s  experiment were o f  Columbia.  One type was  and has s i g h t v i s i o n .  blind.  Detailed  description  (1980). o f experiment  two age g r o u p s .  The f i r s t  was hatched on August 2 4 , 1982 and the second hatched two weeks l a t e r September 7,  1982.  Immediately  banded f o r i d e n t i f i c a t i o n d e n s i t i e s o f 335cm  2  after  at  each hatch a l l  group on  the c h i c k s were wing-  and brooded i n Jamesway b a t t e r y  c h i c k brooders  per b i r d and group s i z e s o f 50 c h i c k s per g r o u p .  two genotypes from each hatch were kept separated but r a i s e d under  at  The  similar  c o n d i t i o n s by a s s i g n i n g c h i c k s to randomized s e c t i o n s o f the b r o o d e r s . Brooding heat was p r o v i d e d up to 4.weeks a f t e r  hatching.  Chick  starter  c o n t a i n i n g 21% p r o t e i n was s u p p l i e d ad l i b i t u m d u r i n g the e n t i r e  brooding  p e r i o d with f r e e access to w a t e r . At the end o f the 4th-week, was doubled to a l l o w  brooder space f o r each group o f 50 c h i c k s  f o r the i n c r e a s e i n body s i z e .  7 weeks, they were moved to l i t t e r e d  f l o o r pens.  When the b i r d s  Eighty  from each genotype and age group were kept (4 g r o u p s ) . a 3.2m x 5.9m pen (approximate mained i n these pens u n t i l  d e n s i t y o f 2350cm  finally  2  birds  attained  ( 2 0 ^ and 60-??)  Each group was kept  per b i r d ) .  The b i r d s  being moved i n t o the experimental  re-  pens on  in  32  January 2 5 , 1983.  During the e n t i r e  growing p e r i o d a grower r a t i o n  t e i n ) and water were p r o v i d e d ad l i b i t u m . l i g h t schedule during e n t i r e III.  All  the b i r d s were under 14L/10D  birds  At the time b i r d s were put i n t o the experimental 22-weeks o l d and the second hatch was 20-weeks o l d .  ad l i b i t u m .  r a t i o n c o n t a i n i n g 16% p r o t e i n .  However,  centimeters  pens the f i r s t All  experiment was a 2 x 2 x 2 x 2  (replications),  pens a t the same t i m e .  o f 1000cm per b i r d 2  received  i n a 24-hour day.  The two d e n s i t i e s used i n t h i s  (high d e n s i t y )  and 2000cm per b i r d (low  s i t u a t i o n s o f high and low d e n s i t y l e v e l s . used 714cm and 1428cm 2  2  with two  2  The  experiment were density).  These  used under experimental  For example, Simmenson et a]_.  per b i r d f o r high and low d e n s i t y c o n d i t i o n s  The b i r d s used were White Leghorn type l a y e r s . Leghorn type p u l l e t s  factorial  i n terms o f age but were put i n t o the e x p e r i -  d e n s i t i e s were used i n the l i g h t o f what o t h e r workers  J o n e s , 1973).  the b i r d s  two genotypes, two d e n s i t i e s and two f l o c k s i z e s .  two hatches were two weeks a p a r t mental  light  All  They  design  The d e s i g n o f t h i s hatches  eight  Wood s h a v i n g 10-12cm deep were used as l i t t e r .  a standard p h o t o p e r i o d o f 14 hours o f a r t i f i c i a l  Experimental  the b i r d s were fed a  Feed and water were provided  were r e p l a c e d from time to time as and when n e c e s s a r y .  IV.  hatch was  feeder space and water space were s t a n d a r d i s e d at  each per b i r d .  pro-  brooding and growing p e r i o d s .  Management o f experimental  commercial l a y e r  (18%  (1980)  respectively.  Normal body weight o f White  d u r i n g housing at 20 weeks i s about 1406g (McClung and  On the o t h e r hand, the b i r d s used i n t h i s experiment were Rhode  33  I s l a n d Red type having much h i g h e r body weight  (average body weight o f  a t housing 1865g) compared to White Leghorn t y p e s .  T h e r e f o r e more space was  allowed per b i r d to compensate f o r the b i g g e r body s i z e . used were one o f 5 b i r d s (IS (4Ji  and 16££) per f l o c k  and 4$$) per f l o c k (small  (large f l o c k ) .  Although i t  The two f l o c k  flock)  flocks.  V.  the s i z e o f f l o o r pens a v a i l a b l e  i s d e s i r a b l e to have l a r g e r  considered in t h i s  Number o f eggs  i i)  experimental  experiment  were:  collected  Egg wei ght  iii)  Amount o f feed taken from feed trough  iv)  Body weight  v)  Fertility  vi)  Feather  vii)  gain  o f eggs pecking and comb damage scores  Leukocyte  viii)  1.  l i m i t e d the s i z e o f the  measured  The parameters  ix)  production  The d u r a t i o n o f the experiment was 8 weeks.  Parameters  i)  sizes  and 20 b i r d s  number o f b i r d s i n the l a r g e f l o c k s t o approximate commercial situations,  pullets  count  Plasma c o r t i c o s t e r o n e Adrenal  level  gland weight  Number o f eggs c o l l e c t e d and egg weight Egg number and egg weight were r e c o r d e d d a i l y .  ment pen were c o l l e c t e d twice a day (at  Eggs from each  10:00 and 16:00 hr)  number o f broken eggs due to pecking and t r a m p l i n g .  treat-  t o minimize the  The c o l l e c t e d eggs were  34  each marked a c c o r d i n g to date and pen number.  The c o l l e c t e d data were then  c o n v e r t e d to egg p r o d u c t i o n on a hen-day b a s i s a f t e r whenever n e c e s s a r y .  adjusting for  A f t e r each days c o l l e c t i o n , eggs from each treatment  were weighed t o g e t h e r to the n e a r e s t gram u s i n g a ' T o l e d o ' eggs were i n c l u d e d i n egg p r o d u c t i o n d a t a , however, Egg weights were converted to mean weight 2.  mortality  balance.  Broken  they were not weighed.  per egg f o r s t a t i s t i c a l  analysis.  Amount o f feed taken from feed trough The amount o f feed taken from the feed troughs i n d i f f e r e n t  ment pens  was  day a f t e r  egg c o l l e c t i o n .  weighed (kg) left  pen  recorded s e p a r a t e l y .  treat-  The feed troughs were f i l l e d twice a  Each sack o f feed used f o r a p a r t i c u l a r  pen was  and marked a c c o r d i n g to pen number f o r i d e n t i f i c a t i o n .  The  over feed at the end o f the experiment was weighed and s u b t r a c t e d from  the t o t a l  feed g i v e n .  per day.  These data were a l s o a d j u s t e d f o r  3.  Body weight Individual  The feed data were then c o n v e r t e d to kg feed per hen mortality  whenever  gain body weight  (g)  twice d u r i n g t h e whole experimental  of a l l  the experimental  period.  'initial  body w e i g h t ' .  body w e i g h t '  The g a i n i n body weight was then c a l c u l a t e d by s u b t r a c t i n g  4.  from ' f i n a l Fertility  plots.  taken This  The b i r d s were weighed again at  end o f the experiment (March 2 1 , 1983) and ' f i n a l  weight'  b i r d s were measured  The f i r s t weight was  immediately b e f o r e p l a c i n g the b i r d s i n t o the experimental c o n s t i t u t e d the  necessary.  weight the  was r e c o r d e d .  'initial  body  body w e i g h t ' .  o f eggs  Eggs from t h r e e sample p e r i o d s d u r i n g the experiment were incubated  35  i n a Jamesway 252 e l e c t r i c  forced a i r  t h r e e sample p e r i o d s were:  (1)  saved f o r f e r t i l i t y  i n c u b a t o r to t e s t  days 8-17, (2)  28-37 and (3)  For each p e r i o d a t o t a l  s t o r e d eggs were s e t f o r i n c u b a t i o n a t the same t i m e .  fertility whether  5.  After that incubation period a l l  determined.  All  they were t r u l y  Fertility  the  'infertile'  infertile  and comb damages o f t h e experimental  determine 1944).  b i r d s due to pecking  Back, rump, comb, wing and t a i l  s i d e r e d f o r e v a l u a t i o n o f such damages. by the procedure  Eggs were i n c u b a t e d  eggs s e t f o r i n c u b a t i o n .  Feather  estimation.  o f 10 days cumulating  or e a r l y embryonic death ( K o s i n ,  pecking and comb damage scores  were r a t e d by v i s u a l  55°F  the eggs were candled and  Feather  i n Table 1.  Eggs  eggs were broken out to  was measured as a percentage o f t o t a l  evaluated  48-57.  The  t e s t were s t o r e d i n a cool room at a temperature o f  and a r e l a t i v e humidity o f 65%.  f o r 8-10 d a y s .  for f e r t i l i t y .  were c o n -  Back and rump f e a t h e r l o s s e s were  d e s c r i b e d by Hughes and Duncan (1972)  and i s  The method used to measure the comb damage scores was as  shown  present-  ed i n T a b l e 2. Wing and t a i l  feather  a.  Birds  b.  Subjectively  c.  Birds  Feather  l o s s e s o f the b i r d s were e v a l u a t e d  with no b r o k e n , no m i s s i n g f e a t h e r  scored 0  scored 1-3 a c c o r d i n g to degree o f f e a t h e r  loss  with s k i n damage and/or b l e e d i n g s c o r e d 4  and s k i n damages o f the experimental  times d u r i n g the experimental  period.  b i r d s were measured two  The f i r s t measurement was made  p r i o r to p l a c i n g the b i r d s i n t o the experimental o f the e x p e r i m e n t .  by:  p l o t s and f i n a l l y  No comb damage was r e c o r d e d d u r i n g the f i r s t  just  at the end  measurement  36  Table 1.  S c o r i n g method to a s s e s s the degree o f pecking damage to back and rump  Score  Table 2.  Description  0  No denuded area o f s k i n  1  Denuded area l e s s than 1 c m  2  Denuded area l e s s than 25 c m  3  Denuded area more than 25 c m  4  S k i n damage (haemorrhage, scab) o f s i z e o f denuded area  2  2  2  regardless  S c o r i n g method to assess the degree o f pecking damage to comb Score  the  Description  0  No s i g n o f pecking damage  1  A s i n g l e mark o f pecking damage  2  Two to t h r e e marks o f pecking i n j u r i e s both s i d e s o f the blade  3  More than t h r e e marks o f pecking on the comb  4  Severe i n j u r i e s , b l e e d i n g , e x t e n s i v e damage to the comb  on  37  nor wing and t a i l 6.  feather  Leukocyte count and plasma c o r t i c o s t e r o n e Immediately  after  samples f o r l e u k o c y t e a total  losses.  the end o f the two months experimental  counts and c o r t i c o s t e r o n e  o f 80 b i r d s , t a k i n g 5 {li and 4 # )  from l a r g e  f l o c k s were picked at random.  each were c o l l e c t e d  level  were c o l l e c t e d  from each treatment  pen.  from  The b i r d s  From each b i r d two samples o f 2ml  i n t o two h e p a r i n i z e d t e s t  puncture o f the wing v e i n .  analysis  p e r i o d blood  tubes by the method o f  Blood samples were c o l l e c t e d  vene-  f o r a p e r i o d o f 8-  days from 1:00pm to 1:30pm each day.  This was done to minimize the e f f e c t  time d i f f e r e n c e ,  level  since corticosterone  d u r i n g the day (Beuving i n g the  and Vonder, 1977).  b i r d and b l e e d i n g v a r i e d  The f i r s t  the c o l l e c t e d  change  The time r e q u i r e d between  catch-  from 40 seconds to one minute i n most c a s e s .  count.  Immediately  after  f o r 15 minutes at 2000rpm.  i n a Sorval  The separated  GLC-I General  The White Blood C e l l  Laboratory  (1976).  Sodium  violet citrate  Distilled  water  was  under the l i g h t microscope at magni-  (WBC)  diluent  used f o r l e u k o c y t e  lO.Omg 3.8g 0.4ml  Formal i n  temperature  Leukocyte  was prepared a c c o r d i n g to the f o l l o w i n g r e c i p e recommended by Schermer Crystal  for  Centrifuge  o f G u e l p h , Canada, where i t  by radio-immunoassay technique o u t l i n e d by Etches  f i c a t i o n o f 40x.  Blood samples  plasma was then s t o r e d a t a  o f - 2 0 ° C pending shipment to the U n i v e r s i t y  number was counted u s i n g haematocytometer  analysis  blood c o l l e c t i o n ,  samples were brought i n t o the l a b o r a t o r y .  c o r t i c o s t e r o n e were c e n t r i f u g e d  analysed  known to  c o l l e c t e d sample from each b i r d was used f o r c o r t i c o s t e r o n e  and the second one f o r l e u k o c y t e all  i n l a y i n g hens i s  of  100.0ml  count (1967):  38  The d i l u t i o n  r a t e o f blood and WBC d i l u e n t was i n the r a t i o o f  Leukocyte number was expressed as the number o f l e u k o c y t e s  1:100.  per ml o f  blood.  