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The effects of calcium carbonate on the apparent digestibility, serum concentration and apparent retention… Cathcart, Edward Byron 1981

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THE EFFECTS OF CALCIUM CARBONATE ON THE APPARENT DIGESTIBILITY, SERUM CONCENTRATION AND APPARENT RETENTION OF DIETARY MINERALS IN DAIRY CATTLE by EDWARD BYRON CATHCART B. S c . ( A g r . ) , U n i v e r s i t y o f B r i t i s h Columbia, 1976  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department o f Animal Science)  We a c c e p t t h i s t h e s i s as conforming t o the r e q u i r e d s t a n d a r d .  THE UNIVERSITY OF BRITISH COLUMBIA August, 1981 (c) Edward Byron C a t h c a r t , 1981  In p r e s e n t i n g  this  thesis i n partial  f u l f i l m e n t of the  r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e of B r i t i s h Columbia, I agree that it  freely  the L i b r a r y s h a l l  a v a i l a b l e f o r r e f e r e n c e and s t u d y .  agree that p e r m i s s i o n for  University  f o r extensive  s c h o l a r l y p u r p o s e s may  for  financial  shall  of  r\ n  Sc.  The U n i v e r s i t y o f B r i t i s h 2075 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5  Columbia  my  It is thesis  n o t be a l l o w e d w i t h o u t my  permission.  Department  thesis  be g r a n t e d by t h e h e a d o f  copying or publication of this  gain  further  copying of t h i s  d e p a r t m e n t 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 . understood that  I  make  written  - i i-  ABSTRACT  The  e f f e c t o f i n c r e a s i n g the c a l c i u m content o f a h a y - g r a i n  d i e t f e d t o p o s t p a r t u r i e n t d a i r y c a t t l e was s t u d i e d .  M i n e r a l apparent  d i g e s t i b i l i t i e s , serum c o n c e n t r a t i o n s and apparent m i n e r a l r e t e n t i o n s were monitored w h i l e the animals  were under the s t r e s s o f peak l a c t a t i o n .  N i n e H o l s t e i n and seven A y r s h i r e cows were randomly a s s i g n e d t o t h e c o n t r o l (0.7% Ca) o r the Ca-treatment (1.5% Ca) based on c a l v i n g order. Each animal . 05)  The d i e t s otherwise  c o n t a i n e d adequate n u t r i e n t s .  was f e d t o a p p e t i t e f o r 80 days w i t h no d i f f e r e n c e (p >  o c c u r r i n g between treatments  t a g e o f body weight.  i n i n t a k e when expessed as a percen-  D a i l y milk production  .05) as was t h e average body weight  (4% FCM) was h i g h e r  (p <  ( p < . 0 1 ) f o r the c o n t r o l animals  r e f l e c t i n g the d i s p r o p o r t i o n a t e number o f young animals  on the c a l c i u m  treatment. A f t e r a minimum o f 60 days on t r i a l ,  5 cows from each t r e a t -  ment were exposed t o a 5 day d i g e s t i b i l i t y c o l l e c t i o n p e r i o d . change i n o r g a n i c matter o r n i t r o g e n apparent d i g e s t i b i l i t y ( p > . 0 5 ) but t h e r e were h i g h e r increased  No  occurred  ( p < . 0 5 ) l e v e l s o f c a l c i u m and i r o n ,  ( p < . 0 1 ) l e v e l s o f copper, and lower ( p < . 0 5 ) z i n c and  molybdenum apparent d i g e s t i b i l i t i e s f o r animals F e c a l pH was h i g h e r  on the Ca-treatment.  ( p < . 0 5 ) i n the c a l c i u m t r e a t e d cows i n d i c a t i n g a  b u f f e r i n g e f f e c t o c c u r r e d as a r e s u l t o f the a d d i t i o n o f the c a l c i u m carbonate.  No change ( p > . 0 5 ) was e v i d e n t i n the s e c r e t i o n o f  m i n e r a l s i n t o the m i l k but u r i n a r y phosphorus e x c r e t i o n was  significantly  - i i i-  higher  ( p < . 0 5 ) i n the c o n t r o l group. M i l k p r o g e s t e r o n e was a n a l y z e d t o correspond b l o o d samples  (average o f 14 p e r animal)  to s p e c i f i c regions o f the e s t r u s c y c l e .  Serum phosphorus, i r o n , copper  and z i n c v a r i e d w i t h r e p r o d u c t i v e  c y c l i n g as phosphorus dropped ( p < . 0 1 ) a t the onset o f r e g u l a r e s t r u s w h i l e the o t h e r m i n e r a l s f l u c t u a t e d w i t h t h e c y c l e .05), i r o n  (p<.01)).  (copper and z i n c  (p<  In the serum o f C a - t r e a t e d a n i m a l s , c a l c i u m and  z i n c c o n c e n t r a t i o n s were h i g h e r ( p < . 0 1 ) , copper and phosphorus was lower  increased (p<.05),  ( p < . 0 1 ) than the l e v e l s f o r the c o n t r o l  mals.  Breed e f f e c t s were apparent  as both phosphorus and copper  higher  (p< .01) i n t h e serum o f A y r s h i r e s than o f H o l s t e i n s .  g l u c o s e c o n c e n t r a t i o n s proved not t o be d i f f e r e n t  aniwere  Plasma  ( p > . 0 5 ) between  treatments. Calcium  supplementation  o f the d i e t a l l o w e d the animals t o go  from a n e g a t i v e t o a p o s i t i v e c a l c i u m balance increased all,  (p<.01).  ( p < . 0 5 ) the amount o f phosphorus apparent  6 e s s e n t i a l m i n e r a l s had a l t e r e d apparent  I t also  retention.  digestibilities  In and/or  serum c o n c e n t r a t i o n s w i t h p o s s i b l e l o n g term e f f e c t s on animal metabolism.  - iv -  TABLE OF CONTENTS  Abstract  i i  L i s t of Tables Acknowledgements  v •  vi  Introduction  1  L i t e r a t u r e Review  3  Materials and Methods  17  a)  Data C o l l e c t i o n and Analysis  17  b)  S t a t i s t i c a l Analysis  22  Results and Discussion  26  Summary and Conclusions  70  Bibliography  75  Appendix  86  -  V  -  LIST OF TABLES  Table 1  Nutrient Content of Rations  27  Table 2  Other Nutrients i n Rations  28  Table 3  Performance Parameters  30  Table 4  Summary of Percentage Digestibilities  Table 5  Apparent 36  O r i g i n a l Milk Progesterone Category Descriptions  49  Additional Hypotheses, ANOVA #1 and #2  49  Combined Milk Progesterone Categories  51  Table 8  Additional Hypotheses, ANOVA #3  51  Table 9  Summary of Serum Constituents  54  Table 10  Total Daily Output of the Macro Elements i n the Milk and Urine  61  Apparent Percentage Retention of the Macro Elements  62  Summary of the Effects of Calcium Carbonate on the Apparent D i g e s t i b i l i t y , Serum Concentration and Apparent Retention of Dietary Minerals  73  Table 6 Table 7  Table 11 Table 12  - vi -  ACKNOWLEDGEMENTS  The author would l i k e to extend appreciation towards a l l those who offered guidance throughout the preparation of t h i s t h e s i s . To Dr. J.A. Shelford and Dr. R.G. Peterson who were f r e e l y open to consultation, I thank you for your stimulating thoughts and discussions.  To the other members of my committee, I thank you for  your encouragement.  For technical assistance I would l i k e to thank  Mabel Striker for her thoughts on computer analyses and G i l l e s Galzy f o r his expertise i n the f i e l d of atomic absorption.  Also, I extend  my appreciation to Evelyn Raine for typing t h i s document.  Finally, I  could not express adequately the support I received from my loving wife Adrienne.  - 1 -  INTRODUCTION  Calcium  has l o n g been r e c o g n i z e d as an e s s e n t i a l component i n  dairy cattle nutrition.  I t s f u n c t i o n s i n c l u d e s k e l e t a l growth and  maintenance as w e l l as many m e t a b o l i c  activities.  In d a i r y c a t t l e ,  m i l k p r o d u c t i o n and f e t a l growth a r e o f prime importance; both o f which depend on an adequate s u p p l y o f c a l c i u m . encountered i n h i g h m i l k p r o d u c i n g  The problem most o f t e n  cows i s the i n c r e a s e d need f o r  c a l c i u m can n o t be met d u r i n g the peak l a c t a t i o n p e r i o d f o l l o w i n g parturition.  The maximum a b s o r p t i o n r a t e o f d i e t a r y c a l c i u m i s i n s u f -  f i c i e n t t o meet the d r a i n o f c a l c i u m i n t o the m i l k r e s u l t i n g i n w i t h d r a w a l o f c a l c i u m from the s k e l e t a l s t o r e s . temporary c o n d i t i o n then the animal  I f t h i s i s only a  can r e c o v e r and r e p l a c e the l o s t  c a l c i u m when m i l k p r o d u c t i o n d e c r e a s e s .  However, i f i t i s prolonged  o r i f t h e demand i s t o o r a p i d t o enable  the m o b i l i z a t i o n procedure t o  i n i t i a t e , then s e r i o u s h e a l t h problems o c c u r . The  minimum l e v e l o f d i e t a r y c a l c i u m recommended by NRC  (1978) has i n the p a s t not allowed  s u f f i c i e n t uptake o f c a l c i u m t o  prevent  a n e g a t i v e c a l c i u m balance  during e a r l y l a c t a t i o n  data).  The apparent d i g e s t i b i l i t y o f t h i s c a l c i u m was low when com-  pared  w i t h t h e optimum l e v e l suggested  (unpublished  by Ramberg e t a l . (1974).  As  t h e r e l a t i o n s h i p was dependent on d i e t a r y i n t a k e l e v e l s , a study was p r o p o s e d t o i n v e s t i g a t e the p o s s i b i l i t y o f i n c r e a s i n g the amount o f c a l c i u m absorbed by f e e d i n g h i g h e r l e v e l s o f c a l c i u m t o p o s t p a r t u r i e n t  - 2 -  d a i r y cows. Factors increased  o t h e r than c a l c i u m a b s o r p t i o n  q u a n t i t i e s o f calcium are fed.  ingredients  within  may be a f f e c t e d when  Interactions  with  the d i g e s t i v e t r a c t , c o m p e t i t i o n f o r a b s o r p t i o n  s i t e s and a l t e r a t i o n s i n s t o r a g e and metabolism o f s e v e r a l can  occur.  minerals  T h i s p r e s e n t s a major d i f f i c u l t y i n e s t a b l i s h i n g minimum  r e q u i r e m e n t s f o r d i e t a r y n u t r i e n t s as these i n f l u e n c e s variable.  dietary  can be q u i t e  As w e l l , homeostatic c o n t r o l o f many o f the body m i n e r a l s  c o m p l i c a t e s any i n v e s t i g a t i o n o f m e t a b o l i c i n t e r a c t i o n s .  Whether  these i n t e r a c t i o n s manifest within  calcium  intake  necessary to allow greater  the range o f i n c r e a s e d absorption  o f c a l c i u m has n o t y e t  been demonstrated. Several  n o n - d i e t a r y f a c t o r s may a l s o a f f e c t d i g e s t i o n and  metabolism o f t h e m i n e r a l s . a major impact.  In a t r i a l  The p h y s i o l o g i c a l s t a t e o f t h e animal has such as t h i s , t h e stage o f l a c t a t i o n and  the m i l k y i e l d would be r e s p o n s i b l e  f o r the c a l c i u m d r a i n on the a n i -  mals.  c y c l i n g and animal h e a l t h  Age, pregnancy, r e p r o d u c t i v e  a l s o been i m p l i c a t e d al.,  1978).  i n a l t e r e d d i g e s t i o n and metabolism  have  (Thompson e t  Such f a c t o r s must be c o n s i d e r e d b e f o r e any meaningful  r e l a t i o n s h i p s can be e s t a b l i s h e d .  I t was the prime purpose o f t h i s study t o i n v e s t i g a t e the p o s s i b i l i t y o f r a i s i n g the amount o f c a l c i u m absorbed by animals under the  s t r e s s o f peak l a c t a t i o n .  A l t e r a t i o n s i n apparent uptake and  serum c o n c e n t r a t i o n s o f the r e l a t e d d i e t a r y n u t r i e n t s were o b s e r v e d . A l s o , an i n v e s t i g a t i o n was undertaken o f some o f the n o n - d i e t a r y f a c t o r s r e l a t e d to absorption  and r e t e n t i o n o f the m i n e r a l s .  - 3 -  LITERATURE REVIEW  The and  there  r o l e o f calcium  i n animal n u t r i t i o n has l o n g been  a r e many w e l l e s t a b l i s h e d f a c t s .  t h e o r i e s t h a t remain u n s u b s t a n t i a t e d to ambiguities sions.  There a r e a l s o many  due t o a l a c k o f documentation o r  from s i m i l a r experiments p r o v i d i n g  In t h i s study, t h e e f f e c t o f i n c r e a s e d  mineral absorption  differing  Unfortunately,  o f these m i n e r a l s r a r e l y does an  experimentor i n n u t r i t i o n d e a l w i t h a b a s i c c a u s a l - e f f e c t tionship.  rela-  Many f a c t o r s t h a t may appear i n c i d e n t a l t o the imposed  treatment o f t e n sent  conclu-  d i e t a r y c a l c i u m on  and the r e s u l t a n t c o n c e n t r a t i o n s  i n t h e serum were o f prime i n t e r e s t .  studied  i n f l u e n c e the outcome o f an experiment.  case these f a c t o r s may be a s s o c i a t e d  In the p r e -  with the f e e d s t u f f ; such as  t h e p h y s i c a l form, t h e c o r r e s p o n d i n g d i e t a r y components, o r the byproducts o f d i g e s t i o n . as age and p r o d u c t i o n conditions.  They c o u l d a l s o be p h y s i o l o g i c a l parameters such stresses or they could  r e s u l t from environmental  The o b j e c t i v e o f the f o l l o w i n g s e c t i o n i s t o i d e n t i f y  some o f t h e secondary i n t e r a c t i o n s t h a t occur w i t h c a l c i u m  and t o gain  i n s i g h t i n t o how these might a l t e r the d i g e s t i o n and metabolism o f dietary  calcium.  The  a d d i t i o n o f calcium  i n the form o f carbonate may r e s u l t  i n an a l t e r a t i o n i n the pH i n the d i g e s t i v e t r a c t . (1977) r e p o r t e d l e v e l s within  highly significant differences  the s m a l l  supplemental c a l c i u m  Wheeler and N o l l e r  ( p < . 0 1 ) between the pH  i n t e s t i n e , c o l o n and f e c e s o f c a t t l e f e d  carbonate v e r s u s those on unsupplemented d i e t s .  - 4 -  Such an a l t e r a t i o n i n the a c i d / b a s e  balance  c o u l d have  profound  e f f e c t s on the a v a i l a b i l i t y o f many o f the d i e t a r y m i n e r a l s . example, Ender and d i e t was  Dishington  For  (1970) proposed the a l k a l i n i t y o f the  the o v e r r i d i n g f a c t o r i n d e t e r m i n i n g  A c c o r d i n g t o Smith and McAllan  calcium  availability.  (1966) a p r e c i p i t a t i o n o f c a l c i u m  phosphate o c c u r r e d i n the s m a l l i n t e s t i n e o f ruminants.  The  degree o f  p r e c i p i t a t i o n i n c r e a s e d s l o w l y w i t h r i s i n g pH t o the l e v e l o f about 6.5  where i t then advanced r a p i d l y .  The  authors  a l s o showed an  i n c r e a s e d nonphosphate b i n d i n g o f c a l c i u m and magnesium i n the e f f l u e n t w i t h i n c r e a s i n g pH.  The  e x a c t nature o f the o r g a n i c  t u e n t s i n v o l v e d i n the b i n d i n g was  unknown.  ileal consti-  Grace e t a l . (1977) were  a b l e t o s e p a r a t e out a d i l u t e a l k a l i - i n s o l u b l e f r a c t i o n a s s o c i a t e d w i t h magnesium b i n d i n g . and  Richards  T h i s f r a c t i o n c o n t a i n e d p e c t i n , which M o l l o y  (1971) observed  magnesium and  calcium.  to be a b l e to b i n d v a r y i n g amounts o f  Smith and McAllan  (1966) observed  a com-  p e t i t i o n between magnesium and c a l c i u m f o r p a r t o f t h i s b i n d i n g m a t e r i a l o f which c a l c i u m was 5.5  and  above.  g e n e r a l l y bound more e f f i c i e n t l y a t  S u b s t a n t i a l pH dependent b i n d i n g o f c a t i o n s by  n o n - c e l l u l o s i c p o l y s a c c h a r i d e s o f the p l a n t c e l l w a l l has demonstrated by Branch e t a l . (1975).  These authors  pH  the  been  suggested  the  i o n i z a t i o n o f the c a r b o x y l groups o f u r o n i c a c i d might be r e s p o n s i b l e for  b i n d i n g a p p r e c i a b l e amounts o f d i e t a r y c a l c i u m . Other f a c t o r s which may  a l t e r c a l c i u m and magnesium a v a i l a b i -  l i t y a r e a l s o i n t e r r e l a t e d w i t h pH change.  Decreasing  the a c i d i t y o f  t h e abomasal d i g e s t a would cause g r e a t e r d i s s o c i a t i o n o f p r o t e i n s ,  - 5 -  carbohydrates  and  o t h e r such o r g a n i c m o l e c u l e s .  T h i s would a l l o w  i n c r e a s e d o p p o r t u n i t y f o r the b i n d i n g o f c a l c i u m and magnesium i o n s by electrostatic attraction shown by Chang and potent  Carr  ( S t o r r y , 1961b).  N u c l e i c a c i d s have been  (1968, c i t e d by B r a i t h w a i t e , 1976)  c a l c i u m b i n d i n g agents down t o pH  5.5.  to be  Also, p r e c i p i t a t i o n of  c a l c i u m and magnesium soaps has o c c u r r e d a t h i g h e r pH l e v e l s espec i a l l y when f a t was Brethour,  1958).  added to the d i e t  ( S t o r r y , 1961b; T i l l m a n  and  E a r l y work done by T a l a p a t r a e t a l . (1948)  d i s c o u n t e d the i n f l u e n c e o f known c a l c i u m b i n d i n g agents, l a t e and p h y t a t e , i n ruminants.  such as oxa-  T h i s pH dependent p r e c i p i t a t i o n  a p p a r e n t l y d i d not occur as these complexes were m e t a b o l i z e d  by rumen  microorganisms. Whether the e f f e c t o f d i e t a r y p r o t e i n on c a l c i u m i s o n l y pH r e l a t e d i s i n c o n c l u s i v e . decreased due  Braithwaite  (1978)  suggested  c a l c i u m r e t e n t i o n i n p r o t e i n d e f i c i e n t sheep may  t o decreased  A v a i l a b i l i t y o f c a l c i u m from i n o r g a n i c  tended to be h i g h e r than t h a t from o r g a n i c sources The  p o s s i b l y be  c a l c i u m b i n d i n g p r o t e i n , hence a decreased  calcium absorption.  1957).  absorption  authors  suggested  decreased  rate of sources  (Hansard e t a l . ,  l e v e l s of d i e t a r y protein  be p a r t i a l l y r e s p o n s i b l e f o r the i n c r e a s e d a v a i l a b i l i t y .  Perhaps up  t o a c e r t a i n amount o f d i e t a r y p r o t e i n i s r e q u i r e d f o r optimum t i o n o f c a l c i u m but f u r t h e r amounts tend to decrease  the  absorp-  availability  o f the c a l c i u m depending on the pH o f the d i g e s t a . A change i n pH w i t h i n the i n t e s t i n a l t r a c t may  may  alter  the  a v a i l a b i l i t y o f c a l c i u m y e t have no e f f e c t on the amount absorbed.  - 6 -  T h i s c o u l d happen i f the a l t e r a t i o n i n a c i d i t y o c c u r r e d a f t e r the where most c a l c i u m was al.,  1975;  absorbed.  Grace e t a l . , 1974;  S e v e r a l authors  K l o o s t e r , 1976)  (Ben-Ghedalia  area  et  r e p o r t e d the major  o f c a l c i u m a b s o r p t i o n i n ruminants t o be the upper s m a l l  site  intestine.  