The method used f o r c o u n t i n g was d e s c r i b e d i n M i n i s t r y o f A g r i c u l t u r e , F i s h e r i e s and Food, Reference Book 365 (1978).  The formula used f o r  l e u k o c y t e number was = (number counted i n 4 squares o f the v 4)  x depth o f the haematocytometer x d i l u t i o n 7.  Adrenal  gland  haematocytometer  rate.  weight  The number o f b i r d s from which adrenal was  total  the same as l e u k o c y t e c o u n t s .  glands were e x c i s e d and weighed  From each l a r g e  f l o c k 5 b i r d s (IS  and 4$$)  were randomly drawn i n d e p e n d e n t l y o f b i r d s used f o r l e u k o c y t e c o u n t s . b i r d s i n the small  f l o c k were u s e d .  drawn, b i r d s were  sacrified,  One week a f t e r  all  the glands by the same p e r s o n .  sensitive until VI.  t i s s u e s were c a r e f u l l y  adrenal  trimmed from  The glands were then weighed u s i n g a  balance ( M e t t l e r H-10 A n a l y t i c a l  Balance).  Glands were kept moist  and d u r i n g w e i g h i n g . Data  analyses  Data were analysed by A n a l y s i s o f V a r i a n c e individual and  the  the blood samples were  d i s s e c t e d arid both the r i g h t and l e f t  glands were e x c i s e d . Connective and f a t  All  using e i t h e r  f l o c k means or  measurements. A n a l y s i s o f V a r i a n c e with Repeated Measures  Torrie,  1980)  periods or ages.  was  a p p l i e d to t r a i t s measured r e p e a t e d l y a t  In these s i t u a t i o n s  (Steel  different  h a t c h e s , genotypes, b i r d d e n s i t i e s  f l o c k s i z e s were the main p l o t f a c t o r s , w h i l e p e r i o d s o r weeks was the plot factor. statistical  All tests.  data i n percentages were a r c s i n transformed  sub-  before  Duncan's M u l t i p l e Range T e s t s were performed to  and  test  39  for differences  among i n d i v i d u a l  means when treatment  one degree o f freedom were found to be s i g n i f i c a n t l y of Covariance  (Steel  with  body w e i g h t '  'initial  i s as Y  =  *  +  +  E 1  (  and T o r r i e , 1980) was used to t e s t as the c o v a r i a t e .  R  G F T  i  +  G  ijkl  j +  >jlm  = 1 , 2; j  +  T  D  m (  +  = 1 , 2;  k  +  +  ^ j m  D F T  F  l  < >jk  +  >klm  GD  +  replication  (  +  ^ k m  +  E 2  Analysis  body weight  The general  gain  statistical  G p  )jl  +  (  < >lm  +  FT  +  D p  )kl  ( G D T )  (  +  G D F  jkm  involving  >jkl  ijklm  Y...-,  is  b i r d s o f the j t h  where Y ^ . ^  the mean f o r the parameter  in  genotype housed under kth  bird  d e n s i t y and 1th f l o c k s i z e , measured d u r i n g the mth p e r i o d , p = the cal  p o p u l a t i o n mean, R.  whether  the b i r d  density,  = effect  o f the i t h  F-| = e f f e c t  = two-factor  o f l a r g e o r small  interactions,  interactions,  = sub-plot error T h i s general The a n a l y s e s (Lee,  flock size,  El-j^  (GDF) =  ,  m  o f high or  = effect  (GF)^ , (DF)^ , ( G T )  (GDT)  j | < m  ,  (GFT)J-J > ( m  of  D F T  low  o f measurements j m  ,  )klm  (DT) =  t  n  k m  r  , e  (FT) e  l m  "  e r r o r term f o r main p l o t c o m p a r i s o n s , and £ 2 ^ ^  term. model was s l i g h t l y m o d i f i e d f o r a n a l y s i s  the  University  of British  the s c o r i n g f o r f e a t h e r  a parametric  j k l  T  the  theoreti-  G. = e f f e c t  = effect  =  o f each  parameter.  were conducted with the a i d o f a computer program, 'UBC - MFAV  1980), a t  Since  replication,  i n v o l v e d was b l i n d or s i g h t e d ,  made d u r i n g the mth time p e r i o d , ( G D ) ^ ,  factor  model  +  k = 1, 2; 1 = 1 , 2; and m = l , . . . , x ;  one o f the dependent v a r i a b l e s . ith  different.  follows:  ijklm  and i  i n v o l v i n g more than  analysis  Columbia Computer C e n t e r .  and comb damage; are c o n s i d e r e d as rank  cannot be a p p l i e d ( S t e e l  and T o r r i e ,  1980).  data,  Instead,  such  40  data were analysed by the Kruskal-VJallis (Siegel,  1956) a p p r o p r i a t e f o r ranked d a t a . k  H  =  N  one-way a n a l y s i s  ^  N  2  E 1  variance  The formula f o r t h i s  analysis  is:  .  ILL' -  * ^ — ^  of  3 (N + 1) ,  3  d i s t r i b u t e d as c h i - s q u a r e with d f  k-1  3  N where H = the s t a t i s t i c  - N used i n the K r u s k a l - W a l l i s  n- = number o f o b s e r v a t i o n s J  in jth  t e s t d e f i n e d by the f o r m u l a ,  sample, N = En., R.  3  k  sample, E = sum over the k samples, T = t  3  - t,  = sum o f ranks i n  jth  where t = number o f t i e d obser-  j vations.  Because o f s i m i l a r i t y  in nature,  back and rump f e a t h e r  each i n d i v i d u a l were added t o g e t h e r and the mean c a l c u l a t e d . mean s c o r e s were then ranked f o r the K r u s k a l - W a l l i s f o r wing and t a i l  feather  there was a two week d i f f e r e n c e this variation  The c a l c u l a t e d  Similar  treatment  l o s s e s was a l s o done.  The o n l y known independent v a r i a t i o n  whether  test.  scores from  between the two r e p l i c a t i o n s  i n the age o f the b i r d s .  caused s i g n i f i c a n t d i f f e r e n c e s  In o r d e r to  between the two  is  determine replica-  t i o n s , data f o r number o f eggs c o l l e c t e d , egg weight and amount o f feed from feed trough (where weekly data were o b t a i n a b l e ) c o r r e c t i n g f o r the age d i f f e r e n c e s by matching data taken d u r i n g weeks  were re-analysed  between the two r e p l i c a t i o n s .  1 (older  taken  after  T h i s was done  3 to 8 from r e p l i c a t i o n 2 (younger  with d a t a taken d u r i n g weeks 1 to 6 from r e p l i c a t i o n  that  birds).  birds) In  other  words, data c o l l e c t e d d u r i n g week 3 from b i r d s i n r e p l i c a t i o n 2 and week 1 from replication  1 would be from b i r d s o f the same a g e .  In these a n a l y s e s ,  data  c o l l e c t e d d u r i n g weeks 7 and 8 from r e p l i c a t i o n 1 and weeks 1 and 2 from r e p l i c a t i o n 2 were not  utilized.  41  RESULTS  I.  Number o f eggs  collected  Analysis of variance  (ANOVA)  t a b l e f o r percent hen-day egg p r o d u c t i o n i s  presented i n T a b l e 17 ( A p p e n d i x ) .  Significant  (P<0.05) d i f f e r e n c e s were  found between genotypes with b l i n d c h i c k e n s producing h i g h e r number o f eggs compared to s i g h t e d c h i c k e n s .  The mean r a t e o f p r o d u c t i o n was 54.0% f o r  b l i n d b i r d s compared to 41.3% f o r s i g h t e d b i r d s  (Table  3).  D e n s i t y e f f e c t on egg p r o d u c t i o n was not s i g n i f i c a n t ( T a b l e 4 ) , was the e f f e c t o f f l o c k s i z e (Table 5 ) . differences  However, when c o r r e c t e d f o r  i n ages o f the two h a t c h e s , f l o c k s i z e became a  (P<0.05) f a c t o r .  Percent  pared to 48.9% f o r l a r g e  flocks.  significant  The d i f f e r e n c e between small and  19 i n A p p e n d i x ) .  three-way  i n v o l v i n g genotype, d e n s i t y o r f l o c k  The r e s u l t s  the  hen-day p r o d u c t i o n f o r small f l o c k s was 58.5% com-  f l o c k s was 9.6% ( T a b l e interactions  neither  There was no s i g n i f i c a n t two-way o r  on percent hen-day egg p r o d u c t i o n  p e r i o d s demonstrated h i g h l y s i g n i f i c a n t  large  (P<0.001)  size.  over d i f f e r e n t period e f f e c t  weekly  (Table  Egg p r o d u c t i o n i n c r e a s e d from 15.4% i n the f i r s t week to 58.0% i n the week,  but remained s t a b l e a f t e r  significant.  the f o u r t h week.  pens ( F i g u r e  1).  fourth  The TX6 i n t e r a c t i o n was not  B l i n d c h i c k e n s had h i g h e r p r o d u c t i o n r a t e i n a l l  d u c t i o n i n the experimental  6).  From Figure 1,  it  weeks o f  pro-  c o u l d be seen  t h a t egg p r o d u c t i o n i n b l i n d c h i c k e n s was u n i f o r m l y b e t t e r over a l l  weeks  compared to s i g h t e d o n e s . The e f f e c t s i n Table 7.  o f the two hatches  The mean f o r the f i r s t  (replications)  on egg p r o d u c t i o n are shown  hatch was 52.3% a g a i n s t 43.2% f o r  the  42  Table 3.  Effects  o f genotype on parameters measured Genotype means  Difference  Parameters Sighted  Blind  between genotypes  Apparent mean egg p r o d u c t i o n (hen-day %)  41.30±  6.90  54.00±  4.30  12.70*  46.82±  4.88  46.07±  4.07  0.75  Mean egg weight (g) Apparent feed requirement ( g , per b i r d per day) Body weight  179.40± 29.00  135.30± 14.00  44.10***  263.30+158.90  267.10±234.80  3.80  36.00*  gain  ( g , females o n l y ) Fertility {%)  84.20±  5.00  48.20± 17.10  19.27±  4.96  20.19±  4.56  0.92  7.30±  1.66  6.69+  1.19  0.61  1.22±  0.59  1.04±  0.74  0.18  Leukocyte count (1,000 per ml) *P<0.05 Adrenal weight ***P<0.001 (mg per lOOg body weight) Corticosterone  level  (ng per ml o f plasma)  43  Table 4 .  Effects  o f d e n s i t y on parameters Density means  Parameters  measured  •  High  Low  Difference between  densities  Apparent mean egg p r o d u c t i o n (hen-day  %)  42.20±  7.40  49.80±  4.50  7.60  46.04±  4.50  46.85±  4.48  0.81  154.40± 26.00  160.40± 38.00  6.00  263.40±121.90  267.10±256.30  3.90  Mean egg weight (g) Apparent (g,  feed.requirement  per b i r d per day)  Body weight (g,  gain  females o n l y )  Fertility (%) Leukocyte  75.70±  9.50  16.90  19.52±  19.94±  4.93  0.42  count  (1,000 per ml)  1  58.80± 18.50  Adrenal None o f weight the d i f f e r e n c e s (mg per lOOg body weight) Corticosterone  4.63  were s i g n i f i c a n t  at 0.05  level.  7.08±  1.30  6.90±  1.63  0.18  1.23+  0.73  1.03±  0.60  0.20  level  (ng per ml o f plasma)  1  44  Table  5.  Effects  o f f l o c k s i z e on parameters  measured  Flock s i z e means  Difference  Parameters Small  Large  between  flocks  Apparent mean egg p r o d u c t i o n (hen-day  %)  52.30±  6.60  43.00±  5.00  9.30  46.55±  4.77  46.34±  4.24  0.21  Mean egg weight (g) Apparent feed (g,  per b i r d per day)  Body weight (g,  requirement 173.60± 35.00  141.10+ 18.00  330.90±209.00  199.60±165.20  32.50***  gain  females o n l y )  131.30**  Fertility (%) Leukocyte (1,000  62.80± 21.10  72.10±  7.80  9.30  19.15±  4.80  20.31±  4.70  1.16  6.75±  1.09  7.23±  1.75  0.48  1.09±  0.67  1.16±  0.68  0.07  count  per ml)  **P<0.01 Adrenal weight ***P< 0.001 (mg per lOOg body weight) Corticosterone  level  (ng per ml o f plasma)  Table 6 .  E f f e c t o f time on egg p r o d u c t i o n and egg weight o f the experimental Week  Parameters  _ _ _  2  1st  Apparent r  U  i0n  Mean egg wei  (g)  1  Means  3rd  4th  5th  6th  7th  8th  mean  (L n-d ay %) 9  2nd  1  birds  Time measured  15.4&5.40  31.20 ±3.20  42.70 ±2.50  58.00 ±2.00  58.8c4l.20  60.7 ±2.80  63.60±4.20  54.70±5.20  39.50±2.50  42.20+3.10  44.70±2.00  46.30±2.60  48.10+2.50  48.90+2.10  50.10±1.80  51.7(8=1.90  since  b  C  the i n i t i a t i o n o f the experiment.  d  0  d  Figure  1.  A comparison o f weekly egg p r o d u c t i o n between and b l i n d  sighted  chickens  100  90  80 =  70  •5  60  o  o  I" K  Sighted  lllim  Blind  ^  50  Z<v  4°  •D I C c  <u o ai  i  H J  JCL.  30 20  10  i!  i i i i n  1st  2nd  3rd  i i  4th , 5th Weeks  II II =! 6th  7th  8th  47  Table  7.  Effects  o f r e p l i c a t i o n (hatch) on parameters measured  %)  Mean egg weight (g)  between  Second  First  Apparent mean egg p r o d u c t i o n (hen-day  Di f f e r e n c e  Hatch means  Parameters  52.30±  5.00  43.20±  6.60  9.10  47.46±  3.66  45.43±  5.02  2.03  10.00  Apparent feed requirement ( g , per b i r d per day)  154.40± 28.00  162.30± 36.00  Body weight g a i n ( g , females o n l y )  192.20±164.60  338.30±205.10  Fertility  hatches  146.10***  16.50  (g)  75.10+  8.80  58.60± 19.10  Leukocyte count (1,000 per ml)  18.72±  4.81  20.74±  4.54  2.02  (mg per lOOg body weight)  6.84±  1.72  7.15±  1.17  0.31  Corticosterone level (.ng per ml o f plasma)  1.07+  0.66  1.19±  0.68  0.12  Adrenal  weight  **P<0.01 ***P< 0.001  48  second h a t c h .  The d i f f e r e n c e  (9.1%) however was not  ANOVA o f same parameter a f t e r  a d j u s t i n g f o r the d i f f e r e n c e s  b i r d s i n the two hatches d i d not r e v e a l  any c o n f l i c t i n g trends  and 19 i n Appendix) compared to the p r e v i o u s  II.  significant. i n age o f (see  the  Tables 18  analysis.  Egg w e i g h t AtlOVA f o r data on egg weight i s  presented i n Table 20 ( A p p e n d i x ) .  No  s i g n i f i c a n t d i f f e r e n c e s were observed f o r genotype, d e n s i t y o r f l o c k However, t h e r e was a s i g n i f i c a n t This i n t e r a c t i o n the h e a v i e s t (48.00g)  is  (P<0.001) d e n s i t y by f l o c k s i z e  reported i n Table 8 .  From Table 8 ,  egg weight was from c h i c k e n s i n small  and the lowest from small  (46.97g)  The f i r s t  second h a t c h .  c o u l d be seen t h a t  f l o c k s a t low  density  between low d e n s i t y  f o r c h i c k e n s kept i n l a r g e  The two hatches d i f f e r e d h i g h l y s i g n i f i c a n t l y (Table 7 ) .  interaction.  f l o c k s a t high d e n s i t y ( 4 5 . 1 1 g ) .  o t h e r hand, t h e r e was no s i g n i f i c a n t d i f f e r e n c e and high d e n s i t y  it  size.  On the (45.76g)  flocks.  (P=0.01) i n mean egg weight  hatch averaged 2.03g more (weight per egg) than  the  Egg weight was a p p a r e n t l y a f f e c t e d by age o f the b i r d s .  the f i r s t week o f p r o d u c t i o n i n the p e n s , egg weight averaged 3 9 . 5 1 g . after  it  i n c r e a s e d at a r a p i d r a t e .  During There-  In the f o l l o w i n g weeks o f 2, 3, 4, 5,  6,  7 and 8, mean egg weight was 4 2 . 1 8 , 4 4 . 6 9 , 4 6 . 3 3 , 4 8 . 1 1 , 4 8 . 9 4 , 50.09 and 51.71 g  respectively.  means (except  Duncan's M u l t i p l e Range T e s t s i n d i c a t e d t h a t any two  between 5 and 6 weeks) i n the above weeks were s i g n i f i c a n t l y  (P<0.05) d i f f e r e n t  from each o t h e r ( T a b l e 6 ) .  (hatch) became n o n - s i g n i f i c a n t a f t e r Table 21 and 19 i n A p p e n d i x ) .  The e f f e c t o f  replication  adjustment f o r the age d i f f e r e n c e s  From the above r e s u l t s , i t  (see  c o u l d be concluded  49  Table 8 .  Significant  DXF i n t e r a c t i o n  f o r egg weight o f experimental Flock  Density  >—  Size  Small  High  45.11  Low  48.00  birds  Large  a b  C  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y Duncan's M u l t i p l e Range T e s t .  46.97 45.70  different  b c  b  (P<0.05) by  50  t h a t , d u r i n g the experimental p e r i o d , e g g weight i n c r e a s e d with age o f the b i r d s .  III.  Amount o f feed taken from feed trough ANOVA t a b l e f o r t h i s  significant  t r a i t i s presented i n Table 22 ( A p p e n d i x ) .  Highly  (P< 0.001) d i f f e r e n c e was found between the two genotypes.  Mean  amount o f feed taken by the b l i n d b i r d s was 135.3g per b i r d per day compared with 179.4g by the s i g h t e d b i r d s  (Table 3 ) .  The d i f f e r e n c e between the two  genotypes i n the mean feed requirements was 4 4 . l g per b i r d per day. was a l s o a s i g n i f i c a n t GXF i n t e r a c t i o n .  The feed requirements f o r  combinations o f genotypes and f l o c k s i z e s are shown i n Table 9. 9, i t  There various  From Table  c o u l d be seen t h a t s i g h t e d b i r d s took more feed per b i r d d a i l y when kept  i n small  f l o c k s (202.Og)  than when kept i n the l a r g e f l o c k s ( 1 5 6 . 8 g ) .  The same  p a t t e r n was a l s o apparent f o r b l i n d b i r d s kept i n small and l a r g e f l o c k s vs 125.4g r e s p e c t i v e l y ) .  The d i f f e r e n c e between s i g h t e d and b l i n d c h i c k e n s ,  however, was much b i g g e r i n small  f l o c k s (56.8g) than i n l a r g e f l o c k s  Flock s i z e was h i g h l y s i g n i f i c a n t o f the b i r d s .  (145.2g  (P<0.001) i n a f f e c t i n g feed requirements  Chickens i n small f l o c k s took more feed per b i r d d a i l y  than b i r d s i n l a r g e f l o c k s ( 1 4 1 . l g ) .  (31.4g).  On the a v e r a g e , . b i r d s  i n small  (173.6 g) f l o c k s took  32.5g more feed per b i r d per day compared to b i r d s i n l a r g e f l o c k s ( T a b l e  5).  D e n s i t y as a main e f f e c t was not s i g n i f i c a n t i n feed requirements o f the b i r d s . However, the i n t e r a c t i o n term DXF was s i g n i f i c a n t (P<0.05). t a b u l a t e d i n Table 10.  From Table 10 i t  T h i s has been  c o u l d be seen t h a t b i r d s kept i n small  f l o c k s a t low d e n s i t y took the h i g h e s t amount o f feed (183.5g) l a r g e f l o c k s at the same d e n s i t y the lowest  (140.lg).  and b i r d s  in  Feed taken by b i r d s  small f l o c k s a t high d e n s i t y was 163.7g compared to 145.Og by b i r d s kept  in  in  51  Table  9.  Significant  GXF i n t e r a c t i o n  by experimental  f o r feed taken from feed troughs  birds Flock  Genotype  Size  Small  Sighted  202.00  Blind  145.20  Large  C  156.80  b  b  125.40  a  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t Duncan's M u l t i p l e Range Test' ;  (P<0.05) by  Table 1 0 .  Significant  DXF i n t e r a c t i o n  by experimental  Density  f o r feed taken from feed troughs  birds  Flock  Size  Small  Large  High  163.70  b  145.00  a  Low  183.50  C  140.10  a  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t Duncan's M u l t i p l e Range T e s t ' , .  (P<0.05) by  53  large  f l o c k s at the same d e n s i t y .  b i r d s i n small  f l o c k s and l a r g e  than i n high b i r d d e n s i t y  f l o c k s was g r e a t e r  i n feed requirements  between  at low b i r d d e n s i t y  (43.4g)  (18.7g).  The e f f e c t o f hatch on t h i s after  The d i f f e r e n c e  t r a i t was not s i g n i f i c a n t  (Table 7 ) .  removing age e f f e c t o f the two r e p l i c a t i o n s d i d not show any  in trends IV.  (see  gain  Body weight gain o f the experimental  covariate  T a b l e 24 i n A p p e n d i x ) .  the two genotypes ( T a b l e significant large  (P<0.01).  flocks.  than t h e i r  3).  body weight  The e f f e c t o f f l o c k s i z e ,  On the a v e r a g e ,  however, was  i n l a r g e f l o c k s over the 2-month p e r i o d ( T a b l e  non-significant.  (P<0.01).  trait,  but the  5).  the  The v a r i o u s combinations o f d e n s i t i e s and f l o c k  seen from Table 11 t h a t hens i n small  significant  in  in-  This c o u l d have rendered  s i z e s a f f e c t i n g body weight gain o f hens are r e p o r t e d i n Table 11.  (141.5g).  highly  f l o c k s gained 131.3g more  o f d e n s i t y was not s i g n i f i c a n t f o r t h i s  (392.7g)  between  gained more weight than those  each hen i n small  t e r a c t i o n term DXF was s i g n i f i c a n t  most weight  period  being the  No d i f f e r e n c e s were observed  Hens i n small* f l o c k s  counterparts  The e f f e c t  main e f f e c t  hens d u r i n g the experimental  to a n a l y s i s o f c o v a r i a n c e w i t h i n i t i a l  (see  difference  T a b l e s 23 and 19 i n A p p e n d i x ) .  Body weight  was s u b j e c t e d  ANOVA  As can be  f l o c k - l o w d e n s i t y c o n d i t i o n s gained  and those i n l a r g e  f l o c k - l o w d e n s i t y c o n d i t i o n s the  the least  On the o t h e r hand, under high d e n s i t y c o n d i t i o n s , f l o c k s i z e was not i n a f f e c t i n g weight  gain.  Furthermore, the two hatches used i n t h i s significantly  (P<0.001) i n body weight g a i n .  experiment d i f f e r e d The f i r s t  highly  hatch ( o l d e r  birds)  54  Table 1 1 .  Significant  DXF i n t e r a c t i o n f o r body weight gain o f experimental Flock  Density  Size  Small  Large  High  269.00  b  257.70  b  Low  392.70  C  141.50  a  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t Duncan's M u l t i p l e Range T e s t - .  (P<0.05) by  hens  55  gained 1 4 6 . l g per b i r d l e s s than the second hatch (younger Regression o f body weight Although c o v a r i a n c e  analysis  weight taken before s t a r t the hens, i t weight.  gain on i n i t i a l  d i d not reveal  body weight was not  removed the e f f e c t o f i n i t i a l  o f experiment) whether  body w e i g h t .  are presented i n T a b l e l 2 .  body weight  o f eggs  Fertility  o f eggs from the experimental  p e r i o d s d u r i n g the e x p e r i m e n t .  nor t h e i r  20.2% (to  and  respectively.  b i r d s was determined over  three  Except f o r genotype, none o f the main  i n t e r a c t i o n s was s i g n i f i c a n t  (Table 2 6 , Appendix).  The mean  f o r the s i g h t e d b i r d s was 84.2% compared to 48.2% f o r the b l i n d b i r d s T h i s d i f f e r e n c e was s i g n i f i c a n t  P e r i o d had a h i g h l y s i g n i f i c a n t was lowest  gains o f  f l o c k s and o l d e r and younger hatches were  Fertility  (Table 3 ) .  interactions  However, means were c a l c u l a t e d  339 and 142g, 277 and 204g, 253 and 228g, and 83 and 398g  fertility  body  The mean weight per b i r d o f b l i n d and s i g h t e d , low  and high d e n s i t i e s , l a r g e and small  effects  gain o f  No s i g n i f i c a n t  involved or t h e i r  sample s i z e s (8 per group)  r o o s t e r s were not analysed s t a t i s t i c a l l y .  different  (body  Table 25 i n Appendix) except the GXDXF i n t e r a c t i o n .  Because o f very small  V.  body weight  there was any d i f f e r e n c e i n i n i t i a l  T h i s was t e s t e d by an ANOVA on i n i t i a l  (see  significant.  d i f f e r e n c e on the body weight  d i f f e r e n c e was found i n any o f the main f a c t o r s thereof  birds).  (P<0.01) e f f e c t  (50.9%) d u r i n g the i n i t i a l 71.1%)  and 28.2% (to 79.1%)  to 37) and the t h i r d  (P<0.05).  p e r i o d (days 8 to 1 7 ) .  It  Fertility i n c r e a s e d by  r e s p e c t i v e l y d u r i n g the second (days 28  (days 48 to 57) p e r i o d s .  p e r i o d as a f a c t o r were not  on f e r t i l i t y .  significant.  All  i n t e r a c t i o n terms  involving  56  Table 12.  Mean body weight g a i n , adrenal weight count o f experimental r o o s t e r s  and  leukocyte  1  Parameters Factors N  Hatch  Genotype  Density  :  Adrenal weight (mg per lOOg body weight)  Leukocyte count (1,000 per ml)  First  : 8  83  7.36  16.64  Second  : 8  398  7.32  22.42  Sighted: 8  142  7.74  20.63  Blind  : 8  339  6.99  18.43  High  : 8  204  6.89  20.29  Low  : 8  277  7.74  18.77  8  228  7.11  19.68  : 8  253  7.54  19.38  Smal 1 Flock s i z e : Large  1  Weight gain (g)  Not t e s t e d  statistically.  57  VI.  Leukocyte c o u n t , plasma c o r t i c o s t e r o n e l e v e l  and adrenal  gland weight  A n a l y s i s o f l e u k o c y t e count per ml o f blood from experimental d i c a t e d no s i g n i f i c a n t e f f e c t s (Table 2 7 , A p p e n d i x ) .  The o n l y s i g n i f i c a n t e f f e c t  was the i n t e r a c t i o n term GXF. Analysis  o f genotype, b i r d d e n s i t y ,  This i n t e r a c t i o n  by Duncan's M u l t i p l e Range T e s t  f l o c k s had the lowest counts and i s b i r d s kept i n l a r g e f l o c k s .  is  f l o c k s i z e or  observed f o r t h i s  hatch  trait  presented i n Table 13.  shows t h a t b l i n d b i r d s i n small  s i g n i f i c a n t l y lower than counts f o r  blind  Between these two extremes were the counts  s i g h t e d b i r d s kept i n small f l o c k s and l a r g e f l o c k s . f o r the b l i n d b i r d s were s i g n i f i c a n t l y d i f f e r e n t b i r d s (Table  hens i n -  However, n e i t h e r  from counts f o r the  for counts  sighted  13).  The e f f e c t s  of different  sented i n Table 12. sample s i z e s )  f a c t o r s on l e u k o c y t e counts o f r o o s t e r s are  Although not t e s t e d f o r l e v e l  pre-  o f s i g n i f i c a n c e (due to small  the means presented i n Table 12 showed l a r g e d i f f e r e n c e s  in  l e u k o c y t e counts i n most o f the c a s e s . The adrenal this  trait,  gland weight was measured as mg per lOOg o f body w e i g h t .  