Other workers showed s i g n i f i c a n t c a l c i u m a b s o r p t i o n p r i o r to t h i s area.  F o r example, C r a g l e  from the abomasum.  (1973) proposed a net a b s o r p t i o n o f c a l c i u m  L e i b h o l z (1974) i n d i c a t e d as much as 50%  c a l c i u m a b s o r p t i o n o c c u r r e d b e f o r e the d i g e s t a reached sheep t h a t were i n p o s i t i v e c a l c i u m b a l a n c e .  of  the duodenum i n  In the c a l f , the aboma-  sum  a c t i v e l y p a r t i c i p a t e d i n c a l c i u m uptake (Yang and  The  p r e c i p i t a t i o n o f i n s o l u b l e c a l c i u m phosphate, a c c o r d i n g t o Smith  and  McAllan  6.5.  (1966), was  Thomas, 1965).  not a p p r e c i a b l e u n t i l the pH exceeded about  Most r e p o r t s i n d i c a t e d the pH o f the m a t e r i a l f l o w i n g through  t h e upper s e c t i o n s o f ruminant's s m a l l i n t e s t i n e remained a c i d i c (Ben-Ghedalia  e t a l . , 1975;  Wheeler, 1980;  Kay,  1969;  Yano e t a l . , 1979).  1977;  Only as the d i g e s t a advanced  t h e i n t e s t i n e d i d the pH r i s e above 6.5 calcium s o l u b i l i t y occurred.  wheeler and N o l l e r ,  along  and a concomitant decrease  T h i s i n f o r m a t i o n would t h e r e f o r e  in  suggest  t h e c a l c i u m a v a i l a b i l i t y i n the prime areas f o r a b s o r p t i o n would not be  i n f l u e n c e d by the i n c r e a s e i n pH r e s u l t i n g from the a d d i t i o n a l  d i e t a r y calcium  carbonate.  S i m i l a r occurrences  c o u l d b e n e f i t o r be d e t r i m e n t a l to o t h e r  m i n e r a l a v a i l a b i l i t i e s depending on t h e i r s i t e s o f a b s o r p t i o n . Magnesium and phosphorus a r e the m i n e r a l s most o f t e n a s s o c i a t e d with c a l c i u m i n terms o f a v a i l a b i l i t y .  Phosphorus appears t o be  absorbed  - 7 -  i n t h e same r e g i o n as does c a l c i u m  (Ben-Ghedalia  e t a l . , 1975; Grace  e t a l . , 1974; K l o o s t e r , 1976) with some n e t a b s o r p t i o n o c c u r r i n g w i t h i n the reticulo-rumen  ( C r a g l e , 1973).  absorption are c o n f l i c t i n g .  Cragle  Reports on magnesium  (1973) and Smith and McAllan  (1966) c l a i m e d the main s i t e t o be the upper s m a l l i n t e s t i n e  while  Ben-Ghedalia e t a l . (1975) and Grace e t a l . (1974; 1977) proposed a b s o r p t i o n t o take p l a c e p r i m a r i l y i n the forestomach and c o l o n Both magnesium and phosphorus have been r e p o r t e d t o decrease b i l i t y p a s t t h e midpoint 1975).  o f the small i n t e s t i n e  (Ben-Ghedalia  L i k e c a l c i u m , phosphorus a b s o r p t i o n s h o u l d be l i t t l e  by a pH change i n the lower s m a l l i n t e s t i n e .  areas.  i n soluet a l . , affected  Depending on the t r u e  s i t e o f a b s o r p t i o n o f magnesium, a r i s e i n a l k a l i n i t y may o r may n o t have a profound  The  interaction.  modifying  i n f l u e n c e o f the r a t i o o f concentrations o f  d i e t a r y c a l c i u m t o phosphorus on a b s o r p t i o n and metabolism o f each o f these minerals  i s o f t e n c i t e d i n the l i t e r a t u r e .  Various  dietary  r a t i o s o f c a l c i u m t o phosphorus have been f e d t o ruminants, r a n g i n g from l e s s than  1:1 t o g r e a t e r than  t h a t r a t i o s lower than 1967;  10:1.  1:1 decreased  There i s g e n e r a l agreement  calcium absorption  (Manston,  Wise e t a l . , 1963) but r a t i o s between 1:1 and 7:1 produced no  a l t e r e d absorption 1963).  (Lomba e t a l . , 1969; Manston, 1967; Wise e t a l . ,  These same authors  concluded  u n a f f e c t e d by a l t e r i n g d i e t a r y Lueker and Lofgreen  a b s o r p t i o n o f phosphorus was  ratios.  (1961) observed  no e f f e c t o f t h e r a t i o  - 8 -  (even up t o 10:1) on a b s o r p t i o n but d i d f i n d an i n f l u e n c e upon the e x c r e t i o n o f m e t a b o l i c f e c a l phosphorus.  The phosphorus appeared t o  be absorbed i n d i r e c t r e l a t i o n t o d i e t a r y phosphorus i n t a k e , whereas c a l c i u m was more i n f l u e n c e d by p h y s i o l o g i c a l parameters. experiment w i t h c a l c i u m d e f i c i e n t sheep, B r a i t h w a i t e  In an  (1975)  summarized  i n t h a t i n s t a n c e , phosphorus r e t e n t i o n was c o n t r o l l e d by t h e r a t e o f calcium retention.  I t t h e r e f o r e appears t h a t w i t h i n a wide range o f  c a l c i u m t o phosphorus r a t i o s , n e i t h e r m i n e r a l w i l l be  differentially  absorbed but phosphorus e x c r e t i o n may be a l t e r e d . T h i s wide v a r i a b i l i t y i n the p r a c t i c a l d i e t a r y r a t i o s o f c a l c i u m t o phosphorus l e v e l s i n ruminant f e e d s t u f f s i s i n c o n t r a s t t o t h e narrow p r o p o r t i o n s a c c e p t a b l e f o r monogastric a n i m a l s .  Most  single  stomached a n i m a l s r e q u i r e the c a l c i u m and phosphorus i n the d i e t t o be t i g h t l y r e g u l a t e d around 2:1, the r a t i o o f c a l c i u m t o phosphorus i n t h e bone. between  Smith and M c A l l a n (1966) demonstrated a d i r e c t  relationship  the c o n c e n t r a t i o n o f i n o r g a n i c phosphate and t h a t o f bound  c a l c i u m i n the i n t e s t i n a l d i g e s t a .  T h i s was dependent on the c a l c i u m  t o phosphorus r a t i o and the i n t e s t i n a l pH l e v e l .  A l t e r i n g the  c a l c i u m t o phosphorus r a t i o i n monogastric d i e t s would have cons i d e r a b l y g r e a t e r e f f e c t on the c a l c i u m and phosphorus a v a i l a b i l i t y as t h e pH o f the duodenal and i l e a l c o n t e n t s i s h i g h e r i n monogastric a n i m a l s than i t i s i n ruminants (Wheeler, 1980).  Through r e c e n t advances i n r a d i o a c t i v e t r a c e r t e c h n i q u e s some o f t h e mechanisms o f c a l c i u m a b s o r p t i o n have been e l u c i d a t e d .  To gain  - 9 -  i n s i g h t i n t o the i n t e r a c t i o n s o f i n c r e a s e d c a l c i u m i n the d i e t other d i e t a r y minerals i t i s necessary  t o a p p r e c i a t e the  of t h i s mineral's absorption process.  The method o f c a l c i u m  with  complexities absorp-  t i o n i n non-ruminants proposed by Wasserman and T a y l o r (1973, c i t e d Braithwaite,  1974)  was  used by the author  t o e x p l a i n the  by sheep t o changes i n c a l c i u m i n t a k e .  T h i s concept  cesses.  d i f f u s i o n a l one  The  f i r s t was  a non-saturable,  c o n c e n t r a t i o n o f c a l c i u m i n the i n t e s t i n e . s a t u r a b l e , a c t i v e process  The  r e l a t e d t o body needs.  by  adaptations  i n v o l v e d two  pro-  r e l a t e d to the  second was  a  Braithwaite  (1976)  p o s t u l a t e d the a c t i v e a b s o r p t i o n method to be the major c o n t r o l mechanism f o r c a l c i u m a b s o r p t i o n and on bone c a l c i u m r e s e r v e s . (1961a) suggested i n t e s t i n e was The  s t a t e d t h a t i t p r o b a b l y was  E a r l i e r work by S c o t t (1965) and  Storry  o n l y a s m a l l f r a c t i o n o f the c a l c i u m i n the sheeps  absorbed by simple d i f f u s i o n o f the f r e e i o n . a c t i v e a b s o r p t i o n o f c a l c i u m has been observed  (1976) to be dependent on v i t a m i n D. cholecalciferol  The m e t a b o l i t e  by DeLuca  1, 25-dihydroxy-  (D.C.C.) as w e l l as v i t a m i n D-induced c a l c i u m -  b i n d i n g p r o t e i n s have been i m p l i c a t e d i n the p r o c e s s . understood  dependent  It i s therefore  t h a t depending on an adequate s u p p l y o f v i t a m i n D,  the  a b s o r p t i o n o f c a l c i u m from the d i e t s f e d t o ruminants can be s t r o n g l y i n f l u e n c e d by t h e i r m e t a b o l i c  requirements  f o r calcium.  Another p o s s i b l e c o m p l i c a t i o n when c o n s i d e r i n g m i n e r a l i n t e r a c t i o n s w i t h c a l c i u m i s the e x c r e t i o n o f m e t a b o l i c the d i g e s t i v e t r a c t .  Braithwaite  calcium  into  (1976) summarized the main l o s s e s o f  c a l c i u m and phosphorus i n t o the i n t e s t i n e as t h a t due  to the d i g e s t i v e  - 10 -  juices.  However, the amount o f endogenous c a l c i u m e x c r e t e d appears t o  be r e l a t i v e l y s t a b l e over v a r i e d c o n d i t i o n s .  Lueker and  Lofgreen  (1961) r e p o r t e d e s s e n t i a l l y c o n s t a n t e x c r e t i o n o f c a l c i u m from d i e t s w i t h a h i g h l y v a r i a b l e c a l c i u m content and phosphorus r a t i o n s (0.8:1 t o 6.0:1). Hansard e t a l . (1954; 1957) suggested  S i m i l a r r e s u l t s were produced by  and Lengemann (1965).  The  latter  author  the amount o f endogenous c a l c i u m l o s t i n t o the d i g e s t i v e  t r a c t o f d a i r y c a t t l e was serum.  a wide range o f c a l c i u m to  dependent on the l e v e l o f c a l c i u m i n the  T h i s dependency was  p r e v i o u s l y r e p o r t e d t o occur  ruminants by Gran (1960, c i t e d by B r a i t h w a i t e , 1976). (1970) i n d i c a t e d a b i a s may i n t o the i n t e s t i n e may calcium.  e x i s t such t h a t m e t a b o l i c  in  non-  Ramberg e t a l . calcium  excreted  be p r e f e r e n t i a l l y absorbed over d i e t a r y  When comparing a b s o r p t i o n r a t e s from d i e t s v a r y i n g i n  c a l c i u m c o n t e n t , A l i and  Evans (1967) i n f e r r e d p a r t o f the reason f o r  lower a b s o r p t i o n from d i e t s s u p p l y i n g l i t t l e c a l c i u m would be due  to  lower c a l c i u m i n the duodenal s e c r e t i o n s and hence l e s s a v a i l a b l e c a l c i u m . V i s e k e t a l . (1953) determined a l a c k o f e f f e c t on e x c r e t i o n due  t o i n c r e a s i n g age when the r a t e s were c o r r e c t e d f o r  bodyweight.  T h i s i n f o r m a t i o n was  i n f e r i t was  p o s s i b l e t o measure the u t i l i z a t i o n o f c a l c i u m  used by Hansard e t a l . (1954) to  v a r i o u s d i e t a r y sources p r o v i d i n g t h e r e was o f animals  calcium  a constancy  o f known age and n u t r i t i o n a l s t a t u s .  from  w i t h i n groups  A b s o r p t i o n measured  by apparent d i g e s t i b i l i t y assumes c o n s t a n t endogenous e x c r e t i o n . Ramberg e t a l . (1974) concluded  t h i s assumption met  were averaged over a week o r more.  i f the f e c a l  data  - 11 -  Many o f t h e above mentioned f a c t o r s may a c t s e p a r a t e l y o r i n combination  such t h a t the type o f f e e d s t u f f i n f l u e n c e s the q u a n t i t y o f  c a l c i u m absorbed.  Calcium  i n m i l k was shown t o be almost  a v a i l a b l e t o ruminants by Hansard e t a l . (1954).  However, i n f o r a g e  d i e t s , l e s s than 40% a v a i l a b i l i t y i s g e n e r a l l y r e p o r t e d 1975;  B r a i t h w a i t e and R i a z u d d i n ,  totally  (Braithwaite,  1971; Paquay e t a l . , 1968).  When  g r a i n was added t o an a l l f o r a g e d i e t , Conrad and Hibbs (1973) i n d i c a t e d an improved c a l c i u m a v a i l a b i l i t y o c c u r r e d . Unsworth (1978) concluded  Stevenson and  the type o f roughage-cereal  diet fed to  sheep had a s i g n i f i c a n t e f f e c t on the apparent a v a i l a b i l i t y and r e t e n t i o n o f calcium.  Calcium  from i n o r g a n i c sources has been demonstrated  t o be s l i g h t l y more a v a i l a b l e than from o r g a n i c sources al.,  1957).  Such r e s u l t s would make i t n e c e s s a r y  (Hansard e t  to u t i l i z e  virtually  i d e n t i c a l d i e t s , v a r y i n g o n l y i n c a l c i u m c o n t e n t , t o determine any true e f f e c t s o f calcium  supplementation.  U t i l i z i n g blood mineral  l e v e l s t o i n d i c a t e the c o n c e n t r a t i o n  o f those m i n e r a l s w i t h i n the body can l e a d t o gross i n a c c u r a c i e s . Most m i n e r a l s e x i s t i n separate ments w i t h i n t h e body.  forms r e f e r r e d t o as p o o l s o r compart-  F o r example, B r a i t h w a i t e e t a l . (1969) pro-  posed t h e e x i s t e n c e o f s i x compartments o f c a l c i u m i n sheep, one o f which was serum.  The c o n c e n t r a t i o n o f c a l c i u m i n any o f these  depended on m e t a b o l i c  needs as w e l l as d i e t a r y i n t a k e .  pools  The main  s t o r a g e compartment appeared t o be t h e bone which was under p o s i t i v e hormonal c o n t r o l .  Copp (1969) i n d i c a t e d the p a r a t h y r o i d hormone  i n c r e a s e d the r a t e o f c a l c i u m a b s o r p t i o n i n t o the bone w h i l e  thyro-  - 12  -  c a l c i t o n i n caused a r e l e a s e o f c a l c i u m  from the bone.  The  intermediate  p o o l s a l l a c t e d t o b u f f e r the system such t h a t the serum most d i d not r e f l e c t t o t a l body s t o r a g e o f c a l c i u m . concluded  Ramberg e t a l . (1976)  the c o n c e n t r a t i o n o f c a l c i u m i n the serum remained  remarkably c o n s t a n t  over wide ranges o f c a l c i u m i n t a k e which r e f l e c t e d  the e f f e c t i v e n e s s o f the homeostatic c o n t r o l .  Blood v a l u e s  however, show enough v a r i a b i l i t y t o p r o v i d e a r e a s o n a b l e d i e t a r y intake  One  (McDonald and  Belonje,  do  estimation of  1975).  o f the more profound f a c t o r s which may  e x e r t an i n f l u e n c e  on the imposed treatments o f an experiment d e a l i n g w i t h balance  likely  i s the p h y s i o l o g i c a l s t a t e o f the a n i m a l s .  mineral  Thompson e t a l .  (1978) s t a t e d t h a t a meaningful q u a n t i t a t i v e r e l a t i o n s h i p between d i e t and  b l o o d c o u l d o n l y be determined when allowances were made f o r  d i e t a r y f a c t o r s which a f f e c t the b l o o d c o n s t i t u e n t s . c o n s i d e r a t i o n s were age, and  Some o f  stage o f l a c t a t i o n , m i l k p r o d u c t i o n ,  non-  these gestation  animal h e a l t h . Braithwaite  (1975) r e p o r t e d the e f f i c i e n c y o f a b s o r p t i o n  d i e t a r y c a l c i u m to be h i g h and calcium  r e l a t i v e l y c o n s t a n t over wide ranges o f  i n t a k e s i n young growing ruminants.  decreased  with i n c r e a s i n g calcium  decreased  w i t h age  young a n i m a l s ,  However, t h i s  The  generally  author s t a t e d t h a t i n  "the r a t e o f a b s o r p t i o n i s l i m i t e d by the whereas i n o l d e r animals,  availability  "the e f f i c i e n c y o f  a b s o r p t i o n does not t o any s i g n i f i c a n t degree r e f l e c t the of dietary calcim."  efficiency  i n t a k e i n o l d e r animals and  ( B r a i t h w a i t e , 1976).  of d i e t a r y calcium,"  of  Here, the decrease i n e f f i c i e n c y o f  availability absorption  - 13 -  w i t h i n c r e a s i n g age was  p o s t u l a t e d t o r e f l e c t decreased  calcium  requirements. T h i s f l u c t u a t i o n , as w e l l as t h a t o f o t h e r m i n e r a l s , has m o n i t o r e d i n the b l o o d by workers a t t e m p t i n g disorders.  I n o r g a n i c phosphorus had year  t o diagnose m i n e r a l  Thompson e t a l . (1978) i n d i c a t e d a g e n e r a l decrease  c a l c i u m , phosphorus, sodium, potassium  and  the most dramatic  group t o the f i v e t o s i x year group.  t h e same c o n c l u s i o n s .  been  in  copper w i t h i n c r e a s i n g age. d e c l i n e from the under t h r e e Not  a l l r e s e a r c h e r s drew  Tumbleson e t a l . (1973) produced  similar  r e s u l t s f o r c a l c i u m and i n o r g a n i c phosphorus but r e p o r t e d no e f f e c t o f age  on sodium o r p o t a s s i u m .  Kitchenham e t a l . (1975) i n d i c a t e d no.  s i g n i f i c a n t r e l a t i o n s h i p e x i s t e d between c a l c i u m , sodium, potassium, copper o r i r o n and  age.  These authors  a l s o s t a t e d t h a t adjustment o f  i n o r g a n i c phosphorus c o n c e n t r a t i o n s f o r age was due  t o the s m a l l s i z e o f the r e d u c t i o n and the r e l a t i v e i n c o n s i s t e n c y  o f the measurement among h e r d s . age  perhaps u n j u s t i f i e d  However, i n c o r p o r a t i n g the e f f e c t o f  i n t o a study on m i n e r a l a b s o r p t i o n and b l o o d c o m p o s i t i o n  sidered  was  con-  necessary. D u r i n g the p e r i o d o f h i g h c a l c i u m demand f o l l o w i n g the  onset  o f l a c t a t i o n , c a l c i u m a b s o r p t i o n has been shown by Symonds e t a l . (1966) to i n c r e a s e .  The  authors  concluded  however, t h i s i n c r e a s e  i n s u f f i c i e n t t o s u p p l y the needs o f l a c t a t i o n and the animal was t h r u s t i n t o negative calcium balance.  was soon  Ramberg e t a l . (1970) a l s o  demonstrated a r i s e i n c a l c i u m a b s o r p t i o n from the gut e a r l y a f t e r o n s e t o f l a c t a t i o n which was  the  independent o f the d i e t a r y c a l c i u m i n t a k e .  -  -  14  T h i s i n c r e a s e i n c a l c i u m a b s o r p t i o n a f t e r c a l v i n g has been d e s c r i b e d by B r a i t h w a i t e  e t a l . (1972) and K l o o s t e r  (1976) t o be p r i m a r i l y an  i n c r e a s e i n e f f i c i e n c y o f a b s o r p t i o n a l o n g w i t h some decrease i n f e c a l endogenous c a l c i u m .  T h i s r e l a t i o n s h i p was apparent i n mature animals  as w e l l , which t e m p o r a r i l y r e v e r s e d the decreased t i o n due t o age.  