the data from r o o s t e r s and hens were a l s o s e p a r a t e l y  The ANOVA T a b l e f o r experimental  hens i s  presented i n Table 28  T h i s T a b l e showed t h a t none o f the main e f f e c t s significant.  nor t h e i r  The means and standard d e v i a t i o n s o f t h i s  presented.  (Appendix).  interactions  trait  For  f o r two  was hatches,  two g e n o t y p e s , two b i r d d e n s i t i e s and two f l o c k s i z e s can be found i n Table 7 , 3 , 4 and 5  respectively.  The mean adrenal  weights  o f r o o s t e r s are presented i n Table 12. There  appears to be l i t t l e v a r i a t i o n i n mean adrenal f e r e n t treatment  groups.  weights  of roosters  from d i f -  58  Table 13.  Significant  GXF i n t e r a c t i o n f o r l e u k o c y t e count o f experimental hens Flock  Genotype  Size  Small  Sighted  19.96  Blind  18.35  3  Large  a b  18.59 22.02  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t Duncan's M u l t i p l e Range T e s t " .  a b  b  (P<0.05) by  59  The plasma c o r t i c o s t e r o n e l e v e l was a n a l y s e d j o i n t l y . nificant  effects  (ng per ml o f plasma) o f r o o s t e r s and hens  The ANOVA Table ( T a b l e 2 9 , Appendix) i n d i c a t e d no s i g -  o f h a t c h , genotype, d e n s i t y and f l o c k s i z e .  c u l a t e d f o r each l e v e l  o f h a t c h , genotype, d e n s i t y and f l o c k s i z e f o r  c o s t e r o n e data are r e p o r t e d i n Tables 7, and three-way  The means c a l -  interactions  3, 4 and 5 r e s p e c t i v e l y .  corti-  All  two-way  i n v o l v i n g genotype, d e n s i t y and f l o c k s i z e were not  signi f i c a n t . VII.  Feather  pecking and comb damage s c o r e s  Means and l e v e l  of s i g n i f i c a n c e for feather  presented i n Table 14. highly s i g n i f i c a n t  l o s s and comb damage s c o r e s  Observations from i n i t i a l  (P<0.001) genotype e f f e c t .  b i r d a g a i n s t 0.2000 f o r s i g h t e d b i r d s .  back and rump scores  are  indicated  B l i n d b i r d s scored 0.0063 per  Back and rump f e a t h e r  the end o f the experiment a l s o had h i g h l y s i g n i f i c a n t  l o s s e s s c o r e d at  (P<0.001) genotype  effect.  The mean s c o r e s per b i r d were 0.0316 f o r b l i n d and 1.1948 f o r s i g h t e d b i r d s . Wing and t a i l  feather  highly s i g n i f i c a n t  l o s s e s scored a t the end o f the experiment a l s o had a  (P<0.001) genotype e f f e c t .  B l i n d c h i c k e n s had s c o r e o f  0.1646 per b i r d compared to 0.5649 f o r s i g h t e d o n e s . e f f e c t on f e a t h e r  term i n v o l v i n g the two  Comb damages were s i g n i f i c a n t l y  a l s o s i g n i f i c a n t GXD and is  nor  factors.  (P<0.001) h i g h e r i n s i g h t e d b i r d s compared  Mean s c o r e f o r s i g h t e d b i r d s was 0.8961 per b i r d as  0.3544 f o r b l i n d o n e s .  interaction  size  s c o r e s o f the two combined areas were not s i g n i f i c a n t  was the i n t e r a c t i o n  to b l i n d b i r d s .  Density or, f l o c k  against  In a d d i t i o n to a s i g n i f i c a n t genotype e f f e c t , GXF i n t e r a c t i o n s  f o r comb damage s c o r e s .  presented i n Table 1 5 ; s i m i l a r l y  the GXF i n t e r a c t i o n  t h e r e was  The GXD i n Table 16.  Table 14.  Mean f e a t h e r  l o s s and comb damage scores o f the experimental  birds  Factors Body  Period-  1  area  Genotype Blind  Sighted  Difference  Flock  Density Low  High  Difference  size  Smal 1  Large  Difference  Initial  Back and rump  0.0063  0.2000  0.1937***  Final  Back and rump  0.0316  1.1948  1.1632***  0.6538  0.5577  0.0961  0.5781  0.6129  0.0348  Wing and t a i l  0.1646  0.5649  0.4003***  0.3462  0.2500  0.0962  0.1875  0.3266  0.1391  Comb  0.3544  0.8961  0.5417***  0.7051  0.5385  0.1666  0.2188  0.7258  0.5070***  Initial Final  period refers  period refers  to score taken p r i o r to s t a r t o f the  to score taken at the end of the  experiment.  experiment.  * * * P<0.001  cn o  Table 15.  S i g n i f i c a n t GXD i n t e r a c t i o n o f experimental b i r d s  f o r comb damage s c o r e s  Density Genotype  — High  Low  Sighted  1.13  c  0.67  b  Blind  0.30  a  0.41  a  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t K r u s k a l - W a l l i s k-sample T e s t .  (P<0.05) by  Table 16.  S i g n i f i c a n t GXF i n t e r a c t i o n o f experimental b i r d s  f o r comb damage scores  Flock Genotype  Size  Small  b  Sighted  0.31  Blind  0.13  3  Means with d i f f e r e n t s u p e r s c r i p t s are s i g n i f i c a n t l y d i f f e r e n t K r u s k a l - W a l l i s k-sample T e s t .  Large  C  1.05  0.41  b  (P<0.05) by  63  Regarding GXD s i g n i f i c a n t i n t e r a c t i o n , s i g h t e d b i r d s kept i n high d e n s i t y had more comb damage s c o r e s than when they were kept i n low d e n s i t y .  On the  other  hand, b l i n d b i r d s kept i n high o r low d e n s i t y had no d i f f e r e n c e i n comb damage scores.  Even when b l i n d b i r d s were kept i n high d e n s i t y c o n d i t i o n s , t h e i r comb  damage- s c o r e s were s i g n i f i c a n t l y conditions.  Significant  lower than s i g h t e d b i r d s kept i n low d e n s i t y  GXF i n t e r a c t i o n  indicated that,  both genotypes kept  in  l a r g e f l o c k s had h i g h e r comb damage s c o r e s than when they were kept i n small flocks.  The d i f f e r e n c e between s i g h t e d and b l i n d c h i c k e n s was b i g g e r i n  f l o c k s than i n small  flocks.  kept i n l a r g e  flocks their  kept i n small  flocks.  The important p o i n t i s t h a t , when b l i n d b i r d s were  comb damage s c o r e s were o n l y s i m i l a r to s i g h t e d b i r d s  D e n s i t y as a main f a c t o r d i d not a f f e c t significantly  (P<0.001) a f f e c t e d t h i s  damage (0.7258)  per b i r d than small  The above r e s u l t s  large  on f e a t h e r  comb damage s c o r e s , but f l o c k  parameter.  flocks  Large f l o c k s s u f f e r e d more  (0.2188).  l o s s and comb damage s c o r e s c o n s i d e r e d t o -  gether i n d i c a t e t h a t s i g h t e d b i r d s s u f f e r e d more f e a t h e r and comb damages blind birds.  than  Histograms d e p i c t i n g the d i s t r i b u t i o n o f b i r d s i n the two genotypes  with r e l a t i o n s h i p to s e v e r i t y Figure 2 and 3 f o r i n i t i a l 4 for final  size  'wing and t a i l '  comb damage s c o r e s .  o f f e a t h e r and comb damages are presented  and f i n a l  'back and rump' f e a t h e r  f e a t h e r s c o r e s and f i n a l l y  scores, in  i n Figure 5 f o r  in Figure final  64  F i g u r e 2.  A comparison o f i n i t i a l  back and rump f e a t h e r damage  between s i g h t e d and b l i n d c h i c k e n s  0  0.5 Scores  1.0  65  F i g u r e 3.  A comparison o f f i n a l  back and rump f e a t h e r  damager  between s i g h t e d and b l i n d c h i c k e n s  80 70 60  -o  <+o S-  50  40  tt> X3  3  30 20 10  Sighted llllllll  1 I I I I I  Wm^mn  Blind  J II II  IL 0.5  1.0  1.5  Scores  2.0  2.5  3.0  3.5  66  Figure 4 .  A comparison o f wing and t a i l  f e a t h e r damage  between s i g h t e d and b l i n d c h i c k e n s  67  F i g u r e 5.  A comparison o f comb damage and b l i n d  chickens  between  sighted  68  DISCUSSION  I.  Performance o f b l i n d c h i c k e n s T h i s study was undertaken to determine the e f f e c t s  of i t  o f s i g h t o r the  on the performance o f c h i c k e n s under two d i f f e r e n t  different  flock sizes.  It  d e n s i t i e s and two  has been r e p o r t e d t h a t a r e d u c t i o n o f f r o n t a l  reduced s t r e s s when hens were wearing specs ( A r b i , total  1978).  It  stress  b r e a k i n g down s o c i a l  h i e r a r c h y which might c o n t r i b u t e to the i n c r e a s e d  ductivity  It  terfere  with f e e d i n g and o t h e r maintenance a c t i v i t i e s  perienced by these c h i c k e n s .  stress  in ex-  Keeping i n mind these c o n f l i c t i n g t e n d e n c i e s , 'The l a c k o f v i s i o n d i d not r e -  performance f o r the b l i n d b i r d s compared to the s i g h t e d ones  through decreased s o c i a l  interactions  because b l i n d n e s s i n t e r f e r e d  f e e d i n g and o t h e r maintenance p r a c t i c e s ' . therefore  pro-  o f the b i r d which  advantage gained by reduced s o c i a l  h y p o t h e s i s was developed which s t a t e d  s u l t in better  by  was a l s o s u s p e c t e d t h a t the l a c k o f s i g h t might i n -  t u r n may a b o l i s h any p o t e n t i a l  a null  vision  might be t h a t  e l i m i n a t i o n o f s i g h t would l e a d to f u r t h e r r e d u c t i o n o f s o c i a l  per b i r d .  lack  to gather evidence e i t h e r  The o b j e c t i v e  of this  with study was  to support or to r e j e c t the n u l l  hypothesis  through a s t u d y o f nine parameters r e l a t e d t o p r o d u c t i v i t y and s t r e s s o f  the  birds. S i g h t e d and b l i n d c h i c k e n s were compared as per t h e i r i n the parameters measured. o f statements  of this  performance  e x p e r i m e n t , a number  can be made and arguments f o r or a g a i n s t each statement can be  discussed. 1.  Based on the r e s u l t s  relative  Statement  number 1  69  'Under the c o n d i t i o n s o f the experiment b l i n d chickens  out-performed  s i g h t e d ones i n egg p r o d u c t i o n . ' . a)  Number o f eggs c o l l e c t e d from pens with b l i n d c h i c k e n s were  significantly  h i g h e r than the number o f eggs c o l l e c t e d from pens w i t h  sighted chickens.  For a 56-day t e s t  p e r i o d b l i n d hens had a p r o d u c t i o n  r a t e o f 54.0% compared to 41.3% f o r s i g h t e d hens. numbers per hen f o r t h i s (56 x 0.413)  The c a l c u l a t e d  p e r i o d were 30.24 (56 days x 0.540)  f o r b l i n d and s i g h t e d hens r e s p e c t i v e l y .  egg  and 23.13  Therefore,  there  was a d i f f e r e n c e o f 7.11 eggs per hen f o r the 2-month study p e r i o d . was no s i g n i f i c a n t  interaction  between genotype and d e n s i t y nor  genotype and f l o c k s i z e i n egg p r o d u c t i o n , i n d i c a t i n g t h a t the  between blind  c h i c k e n s out-performed the s i g h t e d ones i n both types o f d e n s i t i e s flock  and  sizes. b)  The mean egg weight o f the two groups was not d i f f e r e n t  Although egg p r o d u c t i o n can be e v a l u a t e d as a c r i t e r i o n , Total  t h i s may not a c c u r a t e l y  egg mass may be changed e i t h e r  changing the mean egg weight the d i f f e r e n c e s weight  (Wills,  statistically.  by u s i n g number o f eggs reflect  total  collected  egg mass o u t p u t .  by changing the number o f eggs o r by 1974).  It  is  therefore  important  need to be p r o p e r l y balanced a g a i n s t each o t h e r to demonstrate Because o f the s i g n i f i c a n t d i f f e r e n c e  number o f eggs c o l l e c t e d from each genotype, the t o t a l  egg mass  in  to 1082.95g (23.13 x 46.82)  from each s i g h t e d hen.  i s apparent t h a t t o t a l  egg mass c o l l e c t e d  the  the  collected  from each b l i n d hen was c a l c u l a t e d to be 1485.30g (30.24 x 46.07)  it  that  e x h i b i t e d by the two groups o f b i r d s i n egg number and egg  r e l a t i v e egg mass o u t p u t .  tions  There  From the above  compared estima-  from b l i n d chickens  was  70  heavier  (402.35g per hen) than from s i g h t e d o n e s .  The above f a c t a and f i g u r e s suggest egg p r o d u c t i o n to be h i g h e r i n chickens.  On the o t h e r hand, because s i g h t e d b i r d s were observed to be b r e a k -  i n g and e a t i n g eggs more f r e q e n t l y  than b l i n d b i r d s , i t  couTd.be argued t h a t  the number o f eggs c o l l e c t e d d i d not r e f l e c t egg p r o d u c t i o n i n these However, eggs were c o l l e c t e d at l e a s t egg b r e a k i n g and e a t i n g and i t o f eggs c o l l e c t e d can t o t a l l y  twice a day from a l l  Moreover, i t  was observed t h a t b i r d s i n o n l y  f l o c k r e p . 