Braithwaite  (1976) used t h i s i n f o r m a t i o n t o f u r t h e r  e l u c i d a t e on the t h e o r y o f decreased requirements i n o l d e r animals. were r e g e n e r a t e d ,  e f f i c i e n c y o f absorp-  a b s o r p t i o n b e i n g due t o  decreased  Once l a c t a t i o n ceased and body s t o r e s  the e f f i c i e n c y o f a b s o r p t i o n r e t u r n e d t o i t s nor-  m a l l y low l e v e l . In s t u d y i n g the m e t a b o l i c and  p r o f i l e o f d a i r y c a t t l e , Manston  Rowlands (1973) r e p o r t e d the v a r i a t i o n i n plasma i n o r g a n i c c o n s t i -  t u e n t s among cows w i t h i n the same m i l k y i e l d group t o be l e s s than t h a t among a l l cows w i t h i n the h e r d .  Rowlands and Pocock (1976)  suggested the cows s h o u l d be s e l e c t e d by t h e i r stage o f l a c t a t i o n r a t h e r than t h e i r m i l k y i e l d .  T h i s i n c r e a s e d the a c c u r a c y  o f the t e s t  as t h e b l o o d c o n s t i t u e n t s appeared t o be more v a r i a b l e the c l o s e r the date o f sampling was t o c a l v i n g .  I t was t h e r e f o r e i n f e r r e d t h a t both  s t a g e o f l a c t a t i o n and m i l k y i e l d should be c o n s i d e r e d  i n any com-  parisons o f blood c o n s t i t u e n t s . Work done on b l o o d m i n e r a l  concentrations with r e l a t i o n s h i p  t o e s t r u s c y c l i n g has l e d t o i m p l i c a t i o n s t h a t r e p r o d u c t i v e may  i n f l u e n c e serum m i n e r a l  levels.  hormones  Bach and Messervey (1969)  r e p o r t e d p o s s i b l e s u b c l i n i c a l hypocalcemia a f t e r the e s t r u s p e r i o d i n dairy cattle.  The authors  noted a drop i n the d i f f u s i b l e  calcium  -In-  f r a c t i o n over e s t r u s and p o s t u l a t e d t h a t e s t r o g e n enhanced p r o d u c t i o n of  the c a l c i u m b i n d i n g p r o t e i n .  B r a i t h w a i t e e t a l . (1972)  demonstrated t h a t e s t r o g e n a d m i n i s t e r e d to sheep i n c r e a s e d the r a t e o f c a l c i u m a b s o r p t i o n , r e t e n t i o n and bone a c c r e t i o n .  Plasma copper i n  r a t s changed as plasma e s t r o g e n v a r i e d d u r i n g the e s t r u s c y c l e (Sato and  Henkin, 1973).  The  authors c o n s i d e r e d t h i s t o be due  stimulated ceruloplasmin synthesis.  to  estrogen  However, Money e t a l . (1967)  r e p o r t e d no e f f e c t on b l o o d o r l i v e r copper l e v e l s when e s t r o g e n s were a d m i n i s t e r e d t o sheep.  Plasma z i n c c o n c e n t r a t i o n s v a r i e d l i t t l e  in  h e i f e r s taken a t v a r i o u s s t a g e s o f the e s t r u s c y c l e (Dufty e t a l . , 1977).  A c c o r d i n g t o Underwood (1977), manganese metabolism  i n f l u e n c e d by e s t r o g e n i c hormones.  Any  e a r l y pregnancy would most l i k e l y be due  influence of gestation i n t o an a l t e r a t i o n i n hormone  l e v e l s r a t h e r than m i n e r a l demand f o r f e t a l  Breed  growth.  e f f e c t s have been r e p o r t e d i n two p a p e r s .  c a l c i u m , potassium  was  Serum  and magnesium were a n a l y z e d by Kitchenham  and  Rowlands (1976) to be s i g n i f i c a n t l y d i f f e r e n t between H o l s t e i n s and Ayrshires.  South A f r i c a n c a t t l e breeds were shown by Heynes (1971) to  have d i f f e r e n t b l o o d m i n e r a l l e v e l s .  While t h e r e i s r e l a t i v e l y  little  i n f o r m a t i o n on t h i s parameter, these d i f f e r e n c e s warrent f u r t h e r study.  Seasonal to  f l u c t u a t i o n s i n b l o o d m i n e r a l l e v e l s have been t i e d  v a r i a t i o n s i n d i e t s due  t o a l t e r e d c l i m a t e , s o i l c o n d i t i o n s and  methods o f management (Manston and 1979;  Thompson e t a l . ,  excluded  1978).  Rowlands, 1973;  Such environmental  from a c o n t r o l l e d e x p e r i m e n t a l  situation.  Rowlands e t a l . , f a c t o r s can  be  - 16 -  Blood sampling  times and methods were a l s o demonstrated t o  a f f e c t b l o o d parameters.  Plasma volume was i n f l u e n c e d by water i n t a k e  o r by f e e d i n g on d i e t s c o n t a i n i n g h i g h water c o n t e n t 1978).  (Thompson e t a l . ,  T h i s i n t u r n had a d i l u t i n g e f f e c t on component l e v e l s .  The  c o n s t i t u e n t s r e t u r n e d t o t h e i r normal l e v e l s w i t h i n f o u r t o s i x hours after feeding. excitement  Dougherty (1970) concluded v e n i p u n c t u r e  i n the animal  c o u l d cause  r e s u l t i n g i n a l t e r e d g l u c o s e , c a l c i u m and  p o s s i b l y other blood c o n s t i t u e n t s .  C o n s i d e r i n g these f a c t o r s ,  attempt s h o u l d be made t o keep b l o o d sampling  every  times and methods as  c o n s i s t e n t as p o s s i b l e between sample p e r i o d s .  To c o n c l u d e , i t i s e v i d e n t t h a t t h e r e a r e many f a c t o r s which might a f f e c t t h e r e s u l t s o f t h e p r e s e n t experiment.  These  concerns  range from the type o f f e e d s t u f f f e d t o the p h y s i o l o g i c a l s t a t e o f the a n i m a l s used on t h e t r i a l s . the experimental age,  To minimize any confounding  interactions,  d e s i g n s h o u l d i n c l u d e animal parameters such as  s t a g e o f l a c t a c t i o n , m i l k p r o d u c t i o n , r e p r o d u c t i v e c y c l i n g and  breed.  Treatment r a t i o n s s h o u l d be as c h e m i c a l l y and p h y s i c a l l y  simi-  l a r as p o s s i b l e c o n t a i n i n g s u f f i c i e n t n u t r i e n t s t o a l l o w optimum h e a l t h , growth and p r o d u c t i o n .  U n c o n t r o l l a b l e parameters such as  a l t e r e d g a s t r o - i n t e s t i n a l a c i d i t y s h o u l d be monitored  as c l o s e l y as  p o s s i b l e t o g a i n i n f e r e n c e t o any r e s u l t i n g c o m p l i c a t i o n s . b l o o d sampling  procedures  s h o u l d be c o n s i s t e n t throughout  Finally, the t r i a l .  -  ]7  -  MATERIALS AND METHODS  a)  Data C o l l e c t i o n and A n a l y s i s : The experiment was c a r r i e d out between September 1979 and  April  1980 on the U.B.C. campus d a i r y h e r d .  Both H o l s t e i n and  A y r s h i r e cows due t o c a l v e d u r i n g t h i s p e r i o d were used. a p p r o x i m a t e l y e q u a l numbers o f each b r e e d .  There were  One t h i r d o f the a v a i l a b l e  a n i m a l s were h e i f e r s , the o l d e s t cows were between 6 and 7 y e a r s a t c a l v i n g and the average age was 42 months.  The animals from each  b r e e d were randomized a c r o s s 2 t r e a t m e n t s depending on o r d e r o f calving.  Of the 22 a n i m a l s expected t o c a l v e , 2 d i d not c a l v e d u r i n g  the  p e r i o d and 4 o t h e r s were removed from the t r i a l  trial  problems a s s o c i a t e d w i t h abnormal per  calving.  T h i s r e s u l t e d i n 8 cows  t r e a t m e n t , e q u a l numbers o f each b r e e d on the c o n t r o l d i e t but 5  H o l s t e i n s and 3 A y s h i r e s on the c a l c i u m t r e a t m e n t . remained on the t r i a l to  due t o  f o r 80 days postpartum.  enhance any i n t e r a c t i o n s due t o p r o d u c t i o n  Each animal  T h i s p e r i o d was chosen stress.  The d i e t s were f o r m u l a t e d t o i n c l u d e recommended minimun l e v e l s o f a l l n u t r i e n t s as suggested by the N a t i o n a l Research C o u n c i l (1978). (as  A commercial d a i r y c o n c e n t r a t e c o n t a i n i n g 14% crude p r o t e i n  f e d b a s i s ) and a v i t a m i n - m i n e r a l pre-mix was f e d a l o n g w i t h  chopped, o r c h a r d g r a s s hay a t a r a t i o o f 60% hay:40% g r a i n . A g r i c u l t u r a l grade l i m e s t o n e (CaCOj) was added t o the g r a i n of  t h e c a l c i u m treatment t o r a i s e the c o n c e n t r a t i o n o f c a l c i u m from  0.7% t o 1.5% o f the d i e t . in  fraction  advance o f the t r i a l  A l l components o f the d i e t s were c o l l e c t e d  t o reduce the v a r i a b i l i t y i n the i n g r e d i e n t s .  - 18 -  Loose cobalt-iodized s a l t was made available to the cows. Dry cows were brought into maternity s t a l l s approximately one week p r i o r to calving where the orchardgrass hay was introduced to their diet.  After p a r t u r i t i o n , the t r i a l rations were fed i n  increasing quantities u n t i l ad libitum intakes occurred.  Feed intakes  reached upwards of 3.5% of body weight per day f o r most cows by one week postpartum.  The animals were moved to a f r e e - s t a l l barn where  each cow was fed i n d i v i d u a l l y using the Calan door system.  Feed  l e v e l s were adjusted p e r i o d i c a l l y to ensure the animals consumed a l l that was weighed out f o r them.  Small quantities of unspoiled feed  l e f t i n a bunk was removed and mixed with the next feed. Weighbacks were c o l l e c t e d and stored f o r analyses when larger volumes of feedstuffs remained.  Occasional checks of intake l e v e l s were made by  removing some of the animals from the f r e e - s t a l l area and placing them i n stanchions where closer observations were made.  Throughout the  t r i a l , feeding occurred twice d a i l y coinciding with milking. D a i l y records were kept of individual cow feed intakes and milk production.  Once the milk was analyzed f o r milk f a t percentage , +  the t o t a l milk production was adjusted to the standard 4% f a t corrected milk.  Water intakes were not monitored although samples were collected  p e r i o d i c a l l y f o r mineral analyses.  +  Weekly feed samples were collected  I n f r a - R e d Milk Analysis, Provincial Government Dairy Testing  Laboratory, Burnaby, B.C.  - 19 -  and s t o r e d f o r f u t u r e t e s t i n g .  From a p p r o x i m a t e l y 10 days a f t e r  c a l v i n g , m i l k s t r i p p i n g samples were taken e v e r y second morning. P r o g e s t e r o n e l e v e l s were determined on these samples by the method o f S h e l f o r d e t a l . (1979).  Based  on observed heats and p r o g e s t e r o n e p r e d i c t e d h e a t s ,  b l o o d samples were taken from the j u g u l a r v e i n a t v a r i o u s s t a g e s o f the reproductive cycle.  The average number o f samplings per cow was 14  w i t h a range o f 9 to 16.  Blood samples were c o l l e c t e d between the  a f t e r n o o n m i l k i n g p e r i o d and the subsequent  feeding period.  A l l cows  were weighed a f t e r t h e y were b l e d . Approximately  30 ml b l o o d was drawn f o r serum m i n e r a l a n a l y -  s e s as w e l l as 10 ml f o r plasma g l u c o s e d e t e r m i n a t i o n . r e a d i n g s were undertaken not a l t e r g r e a t l y . then f i l t e r  Hematocrit  on random samples t o ensure plasma volume d i d  A f t e r c o a g u l a t i o n , the samples were c e n t r i f u g e d  s e p a r a t e d . Any samples which e x h i b i t e d v i s i b l e  hemolysis  were noted as t h i s c o n d i t i o n can g r o s s l y i n f l u e n c e serum magnesium and potassium  l e v e l s ( C h r i s t i a n and Feldman, 1970).  The serum was d i v i d e d  o i n t o 2 s t o r a g e v i a l s which were kept f r o z e n the  (-18 C) u n t i l the end o f  trial. F i v e cows from each treatment were c o n f i n e d i n s t a n c h i o n s  where data was c o l l e c t e d t o determine apparent d i g e s t i b i l i t i e s o f the feed minerals.  The animals chosen  f o r t h i s t r i a l were ones t h a t had  been consuming the e x p e r i m e n t a l r a t i o n f o r a minimum 60 days and who were n o t expected t o be i n e s t r u s d u r i n g the c o l l e c t i o n p e r i o d .  Each  - 20 -  cow was p l a c e d i n a s t a n c h i o n f o r one week t o a l l o w i t t o become famil i a r with the area.  Feed i n t a k e s were c l o s e l y monitored  p e r i o d t o ensure near t o t a l consumption.  over  this  D u r i n g the 5 day c o l l e c t i o n ,  f e e d i n t a k e s , f e c a l and u r i n a r y e x c r e t i o n s , m i l k p r o d u c t i o n and body weights were r e c o r d e d f o r each a n i m a l . to  The cows were c o n f i n e d  totally  t h e i r s t a n c h i o n s and were m i l k e d w i t h p o r t a b l e m i l k i n g u n i t s . Feed samples c o l l e c t e d from each f e e d i n g were mixed t o g e t h e r  then subsampled f o r f u t u r e chemical a n a l y s e s . composited Values  F e c a l grab samples were  and subsamples were taken f o r d r y matter  determinations.  f o r pH were measured on random f r e s h f e c a l samples.  Urine,  c o l l e c t e d v i a a c a t h e t e r , was n o t sampled u n t i l the f i n a l 2 days o f t h e c o l l e c t i o n p e r i o d due t o b l o o d c l o t s a p p e a r i n g d u r i n g the i n i t i a l p a r t o f the t r i a l .  As suggested  u r i n e was made a c i d i c by adding ml.  by C h r i s t i a n and Feldman (1970), the 1 t o 2 ml g l a c i a l a c e t i c a c i d per 100  T h i s was done t o p r e v e n t the p r e c i p i t a t i o n o f c a l c i u m phosphate  which c o u l d e n t r a p o t h e r m i n e r a l i o n s as w e l l . e v e n i n g m i l k i n g p e r i o d were kept separate Blood  M i l k samples from the  from those o f the morning.  samples were c o l l e c t e d twice d u r i n g the d i g e s t i b i l i t y  Rumen f l u i d was sampled by means o f a hose connected All  trial.  t o a vacuum pump.  samples were s t o r e d f r o z e n (-18 C) f o r f u t u r e a n a l y s e s .  Samples o f the f e e d s t u f f s and f e c e s were d r i e d f o r 48 h r s . at  65°C i n a mechanical  through and  c o n v e c t i o n oven then were ground t o pass  a 0.8 mm mesh s t a i n l e s s s t e e l s c r e e n .  s t o r e d i n p o l y e t h y l e n e bags.  These were subsampled  D i g e s t i o n i n v o l v e d the wet a c i d  -  21  t e c h n i q u e o f P a r k i n s o n and A l l e n  -  (1975).  N i t r o g e n and phosphorus were  s u b s e q u e n t l y a n a l y z e d on a Technicon AutoAnalyzer potassium  Calcium,  and magnesium were read on a P e r k i n Elmer 560 Atomic  A b s o r p t i o n Spectrophotometer. a l s o read by atomic  I r o n , copper, manganese and z i n c were  a b s o r p t i o n s p e c t r o s c o p y but a f t e r a d r y ash method  as d e s c r i b e d by Heckman (1967). o r g a n i c matter by d i f f e r e n c e . al.  II.  Dry a s h i n g a l s o y i e l d e d the t o t a l The t u r b i d i m e t r i c method o f F e r r a r a e t  (1965) was used t o measure s u l f u r w h i l e o r g a n i c e x t r a c t i o n was  r e q u i r e d f o r both molybdenum (Michie et a l . ,  (Stupar e t a l . ,  1974) and selenium  1978).  Most serum m i n e r a l s were a n a l y z e d by atomic spectroscopy.  absorption  The c a l c i u m method was t h a t o f C a l i e t a l . (1973),  magnesium and potassium  were r e a d i n d i l u t e d samples.  Copper and z i n c  were measured by the method o f Parker e t a l . (1967), i r o n by Olson and Hamlin's (1969) technique and manganese was r e a d by methods o f a d d i t i o n s as suggested by Mahoney e t a l . (1969). m i n a t i o n o f phosphorus ( L i t t l e e t a l . , measurement o f s u l f u r a n a l y s i s o f selenium n o t determined  1971), the t u r b i d i m e t r i c  (Kennedy and M i l l i g a n , (Michie e t a l . ,  Colorimetric deter-  1978) and the f l o r o m e t r i c  1978) were used.  Molybdenum was  due t o the low l e v e l s i n the serum and the i n a d e q u a c i e s  o f the p r e s e n t t e c h n i q u e s .  The plasma was a n a l y z e d f o r glucose u s i n g  t h e Sigma T e c h n i c a l method No. 510  (1978).  The m i n e r a l s i n u r i n e and m i l k were a n a l y z e d u s i n g s i m i l a r methods as those f o r serum.  M i l k samples were f i r s t d e p r o t e i n i z e d  a c c o r d i n g t o the t e c h n i q u e o f Brooks e t a l . (1970).  - 22 -  Three o t h e r o r g a n i c c o n s t i t u e n t s o f t h e f e e d s t u f f s were measured as w e l l .  The f i r s t was d i g e s t i b l e energy, t h e d i f f e r e n c e  between t h e g r o s s energy o f t h e f e e d and t h a t o f t h e f e c e s , as d e t e r mined  on t h e Gallenkamp A d i a b a t i c Bomb C a l o r i m e t e r .  Acid detergent  f i b r e was a n a l y z e d u s i n g the m o d i f i e d method o f Waldern  (1971).  L a s t l y , e t h e r e x t r a c t was measured a f t e r e x t r a c t i o n on a G o l d f i s c h u n i t (Labconco).  (b)  S t a t i s t i c a l Analysis: The treatment e f f e c t was o f prime i n t e r e s t i n t h i s experiment  but  t h e r e were o t h e r parameters which a l s o had t o be accounted f o r .  The e f f e c t o f breeds on t h e v a r i a b l e s measured was unknown. by Kitchenham  and Rowlands (1976) was o f s u f f i c i e n t i n t e r e s t t o  i n c l u d e breeds i n t h e model.  Both t r e a t m e n t s and breeds were viewed  as f i x e d e f f e c t s i n a 2 x 2 f a c t o r i a l experiment. were i n i t i a l l y  Work done  considered important.  Four c o v a r i a b l e s  These were; f e e d  intakes  e x p r e s s e d as a p e r c e n t a g e o f body weight, age a t c a l v i n g d a i l y m i l k p r o d u c t i o n (kg 4%FCM) and days f r e s h .  (months),  The f i r s t  three  a p p l i e d t o t h e apparent d i g e s t i b i l i t y data w h i l e a l l but t h e f i r s t one were used i n t h e a n a l y s i s o f t h e serum  constituents.  The i n c o r -  p o r a t i o n o f c a t e g o r i e s o f r e p r o d u c t i v e c y c l i n g i n t o t h e model f o r the a n a l y s i s o f serum t r a i t s r e s u l t e d i n these b e i n g n e s t e d w i t h i n t h e f a c t o r i a l arrangement  o f t h e f e e d i n g experiment.  - 23 -  The model used to determine the effects on apparent d i g e s t i b i l i t y was:  Y i j k = u + T i + Bj + TBij + I i j k + A i j k + Mijk + E i j k where u  = overall mean common to a l l samples.  Ti  = the e f f e c t of the i t h treatment.  Bj  = the e f f e c t of the j t h breed.  TBij  = the interaction of the j t h breed within the i t h treatment  Iijk  = the covariable feed intake expressed as a precentage of body weight.  Aijk  = the covariable age at calving  (months).  Mijk  = the covariable d a i l y milk production recorded i n kg 4%FCM.  