1) developed t h i s  Egg b r e a k i n g by s i g h t e d b i r d s i n o t h e r pens was v e r y s l i g h t i f  statistically  tested)  however,  i n the number  be accounted f o r by the number o f eggs broken  one pen (pen A 5 ; s i g h t e d high d e n s i t y - l a r g e  e x c l u d i n g data from t h i s  birds.  pens to minimize  seems u n l i k e l y t h a t the d i f f e r e n c e  and eaten by the s i g h t e d b i r d s .  birds,  blind  particular  pen t h e r e was s t i l l  at a l l .  a difference  habit. After  (not  i n the means; egg p r o d u c t i o n percentage f o r the s i g h t e d  i n c r e a s e d from 41.13 to 4 5 . 3 6 % .  the two genotypes was s t i l l behavior i n c h i c k e n s , i t  large  takes  (8.64%).  The mean d i f f e r e n c e  S i n c e egg e a t i n g i s a l e a r n e d  time to develop t h i s  e a t i n g was the o n l y reason f o r d i f f e r e n c e  between  habit in a group.  If  egg  i n egg p r o d u c t i o n between these  two  g e n o t y p e s , s i g h t e d b i r d s c o u l d have a t l e a s t equal o r h i g h e r p r o d u c t i o n r a t e d u r i n g the e a r l y weeks b e f o r e t h i s F i g u r e 1 t h a t the weekly over a l l  weeks.  h a b i t was d e v e l o p e d .  It  c o u l d be seen from  p r o d u c t i v i t y o f b l i n d c h i c k e n s was u n i f o r m l y  There was not a s i n g l e week i n which p r o d u c t i v i t y was  in sighted chickens. indeed be i n f e r i o r  This i n d i c a t e s  better better  t h a t egg p r o d u c t i o n i n s i g h t e d hens may  to b l i n d hens.  From the above o b s e r v a t i o n s , i t  c o u l d be argued t h a t under the c o n d i t i o n s  o f the experiment egg p r o d u c t i o n i n b l i n d c h i c k e n s was at l e a s t equal  but may  71  indeed be b e t t e r  than s i g h t e d o n e s .  It  is  t h e r e f o r e , worthwhile  to  investi-  gate how b l i n d c h i c k e n s would perform i n cages under more i n t e n s e c o n d i t i o n s . Egg q u a l i t y  i s an important a s p e c t  of  egg p r o d u c t i o n .  Although no  measurement was made, the eggs from b l i n d hens seem to be comparable to produced by s i g h t e d o n e s . and e x t e r n a l  qualities  environmental  Further  s t u d i e s are r e q u i r e d to compare the  o f eggs from both groups o f c h i c k e n s under  lation  year  production.  between e a r l y  how well  Lowe and Garwood (1980)  c o r r e l a t i o n s o f r a t e o f egg p r o d u c t i o n between e a r l y and o b t a i n e d a c o r r e l a t i o n c o e f f i c i e n t o f 0 . 7 7 .  b l i n d hens w i l l  rates.  which had h i q h e r egg p r o d u c t i o n i n the e a r l y h i g h e r egg p r o d u c t i o n i n the a n n u a l ' r a t e be i n t e r e s t i n g to compare annual  genetic records  Another study (Kinney e t These  period of lay w i l l  of l a y .  corre-  records and annual  In t h i s  al.,  correlations  r e p o r t e d by the above authors among many o t h e r s suggest t h a t the  2.  perform  Such computations  e s t i m a t e d the  1968) a l s o r e p o r t e d such c o r r e l a t i o n to be high ( 0 . 8 0 ) .  may a l t e r  similar  T h i s r e q u i r e s the computation o f g e n e t i c  r a t e s o f p r o d u c t i o n with annual  were made i n the r e c e n t p a s t .  ones to see i f  internal  conditions.  Another a s p e c t o f f u t u r e r e s e a r c h i s over a f u l l  those  individuals tend to have  connection, i t  would  egg p r o d u c t i o n o f b l i n d c h i c k e n s with s i g h t e d  t h e d u r a t i o n o f egg p r o d u c t i o n i s a f f e c t e d by the b l i n d n e s s which  the amount o f p h o t o s t i m u l a t i o n r e c e i v e d by these  Statement  birds.  number 2  'Under the c o n d i t i o n s o f t h i s experiment b l i n d chickens consumed l e s s feed than the s i g h t e d c h i c k e n s . ' The amount o f feed taken from the feed troughs by the b l i n d c h i c k e n s (135.3g per b i r d per day)  was s i g n i f i c a n t l y l e s s  than the s i g h t e d b i r d s  (179.4g).  72  Such a l a r g e d i f f e r e n c e  i n feed requirements suggests d i f f e r e n c e s  in  the  u t i l i z a t i o n o f feed by the two genotypes. Of the d i f f e r e n c e s e x h i b i t e d by the two genotypes i n the amount o f feed t a k e n , a s u b s t a n t i a l  amount o f which c o u l d be a t t r i b u t e d  to feed  with more s p i l l a g e by the s i g h t e d b i r d s than by the b l i n d o n e s .  Arbi  r e p o r t e d reduced feed s p i l l a g e by hens wearing specs p a r t i c u l a r l y troughs were f i l l e d .  spillage (1978)  when the  He a l s o n o t i c e d t h a t s p i l l a g e by the c o n t r o l  feed  hens i n -  creased with an i n c r e a s e i n the amount o f feed placed i n the feed t r o u g h s . O b s e r v a t i o n s from t h i s experiment supported A r b i ' s f i n d i n g s . were observed f r e q u e n t l y to s c r a t c h and s p i l l feed wastage.  Such behavior was r a r e l y  Sighted  birds  feed out o f troughs l e a d i n g to  observed i n the b l i n d c h i c k e n s .  f o r e , feed s p i l l a g e c o u l d account f o r p a r t o f the v a r i a t i o n  There-  i n the amount o f  r e q u i r e d feed between the two genotypes. F l o c k s i z e was a s i g n i f i c a n t f a c t o r i n a f f e c t i n g the amount o f taken from the feed t r o u g h s .  feed  D a i l y feed requirement per b i r d i n the small  flock  was h i g h e r compared to l a r g e f l o c k (see  Table 5 and a l s o l a t e r d i s c u s s i o n on  effects  The i n t e r a c t i o n term GXF f o r  o f f l o c k s i z e on p e r f o r m a n c e ) .  feed was a l s o found to be s i g n i f i c a n t s i g n i f i c a n t l y less  Although b l i n d c h i c k e n s took  feed than s i g h t e d ones i n both the small and l a r g e  s i t u a t i o n s , the d i f f e r e n c e b i g g e r i n small  (P<0.05).  f l o c k s s i t u a t i o n than i n the l a r g e f l o c k s s i t u a t i o n .  to be d e t e c t e d when s t r a i n s  amd environments  greatly affect  The l a r g e s t amount o f feed taken per b i r d by the s i g h t e d c h i c k e n s with small  flock  i n feed taken between the two genotypes was much  e t al_. (1976) s t a t e d t h a t genotype X housing environment i n t e r a c t i o n s likely  required  f l o c k s may be a t t r i b u t e d  to g r e a t e r  Al-Rawi are  productivity. associated  feed s p i l l a g e and a l s o  higher  73  consumption per b i r d .  Previous  r e s e a r c h i n d i c a t e d t h a t when b i r d s were housed  s i n g l y they ate s i g n i f i c a n t l y more feeid than those housed 3 to a group (Jensen e t a]_.,  1976) ,  and  2 b i r d s per group consumed s i g n i f i c a n t l y  feed compared to 3 b i r d s per group (Ouart and Adams, 1982).  higher  Therefore  increased  feed s p i l l a g e and i n c r e a s e d feed consumption by the s i g h t e d c h i c k e n s i n f l o c k s may be r e s p o n s i b l e f o r the s i g n i f i c a n t i n c r e a s e  small  i n amount o f feed  taken  from the t r o u g h . At t h i s  point, i t  should be p o i n t e d out t h a t body weight gains o f  b l i n d and s i g h t e d c h i c k e n s d u r i n g the experimental different.  Nor d i d the body weight measured j u s t  experiment s i g n i f i c a n t l y d i f f e r  p e r i o d were not  significantly  p r i o r to the s t a r t  between the two genotypes.  the  of  The A n a l y s i s  the of  Covariance a l s o demonstrated t h a t t h e r e was no s i g n i f i c a n t r e g r e s s i o n o f body weight gain on i n i t i a l sighted chickens w i l l  body w e i g h t .  Although i t  i s v a l i d to a n t i c i p a t e  put on more weight than the b l i n d ones due to a h i g h e r  feed consumption and l e s s egg mass o u t p u t , t h i s was not r e f l e c t e d Emmans (1974)  that  i n the  results.  demonstrated t h a t the energy r e q u i r e d f o r growth and egg p r o d u c t i o n  not o n l y depends on the energy c o n t e n t s o f the weight but a l s o on the e f f i c i e n c y with which d i e t a r y  gain and egg produced  energy i s c o n v e r t e d to  carcass  and egg mass. 3.  Statement  number 3  ' Higher a c t i v i t y  level  and f e a t h e r damages i n f l o c k s o f s i g h t e d c h i c k e n s  l e a d to h i g h e r energy c o s t not r e l a t e d to  productivity.'  Although feed s p i l l a g e c o u l d be a f a c t o r c o n t r i b u t i n g to the i n feed requirements and s t r e s s  between the two g e n o t y p e s , the impact o f s o c i a l  is also important.  This i s  reflected  i n the amount  of  difference interaction  increased  74  social  activity  damages (Table  shown  by s i g h t e d b i r d s as evidenced from h i g h e r pecking  14) to the combs o f b i r d s i n t h i s  t h a t pecking i n c h i c k e n s i s  group. Wennrich  u s u a l l y d i r e c t e d a t the head o f the  When r o o s t e r s grasp hens i n a mating a t t e m p t , or by the back o f the head.  (1974)  individuals.  they a l s o grasp hens by the comb  Thus the combs o f the b i r d s are a f f e c t e d the most.  A g a i n , when a b i r d pecks another b i r d , the l a t t e r  tries  T h i s leads to i n c r e a s e d b i r d movement (Hughes and B l a c k , o b s e r v a t i o n s on the same experimental  to escape o r 1974).  b i r d s i n t h i s study by Cheng ( u n p u b l i s h e d  by s i g h t e d b i r d s compared to b l i n d o n e s . activity  W i l s o n e t al_. (1959)  increases  energy e x p e n d i t u r e may vary c o n s i d e r a b l y , i t o f maintenance requirements  interactions  demonstrated  energy e x p e n d i t u r e .  Although such  represents a substantial  (Morrison and Leeson, 1978) and i s  the basal metabolism (Card and Nesheim, 1967). assume t h a t more a c t i v i t y  fight.  Behavioral  d a t a ) a l s o demonstrated t h a t t h e r e were s i g n i f i c a n t l y more s o c i a l  t h a t any kind o f p h y s i c a l  stated  It  is  therefore  proportion  u s u a l l y 50% o f logical  to  i n the s i g h t e d b i r d s was accompanied by h i g h e r energy  e x p e n d i t u r e w h i c h , i n t u r n , . l e d to h i g h e r feed consumption t o compensate f o r  the  e x t r a energy e x p e n d i t u r e . In a d d i t i o n to a s i g n i f i c a n t genotype e f f e c t t h e r e were a l s o s i g n i f i c a n t GXD and GXF i n t e r a c t i o n s  f o r comb damage s c o r e s , observed f o r t h i s  trait.  S i g h t e d b i r d s i n high d e n s i t y c o n d i t i o n s had h i g h e r comb damages than i n low density conditions. density. effect  B l i n d c h i c k e n s , however, were not a f f e c t e d by a change  in  T h i s GXD s i g n i f i c a n t i n t e r a c t i o n might have rendered the main d e n s i t y  non-significant.  observed i n c r e a s e d s o c i a l  Al-Rawi and C r a i g (1975) interactions  and P o l l e y  e t al_.  as area per b i r d d e c r e a s e d .  study (Simmonsen e t a l _ . , 1980) a l s o confirmed the same t e n d e n c i e s .  (1974) A later The r i s e  75  in social  activities  (as  evidenced from h i g h e r comb damage scores due to  creased d e n s i t y observed i n the present experiment) sumably be a s s o c i a t e d with i n c r e a s e d p h y s i c a l dividual  o f . s i g h t e d b i r d s may p r e -  c o n t a c t because o f reduced i n -  distances. A significant  indicated that,  GXF i n t e r a c t i o n observed f o r t h i s  a l t h o u g h s i g h t e d b i r d s had more s o c i a l  trait  f l o c k s compared to small  flocks.  However the d i f f e r e n c e  b l i n d b i r d s was much b i g g e r i n l a r g e f l o c k s than i n small (1976)  16)  levels  than  in  Hughes and Black (1974)  large  between s i g h t e d and flocks.  