Eijk  = the unexplained residual error associated with each sample.  -  24  -  The model used to determine the e f f e c t s on serum constituents was:  Y i j k l = u + T i + Bj + Ck + TBij + TCik + A i j k l + M i j k l + Fijkl + Eijkl where u  = overall mean common to a l l samples.  Ti  = the e f f e c t of the i t h treatment.  Bj  = the e f f e c t of the j t h breed.  Ck  = the e f f e c t of the kth category of reproductive cycle.  TBij  = the interaction of the j t h breed within the i t h treatment.  TCik  = the interaction of the kth category with i n the ith  treatment.  Aijkl  = the covariable age at calving (months).  Mijkl  = the covariable d a i l y milk production recorded i n kg 4%FCM.  Fijkl  = the covariable days fresh or number of days from onset of l a c t a t i o n .  Eijkl  = the unexplained residual error associated with each sample.  - 25 -  Analyses were done by least-squares techniques using UBC BMD 10V f o r ANOVA with unequal numbers of observations per c e l l .  The  Newman-Keuls test was used for the comparison of means. Other factors related to the t o t a l feed and energy intakes were analyzed with the package program MFAV, using the following model:  Y i j k = u + T i + Bj + TBij + A i j k + F i j k + Wijk + E i j k where u  = overall mean common to a l l  samples.  Ti  = the e f f e c t of the i t h treatment.  Bj  = the e f f e c t of the j t h breed.  TBij  = the interaction of the j t h breed within the i t h treatment•  Aijk  = the covariable age at calving (months).  Fijk  = the covariable days fresh or number of days from the onset of l a c t a t i o n .  Wijk  = the covariable body weight (kg).  Eijk  = the unexplained residual error associated with each sample.  The parameters measured were feed intakes, milk production, body weight change and plasma glucose concentrations.  - 26 -  RESULTS AND  DISCUSSIONS  C h e m i c a l a n a l y s e s o f t h e f e e d s t u f f s were undertaken on samples  c o l l e c t e d over the p e r i o d o f the t r i a l .  R e s u l t s f o r the com-  ponents o f prime i n t e r e s t a r e p r e s e n t e d i n T a b l e 1 a l o n g w i t h the minimum  l e v e l s suggested by NRC  (1978).  N u t r i e n t s o f secondary  impor-  t a n c e t o t h i s experiment but ones which c o u l d a f f e c t the performance o f the  cows, appear  i n Table 2.  As can be seen, a l l n u t r i e n t s except p o s s i b l y energy, were s u f f i c i e n t t o meet the requirements o f t h e l a c t a t i n g d a i r y  cattle.  Potassium, i r o n and manganese were c o n s i d e r a b l y h i g h e r i n conc e n t r a t i o n than the recommended minimum  levels.  While both i r o n and  manganese were w e l l w i t h i n the s a f e l i m i t s f o r consumption  (Underwood,  1977), t h e h i g h l e v e l s o f potassium may have i n t e r a c t e d t o depress magnesium a b s o r p t i o n ( S u t t l e and F i e l d ,  1967).  t a m i n a t i o n o f t h e l i m e s t o n e used t o supplement  A l s o , due t o cont h e treatment d i e t , the  c o n c e n t r a t i o n s o f i r o n and copper were h i g h e r i n the treatment r a t i o n t h a n i n t h e c o n t r o l one. the  These  f a c t o r s w i l l be d e a l t w i t h l a t e r i n  discussion. Loose, c o b a l t - i o d i z e d s a l t was o f f e r e d f r e e - c h o i c e  the  experiment.  throughout  The amount o f s a l t i n t a k e was n o t monitored and  t h e r e f o r e any p o s s i b l e e f f e c t o f i n c r e a s e d d i e t a r y c a l c i u m carbonate on sodium, c o b a l t and i o d i n e remain undetermined. (1978), t h e l e v e l o f sodium  A c c o r d i n g t o NRC  r e q u i r e d by m i l k i n g d a i r y c a t t l e i s 0.18%.  W h i l e the amount p r e s e n t i n the t r i a l  r a t i o n s was h i g h e r than t h i s , i t  was judged b e s t n o t t o l i m i t the amount o f s a l t a v a i l a b l e t o the a n i m a l s .  - 27 -  TABLE 1 N u t r i e n t Content o f Rations NRC (1978 ) minimum l e v e l s u  Component  Control  O.M.% N % Ca % P % K % Mg % S %  90.31 2.72 0.72 0.50 2.70 0.30 0.35  Fe Cu Mn Zn  ppm ppm ppm ppm  Mo ppb Se ppb  Ca:P  Ca-Treatment 90.31 2.72 1.50 0.50 2.70 0.30 0.35  248 13.2 110 66  275 15.6 110 66  672 169  672 169  1.4: 1  2.08 0.43 0.31  2.56 0.60 0.40 0.80 0.20 0.20  50 10 40 40  100  3: 1  1.4:1 -  1.5:1  f o r l a c t a t i n g d a i r y c a t t l e between 400 and 600 kg p r o d u c i n g between 8 and 36 k g m i l k d a i l y .  - 28 -  TABLE 2 Other  T o t a l Diet (both Treatments)  Component Digestible Mcal/kg  N u t r i e n t s i n Rations  NRC (1978)° minimum l e v e l s  Energy 3. 08  A c i d Detergent Fibre %  2.78  -  3.31  21.8  21  Ether Extract %  3.5  2  Na  0.27  0. 18  %  NaCl %  ad  lib  0  0.46  Co  ad  lib  0  0. 10  I  ppm ppm  ad l i b  V i t a m i n A I.U./kg  3425  V i t a m i n D I.U./kg  310  0.50  0  3200  c  300  c  f o r l a c t a t i n g d a i r y c a t t l e between 400 ween 8 and 36 kg m i l k d a i l y .  and 600  ad l i b i t u m consumption o f c o b a l t - i o d i z e d c a l c u l a t e d from g r a i n source o n l y .  salt,  kg p r o d u c i n g  bet-  - 29 -  Four parameters were measured t o ensure adequate i n t a k e s o f nutrients occurred.  These were f e e d i n t a k e s , m i l k p r o d u c t i o n  (4%FCM),  body weight and plasma g l u c o s e c o n c e n t r a t i o n s (Table 3 ) . Feed i n t a k e s , c o n s i d e r e d as a p e r c e n t a g e o f body weight, d i d not d i f f e r  ( p > . 0 5 ) between t r e a t m e n t s .  on the c o n t r o l r a t i o n was  3.68%  The mean v a l u e f o r animals  (dry matter b a s i s ) .  c a l c i u m treatment consumed an average o f 3.61% f e e d per day. d i e t was  The range o f i n t a k e s o f a l l  from 3.16%  Those cows on the  of t h e i r body weight i n  a n i m a l s once adapted t o the  to 4.22% which i s h i g h when compared t o the  s u g g e s t e d maximum d r y matter i n t a k e s o f the NRC  (1978) o f 2.5%  o f body w e i g h t .  (Table 2) d i d not meet  The energy c o n t e n t o f the d i e t  t h e r e q u i r e m e n t s o f h i g h m i l k y i e l d i n g cows (NRC,  1978).  to 3.5%  However, the  h i g h e r than average f e e d i n t a k e s would p a r t i a l l y b a l a n c e any energy d e f i c i t r e s u l t i n g i n near optimum engery i n t a k e s . The second v a r i a b l e measured was s t a n d a r d i z e d t o the 4% o f 24.49 k g and 23.71  d a i l y milk production.  Once  f a t c o r r e c t e d m i l k l e v e l , the mean p r o d u c t i o n kg f o r the c o n t r o l and treatment a n i m a l s r e s p e c -  t i v e l y were demonstrated t o be s i g n i f i c a n t l y d i f f e r e n t  (p<.05).  This  r e f l e c t e d the d i s p r o p o r t i o n a t e number o f young animals on the c a l c i u m treatment.  In comparison w i t h p a s t r e c o r d s and those o f contemporary  h e r d mates, m i l k p r o d u c t i o n d i d not appear t o be a f f e c t e d by e i t h e r treatment. Body weight measurements were taken f r e q u e n t l y throughout the trial  c o r r e s p o n d i n g w i t h b l o o d sampling t i m e s .  Due  to i n d i v i d u a l a n i -  - 30 -  TABLE 3 Performance  Parameters  Control  Parameter Mean  1,  C a-T reatment  Std.  Dev.  Mean  Std.  Dev.  Feed Intake % o f body weight  3.68  0.14  3.61  0. 16  Daily Milk Production kg 4% FCM  24.49*  7.03  23.71*  5.86  Body Weight kg  522.9**  Plasma Glucose mg/100 ml  45.8  53.18  0.036  Significantly  *(p<.05),  d  n = 8  51.35  8.06  Body Weight Change ( s l o p e )  different  492.5**  33.7  10.68  0.063  **(p<.01)  - 31 -  mal v a r i a b i l i t y , an a n a l y s i s o f c o v a r i a n c e was performed  comparing the  s l o p e s o f t h e l i n e s a s s o c i a t e d w i t h body weight change f o r cows on each t r e a t m e n t .  No s i g n i f i c a n t d i f f e r e n c e  a n i m a l s , once age was accounted  ( p > . 0 5 ) o c c u r r e d as most  f o r , remained a c o n s t a n t weight  ( C o n t r o l s l o p e = 0.036, Ca-Treatment s l o p e = 0.063). weight o f 492.5 Kg f o r t h e treatment  The mean  animals was s i g n i f i c a n t l y  lower  ( p < . 0 1 ) than t h e average weight o f 522.9 Kg f o r t h e c o n t r o l cows. Plasma g l u c o s e has been r e p o r t e d t o be a s t a b l e , d i a g n o s t i c a i d f o r a s s e s s i n g m e t a b o l i c carbohydrate dairy cattle  ( A t h a n a s i o u and P h i l l i p s ,  ( p > . 0 5 ) were observed cose l e v e l 51.32  1978).  reliable  disturbances i n  No treatment  f o r plasma glucose c o n c e n t r a t i o n s .  effects The mean g l u -  f o r t h e c o n t r o l animals was 53.18 mg/100 ml. A v a l u e o f  mg/100 ml was determined  i n the calcium t r e a t e d animals.  Other  r e p o r t s o f g l u c o s e c o n c e n t r a t i o n s i n d a i r y c a t t l e have a range o f means from 36.3 t o 69.9 mg/100 ml (Manston and Rowlands, 1973; Rowlands e t a l . ,  1977; Thompson e t a l . ,  mg/100 ml. Hunter (1977) suggested  1978) with a grand mean near 45  t h e glucose c o n t e n t o f plasma l e s s  t h a n 25 mg/100 ml g e n e r a l l y was i n d i c a t i v e o f i n s u f f i c i e n t s u p p l y which r e s u l t e d i n lower n o n - r e t u r n r a t e s .  energy  In t h e c u r r e n t  s t u d y , no sample was a n a l y z e d t o have l e s s than 38 mg/100 ml glucose concentration. P a r k e r and Blowey (1976) r e l a t e d plasma glucose t o the stage of l a c t a t i o n .  C o n c e n t r a t i o n s o f g l u c o s e i n c r e a s e d from c a l v i n g t o nine  weeks postpartum  then l e v e l e d o f f a t a p p r o x i m a t e l y  most a n i m a l s i n t h i s t r i a l  had lower  60mg/100 ml.  While  glucose c o n c e n t r a t i o n s e a r l y i n  - 32  t h e i r l a c t a t i o n , not a l l animals lack of significance  did.  This v a r i a b i l i t y resulted i n a  ( p > . 0 5 ) between the glucose c o n c e n t r a t i o n  the c o v a r i a b l e days f r e s h .  Hewett (1974) a l s o r e p o r t e d no  e f f e c t o f stage of l a c t a t i o n . v e l y unimportant when u t i l i z i n g mine m e t a b o l i c  -  carbohydrate  Time o f sampling  and  significant  appears t o be  relati-  the glucose c o n c e n t r a t i o n t o d e t e r -  d i s t u r b a n c e s , e s p e c i a l l y a f t e r the  first  few weeks postpartum. C o n s i d e r i n g the t o t a l n u t r i e n t s i n the d i e t as w e l l as  the  above parameters, i t i s apparent t h a t adequate l e v e l s o f d i e t a r y n u t r i e n t s were i n g e s t e d by both groups o f  animals.  In an attempt t o i d e n t i f y any a l t e r a t i o n o f the pH w i t h i n the d i g e s t i v e t r a c t due samples o f rumen f l u i d fluid  and  t o the a d d i t i o n a l c a l c i u m  f e c e s were a n a l y z e d .  ranged from a minimum o f 7.5  Values  level  carbonate, f o r the rumen  t o as h i g h as pH 9.0.  Heavy con-  t a m i n a t i o n w i t h s a l i v a and unknown sample s i t e s w i t h i n the rumen c o n t r i b u t e d t o these h i g h , random v a l u e s . u n r e p r e s e n t a t i v e and were t h e r e f o r e not  These data were c o n s i d e r e d  recorded.  F e c a l pH v a l u e s were more b e f i t t i n g those expected. for  the c o n t r o l group was  7.35  w i t h a s t a n d a r d d e v i a t i o n o f 0.16  t h a t f o r the c a l c i u m t r e a t e d animals difference  was  7.60  ( p < . 0 5 ) e x i s t e d between the two  c a l c i u m carbonate  The mean  ±  0.13.  treatments  A  while  significant  implying  d i d indeed r a i s e the pH i n the d i g e s t i v e t r a c t .  Wheeler and N o l l e r (1977) s t a t e d , " t h a t a pH measurement made on a grab sample o f f e c e s i s an e x c e l l a n t i n d i c a t o r o f pH i n the  small  - 33 -  i n t e s t i n e , " as 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 between t h e average pH o f t h e d i g e s t a w i t h i n the s m a l l i n t e s t i n e and t h a t o f t h e f e c e s . Mean v a l u e s f o r the s m a l l i n t e s t i n e c o n t e n t s and f e c e s o f s t e e r s f e d a high concentrate  d i e t were about 5.8 pH u n i t s .  6.8 when c a l c i u m carbonate  The pH l e v e l rose t o  was added t o the d i e t .  co-workers (1980) a l s o r e c o r d e d  R u s s e l l and  i n c r e a s e d f e c a l pH i n s t e e r s f e d h i g h  g r a i n d i e t s supplemented w i t h l i m e s t o n e .  T h i s r e l a t i o n s h i p was n o t  c o n s i s t e n t w i t h i n sheep (Yano e t a l . , 1979).  No s i g n i f i c a n t  f e r e n c e i n pH was i n d i c a t e d as t h e c a l c i u m carbonate b a s a l r a t i o n r a i s e d the c a l c i u m c o n t e n t  dif-  additions to a  from 0.1% to 1.2%.  The f e c a l  pH mean v a l u e was 8.3 w h i l e t h a t i n the s m a l l i n t e s t i n e was 5.4, 7.4 and 8.5 r e s p e c t i v e l y f o r t h e upper, middle and lower p o r t i o n s . It  i s suggested  t h a t i n t h e p r e s e n t experiment the d i f f e r e n c e  i n pH i n t h e f e c e s was r e p r e s e n t a t i v e o f d i f f e r e n c e s w i t h i n the digestive tract.  U n f o r t u n a t e l y , i t cannot be known whether t h i s  a l t e r a t i o n i n a c i d i t y i t s e l f was s u f f i c i e n t t o cause m o d i f i e d d i e t a r y mineral  availability.  In f i r s t p e r f o r m i n g bility trial  the s t a t i s t i c a l a n a l y s i s o f t h e d i g e s t i -  d a t a , t h r e e c o v a r i a b l e s were i n c l u d e d i n the model.  These were; f e e d i n t a k e s expressed at  as a p e r c e n t a g e o f body weight, age  c a l v i n g (months) and d a i l y m i l k p r o d u c t i o n  (4% FCM).  f a c t o r s have been r e p o r t e d t o a f f e c t some m i n e r a l  Each o f these  absorptions,  however, none o f t h e c o v a r i a b l e s proved t o be s i g n i f i c a n t f o r any o f the v a r i a b l e s . experiment.  T h i s can be e x p l a i n e d by t h e c o n t r o l imposed on the  F i r s t l y , the f e e d i n t a k e s were m a i n t a i n e d  a t o r near aid  - 34 -  l i b i t u m and when compared on a b a s i s o f body weight p e r c e n t a g e , were d i s c o v e r e d t o be u n a f f e c t e d by t r e a t m e n t . a n i m a l s would produce tract.  High i n t a k e s o f f e e d by a l l  s i m i l a r r a t e s o f passage through the d i g e s t i v e  C o n s i d e r a b l e v a r i a t i o n i n d i g e s t a passage r a t e c o u l d r e s u l t i n  a l t e r e d uptakes o f many o f t h e d i e t a r y n u t r i e n t s i n c l u d i n g the m i n e r a l s (Underwood, 1977). vely l i t t l e  variation.  The second c o v a r i a b l e , age, had r e l a t i -  The youngest  animal was twenty-four months a t  c a l v i n g and t h e o l d e s t was s i x t y - f o u r months. of  Most r e p o r t s on e f f e c t s  age on a l t e r e d m i n e r a l a b s o r p t i o n s i n d i c a t e these e f f e c t s occur i n  v e r y young o r v e r y o l d a n i m a l s .  F o r example, obvious  decreased  a b s o r p t i o n o f c a l c i u m w i t h i n c r e a s i n g age may n o t appear a n i m a l s a r e over t e n y e a r s o l d (Hansard  et a l . ,  1954).  u n t i l the Other m i n e r a l  a b s o r p t i o n s a r e e i t h e r u n a f f e c t e d by age o r the e f f e c t s a r e n e g l i g i b l e as t o be masked by the v a r i a b i l i t y among animals ( S c o t t ,  1965).  While  t h e average d a i l y m i l k p r o d u c t i o n v a r i e d w i d e l y between a n i m a l s , each a n i m a l was i n i t s peak l a c t a t i o n over the t r i a l .  I t can t h e r e f o r e be  argued t h a t t h e n u t r i e n t requirements would be a t t h e i r h i g h e s t d u r i n g t h i s term.  F o r example, even i f c a l c i u m a b s o r p t i o n were a t a maximum  i t may n o t be a b l e t o s u p p l y t h e t o t a l amount o f c a l c i u m r e q u i r e d f o r the m i l k (Symonds e t a l . ,  1966).  The v a r i a b i l i t y i n m i l k p r o d u c t i o n  d u r i n g t h i s phase would have a l e s s e r e f f e c t than i t would a t a l a t e r stage o f the l a c t a t i o n curve. Due  t o the l a c k o f s i g n i f i c a n c e o f the c o v a r i a b l e s , a second  a n a l y s i s o f v a r i a n c e was undertaken  d e l e t i n g the c o v a r i a b l e s .  This  made the t e s t more r o b u s t by i n c r e a s i n g the degrees o f freedom i n  - 35 -  the e r r o r term which decreased and  the e r r o r mean square.  The mean v a l u e s  s t a n d a r d d e v i a t i o n s o f t h e apparent d i g e s t i b i l i t i e s o f o r g a n i c  m a t t e r , n i t r o g e n and e l e v e n m i n e r a l s a r e r e p o r t e d i n Table 4.  Measurement o f o r g a n i c matter and n i t r o g e n apparent b i l i t i e s were i n c l u d e d t o ensure two t h i n g s .  F i r s t o f a l l , the e f f e c t  of d i e t a r y calcium, or i n d i r e c t l y that o f d i e t a r y calcium on the o r g a n i c c o n s t i t u e n t s was a s s e s s e d . ensure t h e r e was no obvious  carbonate,  I t was a l s o n e c e s s a r y t o  d e f i c i e n c y i n the o r g a n i c content  might have i n f l u e n c e d the i n o r g a n i c component apparent ties.  digesti-  which  digestibili-  Both o r g a n i c matter and n i t r o g e n apparent d i g e s t i b i l i t i e s  shown t o be u n a f f e c t e d centration.  were  ( p > . 0 5 ) by t h e i n c r e a s e d c a l c i u m con-  The mean v a l u e s f o r the o r g a n i c matter were 75.41% and  75.88% f o r the c o n t r o l group and c a l c i u m t r e a t e d cows r e s p e c t i v e l y . The n i t r o g e n v a l u e s were even c l o s e r t o g e t h e r a t 74.79% f o r animals on t h e c o n t r o l r a t i o n and 74.76% f o r those on the c a l c i u m  treatment.  Smith e t a l . (1966) f e d a l t e r e d q u a n t i t i e s and r a t i o s o f c a l c i u m and phosphorus (1:1 t o 4:1, 8:1 t o 8:8) t o d a i r y s t e e r s and noted no s i g n i f i c a n t change i n o r g a n i c matter o r n i t r o g e n apparent ties.  digestibili-  The mean o r g a n i c matter d i g e s t i b i l i t y ranged from 67% to 71%  w h i l e t h e means f o r n i t r o g e n v a r i e d from 57% t o 64%.  Varner and Woods  (1972) r e c o r d e d d i g e s t i o n c o e f f i c i e n t s f o r o r g a n i c matter o f 74.2% and f o r p r o t e i n o f 71.0% f o r a c a l c i u m carbonate to steers.  supplemented r a t i o n f e d  T h e r e f o r e , i t can be assumed t h e r e was adequate d i e t a r y  o r g a n i c matter and n i t r o g e n p r e s e n t and t h a t c a l c i u m d i d n o t a l t e r the  - 36 -  TABLE 4 Summary o f Percentage Apparent D i g e s t i b i l i t i e s  Component (%)  O.M. N Ca  Mean  e  Ca-Treatment  Std.Dev.  Mean  e  Std.Dev.  75.41  2.34  75.88  3.49  74.79  3.25  74.76  2.57  4.53  26.60*  12.13  5.57*  P  33.87  7.15  36.89  10.39  K  93.73  1.78  93.41  2.24  Mg  28.02  11.13  31.18  5.80  S  61.58  2.65  61.80  4.67  Fe  -13.61*  10.55  2.98*  12.04  Cu  15.00**  5.43  34.98**  2.70  Zn  27.46*  9.40  10.40*  4.61  Mn  13.77  9.58  11.32  5.33  Mo  20.83*  6.05  Se  45.49  8.09  Significantly e  Control  n = 5  different  *(p<.05),  9.32* 43.66  **(p<.01)  10.44 9.01  - 37 -  a v a i l a b i l i t y of these components.  The apparent d i g e s t i b i l i t i e s of calcium associated with the two  treatments did prove to be s i g n i f i c a n t l y d i f f e r e n t ( p < . 0 5 ) .  The  l e v e l of 26.60% for animals on the calcium treatment approached the upper l i m i t s for apparent absorption from adequate diets according to Braithwaite et a l . (1969).  U t i l i z i n g radioactive l a b l i n g  Braithwaite (1974) and Braithwaite and Riazuddin  procedures,  (1971) indicated the  true absorption of calcium i n sheep to be 37% to 40%.  The  10% to 13%  difference between the true calcium a v a i l a b i l i t y and that which was apparent was  due to endogenous excretion.  stated that 28% was  Ramberg et a l . (1974)  about maximum apparent absorption but at lower  intakes the absorption was  less.  This r e l a t i o n s h i p was reported to be  l i n e a r down to low intakes where i t became c u r v i l i n e a r .  As the mean  value of apparent d i g e s t i b i l i t y of the control ration calcium was  only  5.57%, t h i s would imply the r a t i o n contained less than optimum l e v e l s of calcium. The only explanation for t h i s decreased  absorption on the  control ration would be due to lower calcium a v a i l a b i l i t y .  Hansard et  a l . (1957) reported the calcium a v a i l a b i l i t y from ground limestone to be only marginally higher than that from orchardgrass hay.  If such was  the case then the increased a v a i l a b i l i t y of calcium probably was due to the source.  Additional limestone was  not  thought to have adjusted  the pH throughout the digestive t r a c t as evidenced by the r i s e i n f e c a l pH.  However, t h i s would be expected to have an adverse e f f e c t  - 38  -  b y i n c r e a s i n g the p r e c i p i t a t i o n o f c a l c i u m phosphate (Smith McAllan,  1966).  and  I f t h i s change i n a c i d i t y d i d o c c u r , i t must not have  been s u f f i c i e n t t o cause p r e c i p i t a t i o n i n the f i r s t h a l f o f the  small  i n t e s t i n e where c a l c i u m i s r e p o r t e d l y absorbed. I t t h e r e f o r e appears n e c e s s a r y  t o have a c e r t a i n p r e c e n t a g e  c a l c i u m i n the d i e t t o overcome the c a l c i u m b i n d i n g f a c t o r s p r e s e n t i n the d i g e s t a . suggested  Under the d i e t a r y c o n d i t i o n s o f t h i s experiment, i t i s  the NRC  (1978) recommended l e v e l s o f 0.43  would be too low t o s u p p l y adequate c a l c i u m . p o s t p a r t u r i e n t d a i r y c a t t l e , two  t o 0.60%  calcium  C o n s i d e r i n g the needs o f  t o t h r e e times the recommended  levels  would be r e q u i r e d t o r e a c h maximum c a l c i u m a b s o r p t i o n r a t e s .  To carbonate  f u r t h e r the arguement t h a t the i n c r e a s e d d i e t a r y c a l c i u m  d i d not a p p r e c i a b l y a l t e r the pH l e v e l i n the upper  i n t e s t i n e , 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 ( p > . 0 5 ) i n phosphorus  apparent d i g e s t i b i l i t i e s .  Had  the p r e c i p i t a t i o n o f c a l c i u m phosphate  o c c u r r e d w i t h i n the area o f a b s o r p t i o n t h e r e would have been a decreased  d i g e s t i b i l i t y o f both c a l c i u m and phosphorus f o r animals  the c a l c i u m treatment.  on  T h i s l a c k o f d i f f e r e n c e agrees w i t h Manstons'  (1967) f i n d i n g s o f no a f f e c t on the a b s o r p t i o n o f phosphorus by v a r i a t i o n i n c a l c i u m i n t a k e by d a i r y c a t t l e . a s i g n i f i c a n t decrease  be due  (1963) r e p o r t e d  i n the p e r c e n t a g e o f phosphorus absorbed with  i n c r e a s e d c a l c i u m l e v e l s i n the d i e t s o f r a t s . t i a t i o n may  Toothill  This species  differen-  to the h i g h e r pH l e v e l o f the m a t e r i a l f l o w i n g  t h r o u g h the upper s e c t i o n o f the monogastric i n t e s t i n e  (Ben-Ghedalia  - 39 -  e t a l . , 1975). The mean v a l u e s f o r phosphorus apparent d i g e s t i b i l i t y o f 33.87% and 36.89% f o r the c o n t r o l and fall  c a l c i u m treatments r e s p e c t i v e l y ,  w i t h i n the range r e p o r t e d by o t h e r workers.  Lomba e t a l . (1969)  i n d i c a t e d phosphorus d i g e s t i b i l i t i e s t o be between 30  and 45%  while  Grace e t a l . (1977) s t a t e d apparent a b s o r p t i o n o f phosphorus from many d i e t s f e d to ruminants was the c a l c i u m treatment  u s u a l l y l e s s than 30%.  As the animals  absorbed c o n s i s t e n t l y h i g h l e v e l s o f phosphorus  and much more c a l c i u m than those on the c o n t r o l r a t i o n , the r a t i o c a l c i u m t o phosphorus o f 3:1 of  on  appears t o be more b e n e f i c i a l than  of  that  1.4:1.  Magnesium a b s o r p t i o n was  also unaffected  change i n c a l c i u m l e v e l s i n the d i e t .  The  ( p > . 0 5 ) by  apparent  the  digestibilities  were 28.02% f o r the c o n t r o l and 31.18% f o r the c a l c i u m t r e a t e d cows. These a r e c l o s e t o the average o f 27.8%  r e p o r t e d by Lomba e t a l . i  (1968) f o r l a c t a t i n g d a i r y c a t t l e . There i s evidence  i n mongastric  s p e c i e s which r e l a t e s magne-  sium u t i l i z a t i o n t o the l e v e l o f d i e t a r y c a l c i u m . and  For example, Nugara  Edwards (1963) i n d i c a t e d h i g h l e v e l s o f c a l c i u m i n the d i e t o f the  c h i c k prevented concluded lent ions.  the d e p o s i t i o n o f magnesium i n the bone.  t h i s t o be due Toothill  The  authors  t o a common mechanism o f a b s o r p t i o n f o r d i v a -  (1963) noted  a s i m i l a r r e s u l t i n the r a t where  a d d i t i o n o f c a l c i u m c h l o r i d e t o the water s u p p l y s i g n i f i c a n t l y  reduced  t h e a b s o r p t i o n o f magnesium as i n d i c a t e d by i n c r e a s e d f e c a l magnesium. Such an i n t e r a c t i o n was  a l s o evidenced  i n guinea p i g s .  Morris  and  - 40  O'Dell  -  (1963) p o s t u l a t e d the d i r e c t p h y s i o l o g i c a l antagonism between  c a l c i u m and magnesium to be r e s p o n s i b l e f o r the decreased of  absorption  magnesium. Whether t h i s i n t e r a c t i o n o s t e n s i b l y m a n i f e s t s  nants i s undetermined. d i g e s t a reduced 1967).  Increased  i t s e l f i n rumi-  c a l c i u m c o n c e n t r a t i o n s i n the  a b s o r p t i o n o f magnesium i n c a l v e s (Smith and  T h i s was  McAllan,  i r r e s p e c t i v e o f phosphate c o n c e n t r a t i o n s and pH  w i t h i n the d i g e s t i v e t r a c t which i m p l i e s magnesium a b s o r p t i o n p r i o r t o the middle to lower s m a l l i n t e s t i n e .  The  above two  e x h i b i t e d marked r e d u c t i o n i n magnesium u l t r a f i l t r a b i l i t y s e c t i o n s o f the s m a l l i n t e s t i n e (1965) c l a i m e d ,  (Smith and M c A l l a n ,  occurred factors  i n the  1966).  level  lower  Scott  " t h a t any c o m p e t i t i o n between c a l c i u m and magnesium i n  a b s o r p t i o n i n the sheep i s s u f f i c i e n t l y s m a l l to be c o n c e a l e d  i n the  v a r i a b i l i t y which e x i s t s between experiments."  suggested  Smith (1969)  magnesium a b s o r p t i o n a c r o s s the i n t e s t i n a l w a l l was  passive.  Assuming  t h i s and presuming a c o n s i s t e n t f l o w o f d i g e s t a , any a l t e r a t i o n i n the e f f i c i e n c y o f a b s o r p t i o n o f magnesium would be due availability.  As t h i s d i d not occur  to a l t e r e d  i n the p r e s e n t experiment, i t  must be c o n s i d e r e d t h a t any antagonism between c a l c i u m and magnesium in  the gut i s o f a c u r v i l i n e a r r e l a t i o n s h i p .  c o n t e n t o f the treatment  d i e t was  The  change i n c a l c i u m  not s u f f i c i e n t t o cause a change i n  t h e a v a i l a b i l i t y o f magnesium.  The  h i g h potassium  c o n c e n t r a t i o n i n the d i e t s was  as t o i t s e f f e c t on magnesium a b s o r p t i o n .  S u t t l e and  Field  of  concern  (1967)  - 41 -  c o n c l u d e d h i g h potassium i n t a k e s depressed magnesium a b s o r p t i o n i n sheep. to  Because the apparent d i g e s t i b i l i t i e s o f magnesium were r e l a t i v e  the range r e p o r t e d by o t h e r workers, i t i s suggested t h a t the h i g h  p o t a s s i u m c o n t e n t d i d not a p p r e c i a b l y a f f e c t magnesium  availability.  The apparent d i g e s t i b i l i t y o f potassium bore no s i g n i f i c a n t relationship  ( p > . 0 5 ) with t h a t o f c a l c i u m .  Both the apparent and  t r u e d i g e s t i b i l i t i e s o f potassium a r e r e p o r t e d t o be v e r y h i g h , unrel a t e d t o potassium i n t a k e s and f a i r l y c o n s t a n t (Paquay These the  et a l . ,  1969).  a u t h o r s were unable t o show a s i g n i f i c a n t c o r r e l a t i o n between  f a t e o f potassium and t h a t o f c a l c i u m , magnesium o r phosphorus i n  dairy cattle.  The work r e p o r t e d here i s i n agreement w i t h these con-  c e p t s as t h e mean apparent d i g e s t i b i l i t y  f o r animals on the c o n t r o l  r a t i o n was 93.73% and f o r those on the c a l c i u m teatment was 93.41%.  The apparent d i g e s t i b i l i t i e s o f s u l f u r , copper and molybdenum w i l l be d i s c u s s e d t o g e t h e r due t o t h e i r r e p o r t e d i n t e r a c t i o n s (Underwood, 1977). the  In the r e v i e w a r t i c l e o f H u i s i n g h e t a l . (1973),  mechanisms i n v o l v e d i n the i n t e r a c t i o n s were e x p l a i n e d as an anta-  gonism  between s u l f a t e and molybdate  f o r t r a n s p o r t systems and between  c o p p e r , s u l f a t e and molybdenum as t h e f o r m a t i o n o f u n a v a i l a b l e c u p r i c thiomolybdate. In  t h e p r e s e n t study, t h e r e was no s i g n i f i c a n t  difference  ( p > . 0 5 ) between s u l f u r d i g e s t i b i l i t i e s y e t t h e r e was a h i g h l y difference  ( p < . 0 1 ) f o r copper and a s i g n i f i c a n t d i f f e r e n c e  f o r molybdenum apparent d i g e s t i b i l i t i e s .  significant  (p<.05)  The v a l u e f o r copper  - 42 -  apparent d i g e s t i b i l i t y rose from 15.00% on the c o n t r o l r a t i o n t o 34.98% f o r animals  on the c a l c i u m treatment.  The s u l f u r d i g e s t i b i l i -  t i e s were v e r y c o n s t a n t w i t h l e v e l s o f 61.58% and 61.80% f o r the two treatments.  Molybdenum decreased  calcium l e v e l s increased.  i n apparent d i g e s t i b i l i t y as the  The c o n t r o l r a t i o n mean was 20.83% w h i l e  t h a t o f t h e c a l c i u m treatment  was o n l y 9.32%.  Because the d i e t a r y c o n c e n t r a t i o n o f s u l f u r d i d not v a r y nor did  the apparent d i g e s t i b i l i t y , i t i s suggested  molybdenum and s u l f u r was n o t the reason digestibility.  the antagonism between  f o r decreased  molybdenum  The o t h e r two p o s s i b i l i t i e s e x i s t i n g a r e a  molybdenum a v a i l a b i l i t y a l l o w e d  decreased  an i n c r e a s e d copper a b s o r p t i o n o r an  i n c r e a s e d copper a v a i l a b i l i t y caused t h e concomitant decrease i n molybdenum apparent d i g e s t i b i l i t y . i n t a k e s o f c a l c i u m carbonate i n t h e l i v e r o f a d u l t sheep. to  The  (1954) i n d i c a t e d v e r y h i g h  (90 g/day) l i m i t e d the s t o r a g e o f copper However, f e e d i n g lower l e v e l s (35 g/day)  sheep d i d not a f f e c t t h e l i v e r copper c o n c e n t r a t i o n (Hemingway e t  al., in  Dick  1962).  Kirchgessner  (1965) r e p o r t e d a drop i n copper r e t e n t i o n  sheep and d a i r y h e i f e r s when i n c r e a s e d l e v e l s o f c a l c i u m were f e d . author  concluded  r e c o r d e d no e f f e c t on the copper a b s o r p t i o n by p i g s and t h i s may be due t o pH d i f f e r e n c e s i n the d i g e s t i v e t r a c t o f  t h e two s p e c i e s . present t r i a l  These r e p o r t s a r e c o n t r a r y t o the r e s u l t s o f t h e  and as t h e r e a r e no r e p o r t s on t h e e f f e c t o f c a l c i u m on  molybdenum a v a i l a b i l i t y , no d e f i n i t i v e c o n c l u s i o n i s p o s s i b l e . T h i s author  does favour the concept  o f t h e i n c r e a s e d copper  a v a i l a b i l i t y w i t h i n c r e a s e d d i e t a r y c a l c i u m carbonate  intake.  The  - 43 -  f i r s t o f two  reasons f o r t h i s o p p o s i n g view concerns the amount and  form o f copper i n the c a l c i u m treatment d i e t .  There was  a copper con-  t a m i n a t i o n o f the l i m e s t o n e r e s u l t i n g i n a s l i g h t i n c r e a s e i n the copper l e v e l s i n the treatment #2 may  (13.2 ppm  v s 15.6 ppm).  While  this  be s m a l l , i t c o u l d p o s s i b l y have had a s i g n i f i c a n t e f f e c t on the  a v a i l a b i l i t y o f the copper.  The form o f t h i s e x t r a copper was  pro-  b a b l y as carbonate as i t was  associated with calcium carbonate.  Underwood (1977) i n d i c a t e d the copper i n carbonate form was more e a s i l y d i g e s t i b l e than from any o t h e r form i n the d i e t . o f the contaminated l i m e s t o n e , the copper l e v e l i n the g r a i n p o r t i o n o f treatment #2 was  As a r e s u l t supplemented  22% g r e a t e r than i n the unsupple-  mented g r a i n p o r t i o n o f the c o n t r o l r a t i o n .  T h i s c o u l d have been the  main r e a s o n f o r the i n c r e a s e d copper apparent a b s o r p t i o n .  To expand on the second l i n e o f r e a s o n i n g r e g a r d i n g p o s s i b l e i n c r e a s e d copper d i g e s t i b i l i t y r e q u i r e s i n c l u s i o n o f another dietary zinc. ficantly  factor,  The amount o f z i n c apparent d i g e s t i b i l i t y dropped  signi-  ( p < . 0 5 ) from 27.46% i n animals on the c o n t r o l d i e t t o 10.40%  f o r cows consuming the e x t r a c a l c i u m c a r b o n a t e .  Zinc absorption i s  r e p o r t e d t o v a r y from a low l e v e l t o g r e a t e r than 80% of d i e t a r y i n t a k e depending on the source o f the d i e t and o t h e r r e l a t e d f a c t o r s 1973).  One  o f t h e s e f a c t o r s was  dietary calcium.  (Miller,  Newland e t a l .  (1958) surmised t h a t i n c r e a s e d c a l c i u m uptake would i n t e r f e r e w i t h z i n c r e t e n t i o n i n growing p i g s but S u t t l e and M i l l s  (1966) c l a i m e d  t h i s t o be due t o a lower z i n c a v a i l a b i l i t y i n c a l c i u m supplemented  - 44  rations.  -  Other authors have concluded  w h i l e t h e r e appeared t o  be  lower a v a i l a b i l i t i e s o f z i n c when h i g h l e v e l s o f c a l c i u m were p r e s e n t i n the d i e t , t h e r e was (Kirchgessner, According  1965;  to O ' D e l l  Miller,  1973;  M i l l s and W i l l i a m s ,  (1969), d i e t a r y p h y t a t e  s o l u b i l i t y of zinc. excess  a paradoxical increase i n zinc retention  T h i s p r o c e s s was  r e a c t e d to decrease  the  a c c e l e r a t e d upon a d d i t i o n o f  c a l c i u m both by mass a c t i o n f o r m a t i o n o f c a l c i u m z i n c phytate  w e l l as by e l e v a t i n g i n t e s t i n a l pH. pH  1971).  6 and  above.  However, M i l l e r  t i o n w i t h z i n c was  Z i n c p h y t a t e was  lower z i n c a v a i l a b i l i t y ,  If high calcium  interacdiets  t h e r e s h o u l d be an i n c r e a s e i n copper  b i l i t y as both copper and s i t e s i n the i n t e s t i n e  l e a s t s o l u b l e at  (1975) i n d i c a t e d the phytate  not e v i d e n t i n ruminants.  as  availa-  z i n c compete f o r the p r o t e i n m e t a l - b i n d i n g  (Underwood, 1977).  U n f o r t u n a t e l y , the depth o f t h i s experiment w i l l not a l l o w a c o n c l u s i o n to be drawn.  D i e t a r y c a l c i u m may  have i n c r e a s e d the  a v a i l a b i l i t y o f d i e t a r y copper c a u s i n g an i n t e r f e r e n c e i n z i n c and molybdenum a b s o r p t i o n .  I t may  a l s o have decreased  the a v a i l a b i l i t y  of  d i e t a r y z i n c and molybdenum r e s u l t i n g i n i n c r e a s e d copper availability.  A l t e r n a t i v e l y , c a l c i u m carbonate  may  s i m p l y have a c t e d  as a c a r r i e r f o r a more h i g h l y a v a i l a b l e form o f contaminant copper which i n t u r n i n t e r a c t e d to reduce the l e v e l o f z i n c and molybdenum absorption.  The  e f f e c t o f a l t e r e d pH can not be r u l e d out as  a v a i l a b i l i t y o f copper and the g a s t r o - i n t e s t i n a l t r a c t i s necessary  in this  area.  the  z i n c were g r e a t l y i n f l u e n c e d by the pH i n (Kirchgessner  e t a l . , 1977).  