Al-Rawi  a l s o r e p o r t e d more p e c k i n g  damages i n groups o f 4 b i r d s than i n groups o f 2 b i r d s . t h a t l a r g e f l o c k s p r o v i d e more o p p o r t u n i t i e s  P e r r y (1977)  reported  f o r a g o n i s t i c b e h a v i o r than small  S i g h t e d b i r d s , t h e r e f o r e , were more a f f e c t e d by the d i f f e r e n c e  flock s i z e ,  blind  observed h i g h e r a g o n i s t i c behavior i n groups o f 8 and 14 b i r d s  compared to 4 b i r d s .  flocks.  (Table  interactions  b i r d s , both s i g h t e d and b l i n d c h i c k e n s had h i g h e r a c t i v i t y  et a]_.  in-  b e c a u s e , l a c k o f s i g h t i n b l i n d b i r d s hindered i n t e n s e  in  social  interactions. The d i f f e r e n c e periment (see  i n t h e amount o f f e a t h e r  l o s s as evidenced i n t h i s  Table 14 and a l s o F i g u r e s 2, 3 and 4) c o u l d be another  f o r the v a r i a t i o n  i n feed requirements o f the two genotypes.  was f a r more s e v e r e i n s i g h t e d b i r d s compared to b l i n d b i r d s . by the end o f the e x p e r i m e n t , a l l Emmans and C h a r l e s extensive  feather  e t al_. (1983)  (1976)  b l i n d b i r d s were s t i l l  fully  reason  Feather  loss  Practically, feathered.  r e p o r t e d t h a t heat l o s s from exposed s u r f a c e  l o s s may be up to 40% more than f u l l y  ex-  feathered hens.  under Lee  found t h a t when hens were d e f e a t h e r e d they had s i g n i f i c a n t l y  h i g h e r heat l o s s compared to f u l l y  f e a t h e r e d hens.  Another study u s i n g naked  76  neck (na/na) fowls efficiency  (Touchburn e t aj_., 1980) observed i n f e r i o r  i n these b i r d s compared to normal f e a t h e r e d o n e s .  r e p o r t ( E r n s t and B o a s , 1933) i n d i c a t e d t h a t  ' f r i z z l e (F/f  thermochemical Still  another  o r F/F)  fowl'  with  scanty plumage had a high basal metabolism and i n c r e a s e d feed consumption. is  t h e r e f o r e , obvious t h a t more heat was l o s t from exposed s u r f a c e o f  s i g h t e d b i r d s compared to b l i n d b i r d s must t h e r e f o r e and M o r r i s o n (1978)  ones.  The e x t r a heat l o s s by the  the  sighted  be compensated by i n c r e a s e i n feed consumption.  Leeson  a l s o s t a t e d t h a t poor f e a t h e r cover i s a s s o c i a t e d with i n -  creased feed consumption to compensate f o r e x t r a heat It  It  loss.  has been demonstrated t h a t hens wearing specs had h i g h e r egg p r o -  d u c t i o n and lower feed consumption than c o n t r o l s (Cumming and E p p s , 1976 and Arbi,  1978).  These authors concluded t h a t the phenomenon was p a r t l y  o f reduced i n c i d e n c e o f s t r e s s f u l Wells and Wright (1971)  because  s i t u a t i o n s encountered by hens wearing specs  suggested t h a t r e g a r d l e s s o f f e a t h e r c o v e r ,  stressful  situations could also a l t e r  t h e r m o r e g u l a t o r y responses i n c h i c k e n s and render  them l e s s e f f i c i e n t .  not c o n c l u s i v e whether  It  is  b i r d s e x p e r i e n c e d more s t r e s s however,  indicates  s k i n and f e a t h e r drastic  than the b l i n d o n e s .  s t u d y , the  Circumstantial  sighted  evidence,  t h a t t h i s may be t r u e because s i g h t e d b i r d s s u f f e r e d more  damages than b l i n d b i r d s .  had pine t a r not been a p p l i e d to a l l  to a v o i d unnecessary s u f f e r i n g deter further  in this  The d i f f e r e n c e c o u l d be even more wounds caused by pecking i n o r d e r  by the experimental  pecking on the wounds because o f i t s  birds. bitter  Pine t a r taste.  Despite  remedy, t h r e e b i r d s from the s i g h t e d groups d i e d because o f p e c k i n g d u r i n g the experiment but none from the b l i n d groups d i e d .  tends  to this  injuries  There was no  s i g n i f i c a n t d i f f e r e n c e between the two genotypes i n l e u k o c y t e c o u n t ,  adrenal  77  weight and plasma c o r t i c o s t e r o n e l e v e l . and plasma c o r t i c o s t e r o n e l e v e l o f the f o u r f a c t o r s they i n d i c a t e  However, t h e means f o r adrenal  were both lower  weight  f o r the b l i n d genotype.  taken s e p a r a t e l y may not be m e a n i n g f u l , but  t h a t the s i g h t e d b i r d s were under more s t r e s s  Each  taken'together,  than the  blind  chickens. Although u n l i k e l y ,  the gene  'rc'  c o u l d a l s o be c a u s i n g d i f f e r e n c e s  in  feed requirements o f the two genotypes through gene a c t i o n s other than  those  c a u s i n g b l i n d n e s s i n the homozygotes.  because  o f s i n g l e gene d i f f e r e n c e s white hens ( I / i , hens ( i / i ) .  I/I)  i n feed u t i l i z a t i o n  has been observed by Merat e t al_. ( 1 9 7 9 ) .  consumed s i g n i f i c a n t l y l e s s  Although i t  t h a t o f Merat e t a]_.  Differences  i s not f a i r  feed compared to c o l o u r e d  to compare the r e s u l t s  (because o f a l a c k o f s i m i l a r i t y  c o n d i t i o n s and type o f b i r d s used)  it  Their  i n the  of this  study with  experimental  n e v e r t h e l e s s , does i n d i c a t e t h a t g e n o t y p i c  d i f f e r e n c e at one l o c u s c o u l d cause a s i g n i f i c a n t v a r i a t i o n  i n feed  utilization  through unknown mechanisms. 4.  Statement  number 4  ' B l i n d c h i c k e n s may have b e t t e r  feed e f f i c i e n c y  Based on arguments presented under the f i r s t  than normal c h i c k e n s . '  three s t a t e m e n t s , one can  conclude t h a t when compared i n terms o f feed e f f i c i e n c y , efficient  in using f e e d .  b l i n d b i r d s were more  Because, while they consumed l e s s  feed they produced  h i g h e r egg mass. Moreover, t h e r e was no d i f f e r e n c e i n body weight gain b l i n d and s i g h t e d hens. feed more e f f i c i e n t l y (Table  12).  Further  i n d i c a t i o n t h a t b l i n d b i r d s were u t i l i z i n g  can be found by examining the body weight  Although the means were not s t a t i s t i c a l l y  on the average  between  gain o f  roosters  tested, blind roosters  gained more than double i n body weight compared to s i g h t e d o n e s .  78  This i n d i c a t e s products.  t h a t b l i n d c h i c k e n s were e f f i c i e n t  However,  it  o f feed  into  i s worthwhile to f u r t h e r e x p l o r e the p o t e n t i a l  b l i n d c h i c k e n s under modern system o f management 5.  converters  of  practices.  Other c o n s i d e r a t i o n s Whatever may be the  reason  f o r h i g h e r number o f eggs c o l l e c t e d and  l e s s amount o f feed taken by the b l i n d b i r d s compared to s i g h t e d o n e s , former would s t i l l of  'Global  be  Poultry  beneficial  Industry ,  flock.  In a r e c e n t  review  J a s p e r (1979) r e p o r t e d t h a t changes i n the c o s t  1  o f l i v i n g and o t h e r f a c t o r s  i n farm y a r d s i t u a t i o n s .  the  have r e v i v e d ,  to a small  d e g r e e , the  backyard  As a matter o f f a c t , many d e v e l o p i n g c o u n t r i e s o f A s i a , South America  and A f r i c a have not developed an i n t e n s i v e In those c o u n t r i e s  poultry  and modernized p o u l t r y  i s predominantly a backyard e n t e r p r i s e .  industry. Under those  c o n d i t i o n s b l i n d b i r d s would be more e c o n o m i c a l , because o t h e r t h i n g s e q u a l , the farmers would s t i l l  being  c o l l e c t more eggs f o r l e s s feed compared to  sighted ones. II.  Additional observations 1.  from experiment  Fertility A particular  is considered i t s vironmental  behavior or component o f a behavior e x h i b i t e d by an animal  phenotype.  factors.  a u d i t o r y and v i s u a l  As s u c h , i t  is  affected  Learning u s u a l l y involve modalities.  by both g e n e t i c and e n -  the i n t e r a c t i o n s  B l i n d animals can be u s e f u l  o f both the  for studying l e a r n -  i n g i n animals., because they a l l o w the experimenter to h o l d c o n s t a n t the sensory i n p u t from one m o d a l i t y w h i l e s t u d y i n g the  other.  A thorough search i n the l i t e r a t u r e has f a i l e d to t u r n up with any  79  i n s t a n c e s o f p r e v i o u s r e s e a r c h d e a l i n g with mating behavior o f blind animals.  T h i s c o u l d be due to l a c k o f a v a i l a b i l i t y  animals which are g e n e t i c a l l y  blind.  genetically  o f experimental  The b l i n d c h i c k e n s used i n t h i s  periment would p r o v i d e a good o p p o r t u n i t y to study such b e h a v i o r a l Previous c a s u a l  observations  (Cheng, personal communication)  ex-  patterns.  o f b l i n d chickens  d i d not i n d i c a t e t h a t b l i n d b i r d s c o u l d mate s u c c e s s f u l l y under n a t u r a l situations.  For p r o p a g a t i o n o f t h i s  line a r t i f i c i a l  From Cheng's o b s e r v a t i o n s , i t fertility to t h i s  is  Percent f e r t i l i t y  mating from b l i n d b i r d s .  Contrary  o b t a i n e d i n the p r e s e n t study were s u r p r i s i n g .  o f eggs from the b l i n d c h i c k e n s was 48.2% compared to 84.2%  f o r the s i g h t e d b i r d s ( T a b l e Adams e t a]_. Leghorns (normal  used.  a n t i c i p a t e d t h a t very low o r no  c o u l d be expected through n a t u r a l  e x p e c t a t i o n , the r e s u l t s  i n s e m i n a t i o n was  mating  3).  (1978) r e p o r t e d the f e r t i l i t y  vision)  and 36.2% r e s p e c t i v e l y .  o f two s t r a i n s  kept with a male to female r a t i o Under t h i s  particular  o f 1:10 to be 48.7%  s i t u a t i o n , the performance o f  b l i n d c h i c k e n s i n the p r e s e n t study was not too much out o f l i n e Moreover, f e r t i l i t y varied considerably. low d e n s i t y - s m a l l  o f eggs from d i f f e r e n t  The f e r t i l i t y  flock)  o f White  pens o f the b l i n d b i r d s  o f eggs from one p a r t i c u l a r  was 85% d u r i n g the f i r s t  i n comparison.  pen (Pen A3  p e r i o d (8-17 d a y s ) , 92%  d u r i n g the second p e r i o d (28-37 days) and 100% d u r i n g the t h i r d p e r i o d (48-57 days).  Fertility  from a pen o f s i g h t e d b i r d s under the same c o n d i t i o n s was  o n l y 6 4 . 4 % , 78.3% and 77.3% r e s p e c t i v e l y periods.  However,  from s i g h t e d b i r d s . fertility  fertility  f o r the f i r s t ,  second and t h i r d  o f eggs from b l i n d b i r d s was u s u a l l y lower than  In one p a r t i c u l a r  pen (pen B2, high d e n s i t y - s m a l l  was 0% throughout the e x p e r i m e n t .  flock)  80  As evidenced from the r e s u l t s p e r i o d s i n c r e a s e d over t i m e .  (see  In the f i r s t  page 5 5 ) . f e r t i l i t y  in  different  p e r i o d , the mean f e r t i l i t y  of  and b l i n d b i r d s was 5 0 . 9 % , i n the s e c o n d , 71.1% and i n the t h i r d 7 9 . 1 % . increases  in f e r t i l i t y  Adams e t aj_. (1978)  may be a t t r i b u t e d  These  to l e a r n i n g e x p e r i e n c e o f the  also reported higher f e r t i l i t y  sighted  roosters.  from e x p e r i e n c e d males com-  pared to i n e x p e r i e n c e d m a l e s . The v a r i a b i l i t y different ability  pens, r e f l e c t  observed f o r f e r t i l i t y  t h a t b l i n d r o o s t e r s may v a r y c o n s i d e r a b l y i n  to s u c c e s s f u l l y mount f e m a l e s .  q u i c k l y than o t h e r s .  parameter among b l i n d b i r d s  Therefore, i t  would be o f i n t e r e s t  to (a)  examine  determine  frequency o f s u c c e s s f u l mating can be i n c r e a s e d through s e l e c t i v e  breeding.  studies.  Flock s i z e and d e n s i t y Most o f the e a r l i e r  s t u d i e s i n v o l v i n g b i r d d e n s i t y and f l o c k s i z e were  not well designed to separate reviewed  whether  experiment i n d i c a t e t h a t the b l i n d c h i c k e n would  be a good model f o r b e h a v i o r a l 2.  learning  As e v i d e n c e d , some c o u l d l e a r n more  s i t u a t i o n s where s u c c e s s f u l mating can be enhanced and (b)  Observations i n t h i s  in  the e f f e c t s  a wide range o f l i t e r a t u r e  t h a t much o f the e a r l i e r  o f these two f a c t o r s .  d e a l i n g with ' s t o c k i n g d e n s i t y '  work was p o o r l y designed i n t h a t i t  c o l o n y s i z e (number o f b i r d s per cage) and area per b i r d . have attempted to s e p a r a t e  the e f f e c t s  o f these two f a c t o r s  have been g i v e n on the importance o f i n t e r a c t i o n s (Adams and J a c k s o n , above f a c t s ,  this  Hughes  (1975)  and s t a t e d  m o s t l y confounded  More r e c e n t but l i t t l e  i n v o l v i n g these two  1970; Al-Rawi e t a l _ . , 1976; P e r r y , 1977).  studies emphasis factors  In view o f  study was planned i n an attempt to s e p a r a t e the e f f e c t s  the of  f l o c k s i z e and b i r d d e n s i t y upon the parameters measured and a l s o to examine  81  the i n t e r a c t i o n  between these two  factors.  F l o c k s i z e s i g n i f i c a n t l y a f f e c t e d some o f the parameters Percent  studied.  hen-day egg p r o d u c t i o n was s i g n i f i c a n t l y h i g h e r (P<0.05) i n small  compared t o l a r g e f l o c k s .  Higher egg p r o d u c t i o n o b t a i n e d from the small  flocks flocks  confirmed the work o f Al-Rawi e t al_. (1976) who, working w i t h group s i z e s o f 4 , 8 and 14 b i r d s per g r o u p , found lowest  p r o d u c t i o n r a t e i n group s i z e o f 14.  P r o d u c t i o n d e c l i n e d as group s i z e i n c r e a s e d . effect  can be found i n H i l l  and Binns  (1973)  Similar  r e s u l t s on group s i z e  and A i t k e n e t al_. ( 1 9 7 3 ) .  No  e x p l a n a t i o n however, was p r o v i d e d by these authors f o r such r e s u l t s . The e f f e c t o f f l o c k s i z e on feed consumption, body weight g a i n and comb damage ( p e c k i n g a c t i v i t y ) o f the experimental (P<0.001).  Birds  i n small  and l e s s comb damages.  study.  i n the number o f t o t a l  How much o f t h i s  accounted f o r by i n c r e a s e s in this  f l o c k s had h i g h e r feed i n t a k e ,  However,  significant  gained more w e i g h t ,  A h i g h e r feed requirement by b i r d s i n small  be accounted f o r i n c r e a s e s body weight g a i n .  b i r d s were h i g h l y  collectable  flocks could  eggs and h i g h e r  excess feed consumption i n small  f l b c k was  i n egg number and body weight gain was not  quantitated  p r e v i o u s r e s e a r c h i n d i c a t e d t h a t feed consumption d e -  c r e a s e s as b i r d number per group i n c r e a s e s  (eg.  Jensen ejt a]_.,  1976; Ouart and  Adams, 1982). Higher body weight  gain by b i r d s i n the small  f l o c k s as observed i n  s t u d y is i n agreement w i t h t h a t o f Cunningham and O s t r a n d e r ( 1 9 8 2 ) . found s i g n i f i c a n t l y h i g h e r body weight 5 birds.  From t h e i r  to group s i z e .  results  it  this  These a u t h o r s  gain i n groups o f 4 b i r d s compared to  appeared t h a t body weight g a i n c o u l d be  related  The p r e s e n t study with a b i g g e r d i f f e r e n c e i n group s i z e s (5  20) confirmed Cunningham and O s t r a n d e r ' s  findings.  Significantly  h i g h e r comb  vs  82  damage i n the l a r g e i n those f l o c k s .  f l o c k s i n d i c a t e d h i g h e r a g o n i s t i c and sexual  Al-Rawi and C r a i g (1975) observed a p o s i t i v e  between group s i z e and i n d i v i d u a l 8, 14 and 28 b i r d s .  The l e v e l  activities  relationship  f r e q u e n c i e s o f a g g r e s s i o n with f l o c k s o f 4 ,  o f a g g r e s s i o n v a r i e d d i r e c t l y with group s i z e  and was most e v i d e n t d u r i n g f e e d i n g t i m e .  Therefore, i t  is  possible that feeding  i n t e r r u p t i o n s o c c u r under those c o n d i t i o n s more f r e q u e n t l y i n l a r g e f l o c k s i n small  flocks.  Due to a reduced i n t e r r u p t i o n i n f e e d i n g , b i r d s i n small  group s i z e s have the o p p o r t u n i t y to eat more and perform  better.  Flock s i z e was not o n l y the f a c t o r which a f f e c t e d these t r a i t s , a l s o played a s i g n i f i c a n t r o l e . s i g n i f i c a n t i n any c a s e , interactions  4  out o f  9  parameters  Significant  DXF i n t e r a c t i o n s  body weight g a i n .  In a l l  was n o t i c e d i n t h a t small heaviest  significant  (see  o f these i n t e r a c t i o n s  a general  for  page 7 4 ) .  o t h e r s were i n v o l v i n g d e n s i t y and f l o c k  were observed f o r egg w e i g h t ,  size.  feed consumption and and c o n v i n c i n g t r e n d  f l o c k s i n low d e n s i t y took the h i g h e s t f e e d , had the  f l o c k s i n low d e n s i t y ,  On the o t h e r hand,  the r e s u l t s were the o p p o s i t e (Table 8, 10 and  The d i f f e r e n c e s e x h i b i t e d by these two f l o c k s i z e s i n low and high d e n s i t y  s i t u a t i o n s were g r e a t e r it  earlier  egg weight and had the most gain i n body w e i g h t .  for large 11).  s t u d i e d showed  A s i g n i f i c a n t GXD i n t e r a c t i o n  comb damage s c o r e s has a l r e a d y been d i s c u s s e d .:. interaction, all  density  Although d e n s i t y as a main f a c t o r was not  i n v o l v i n g d e n s i t y as a f a c t o r .  A s i d e from t h i s  than  i n low d e n s i t y than i n h i g h d e n s i t y .  c o u l d be concluded t h a t f l o c k s i z e as a f a c t o r i s  d e n s i t y as i n low d e n s i t y .  Therefore, i t  From these  results  not as important i n high  c o u l d be suggested t h a t when b i r d s  are to be housed i n low d e n s i t y they should be housed i n small  group s i z e s .  The above d i s c u s s i o n s emphasised the need o f examining i n t e r a c t i o n s  in  83  a factorial  experiment l i k e  e f f e c t o f each f a c t o r  the p r e s e n t one f o r a v a l i d i n t e r p r e t a t i o n  involved.  For example, i n t h i s  study, i f  the  of  the  interactions  between genotype and d e n s i t y o r d e n s i t y and f l o c k s i z e were not examined and s e p a r a t e d from the main e f f e c t s , the r e s u l t s  c o u l d be m i s i n t e r p r e t e d  because  these i n t e r a c t i o n s masked the s i g n i f i c a n c e o f d e n s i t y as a main e f f e c t . ever, It  t h e r e c o u l d be o t h e r reasons f o r d e n s i t y e f f e c t  may be t h a t the two d e n s i t i e s used i n t h i s  enough to cause a c l e a r were o f t e n q u i t e small  h i g h e r standard d e v i a t i o n s  f o r most t r a i t s  significant.  experiment were not  separation of density e f f e c t s . l e a d i n g to g r e a t e r  b e i n g not  4).~  different  The sample s i z e s used  sampling v a r i a t i o n s (Table  How-  reflected  in  the  84  SUMMARY The impact o f v i s u a l  c o n t a c t or l a c k o f i t  was accessed i n two  genetic  groups o f c h i c k e n s maintained a t the A v a i n G e n e t i c s L a b o r a t o r y o f  the  University  of B r i t i s h  (sighted  and b l i n d )  were r e a r e d i n two f l o o r d e n s i t i e s and two f l o c k s i z e s .  Columbia.  Each o f the two g e n o t y p i c groups  A total  o f nine parameters was measured to compare the r e l a t i v e performance o f each g e n e t i c group under these experimental  conditions.  Although i t was o r i g i n a l l y suspected t h a t b l i n d n e s s w i l l  interfere  with  f e e d i n g and o t h e r maintenance p r a c t i c e s , there was no such i n d i c a t i o n from data collected in this  experiment.  ones i n the number o f t o t a l  c o l l e c t a b l e eggs and had lower  body weight  gain was s i m i l a r .  birds.  these f a c t o r s  All  efficient  Moreover, b l i n d b i r d s performed b e t t e r  than  feed requirements  T o t a l egg mass output was a l s o h i g h e r i n  while  blind  i n combinations i n d i c a t e d t h a t b l i n d b i r d s were more  i n u t i l i z i n g feed f o r body weight gains and egg p r o d u c t i o n .  From o t h e r parameters measured i n t h i s e x p e r i m e n t , p o s s i b l e reasons the b e t t e r  performance i n b l i n d c h i c k e n s can be o f f e r e d .  b i r d s were a p p a r e n t l y  Rather,  for  Although s i g h t e d  b r e a k i n g and e a t i n g eggs more f r e q u e n t l y than b l i n d o n e s ,  the d i f f e r e n c e i n number o f eggs c o l l e c t e d cannot be t o t a l l y factor.  sighted  a t t r i b u t e d to  this  s i g h t e d b i r d s may be u t i l i z i n g more energy f o r o t h e r purposes  than egg p r o d u c t i o n , b e c a u s e , they were seemingly more a c t i v e and may a l s o be under more s t r e s s compared to b l i n d b i r d s .  Though no c o n c l u s i v e evidence  support t h i s c l a i m can be d e r i v e d from t h i s  e x p e r i m e n t , the s i g h t e d b i r d s were  observed to s u f f e r more f e a t h e r and s k i n damages than b l i n d b i r d s . a l t h o u g h not s t a t i s c a l l y  s i g n i f i c a n t , mean adrenal  to  In a d d i t i o n ,  weight and c o r t i c o s t e r o n e  85  level  f o r s i g h t e d b i r d s were h i g h e r than b l i n d o n e s .  Higher amount o f feed taken from the feed troughs by the s i g h t e d b i r d s was p a r t l y due to feed s p i l l a g e and p a r t l y due to i n c r e a s e d a c t i v i t y group.  level  Another p o s s i b l e reason f o r h i g h e r feed requirements by the  c h i c k e n s c o u l d be a t t r i b u t e d  to i n c r e a s e d s k i n and f e a t h e r damages.  in  that  sighted Under  those s i t u a t i o n s , heat l o s s e s from exposed s u r f a c e o f the bared s k i n would i n c r e a s e energy  requirement.  Although f e r t i l i t y  from n a t u r a l  mating was much lower i n b l i n d b i r d s com-  pared with s i g h t e d o n e s , and may be c o n s i d e r e d as an adverse e f f e c t due to lack of s i g h t , i t  was s u r p r i s i n g  t h a t they d i d show s u c c e s s f u l mating behavior  and l e a r n e d how to mount f e m a l e s .  These b l i n d b i r d s c o u l d be u s e f u l  models f o r s t u d y i n g l e a r n i n g behavior i n g , r e s t i n g and r e p r o d u c t i v e  the  in  animal  those a s p e c t s such as f e e d i n g , d r i n k -  behaviors.  Under the c o n d i t i o n s o f the e x p e r i m e n t , the r e s u l t s o b t a i n e d suggest t h a t b l i n d b i r d s were a t efficiency  l e a s t as good as o r b e t t e r  i n feed c o n v e r s i o n .  s i g h t d i d not i n t e r f e r e mating b e h a v i o r ) . terfere  It  than s i g h t e d b i r d s i n terms o f  could therefore  be concluded t h a t l a c k  with f e e d i n g and o t h e r maintenance p r o c e s s e s  T h e r e f o r e , the n u l l  hypothesis that  (except  'lack of sight will  with f e e d i n g and o t h e r maintenance processes which may i n t e r f e r e  the normal performance o f the b i r d s ' can be r e j e c t e d .  of  in-  with  86  REFERENCES Abplanalp, H . , and I.L. 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Y o r k , H e i d e l b e r g and B e r l i n .  and Procedures o f  3rd E d i t i o n .  Statistics.  S p r i n g e r - v e r l a g , New  Sunde, M . L . , and H.R. B i r d , 1959. The e f f e c t o f p u l l e t m a t u r i t y on and h a t c h a b i l i t y o f e g g s . P o u l t r y S c i . 38:272-279.  fertility  Syme, G . J . , and L . A . Syme, 1974. The r e l a t i o n s h i p between peck o r d e r and p e r formance i n a c o m p e t i t i v e group f e e d i n g s i t u a t i o n by two groups o f c o c k e r e l . Behav. B i o l o g y . 12:547-550. T i n d e l , D . , and J . V . C r a i g , 1959. E f f e c t s o f s o c i a l c o m p e t i t i o n on l a y i n g house performance i n the c h i c k e n . P o u l t r y S c i . 