F u r t h e r work  - 45 -  The confusing.  i n t e r p r e t a t i o n o f t h e apparent d i g e s t i b i l i t y o f i r o n i s A significant difference  ( p < . 0 5 ) e x i s t e d between the  means o f t h e two treatments y e t t h e mean v a l u e f o r the animals on the c o n t r o l r a t i o n was n e g a t i v e (-13.61%).  I t i s g e n e r a l l y agreed  e x c e p t t h r o u g h b l e e d i n g , i r o n e x c r e t i o n i n the gut o f d a i r y i s very limited  (Underwood, 1977).  cattle  Because o f t h i s , a l t e r a t i o n s i n  b o d i l y i r o n c o n t e n t s o c c u r s through adjustment The  that  i n absorption rates.  author r e c o r d e d i r o n a b s o r p t i o n t o be n i l when body s t o r e s were  adequate  and o n l y d u r i n g p e r i o d s o f need was i r o n absorbed a c r o s s the  i n t e s t i o n a l mucosa.  The low mean v a l u e f o r apparent a b s o r p t i o n o f  i r o n by a n i m a l s on t h e c a l c i u m treatment mals had adequate  body s t o r e s o f i r o n .  (2.98%) i n s i n u a t e s these a n i Some o f these animals a l s o were  i n n e g a t i v e a b s o r p t i o n s t a t e s as i n d i c a t e d by the h i g h s t a n d a r d deviation  (12.04%) a s s o c i a t e d w i t h the mean.  As t o why t h e c o n t r o l  group's mean i r o n d i g e s t i b i l i t y v a l u e proved t o be n e g a t i v e can o n l y be s p e c u l a t e d upon.  N e g a t i v e i r o n r e t e n t i o n has been demonstrated t o  o c c u r i n h o r s e s by Spais e t a l . (1977).  The v a l u e s ranged from -34.9%  t o 59.8% w i t h a mean r e t e n t i o n o f 9.5%.  These r e s u l t s were i n f l u e n c e d  by copper c o n c e n t r a t i o n but n o t by z i n c o r manganese l e v e l s .  Possible  forms o f c o n t a m i n a t i o n were removed from the a r e a where the animals were housed and l e s s than  1% o f t h e t o t a l d a i l y i n t a k e o f i r o n c o u l d  have found i t s way i n t o the animals through i n g e s t i o n o f water.  It  was t h e r e f o r e assumed t h e r e was n e t e x c r e t i o n o f i r o n i n t o the g u t . A l s o , t h i s e x c r e t i o n was b e i n g a f f e c t e d by one o r more f a c t o r s t h a t  - 46 -  became l i m i t e d when a h i g h e r l e v e l the  was  added t o  diet. The  be  o f c a l c i u m carbonate  due  d i f f e r e n c e between the two  t o s i m i l a r reasons  as those  i r o n d i g e s t i b i l i t y means  expressed  f o r copper.  Little is  known about the a v a i l a b i l i t y o f i r o n from v a r i o u s s o u r c e s . t h e r e was due  and W i l l i a m s  o f the c a l c i u m carbonate  cannot be  (1971) i m p l i e d i r o n a b s o r p t i o n was  m o d i f i e d by c a l c i u m . be  (Kirchgessner  e t a l . , 1977), the c a l c i u m treatment  tract  to the t a c i t i n c r e a s e i n pH.  Copper,  and manganese have a l l been a s s o c i a t e d w i t h lowered i r o n  I f copper was  the  competing f o r a b s o r p t i o n  s i t e s then t h e r e s h o u l d have been a drop not a r i s e on the c a l c i u m treatment.  I t i s t h e r e f o r e suggested  in iron the  absorption  decreased  a v a i l a b i l i t y i n the c a l c i u m supplemented r a t i o n p r o b a b l y  influential  absorp-  (Underwood,  Z i n c a l s o i n t e r f e r e d w i t h the i n c o r p o r a t i o n i n t o and  r e l e a s e o f i r o n from f e r r i t i n .  of  adversely  should have lowered  t i o n through d i r e c t competition f o r absorption s i t e s  zinc  diet  A l s o , as the a v a i l a b i l i t y o f i r o n i s r e p o r t e d to  t h e d i g e s t i b i l i t y o f i r o n due  1977).  fact  ignored.  g r e a t l y i n f l u e n c e d by the pH i n the g a s t r o i n t e s t i n a l  zinc  The  a h i g h e r c o n c e n t r a t i o n o f i r o n i n the c a l c i u m treatment  to c o n t a m i n a t i o n  Mills  may  i n b r i n g i n g about the i n c r e a s e i n apparent  was  digestibility  iron.  The animals  mean v a l u e f o r manganese apparent d i g e s t i b i l i t y f o r those  on the c o n t r o l  treatment  cows on the c a l c i u m treatment.  d i d not d i f f e r The  ( p > . 0 5 ) from t h a t f o r  l e v e l s were 13.77% and  11.32%  - 47  respectively.  -  In r a t s , L a s s i t e r e t a l . (1972) r e p o r t e d a major e f f e c t  o f low d i e t a r y c a l c i u m on manganese metabolism both a t the t i s s u e and 0.1%  i n the g u t . and 0.6%  The  level  l e v e l s o f c a l c i u m i n the above experiment were  w i t h the r e s u l t i n g manganese d i g e s t i b i l i t i e s o f 6.3%  t h e low c a l c i u m r a t i o n and t h e r e f o r e understood  18.6%  f o r the h i g h c a l c i u m d i e t .  for  It is  t h a t i f t h i s r e l a t i o n s h i p does m a n i f e s t  itself in  d a i r y c a t t l e , the c o n c e n t r a t i o n o f c a l c i u m i n the c o n t r o l d i e t was low enough t o a l t e r manganese metabolism.  High d i e t a r y c a l c i u m  phosphorus appeared to i n c r e a s e the requirement  not  and  f o r manganese i n  c a t t l e by a f f e c t i n g a b s o r p t i o n i n the s m a l l i n t e s t i n e as w e l l as r e t e n t i o n i n the t i s s u e  (Vagg and  Payne, 1971).  l e v e l r e q u i r e d to a c h i e v e t h i s r e s u l t was imposed on the p r e s e n t experiment. phosphorus l e v e l ,  w h i l e t h e r e may  A g a i n , the  calcium  o u t s i d e the range o f t h a t  T h i s was  e s p e c i a l l y t r u e o f the  be a r e l a t i o n s h i p between the  amount o f c a l c i u m i n the d i e t and manganese a b s o r p t i o n and r e t e n t i o n , t h e moderate c o n c e n t r a t i o n s o f d i e t a r y c a l c i u m appear t o bear  no  consequence.  Selenium c o n c e n t r a t i o n i n the f e c e s was t h a t i n the d i e t f o r both t r e a t m e n t s . f o r the c o n t r o l animals was ferent  (43.66%). Cairney,  A r e p o r t o f selenium 1961 ) concluded  t i t y o f selenium  The mean apparent  45.49% which was  ( p > . 0 5 ) from t h a t o f animals  between 54 and  dif-  treatment  d i g e s t i b i l i t y i n hoggets (Cousins  the f e c e s c o n t a i n e d r o u g h l y 40%  f e d . B u t l e r and P e t e r s o n  of  digestibility  not s i g n i f i c a n t l y  on the c a l c i u m  57%  and  of the quan-  (1961) suggested  this  level  - 48 -  was  low f o r sheep as t h e i r r e s u l t s showed g r e a t e r than 50%  selenium  appeared  monogastrics Formation  i n the f e c e s .  These v a l u e s are h i g h e r than those f o r  whose main r o u t e o f selenium e x c r e t i o n i s v i a the u r i n e .  o f i n s o l u b l e , u n a v a i l a b l e forms o f selenium occur i n the  rumen under h i g h l y r e d u c i n g c o n d i t i o n s (Underwood, 1977) e x p l a i n s t h i s c o n t r a s t i n methods o f e x c r e t i o n . of in  dietary  which  There are no r e p o r t s  c a l c i u m a l t e r i n g the a v a i l a b i l i t y o r a b s o r p t i o n o f d i e t a r y  selenium  ruminants.  M i l k progesterone sampling  l e v e l s were a n a l y z e d t o i d e n t i f y the b l o o d  times w i t h s p e c i f i c r e g i o n s o f the r e p r o d u c t i v e c y c l e .  a c t u a l progesterone  v a l u e was  a s s i g n e d t o an i n t e g r a l  The  category  depending on i t s a s s o c i a t i o n w i t h r e s p e c t t o the samples taken b e f o r e and  after i t .  O r i g i n a l l y , t h e r e were n i n e such c a t e g o r i e s which are  d e f i n e d i n Table 5. Of the e i g h t animals on each treatment, two c y c l i n g d u r i n g the e i g h t y day t r i a l . diagnosed  d i d not begin  These f o u r animals were  as h a v i n g c y s t i c o v a r i e s , which when t r e a t e d r e s u l t e d i n  normal c y c l i n g .  A l l o t h e r animals v a r i e d i n l e n g t h o f time between  c a l v i n g and the onset o f e s t r u s .  T h i s ranged  from 32 t o 48  days.  complete r e p r o d u c t i v e c y c l e o c c u r r e d b e f o r e i n s e m i n a t i o n was and  a l l cows e x h i b i t e d a t l e a s t one  period.  To determine  The  first  attempted  complete c y c l e w i t h i n the  the e f f e c t o f the r e p r o d u c t i v e c y c l e on  serum c o n s t i t u e n t s , two  s e p a r a t e a n a l y s e s o f v a r i a n c e were  u t i l i z e d the data o f a l l cows w h i l e the second  One  trial the  undertaken.  combined o n l y  - 49 -  TABLE 5 O r i g i n a l M i l k Progesterone Category D e s c r i p t i o n s  Category  Description  1  Before  2  Random peak n o t a s s o c i a t e d with  Progesterone L e v e l s  any a c t i v i t y .  7-15  cycling.  3  First  4  Estrus  5  Metestrus  6  Metestrus t o Diestrus  7  Diestrus  8  Diestrus to Proestrus  9  (ng/ml) 1 - 3  Proestrus  7-15 1 - 3 10 - 35 35 - 50 50 50 - 35 35 - 10  Proestrus  Maximum d e t e r m i n a b l e l e v e l = 50 ng/ml  TABLE 6 A d d i t i o n a l Hypotheses ANOVA #1 and #2  a , b, c , d, e  Ho:  u l  Ho:  u  Ho:  U  c 3  = u° = u  d 5  e - u e = ue 6  ?  8  Means i n the same l i n e w i t h d i f f e r e n t s u p e r s c r i p t l e t t e r s d i f f e r s i g n i f i c a n t l y (p<.05).  - 50 -  those  animals  that cycled.  Treatment and breed  s i d e r e d as were the c o v a r i a b l e s o f age t i o n and  e f f e c t s were con-  a t c a l v i n g , d a i l y m i l k produc-  the number o f days s i n c e c a l v i n g . The  f i r s t a n a l y s i s o f v a r i a n c e y i e l d e d s e v e r a l treatment  c a t e g o r y i n t e r a c t i o n s whereas the second d i d n o t . i n t e r p r e t e d t o mean the n o n c y c l i n g animals r e s u l t s due c a t e g o r y and  This  by  was  were i n f l u e n c i n g the  t o h a v i n g a l l t h e i r sample v a l u e s p l a c e d i n the  first  s h o u l d t h e r e f o r e not be i n c l u d e d when attempting  determine the e f f e c t s o f the r e p r o d u c t i v e c y c l e .  The  to  second a n a l y s i s  showed no d i f f e r e n c e ( p > . 0 5 ) between many o f the c a t e g o r i e s when the a d d i t i o n a l hypotheses l i s t e d i n Table 6 were t e s t e d .  I t was  combine some o f the c a t e g o r i e s t o i n c r e a s e the number o f in was  each one.  These new  decided  observations  c a t e g o r i e s are d e s c r i b e d i n Table 7.  r e - a n a l y z e d u s i n g the a d d i t i o n a l hypotheses i n Table Serum i n o r g a n i c phosphorus had  (p<.01) i n category e f f e c t s .  The  to  The  data  8.  a highly significant difference  v a l u e s a s s o c i a t e d with p r e c y c l i n g  ( c a t e g o r y P) were h i g h e r than those o f the o t h e r t h r e e c a t e g o r i e s . The  p r e d i c t e d means were 6.42  and  5.70  mg/100 ml f o r c a t e g o r y P and 5.13,  f o r c a t e g o r i e s E, T and  D r e s p e c t i v e l y . None o f the  c o v a r i a b l e s exerted a s i g n i f i c a n t e f f e c t It  t h e r e f o r e was  concluded  ( p > . 0 5 ) on the serum  trait.  r e p r o d u c t i v e c y c l i n g caused a d e p r e s s i o n i n  t h e serum i n o r g a n i c phosphorus  levels.  Serum i r o n proved to be h i g h l y s i g n i f i c a n t l y ( p < . 0 1 ) when comparing c a t e g o r i e s P and It  5.34,  a l s o approached s i g n i f i c a n c e  different  E w i t h c a t e g o r i e s T and  (p = 0.06)  when c a t e g o r y P was  D. com-  -  -  51  TABLE 7 Combined M i l k Progesterone  Previous Progesterone Categories  Description Pre  Categories  Cycling  Observations per category  1, 2, 3  47  4  28  Estrus Transition - Includes Proestrus and Metestrus  5,  9  Diestrus  6,  7,  38  8  TABLE 8  A d d i t i o n a l Hypotheses, ANOVA #3 u t i l i z i n g combined m i l k p r o g e s t e r o n e c a t e g o r i e s  Ho  3u  Ho  u  Ho  2u  Ho  u^  T  - u  p  P  E  U  T  "  + u _ - u _ - u  E  u - u  D  T  T  - u = 0  D  U  D D  = 0  =0  49  - 52 -  pared w i t h the o t h e r s and when c a t e g o r y E was c o n t r a s t e d w i t h T and D. The o n l y r e a l l a c k o f d i f f e r e n c e o c c u r r e d between c a t e g o r y T and D. Because o f the d e f i n i t e d i f f e r e n c e between v a l u e s a s s o c i a t e d with low progesterone  c o n c e n t r a t i o n and those w i t h h i g h progesterone  con-  c e n t r a t i o n , i t can be s t a t e d t h a t the r e p r o d u c t i v e hormones e x e r t e d an e f f e c t on serum i r o n c o n c e n t r a t i o n s . b e i n g t e s t e d were E versus  1.22 mg/1  1.12 mg/1  In t h i s case the p r e d i c t e d means  f o r c a t e g o r y P and 1.19 mg/1  f o r c a t e g o r y T and 1.09 mg/1  f o r category  f o r c a t e g o r y D.  Both serum copper and serum z i n c showed a s i g n i f i c a n t ference  dif-  ( p < . 0 5 ) when the mean o f c a t e g o r y T was c o n t r a s t e d with the  o t h e r c a t e g o r y means.  The p r e d i c t e d means t e s t e d f o r the f o u r c a t e -  g o r i e s f o r copper were 0.68, were 0.96,  0.93,  0.70,  0.89 and 0.98  from p r o e s t r u s and metestrus  0.67  mg/1.  and 0.71  mg/1  and f o r z i n c  As c a t e g o r y T c o n t a i n e d data  t h e r e c o u l d p o s s i b l y have been an e f f e c t  o f the t r a n s i t i o n i n hormone l e v e l s on serum copper and serum  zinc.  The serum i n o r g a n i c s u l f a t e l e v e l s i n c a t e g o r y P were ficantly different  signi-  ( p < . 0 5 ) from those i n c a t e g o r i e s E, T and D.  However, t h e r e was a l s o a h i g h l y s i g n i f i c a n t c o v a r i a b l e , days f r e s h .  ( p < . 0 1 ) e f f e c t o f the  T h i s c a t e g o r y d i f f e r e n c e was d i s m i s s e d due  t o the c o i n c i d e n c e o f c a t e g o r y P b e i n g p r e s e n t o n l y i n the e a r l y p o s t parturient  stage.  No o t h e r serum components were found t o v a r y w i t h tive cycling.  reproduc-  The r e p o r t o f Bach and Messervey (1969) r e g a r d i n g the  p o s s i b l e i n f l u e n c e o f e s t r o g e n on serum c a l c i u m c o u l d not be  substan-  t i a t e d here as the d i f f u s a b l e c a l c i u m f r a c t i o n was not measured.  - 53 -  Two o f t h e serum m i n e r a l s e x h i b i t e d s i g n i f c a n t l y h i g h e r ( p < . 0 1 ) c o n c e n t r a t i o n i n t h e A y r s h i r e s than i n the H o l s t e i n s . c o n s t i t u e n t s were phosphorus and copper.  The mean phosphorus  These  con-  c e n t r a t i o n f o r t h e A y r s h i r e s was 6.29 mg/100 ml with a s t a n d a r d d e v i a t i o n o f 1.30 mg/100 ml.  The H o l s t e i n serum c o n t a i n e d an average  o f 5.19 mg/100 ml phosphourus w i t h a s t a n d a r d d e v i a t i o n o f 1.41 mg/100 ml.  Copper average v a l u e s were 0.74 mg/1  mg/1  f o r t h e H o l s t e i n s w i t h s t a n d a r d d e v i a t i o n s o f 0.09 mg/1  group.  f o r the A y r s h i r e s and 0.65  As t h e r e was no breed e f f e c t i n apparent  f o r each  digestibilities of  any o f t h e m i n e r a l s , these d i f f e r e n c e s must be m e t a b o l i c a l l y controlled.  Kitchenham and Rowlands (1976) d i d n o t study  l e v e l s b u t d i d c o n s i d e r phosphorus.  copper  These authors r e p o r t e d no s i g n i -  f i c a n t d i f f e r e n c e i n phosphorus c o n c e n t r a t i o n s between A y r s h i r e s and H o l s t e i n s but d i d f i n d lower potassium  l e v e l s o f c a l c i u m , magnesium and  i n the blood o f the A y r s h i r e s .  I t i s assumed t h e r e was a  n u t r i t i o n a l e f f e c t as w e l l which confounded t h e comparison o f the p r e s e n t s t u d y w i t h t h a t o f Kitchenham and Rowlands  (1976).  A summary o f t h e mean and s t a n d a r d d e v i a t i o n v a l u e s f o r the serum c o n s t i t u e n t s f o r t h e animals o f each treatment 9.  appear i n Table  I n d i c a t i o n s o f t h e c o v a r i a b l e e f f e c t s on t h e serum components a r e  p r e s e n t e d i n Table A o f t h e appendix. Serum c a l c i u m l e v e l s showed a h i g h l y s i g n i f i c a n t response,  (p<.01)  i n c r e a s i n g from 9.87 mg/100 ml f o r animals on the c o n t r o l  - 54 -  TABLE 9 Summary o f Serum C o n s t i t u e n t s  Ca-Treatment  Control  Component  Std.Dev.  Mean 9  std.Dev.  Mean  Ca mg/100 ml  9.87**  0.80  10.22**  0.70  P  mg/100 ml  5.79**  1.46  5.42**  1.46  K  meq/1  5.36  0.94  5.26  0.80  2.39  0.35  2.41  0.22  48. 1  7. 1  Mg mg/100 ml S  mg/100 ml  6.3  47.2  1  Fe mg/1  1.16  0.23  1. 16  0. 19  Cu mg/1  0.67*  0. 10  0.69*  0. 10  Zn mg/1  0.90**  0.21  1.02**  0.20  Se ug/1  66. 1*  Significantly different 9 n n Mo Mn h  = = -  78 84 not a n a l y z e d grand mean 12 ug/1  19.4  *(p<.05),  70.7*  **(p<.01)  20.0  - 55 -  r a t i o n t o 10.22 mg/100 ml f o r those animals r e c e i v i n g calcium. was  additional  While t h e l e v e l o f t h e serum c a l c i u m i n the c o n t r o l animals  w e l l w i t h i n t h e p h y s i o l o g i c a l range expected f o r d a i r y  (8.78 - 10.38 mg/100 ml : Rowlands e t a l . ,  cattle  1977), i t was a p p a r e n t l y  b e i n g l i m i t e d by t h e c o n c e n t r a t i o n o f c a l c i u m i n t h e d i e t and the a v a i l a b i l i t y o f such. a u t h o r s t h a t serum  T h i s r i s e c o r r e s p o n d s t o the f i n d i n g s o f o t h e r  c a l c i u m shows a s m a l l e f f e c t o f d i e t a r y c o n d i t i o n s  (McDonald and B e l o n j e ,  1975; Payne e t a l . ,  1970; Thompson e t a l . ,  1978). The change i n c a l c i u m l e v e l s i n t h e serum was i n v e r s e l y r e l a t e d t o t h e change i n serum  i n o r g a n i c phosphorus  (p<.01).  The  mean f o r t h e c o n t r o l group (5.79 mg/100 ml) was h i g h e r than t h a t f o r t h e c a l c i u m treatment (5.42 mg/100 m l ) .  In s i m i l a r work r e p o r t e d by  Bushman e t a l . (1965), Hoar e t a l . (1970) and Smith e t a l . (1966), t h e l e v e l o f phosphorus  i n serum  dropped when t h e c a l c i u m c o n t e n t o f t h e  d i e t was r a i s e d i n r e l a t i o n t o t h e c o n s t a n t amount o f d i e t a r y phosphorus.  