38:95-105. Tomhave, A . E . , 1958.  Fertility  and h a t c h a b i l i t y  Hampshire breeders d u r i n g t h e i r  first  o f eggs produced by New  365 days o f p r o d u c t i o n .  Poultry  Sci.  37:27-29. Touchburn, S . P . , J . G u i l l a u m e , B. L e c l e r c q , and J . C . Blum, 1980. L i p i d and energy metabolism i s c h i c k s a f f e c t e d by dwarfism (dw) and naked neck (Na). P o u l t r y S c i . 59:2189-2197. Touson, R., 1977. Varphonsens r e a k t i o n f o r v a r i e r a n d e t e k n i s k n a r m i l j o . Pages 1-22. In Rapport n r . 4 6 . I n s t , f o r Husdjurens u t f o d r i n g and v a r d . Uppsala ( C i t e d by Simmenson e t a l _ . , 1980). Tower, B . A . , A . J . O l i n d e , F.R. Baker and E.P. Roy, 1967. Performance o f confined in s i n g l e v s . colony cages. Poultry S c i . 46:1330.  layers  Twisselmann, N . M . , 1939. A s t u d y o f the c e l l c o n t e n t o f the blood o f normal c h i c k e n s , with s p e c i a l r e f e r e n c e to comparative d i f f e r e n t i a l l e u k o c y t e counts made w i t h s u p r a - v i t a l and W r i g h t ' s s t a i n i n g t e c h n i q u e s . Poultry S c i . 18:151-159. V a r g a s , A . E . , and C. Edward, 1982. E f f e c t o f n u t r i e n t d e n s i t y i n the d i e t on energy and n i t r o g e n b a l a n c e , egg y o l k c h o l e s t e r o l and r e p r o d u c t i v e performance o f l a y i n g hens. P o u l t r y S c i . 61:1559. Warren,  D . C . , 1953.  Practical  Poultry  Breeding.  The McMillan Comp. New York.  Page 7 8 . Watanabe, K., Y. Yamada and S. Ebisawa, 1975. B r e e d i n g f o r improvement o f feed e f f i c i e n c y i n egg l a y e r s . 1. E s t i m a t i o n o f g e n e t i c parameters. Japanese P o u l t r y S c i . 12:219-229. Weatherup, S . T . C . , and W.H. F o s t e r , 1980. A d e s c r i p t i o n o f the curve to egg weight and age o f hen. B r . P o u l t r y S c i . 21:511-519.  relating  100  W e l l s , J.W. and P . A . L . W r i g h t , 1971. The adrenal g l a n d s . Pages 489-520 i n P h y s i o l o g y and B i o c h e m i s t r y o f the Domestic Fowl. D.J. B e l l and B.N. Freeman e d . Academic P r e s s . W e l l s , R . G . , 1973. S t o c k i n g d e n s i t y and c o l o n y s i z e f o r caged l a y e r s . Europian P o u l t r y C o n f . , London. Pages 617-622.  4th  Wennrich, G. 1974. E t h o l o g i c a l s t u d i e s o f f e a t h e r pecking and c a n n i b a l i s m i n domestic c h i c k e n s ( G a l l u s domesticus) i n f l o o r management. 15th W o r l d ' s P o u l t r y Cong, and E x p o s i t i o n New O r l e a n s , L o u i s i a n a Pages 553-554. W i l l i a m s , C . G . , P.B. S i e g e l and W.B. Gross ,1977. S o c i a l s t r i f e i n c o c k e r e l f l o c k s d u r i n g the formation o f peck r i g h t s . A p p l . Anim. E t h o l . 3:35-45. W i l l s , R . J . R . , 1974. Economic components o f egg p r o d u c t i o n . Pages 105-120 i n Economic F a c t o r s A f f e c t i n g Egg P r o d u c t i o n . B.M. Freeman and N.K. Boorman ed. Br. Poultry S c i . L t d . W i l s o n , E . D . , K.H. F i s h e r and M.E. Faqua, 1959. Wiley and S o n s , I n c . New York. Page 8 9 .  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Adrenal w e i g h t , adrenal a s c o r b i c a c i d , adrenal c h o l e s t e r o l and d i f f e r e n c i a l l e u k o c y t e counts as p h y s i o l o g i c a l i n d i c a t o r s o f s t r e s s o r agents i n l a y i n g hens. P o u l t r y S c i . 41:1521-1529.  101  APPENDIX  Table 17.  A n a l y s i s o f Variance f o r o f experimental birds  Source  df  production  MS  4.54  889.58  889.58  Genotype  1  1715.40  1715.40  1  7.83  7.83  0.04  1  919.35  919.35  4.69  1  202.26  202.26  1.03  1  0.00  0.00  0.00  DXF  1  8.61  8.61  0.04  GXDXF  1  284.65  284.65  1.45  (G) (D)  size  (F)  GXD GXF  2  8.75*  Error  1  7  1372.20  196.03  Week  (W)  7  12182.00  1740.30  WXG  7  358.12  51.16  0.60  WXD  7  597.06  85.30  1.00  WXF  7  390.18  55.74  0.65  WXGXD  7  144.65  20.66  0.24  WXGXF  7  643.15  91.88  1.07  WXDXF  7  209.24  29.89  0.35  63  5386.70  127  25311.00  Error 2 Total  Arcsin SS  SS  egg  1  Flock  2  hen-day  Replication  Density  1  percent  is  transformation equal  *P<0.05 ***P< 0.001  to  0.0032.  applied  to the data  '  85.50  before  analysis.  20.35*  1  103  Table 18.  A n a l y s i s o f Variance f o r percent hen-day egg p r o d u c t i o n o f experimental b i r d s with adjustment f o r age d i f f e r e n c e s between r e p l i c a t i o n s 1  F  0.65  Replication  1  67.55  67.55  Genotype  1  875.74  875.74  8.39*  1  159.62  159.62  1.53  1  734.22  734.22  7.04*  GXD  1  14.92  14.92  0.14  GXF  1  0.03  0.03  0.00  DXF  1  7.35  7.35  0.07  GXDXF  1  180.48  180.48  1.73  Density  (G) (D)  Flock s i z e  (F)  Error  1  7  730.29  104.33  Week  (W)  5  4762.80  952.55  WXG  5  314.94  62.99  1.48  WXD  5  226.13  45.23  1.07  WXF  5  214.34  42.87  1.01  WXGXD  5  242.15  48.43  1.14  WXGXF  5  219.01  43.80  1.03  WXDXF  5  40.06  8.01  0.19  45  1910.40  42.45  95  10700.00  Error  2  Total  1  MS  SS  df  Source  Arcsin transformation  *P<0.05 ***P< 0.001  a p p l i e d to the data before  analysis.  22.44***  104  Table 1 9 . Apparent mean p e r c e n t hen-day egg p r o d u c t i o n , egg weight.(g,<> and apparent feed-requirements ( g ) o f b i r d s with adjustment f o r age d i f f e r e n c e s o f b i r d s between r e p l i c a t i o n s  Replication  Egg weight  First  52.3±4.4  46.07±2.98  155.6+30  Second  55.2±2.3  27.68+3.38  163.U38  Di f f e r e n c e •  Genotype  ***P< 0.001  8.0  47.2U3.67  182.8±31  Blind  58.9±2.1  46.54±2.80  136.0±16  9.5*  0.67  48.8***  High  57.7±4.0  46.42±2.81  156.1+27  Low  51.4±2.7  47.33±3.64  162.6140  6.3  0.91  3.9  Small  58.5±3.8  46.95±3.76  174.5137  Large  48.9±2.6  46".80±2.72  144.2123  Difference  *P<0.05  1.66*  48.4±4.3  Difference  Flock s i z e  2.9  Sighted  Difference  Density  Feed requirements  Egg p r o d u c t i o n  Factor  9.6*  0.15  30.0***  105  Table 2 0 .  Analysis of  Variance  SS  df  Source  f o r egg weight o f experimental MS  F  14.41**  Replication  1-  132.57  132.57  Genotype  1  18.41  18.41  2.00  1  21.12  21.12  2.30  1  1.50  1.50  0.16  GXD  1  18.73  18.73  2.04  GXF  1  1.39  1.39  0.15  DXF  1  138.73  138.73  GXDXF  1  6.99  6.99  Density  (G) (D)  Flock s i z e  (F)  birds  15.08*** 0.76  Error  1  7  64.42  9.20  Week  (W)  7  1908.70  272.68  WXG  7  24.44  3.49  1.39  WXD  7  21.42  3.06  1.22  WXF  7  11.67  1.67  0.66  WXGXD  7  7.67  1.10  0.44  WXGXF  7  8.68  1.24  0.49  WXDXF  7  23.40  3.34  1.33  63  158.06  2.51  127  2567.90  Error 2 Total  **P< 0.01 ***P< 0.001  108.69***  106  Table  21.  A n a l y s i s o f V a r i a n c e f o r egg weight o f experimental b i r d s with adjustment f o r age d i f f e r e n c e between r e p l i c a t i o n s SS  df  Source  MS  F  Replication  !  61.99  61.99  7.00*  Genotype  1  10.83  10.83  1.22  1  19.64  19.64  2.22  1  0.50  0.50  0.06  GXD  1  10.02  10.02  1.13  GXF  1  2.98  2.98  0.34  DXF  1  125.17  125.17  GXDXF  1  4.38  4.38  Density  (G) (D)  Flock s i z e  (F)  14.13** 0.49  Error  1  7  62.00  8.86  Week  (W)  5  594.90  118.98  WXG  5  5.15  1.03  0.63  WXD  5  16.35  3.27  2.01  WXF  5  13.90  2.78  1.71  WXGXD  5  3.22  0.64  0.40  WXGXF  5  2.87  0.57  0.35  WXDXF  5  7.60  1.52  0.93  Error 2  45  73.23  1.63  Total  95  1014.70  *P<0.05 **P=0.01 ***Pc 0.001  73.12***  107  Table  22.  A n a l y s i s o f Variance f o r amount o f feed taken by experimental b i r d s df  Source  from feed  SS  MS  F  3.65  troughs  Repl i c a t i o n  !  0.00040  0.00040  Genotype  1  0.00778  0.00778  1  0.00014  0.00014  1  0.00423  0.00423  GXD  1  0.00004  0.00004  0.34  GXF  1  0.00064  0.00064  5.89*  DXF  1  0.00075  0.00075  6.93*  GXDXF  1  0.00017  0.00017  1.55  Error  7  0.00076  0.00011  Total  15  0.01491  Density  (G) (D)  Flock s i z e  *P<0.05 ***P<0.001  (F)  71.42*** 1.33 38.84***  108  Table  23.  A n a l y s i s o f Variance f o r amount o f feed taken from feed troughs by experimental b i r d s w i t h adjustment f o r age d i f f e r e n c e s between r e p l i c a t i o n s df  Source  SS  MS  F  1.69  Replication  !  0.0013  0.0013  Genotype  1  0.0525  0.0525  1  0.0010  0.0010  1  0.0220  0.0220  GXD  1  0.0003  0.0003  0.36  GXF  1  0.0033  0.0033  4.16  DXF  1  0.0051  0.0051  6.51*  GXDXF  1  0.0014  0.0014  1.76  Density  (G) (D)  Flock s i z e  (F)  66.67*** 1.27 27.94***  Error  1  7  0.0055  0.0008  Week  (W)  5  0.0013  0.0003  1.10  WXG  5  0.0012  0.0002  0.98  WXD  5  0.0006  0.0001  0.51  WXF  5  0.0009  0.0002  0.74  WXGXD  5  0.0007  0.0001  0.56  WXGXF  5  0.0004  0.0001  0.33  WXDXF  5  0.0012  0.0002  1.00  45  0.0108  0.0002  95  0.1095  Error Total  *P<0.05 ***P< 0.001  2  109  Table  24.  Analysis  o f Covariance df  Source  for  body weight g a i n o f experimental MS  SS  F  Replication  !  346320  346320  Genotype  1  1586  1586  0.06  1  769  769  0.03  1  282400  282400  GXD  1  11900  11900  0.46  GXF  1  478  478  0.02  DXF  1  220510  220510  GXDXF  1  63623  63623  Error  54  1392700  25792  Total  62  2320286  Density Flock  **P<0.01 ***P< 0.001  (G) (D)  size  (F)  13.43***  10.95**  8.55** 2.47  hens  110  Table 25 .  Analysis  of Variance for  body weight o f experimental MS  F  Replication  1  2197.3  2197.3  0.06  Genotype  1  84463.0  84463.0  2.36  1  21572.0  21572.0  0.60  1  7119.1  7119.1  0.20  GXD  1  5166.0  5166.0  0.14  GXF  1  11963.0  11963.0  0.33  DXF  1  10635.0  10635.0  0.30  GXDXF  1  530170,0  530170.0  Error  55  1966500.0  35754.0  Total  63  2639800.0  D en si t y Flock  1  1  SS  df  Source  initial  (G) (D)  size  (F)  Body weight taken before  ***P<0.001  s t a r t of  experiment.  14.83***  hens  Ill  Table 26-  Analysis  of  percent  fertility  SS  df  Source  1  o f experimental  MS  F  Replication  !  1364.60  1364.60  1.54  Genotype  1  6151.50  6151.50  6.93*  1  1294.30  1294.30  1.46  1  383.92  383.92  0.53  GXD  1  1203.10  1203.10  0.28  GXF  1  2.75  2.75  0.00  DXF  1  303.36  303.36  0.34  GXDXF  1  367.47  367.47  0.41  7  6216.40  888.06  2  2524.90  1262.50  PXG  2  312.32  156.16  1.16  PXD  2  344.44  172.22  1.28  PXF  2  100.77  50.39  0.37  PXGXD  2  107.10  53.55  0.40  PXGXF  2  101.24  50.62  0.38  PXDXF  2  449.57  224.79  1.67  Error 2  18  2428.60  134.92  Total  47  23656.00  D en si t y Flock  Error  Arcsin  *P<0.05 **P<0.01  (G) (G)  size  (F)  1  Period  1  Var ance f o r  (P)  transformation  applied  to the data  before  analysis.  9.36**  birds  112  Table 2 7 .  A n a l y s i s o f Variance f o r l e u k o c y t e count o f experimental  Source  df  SS  MS  F  Repl i c a t i o n  1  65675000  65675000  3.07  Genotype  1  13443000  13443000  0.63  1  2847700  2847700  0.13  1  21199000  21199000  0.99  GXD  1  5299200  5299200  0.25  GXF  1  101460000  101460000  DXF  1  22069000  22069000  1.03  GXDXF  1  12105000  12105000  0.57  Error  55  1177100000  21403000  Total  63  1421200000  Density  (G) (D)  Flock s i z e  *P< 0.05  (F)  4.74*  hens •  113  Table 2 8 .  Analysis  o f Variance df  Source  f o r adrenal SS  weight o f experimental MS  F  Replication  1  1.5252  1.5252  0.68  Genotype  1  5.9231  5.9231  2.65  1  0.5123  0.5123  0.23  1  3.6864  3.6864  1.65  GXD  1  0.0030  0.0030  0.00  GXF  1  0.2207  0.2207  0.10  DXF  1  0.1189  0.1189  0.05  GXDXF  1  0.0007  0.0007  0.00  Error  55  123.1300  2.2388  Total  63  135.1200  Density  (G) (D)  Flock s i z e  (F)  hens  114  Table 2 9 .  Analysis of Variance  o f experimental Source  birds  df  f o r plasma c o n c e n t r a t i o n o f  SS  corticosterone  MS  Replication  1  0.2771  0.2771  0.62  Genotype  1  0.6344  0.6344  1.42  1  0.7940  0.7940  1.77  1  0.0854  0.0854  0.19  GXD  1  0.8137  0.8137  1.82  GXF  1  1.0848  1.0848  2.42  DXF  1  0.0001  0.0001  0.00  GXDXF  1  0.0100  0.0100  0.02  Error  71  31.8070  0.4480  Total  79  35.5060  Density  (G) (D)  Flock s i z e  (F)  

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