Smith e t a l .  t o phosphorus  (1966) d e s c r i b e d t h a t a l t e r i n g t h e c a l c i u m  r a t i o i n the f e e d s t u f f from 1:1 t o 2:1 t o 4:1 lowered t h e  serum phosphorus but t h e a u t h o r s r e p o r t e d i t ,  " d i d not, a t any t i m e ,  d r o p below t h e range n o r m a l l y expected f o r d a i r y cows."  T h i s range i s  g e n e r a l l y agreed t o be between 4.6 and 7.8 mg/100 ml (Rowlands 1977)  et a l . ,  w i t h a mean near 5.5 mg/100 ml (Hunter, 1977, based on 1157 ana-  l y s e s from l a c t a t i n g d a i r y c a t t l e . )  The c a l c i u m t o phosphorus  change d i d n o t c o n s i s t e n t l y produce a change i n plasma phosphorus  ratio  inorganic  l e v e l s i n o t h e r s t u d i e s such as those by Parker and Blowey  - 56 -  (1976) and Swenson e t a l . (1962). S e v e r a l authors have r e p o r t e d t h e phosphorus l e v e l i n the b l o o d t o be d i r e c t l y r e l a t e d t o phosphorus i n t a k e but n o t t o the phosphorus l e v e l s i n t h e body (McDonald and B e l o n j e , 1970; Wise e t a l . , 1963).  1975; Payne e t a l . ,  As 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  ( p > . 0 5 ) between the two treatments  f o r apparent d i g e s t i b i l i t y o f  phosphorus, t h e i n c r e a s e d c a l c i u m can be assumed t o have had an e f f e c t on phosphorus metabolism. Serum potassium  l e v e l s were n o t s i g n i f i c a n t l y  ( p > . 0 5 ) between t h e two t r e a t m e n t s .  different  The r e s p e c t i v e v a l u e s f o r the  c o n t r o l and t h e c a l c i u m t r e a t e d animals  were 5.36 and 5.26 meg/1.  Rowlands e t a l . (1977) r e p o r t e d t h e range o f serum potassium 351  levels of  l a c t a t i n g d a i r y cows between 40 and 100 days p o s t - c a l v i n g t o be  4.11 t o 6.11 meg/1 w i t h a mean o f 5.06 meq/1. Magnesium  l e v e l s i n t h e serum were a l s o u n a f f e c t e d by  increased calcium intakes (p>.05).  The mean v a l u e s o f 2.39 mg/100 ml  f o r t h e c o n t r o l group and 2.41 mg/100 ml f o r the c a l c i u m animals  correspond  t o t h e p u b l i s h e d range o f 2.28 t o 3.08 mg/100 ml  w i t h a mean o f 2.63 mg/100 ml (Rowlands e t a l . , 1977). Blowey (1976) r e p o r t e d serum mangesium with calcium trial.  l e v e l s i n animals  Parker and fed diets  : phosphorus r a t i o s more c l o s e l y a l i g n e d with those o f t h i s  T h e i r mean v a l u e s were 2.29 to 2.45 mg/100 ml w i t h no s i g n i f i -  c a n t d i f f e r e n c e due t o t h e c a l c i u m reports  treatment  (Bushman  magnesium  : phosphorus r a t i o .  There a r e  e t a l . , 1965; Hoar e t a l . , 1970) i n d i c a t i n g serum  was a d v e r s e l y a f f e c t e d by i n c r e a s e d d i e t a r y c a l c i u m .  - 57 -  However, t h i s o c c u r r e d o n l y when magnesium d i g e s t i b i l i t y was due  lowered  t o an i n t e r a c t i o n i n the gut w i t h the i n c r e a s e d c a l c i u m .  was no change i n the apparent experiment, concluded  As t h e r e  d i g e s t i b i l i t y o f magnesium i n t h i s  and no d i f f e r e n c e i n serum magnesium l e v e l s , i t can be  t h e r e was no s i g n i f i c a n t p h y s i c a l o r m e t a b o l i c  interaction  between c a l c i u m and magnesium. Kennedy and M i l l i g a n i n o r g a n i c s u l f a t e i n sheep. w i t h a mean o f 45.0 mg/1.  (1978) monitored The v a l u e s ranged  the l e v e l o f serum from 32.5 t o 60.0 mg/1  The mean v a l u e s r e p o r t e d here a r e 47.2 mg/1  f o r the c o n t r o l group and 48.1 mg/1 f o r the animals r e c e i v i n g e x t r a calcium.  These means were n o t s i g n i f i c a n t l y d i f f e r e n t  t h e r e was no change i n apparent obvious  ( p > . 0 5 ) and as  d i g e s t i b i l i t y o f s u l f u r , t h e r e a r e no  i n t e r a c t i o n s between s u l f u r and c a l c i u m . Serum i r o n l e v e l s were a p p a r e n t l y equal f o r animals on e i t h e r  treatment.  The mean v a l u e s were the same w i t h o n l y a s l i g h t  dif-  f e r e n c e i n t h e s t a n d a r d d e v i a t i o n s (1.16 ± 0.23 mg/1 f o r the c o n t r o l versus  1.16 ± 0.19 mg/1 f o r the c a l c i u m t r e a t m e n t ) .  The  w i d e s t range i n v a l u e s r e p o r t e d i n the l i t e r a t u r e was t h a t o f Stout e t al.  (1976), b e i n g 0.37 t o 3.21 mg/1 w i t h a mean o f 1.72 mg/1.  change i n apparent  The  a b s o r p t i o n o f i r o n when c a l c i u m was added t o the  d i e t d i d not f o l l o w through t o the serum. Copper l e v e l s i n the serum o f the animals on the c a l c i u m treatment treatment. and  were s i g n i f i c a n t l y h i g h e r  ( p < . 0 5 ) than those on the c o n t r o l  The means o f 0.67 mg/1 and 0.69 mg/1 were q u i t e s i m i l a r  c o n s i d e r i n g the s t a n d a r d d e v i a t i o n o f 0.10 mg/1 i n each c a s e , i t  - 58 -  i s q u e s t i o n a b l e as t o whether these means a r e indeed  different.  Copper i n serum i s m e t a b o l i c a l l y c o n t r o l l e d by the l i v e r and except i n t h e case o f d e f i c i e n c y o r t o x i c i t y , s h o u l d be l i t t l e a f f e c t e d (Underwood, 1977).  However, as t h e r e was a h i g h l y s i g n i f i c a n t  i n c r e a s e i n copper apparent d i g e s t i b i l i t i e s i n the c a l c i u m t r e a t e d animals,  i t i s p o s s i b l e t h i s i n c r e a s e d copper c o u l d have c o n t r i b u t e d  to this rise  i n serum copper.  Hemingway e t a l . (1962) r e p o r t e d a  s l i g h t b u t s i g n i f i c a n t r e d u c t i o n i n serum copper l e v e l s i n sheep drenched d a i l y w i t h c a l c i u m c a r b o n a t e . any  The authors  d i d n o t mention  i n f o r m a t i o n r e g a r d i n g d i g e s t i b i l i t y o f copper so i t i s i m p o s s i b l e  t o conclude  as t o whether t h i s e f f e c t was due t o an i n t e r f e r e n c e i n  a b s o r p t i o n o r metabolism.  The range o f serum v a l u e s f o r l a c t a t i n g  d a i r y c a t t l e r e p o r t e d by Rowlands e t a l . (1977) was from 0.56 to 0.96 mg/1.  The mean v a l u e was s t a t e d t o be 0.73 mg/1. Increased  decrease cant  d i e t a r y calcium r e s u l t e d i n a s i g n i f i c a n t  i n z i n c a b s o r p t i o n but c o n c o m i t a n t l y  ( p < . 0 1 ) i n c r e a s e i n serum z i n c .  by K i r c h g e s s n e r  mg/1 whereby t h a t from the animals mg/1.  caused a h i g h l y s i g n i f i -  T h i s paradox was f i r s t  e t a l . (1960; c i t e d by M i l l s and W i l l i a m s ,  mean v a l u e o f serum z i n c i n the animals  (p<.05)  reported  1971).  The  on the c o n t r o l r a t i o n was 0.90  on the h i g h c a l c i u m d i e t was 1.02  Depending on the stage o f e s t r u s , Dufty e t a l . (1977) r e p o r t e d  mean serum z i n c v a l u e s o f 1.01 ± 0.16 mg/1 t o 1.15 ± 0.27 mg/1.  One  mechanism t h a t c o u l d p o s s i b l y account f o r t h i s i n c r e a s e i n serum z i n c would be a m e t a b o l i c suggested  i n t e r a c t i o n between c a l c i u m and z i n c .  It is  i n c r e a s e d l e v e l s o f c a l c i u m i n the serum caused an i n c r e a s e d  - 59 -  r e l e a s e o f z i n c from the t i s s u e s t o the serum or a b l o c k a g e i n the deposition of zinc. Serum manganese l e v e l s were a n a l y z e d but due t o l i m i t a t i o n s in  the t e c h n i q u e s a v a i l a b l e , o n l y an e s t i m a t e c o u l d be r e p o r t e d .  amount p r e s e n t i n the serum o f the cows on both treatments about the mean o f 12 ug/1.  The  t e c h n i q u e was  not  The  varied  sufficiently  a c c u r a t e t o enable a d i f f e r e n c e t o be determined between the t r e a t ments. al.  As t o the p o s s i b l e e f f e c t o f c a l c i u m on manganese, L a s s i t e r e t  (1972) u t i l i z e d the i s o t o p e  manganese metabolism.  Mn  t o determine  a major change i n  T h i s o c c u r r e d both i n the t i s s u e and w i t h i n the  i n t e s t i n e s when d e f i c i e n t l e v e l s o f c a l c i u m were f e d t o r a t s . i s widespread  disagreement  There  i n the l i t e r a t u r e as t o the e x a c t range o f  manganese i n serum (Underwood, 1977).  U n t i l f u r t h e r methods become  a v a i l a b l e , any e f f e c t o f c a l c i u m on serum manganese i n d a i r y c a t t l e will  remain  unknown.  Serum molybdenum c o u l d not be a n a l y z e d due t o the low  levels  e x p e c t e d and the p r e s e n t i n a d e q u a c i e s o f equipment. There was  a s i g n i f i c a n t i n c r e a s e ( p < . 0 5 ) i n the l e v e l o f  serum selenium i n the animals exposed calcium.  However, t h e r e was  breed i n t e r a c t i o n .  to a higher l e v e l of d i e t a r y  also a significant  ( p < . 0 5 ) treatment :  On examination o f the data i t appeared  t h a t the  low serum selenium v a l u e s a s s o c i a t e d w i t h one animal unduly a f f e c t e d t h e mean.  T h i s s i g n i f i c a n t d i f f e r e n c e must t h e r e f o r e be r e j e c t e d as a  r e a l d i f f e r e n c e due t o t r e a t m e n t . mal  Removing the data o f t h i s one  from the a n a l y s i s d e l e t e d the s i g n i f i c a n t d i f f e r e n c e .  ani-  The mean  - 60  v a l u e s o f the remaining o f serum selenium  -  animals were 72 + 20 ug/1  i n the cow  i n q u e s t i o n was  whereas the  only 4 4 + 1 3  level  ug/1.  Underwood (1977) i n d i c a t e d the mean v a l u e o f whole bood selenium ruminants was  80 ug/1  w i t h a range o f 40 t o 200  can be o f f e r e d as t o why  M i l k and  the selenium  ug/1.  No  l e v e l i n the one  explanation  animal was  so  to enable e s t i m a t i o n  of  t h e p e r c e n t a g e r e t e n t i o n o f the v a r i o u s m i n e r a l s w i t h i n the c a t t l e  on  each t r e a t m e n t .  u r i n e samples were a n a l y z e d  in  Due  m i l k and u r i n e and  to the v e r y low l e v e l s o f t r a c e elements i n the  the d i f f i c u l t y i n a s s e s s i n g these  a c c u r a t e l y , a d e l i n e a t i o n o f l e s s than 3% t o be n e g l i g i b l e .  sented Table  As a r e s u l t , o n l y the macro m i n e r a l The  10 p r o v i d e s  d a i l y output  minerals  assumed  l e v e l s were  assumption t h e r e -  the apparent d i g e s t i b i l i t i e s o f the t r a c e elements r e p r e -  c l o s e l y enough the p e r c e n t a g e o f the m i n e r a l  the two  concentrations  of i n t a k e v a l u e s was  used i n the e s t i m a t i o n o f the r e t e n t i o n r a t e . f o r e was  low.  the means and  standard  d e v i a t i o n s f o r the  o f macro elements i n the m i l k and  treatments.  The  are p r e s e n t e d  intake retained.  u r i n e o f the animals on  apparent p e r c e n t a g e r e t e n t i o n f o r these  i n Table  r e p o r t e d to be both m a r g i n a l 1974;  and  Braithwaite,  same  11.  In ruminants, the u r i n a r y e x c r e t i o n o f c a l c i u m has  (Braithwaite,  total  been  s t a b l e over wide ranges i n i n t a k e s 1975,  Ramberg e t a l . , 1974).  These  l o s s e s were not s i g n i f i c a n t l y a f f e c t e d by changes i n a b s o r p t i o n by ( B r a i t h w a i t e and  Riazuddin,  1971).  age  Ramberg e t a l . (1976) s t a t e d t h a t i n  g e n e r a l , the s m a l l v a r i a t i o n s observed i n u r i n a r y c a l c i u m c o u l d have  - 61 -  TABLE 10 Total  D a i l y Output o f the Macro Elements i n the M i l k and U r i n e  MILK  Control  Component (g/day)  Mean  1  Ca-Treatment  Std.Dev.  Mean  1  Std.Dev.  Ca  27.51  7. 06  27.34  1.99  P  15.32  3.50  14.31  3.45  K  32.09  9.83  33.20  5.56  Mg  2.56  0.67  2.51  0.25  S  6. 15  3. 18  6.33  2.81  URINE  Ca  0.34  0. 18  0.57  0. 30  P  8.84*  3.54  6.53*  1. 15  247.40  87.39  256.20  85.29  Mg  3.96  1.92  3.44  2.24  S  3.26  1.82  4. 18  2.33  K  Significantly  different  * (p<.05)  - 62 -  TABLE 11 Apparent Percentage R e t e n t i o n o f the Macro Elements  Std.Dev.  -18.6**  6.0  14.5**  10.4  10.3*  P  3.1*  Std.Dev. 12.8 6.0  K  27.3  23.4  25.7  20.1  Mg  14.1  9.0  18.7  5.0  S  13.4  6.7  14.0  8.1  Significantly j  MeanJ  Mean'  (%) Ca  Ca-Treatment  Control  Component  n = 5  different  * (p<.05),  **  (p<.01)  - 63  only a t r i v i a l present  -  e f f e c t on c a l c i u m metabolism.  study where t h e r e was  Such was  i n the  a s l i g h t but n o n s i g n i f i c a n t ( p > . 0 5 )  d i f f e r e n c e between the means o f the two  treatments.  e x c r e t i o n i n the u r i n e f o r the c o n t r o l animals s e n t e d 0.31%  the case  The mean c a l c i u m  (0.34  g/day) r e p r e -  of the average d a i l y i n t a k e o f c a l c i u m w h i l e t h a t f o r the  c a l c i u m treatment  group (0.57  g/day) comprised 0.23%.  Paquay e t a l .  (1968) determined a h i g h l y s i g n i f i c a n t c o r r e l a t i o n between d i g e s t i b l e c a l c i u m and the c a l c i u m i n the m i l k .  such r e l a t i o n s h i p e x i s t e d i n  this trial  as t h e r e was  treatments  f o r c a l c i u m c o n t e n t s o f the m i l k y e t t h e r e was  digestibilities. b o t h treatments  The  no  No  s i g n i f i c a n t d i f f e r e n c e ( p > . 0 5 ) between  l e v e l s o f c a l c i u m i n the m i l k o f the animals  were c o n s i s t e n t w i t h the mean v a l u e r e p o r t e d  Ramberg e t a l . (1974) o f 1.2 r e s u l t e d i n means o f c o n t r o l and  f o r apparent  1.13  g/1  g/1. and  Converting 1.15  g/1  by  the v a l u e s i n Table  c a l c i u m t r e a t e d groups.  c a l c i u m i n t a k e i n c r e a s e s ( B r a i t h w a i t e , 1975; former author  Bushman e t a l . , 1965).  "When the c a l c i u m i n t a k e was  absorbed and bone r e s o r p t i o n decreased.  phosphorus from bone was decreased."  as  d e s c r i b e d the h y p o t h e t i c a l mechanism f o r such a c t i o n  i n the f o l l o w i n g manner. c a l c i u m was  10  r e s p e c t i v e l y f o r the  Phosphorus i n the u r i n e has been r e p o r t e d to decrease  The  on  reduced  i n c r e a s e d , more  The  supply of  and u r i n a r y e x c r e t i o n o f phosphorus  T h i s would e x p l a i n the s i g n i f i c a n t l y lower  phosphorus e x c r e t i o n i n the u r i n e o f animals  (p<.05)  f e d supplemental  when compared w i t h the cows on the c o n t r o l r a t i o n .  The  calcium  range o f  phosphorus e x c r e t i o n determined by Lomba e t a l . (1969) was  from  0.3  - 64 -  t o 3 0.5 g/day w i t h a mean o f 6.6 g/day i n the l a c t a t i n g cow. phosphorus mean e x c r e t i o n r a t e s o f the c o n t r o l group  The  (8.84 g/day) and  t h e c a l c i u m t r e a t e d animals (6.53 g/day), were w e l l w i t h i n the normal range.  There was no s i g n i f i c a n t d i f f e r e n c e  f o r phosphorus s e c r e t i o n i n t o the m i l k . by the c o n t r o l group was group was  14.31  g/day.  ( p > . 0 5 ) between  The average amount  groups secreted  15.32 g/day and t h a t o f the c a l c i u m t r e a t e d The mean v a l u e (10.4 g/day) p r e s e n t e d by Lomba  e t a l . (1969) was low but the range (3.2 t o 21.4 g/day) covered the l e v e l s encountered i n the p r e s e n t t r i a l . The potassium l e v e l s i n the m i l k and u r i n e v a r i e d w i d e l y w i t h i n t r e a t m e n t s but t h e r e was no d i f f e r e n c e q u a n t i t i e s o f the two t r e a t m e n t s .  ( p > . 0 5 ) i n the mean  The range o f m i l k potassium  losses  quoted by Paquay e t a l . (1969) v a r y from 10.9 to 33.0 g/day w i t h a mean o f 23.7 g/day.  The average potassium l o s s e s o f the c o n t r o l and  c a l c i u m t r e a t e d a n i m a l s , 32.09 and 33.20  g/day r e s p e c t i v e l y , were a t  t h e h i g h end o f the range most l i k e l y due t o the h i g h d i e t a r y c o n t e n t o f potassium. tion  (Miller,  As the u r i n e i s the p r i m a r y r o u t e f o r potassium e x c r e 1975) i t was n o t s u r p r i s i n g t h a t almost 60% of the  d i e t a r y potassium i n t a k e appeared i n the u r i n e .  The average  e x c r e t i o n o f potassium by animals on the c o n t r o l d i e t was  daily  247.40g  (59.18% o f i n t a k e ) and the amount f o r the c a l c i u m t r e a t e d cows was 256.20  g (59.82% of i n t a k e ) . The average d a i l y s e c r e t i o n o f magnesium  t h e c o n t r o l animals (2.56 g/day) d i d not d i f f e r amount  i n t o the m i l k f o r  (p>.05)  from the  s e c r e t e d by the animals on the c a l c i u m treatment (2.51 g/day).  - 65 -  The  range o f v a l u e s r e p o r t e d by Lomba e t a l . (1968) f o r magnesium  l o s s e s t o the m i l k was 0.62 t o 2.83  g/day w i t h a mean o f 1.85 g/day.  W h i l e these authors i n d i c a t e d t h e r e was a n o n s i g n i f i c a n t c o r r e l a t i o n between d i g e s t i b l e magnesium and m i l k magnesium, t h e y i m p l i e d a s h i f t i n magnesium i n t a k e s most l i k e l y would i n f l u e n c e the m i l k magnesium content.  The mean i n t a k e l e v e l s t h a t were r e p o r t e d were h a l f o f the  average f o r animals on t h i s experiment which would j u s t i f y the added s e c r e t i o n i n t o the m i l k .  The u r i n a r y magnesium was a l s o r e p o r t e d t o  be s i g n i f i c a n t l y c o r r e l a t e d with magnesium i n t a k e .  A g a i n , the mean  d a i l y u r i n a r y e x c r e t i o n s o f magnesium f o r the animals on the p r e s e n t trial  (3.96 g/day f o r the c o n t r o l , 3.44 g/day f o r the c a l c i u m  treatment)  were s l i g h t l y h i g h e r than t h a t d e r i v e d by Lomba e t a l .  (1968) o f 2.9 g/day. There was no d i f f e r e n c e ( p > . 0 5 ) i n m i l k o r u r i n e s u l f u r cont e n t s when expressed  as a t o t a l d a i l y o u t p u t .  Jenny and O ' D e l l (1979)  demonstrated the u r i n a r y s u l f u r e x c r e t i o n i n d a i r y s t e e r s t o be between 13.4 and 15.1% o f the d i e t a r y i n t a k e l e v e l s . recorded  i n Table  10 amount t o a p p r o x i m a t e l y  f o r the animals on both t r e a t m e n t s . be i n the amount o f s u l f u r absorbed  The r e s u l t s  14% of the d i e t a r y i n t a k e  The major d i f f e r e n c e appears t o as t h e r e was about  11/2 times  g r e a t e r a b s o r p t i o n o f s u l f u r by the l a c t a t i n g d a i r y cows than by the d a i r y s t e e r s s t u d i e d by Jenny and O ' D e l l  (1979).  T h i s s u l f u r was most  l i k e l y d e p o s i t e d i n the m i l k .  F e e d i n g h i g h e r l e v e l s o f c a l c i u m t o postpartum d a i r y c a t t l e  - 66  resulted in a highly significant calcium  retained.  The  -  ( p < . 0 1 ) i n c r e a s e i n the p e r c e n t a g e  animals on the c o n t r o l r a t i o n were i n a d e f i -  cit  calcium  b a l a n c e r e q u i r i n g an average o f  all  t h e i r p h y s i o l o g i c a l requirements.  18.6%  more c a l c i u m  Presumably, these animals would  a t t a i n a p o s i t i v e b a l a n c e once the heavy l a c t a t i o n s t r e s s was Braithwaite up  (1974) i n d i c a t e d c a l c i u m  to meet  removed.  r e t e n t i o n would be i n c r e a s e d f o r  t o f i f t e e n weeks a f t e r animals were a b l e to absorb adequate  s u c h t h a t body s t o r e s c o u l d be r e p l e n i s h e d . t i o n returned  to near z e r o .  The  calcium  calcium  After this period, reten-  t r e a t e d cows were i n a p o s i -  t i v e b a l a n c e (14.5% apparent r e t e n t i o n ) which would i n f e r a n i m a l s were s t r e s s e d e a r l y i n t h e i r l a c t a t i o n s and  these  were i n the  pro-  c e s s o f r e b u i l d i n g body s t o r e s . The  phosphorus apparent r e t e n t i o n a l s o i n c r e a s e d  o f 3. 1% to a mean o f feedstuff.  10.3%  ( p < . 0 5 ) with the a d d i t i o n o f c a l c i u m  As the apparent a b s o r p t i o n was  serum phosphorus l e v e l s and would support  not i n f l u e n c e d , but  to  the  the  u r i n a r y phosphorus l e v e l s were lower, t h i s  the h y p o t h e s i s  i n c r e a s e d d i e t a r y c a l c i u m was of calcium  from a mean  of Braithwaite  (1975).  I t i s evident  the  s u f f i c i e n t to cause a net uptake  i n t o the bone which p r e v e n t e d the r e l e a s e o f phosphorus.  P o t a s s i u m , magnesium and  s u l f u r d i d not v a r y i n apparent  a b s o r p t i o n , m i l k s e c r e t i o n or u r i n e e x c r e t i o n l e v e l s so the r e t e n t i o n i t s e l f a l s o d i d not change ( p > . 0 5 ) . i n c r e a s e d d i e t a r y c a l c i u m had  In t h i s  no e f f e c t on these m i n e r a l  apparent  case, elements.  I n t e r p r e t a t i o n o f the t r a c e element apparent r e t e n t i o n remain gaurded as the c o n c e n t r a t i o n s  i n the m i l k and  u r i n e were  values  - 67  unattainable.  -  M i l l s and W i l l i a m s  (1971) s t a t e d t h a t copper, z i n c  manganese u r i n a r y output r e p r e s e n t s mineral  excreted.  r a t e s were o n l y  Kirchgessner  1 - 3%  only  1 - 2%  (1965) claimed  of the t o t a l o f each the m i l k  of the d i e t a r y i n t a k e and  were r e t a i n e d a t a r a t e o f  10 t o 20%.  u r i n e are both l e s s than 0.5%  and  secretion  the above  minerals  I r o n l o s s e s t o the m i l k  and  of d i e t a r y l e v e l s (Underwood, 1977).  T h i s a u t h o r a l s o quoted the m a j o r i t y o f molybdenum and  selenium  excre-  t i o n i n ruminants appeared i n the f e c e s u n l i k e m o n o g a s t r i c s whose main route  o f e x c r e t i o n f o r these two  minerals  was  the u r i n e .  apparent d i g e s t i b i l i t y r a t e s o f the t r a c e m i n e r a l s  are an  While  the  overestima-  t i o n o f the r e t e n t i o n o f these elements, t h e y most l i k e l y r e f l e c t a  The  i m p l i c a t i o n s from such a study as t h i s can be  towards d a i r y c a t t l e p r o d u c t i v i t y .  extended  B e s i d e s obvious parameters which  a f f e c t growth, maintenance, m i l k p r o d u c t i o n  and  fertility,  many f a c -  t o r s have more s u b t l e e f f e c t s depending on t h e i r a s s o c i a t i o n w i t h dietary ingredients. apparent absorptions t h e i r greatest Hideroglou, months.  and  s l i g h t a l t e r a t i o n s i n some o f the serum c o n c e n t r a t i o n  i n f l u e n c e on f e r t i l i t y .  1979)  The  The  reproduction.  minerals  (1974, c i t e d  by  monitored f e e d s t u f f s f e d to cows over a p e r i o d  author noted t r a c e element l e v e l s i n the  reports consider  of  feed a l t e r e d  fertility.  the e f f e c t o f i n c r e a s e d  calcium  Swenson et a l . (1962) added excess c a l c i u m  d i e t s f e d to d a i r y c a t t l e and  other  would most l i k e l y have  Valyuskin  t h o s e i n the b l o o d which caused a response i n Few  trend.  on  to non-legume  n o t i c e d i n h i b i t e d o v u l a t i o n and  estrus  - 68 -  cycling.  By adding t r a c e elements t o the d i e t , f e r t i l i t y  The c a l c i u m t o phosphorus Lewis  improved.  r a t i o has been s t u d i e d by L i t t l e j o h n  and  (1960) and Parker and Blowey (1976), both o f whom concluded t h a t  o v e r a wide range the r a t i o appeared not t o a f f e c t M o d e r a t e l y low (40 ppm) t i l i t y u n l e s s combined fertility  was  fertility.  d i e t a r y manganese had no obvious e f f e c t on w i t h a h i g h c a l c i u m t o phosphorus  depressed (Hignett,  1960).  r a t i o whereby  No d e f i n i t e c o n c l u s i o n s can  be drawn from t h i s experiment as t o the e f f e c t s o f i n c r e a s e d i n t a k e s on  fer-  calcium  fertility.  S e v e r a l i n f e r e n c e s can be made on the p o s s i b l e a l t e r a t i o n s i n fertility Hunter  brought about w i t h the change i n d i e t a r y c a l c i u m  levels.  (1977) noted changes i n the plasma i n o r g a n i c phosphate  and  b l o o d g l u c o s e c o n c e n t r a t i o n s around mating time appeared t o produce the  g r e a t e s t e f f e c t on f e r t i l i t y .  With lower serum phosphorus  con-  c e n t r a t i o n s i n a n i m a l s on the c a l c i u m treatment, the p o s s i b i l i t y o f t h i s o c c u r r i n g would be g r e a t e r .  Both serum copper and serum  zinc  l e v e l s were i n c r e a s e d w i t h the a d d i t i o n o f c a l c i u m c a r b o n a t e . Copper  l e v e l s i n the b l o o d were s t u d i e d by H i g n e t t  L i t t l e j o h n and Lewis (1960).  (1960) and  No s i g n i f i c a n t r e l a t i o n s h i p was  between copper i n the b l o o d and r e p r o d u c t i v e performance. low f e r t i l i t y  apparent  However,  i n d a i r y c a t t l e i n d i c a t i v e o f d e l a y e d or depressed  e s t r u s has been shown t o be due t o copper d e f i c i e n c y (Underwood, 1977).  Manickam (1977, c i t e d by H i d e r o g l o u , 1979) r e p o r t e d  signifi-  c a t l y h i g h e r s e r a l e v e l s o f copper and z i n c as w e l l as i r o n and manganese i n r e g u l a r breeder cows v e r s u s r e p e a t b r e e d e r s .  These  results  - 69  favour  the animals on the c a l c i u m  a d d i t i o n a l calcium  carbonate had  serum selenium i s unknown.  -  treatment.  Whether the l a c k o f  a t r u e i n f l u e n c e on the  Such a d e f i c i e n c y has  r e p r o d u c t i v e performance i n a l l s p e c i e s s t u d i e d I n c r e a s i n g the recommended c a l c i u m r a t i o n s from 0.7%  to 1.5%  by  of impaired  (Underwood, 1977). of dairy  by adding supplemental c a l c i u m  i n c r e a s i n g the l e v e l o f copper and higher  resulted in  content  improve the f e r t i l i t y o f the a n i m a l s . T h i s may  level  cattle  carbonate  may  be brought about  z i n c and p o s s i b l y selenium i n the  serum.  The  l e v e l of d i e t a r y calcium  would a l s o a d j u s t  calcium  to phosphorus r a t i o c l o s e r t o the range K e n d a l l  the  e t a l . (1970)  recommended when c o n s i d e r i n g the needs o f p a r t u r i e n t cows.  - 70 -  SUMMARY AND CONCLUSIONS  T h i s study was i n i t i a t e d t o determine i f i t was p o s s i b l e t o i n c r e a s e the amount o f c a l c i u m absorbed by p o s t p a r t u r i e n t d a i r y c a t t l e under the s t r e s s o f peak l a c t a t i o n .  I t was a l s o o f prime i n t e r e s t t o  d i s c o v e r any d e t r i m e n t a l e f f e c t s o f such an i n c r e a s e .  I t was d e t e r -  mined t h a t by i n c r e a s i n g the c a l c i u m content o f the d i e t t o approximat e l y t w i c e the recommended l e v e l , the apparent a b s o r p t i o n o f c a l c i u m r o s e from a low l e v e l t o near the maximum p o s s i b l e .  T h i s l e d t o an  i n c r e a s e i n c a l c i u m apparent r e t e n t i o n such t h a t the animals a negative to a p o s i t i v e calcium balance.  went from  The d i e t a r y i n t e r a c t i o n s  were confounded due t o the form o f the c a l c i u m added t o the d i e t . However, i n many cases i t was p o s s i b l e t o separate out the e f f e c t s o f t h e a d d i t i o n a l c a l c i u m such t h a t c o n c l u s i o n s c o u l d be drawn. F i r s t l y , t h e r e was no a l t e r a t i o n i n the ad l i b i t u m i n t a k e s o f t h e d i e t s o r were t h e r e any change i n the d i g e s t i b i l i t i e s o f the organic constituents.  N e i t h e r m i l k p r o d u c t i o n , body weight change nor  plasma g l u c o s e were a f f e c t e d by t h e treatment. had  A d d i t i o n o f calcium  no gross p h y s i c a l o r p h y s i o l o g i c a l e f f e c t s on the cows over the  duration o f the t r i a l .  The one minor p h y s i c a l v a r i a t i o n which  o c c u r r e d as a r e s u l t o f the supplemental c a l c i u m carbonate  was the  i n f e r r e d i n c r e a s e i n i n t e s t i n a l pH. Of t h e s i x m i n e r a l s which e x h i b i t e d d i f f e r e n c e s i n apparent a b s o r p t i o n and/or serum c o n c e n t r a t i o n , t h r e e agree w e l l with the document a t i o n i n the l i t e r a t u r e .  The i n c r e a s e d c a l c i u m i n t a k e s were  r e f l e c t e d by a r i s e i n serum c a l c i u m l e v e l s .  The z i n c d i g e s t i b i l i t i e s  - 71 -  were lower due  to an i n t e r a c t i o n w i t h c a l c i u m i n the  intestine.  However, the serum v a l u e s o f z i n c were h i g h e r most l i k e l y because o f a metabolic  i n t e r a c t i o n with the c a l c i u m a t the t i s s u e l e v e l .  Although  phosphorus d i g e s t i b i l i t i e s were a p p a r e n t l y u n a f f e c t e d by the e x t r a c a l c i u m , the serum c o n c e n t r a t i o n s were lower as was tion rate.  T h i s was  the u r i n a r y e x c r e -  a r e s u l t o f i n c r e a s e d d e p o s i t i o n o f c a l c i u m which  l e d t o a lower m o b i l i z a t i o n o f phosphorus from the bone. The The  remaining  element i n t e r a c t i o n s are l e s s c l e a r l y d e f i n e d .  e f f e c t on copper d i g e s t i b i l i t y was  workers.  The  contamination  o p p o s i t e t h a t r e p o r t e d by  apparent d i g e s t i b i l i t y i n c r e a s e d p r o b a b l y due o f the l i m e s t o n e w i t h copper.  t h i s i n c r e a s e was  due  t o the decreased  i n the serum copper l e v e l s .  l i t y may  a v a i l a b i l i t y o f the z i n c .  S i m i l a r l y , i r o n apparent  zinc a v a i l a b i l i t y .  The  The  r e s p o n s i b l e f o r the digestibi-  have been a f f e c t e d by the contaminant i r o n i n the  o r by the decreased  to the  It i s possible part of  i n c r e a s e d copper d i g e s t i b i l i t y most l i k e l y was rise  other  limestone  e f f e c t s o f the treatment  on  molybdenum remains undetermined as i t i s unknown whether c a l c i u m or copper was  r e s p o n s i b l e f o r the decrease  i n apparent d i g e s t i b i l i t y .  work i s r e q u i r e d to e l u c i d a t e these E q u a l l y as important  Further  matters.  to the e v a l u a t i o n o f the main e f f e c t  t h e m i n e r a l s which were u n a f f e c t e d by the treatment.  Both phosphorus  and magnesium a b s o r p t i o n s remained c o n s t a n t d e s p i t e r e p o r t s o f  these  elements c l o s e l y i n t e r a c t i n g w i t h c a l c i u m i n the d i g e s t i v e t r a c t . was  concluded  are  the main s i t e s o f a b s o r p t i o n o f these two  It  m i n e r a l s must  be p r i o r to the middle to lower s m a l l i n t e s t i n e otherwise  precipita-  -  -  72  t i o n o f the c a l c i u m and magnesium phosphates would have r e s u l t e d i n lower apparent a b s o r p t i o n s .  A l s o , the i m p l i e d a l t e r a t i o n i n the  l e v e l o f the d i g e s t a p r o b a b l y was  not a major f a c t o r governing  a v a i l a b i l i t i e s o f c a l c i u m , magnesium o r phosphorus.  The  the m i n e r a l s but may  the  increased  c a l c i u m to phosphorus r a t i o appeared not to i n f l u e n c e the of  pH  absorption  have been r e s p o n s i b l e f o r the decrease  in  phosphorus e x c r e t i o n i n t o the u r i n e and the lower serum phosphorus levels.  The  i n c r e a s e i n d i e t a r y c a l c i u m had  magnesium o r s u l f u r . animals  on the treatment  responsible.  The  digestibility, minerals  Serum selenium  no e f f e c t on potassium,  c o n c e n t r a t i o n s were h i g h e r i n the  d i e t but i t i s d o u b t f u l whether c a l c i u m  e f f e c t s o f c a l c i u m carbonate  on the  apparent  serum c o n c e n t r a t i o n and apparent r e t e n t i o n o f d i e t a r y  i n the p r e s e n t experiment are summarized i n Table Two  was  secondary e f f e c t s were s t u d i e d as w e l l .  12.  These were the  i n f l u e n c e o f breeds and o f r e p r o d u c t i v e c y c l i n g on serum c o n s t i t u e n t levels.  Phosphorus and  copper were i n h i g h e r c o n c e n t r a t i o n i n the  serum o f A y r s h i r e cows than i n t h a t o f the H o l s t e i n s .  These  two  m i n e r a l s were a l s o shown to f l u c t u a t e w i t h the r e p r o d u c t i v e hormones as were z i n c and mineral  iron.  Any  study d e a l i n g w i t h comparisions  l e v e l s s h o u l d account f o r these The  postulated.  factors.  l o n g term e f f e c t s o f such a treatment Calcium  supplementation  b o t h macro and t r a c e m i n e r a l s . a l t e r e d metabolism may  o f serum  as t h i s can o n l y  be  r e s u l t e d i n i n t e r a c t i o n s with  As a r e s u l t , i t would be expected  that  e v e n t u a l l y show up most l i k e l y m a n i f e s t i n g  i t s e l f i n the f e r t i l i t y and  r e p r o d u c t i o n o f the cows.  A study on  this  - 73  -  Table  12  Summary o f the E f f e c t s o f Calcium Carbonate on the Apparent D i s g e s t i b i l i t y , Serum C o n c e n t r a t i o n and Apparent R e t e n t i o n o f D i e t a r y M i n e r a l s  Mineral  Apparent Digestibility  Serum Concentration  Ca  +  P  0  K  0  0  0  Mg  0  0  0  S  0  0  0  Fe  +  0  N.A.  Cu  ++  +  N.A.  Zn  -  ++  N.A.  Mn  0  N.A.  N.A.  Mo  -  N.A.  N.A.  Se  0  0 + ++ N.A.  ++  Apparent Retention ++ +  Unaffected Rose S i g n i f i c a n t l y ( p < . 0 5 ) Rose H i g h l y S i g n i f i c a n t l y ( p < . 0 1 ) Dropped S i g n i f i c a n t l y ( p < . 0 5 ) Dropped H i g h l y S i g n i f i c a n t l y (p < .01) Not Analyzed  +  N.A.  - 74  -  a s p e c t s h o u l d be i n i t i a t e d to determine whether the l o n g term e f f e c t s are b e n e f i c i a l or d e t r i m e n t a l .  T h i s study has  i d e n t i f i e d the f a c t t h a t the NRC  (1978) recom-  mended d i e t a r y c a l c i u m l e v e l s were too low t o m a i n t a i n p o s t p a r t u r i e n t d a i r y c a t t l e i n p o s i t i v e calcium balance.  I t has a l s o e x h i b i t e d i t  p o s s i b l e t o i n c r e a s e the l e v e l o f c a l c i u m absorbed by r a i s i n g  the  c a l c i u m c o n t e n t o f the d i e t by 2 t o 3 times the recommended r a t e .  A  suggested  1.5%  more b e n e f i c i a l l e v e l o f c a l c i u m i n the r a t i o n would be  w i t h a c a l c i u m to phosphorus r a t i o o f 3:1. s u c h a treatment  require further research.  The  l o n g term e f f e c t s o f  BIBLIOGRAPHY Ali,  R. and J . L . Evans, 1967. E f f e c t o f d i e t a r y c a l c i u m , b u f f e r i n g c a p a c i t y , l a c t o s e and EDTA on pH and c a l c i u m a b s o r p t i o n from g a s t r o n i n t e s t i n a l segments i n the growing r a t . J . 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A b s o r p t i o n and s e c r e t i o n o f some o r g a n i c and i n o r g a n i c c o n s t i t u e n t s and the d i s t r i b u t i o n o f these c o n s i t i t u e n t s throughout the a l i m e n t a r y t r a c t o f young c a l v e s . J . N u t r . 87:444.  Yano, H., H. Matsui and R. Kawashima, 1979. E f f e c t s o f d i e t a r y c a l c i u m l e v e l s on c o n c e n t r a t i o n and s o l u b i l i t y o f macro m i n e r a l s i n the d i g e s t i v e t r a c t o f sheep. J . Anim. S c i . 48:954 960.  APPENDIX • F'  Values  of  Serum C o n s t i t u e n t s  TB^  i j k l  Y  (d.f.)  Ca  Table  (3)  (1)  (1)  21.2**  for  A  Related  A  ANOVA M o d e l  i j k l  Mijkl  Terms  +  F  i j k l  (1)  (3)  (1)  (1)  (1)  1.2  1.2  1.9  0.2  0.9  3.8*  0.4  P  6.8**  6.8**  4.9*  0  0.2  0  1.5  2.8  K  0.3  0.2  0  1.3  0.8  3.0  0.3  4.9*  Mg  2.8  1.0  1.7  0  2.4  6.2*  0.2  7.4**  S  2.6  0  2.0  0.3  0.2  0  0.1  12.2**  Fe  0  0  2.6  0.6  1.3  8.2**  4.2*  Cu  4.2*  9.5**  1.7  0.4  0.4  12.4**  4.6*  Zn  23.4**  1.5  1.5  1.7  2.0  1.3  0.8  4.5*  Se  4.2*  0.2  5.5*  1.6  6.3*  7.3**  1.1  +  See  page 24  Significantly  13.9**  for explanation different  *(p  of  terms.  < .05),  **(p  <  .01)  0.4 30.2**  

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