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Effect of corticosterone injection on carbohydrate metabolism and tenderness of broiler breast muscle Whalley, Linda Louise 1974

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a EFFECT OF CORTICOSTEROID INJECTION ON CARBOHYDRATE METABOLISM AND TENDERNESS OF BROILER BREAST MUSCLE BY LINDA LOUISE WHALLEY B.Sc. (Agr.), U n i v e r s i t y of B r i t i s h Columbia, 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Food Science We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA APRIL, 1974. In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission fo r extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by h i s representatives. It i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of o .5r„/ /- /v The University of B r i t i s h Columbia Vancouver 8, Canada ABSTRACT The e f f e c t of i n t r a m u s c u l a r c o r t i c o s t e r o n e i n j e c t i o n on post mortem muscle metabolism and shear r e s i s t a n c e of P e e t o r a l i s Major muscle was s t u d i e d . Short term s t u d i e s , conducted over an 8 hour p o s t -i n j e c t i o n p e r i o d , showed no s i g n i f i c a n t e f f e c t of i n j e c t i o n u n t i l 6 hours post i n j e c t i o n a t which time shear v a l u e s i n c r e a s e d from those of the c o n t r o l s . Blood glucose l e v e l s rose s i g n i f i c a n t l y from 2 to 8 hours post i n j e c t i o n . A comparison of shear v a l u e s of P. Major muscle from 6 week-old b r o i l e r s and 8 week-old b r o i l e r s a f t e r both had r e c e i v e d c o r t i c o s t e r o n e i n j e c t i o n s showed t h a t the only d i f f e r e n c e was due to the d i f f e r e n c e of age not to any a l t e r a t i o n i n the p h y s i o l o g i c a l h a n d l i n g of the i n j e c t e d c o r t i c o s t e r o n e . The g r e a t e s t d i f f e r e n c e i n treatment e f f e c t was found between b i r d s of d i f f e r e n t s t r e s s l e v e l . S t r e s s l e v e l was s u b j e c t i v e l y e v a l u a t e d with r e s p e c t to the b i r d s r e a c t i o n to a person e n t e r i n g the range house and to the b i r d s response to h a n d l i n g . Long term s t u d i e s conducted over 5 and 15 days i l l u s t r a t e d homeostatic adjustments to d a i l y c o r t i c o s t e r o n e i n j e c t i o n s and r e c o v e r y a f t e r c e s s a t i o n of i n j e c t i o n s . Shear t e s t i n g was performed on P. Major muscle which was c h i l l e d on the c a r c a s s and on muscle e x c i s e d a t death. E x c i s e d muscle d i s p l a y e d a g r e a t e r r e a c t i o n to i n j e c t i o n and c e s s a t i o n of i n j e c t i o n than d i d i n t a c t muscle due to a l a c k of s k e l e t a l r e s t r i c t i o n . Shear valu e s decreased on i n i t i a l i n j e c t i o n and i n c r e a s e d upon c e s s a t i o n of i n j e c t i o n . Homeostatic adjustments r e t u r n e d v a l u e s to near-normal between these times. Chemical t e s t s were found to d i s p l a y a much more d e f i n i t e r e a c t i o n to c o r t i c o s t e r o n e i n j e c t i o n than d i d shear t e s t i n g . Blood glucose and t i s s u e glycogen i n c r e a s e d s t e a d i l y on i n j e c t i o n of c o r t i c o s t e r o n e and decreased r a p i d l y a t c e s s a t i o n . As expected u l t i m a t e muscle pH decreased with muscle glycogen i n c r e a s e . Blood c h o l e s t e r o l i n c r e a s e d d u r i n g i n j e c t i o n p e r i o d as endogenous c o r t i c o s -terone p r o d u c t i o n , f o r which i t i s a p r e c u r s o r , was not r e q u i r e d . ACKNOWLEVGEMENTS The authon ootAheA to thank heA adviAon, VA. J.F. RtchaAdA, AAAoclate PAO&ZAAOA, VepanMnent o^ Food Science, ^OA 'hlA kind 6uggeAtlonA duAlng the couAAe o& thJj, Atudy. She OIAO uxliheA to thank the. membeAA ofa heA Graduate Committee: • VA. P.M. TownAley, Ve.pantme.nt ofi food Science VA. J. [/andeAAtoep, VepaAtment oi food Science Vh.. R.C. FXXzAlmmonA, VepaAtment o£ Foult/iy Science ^OA fievtew ofa thtA theA-iA. Financial AuppoAt &Aom the UntveAA-lty o& BAltiAh Columbia thn.ou.gh a Post-GAaduate FeJLlomhlp and finom the National ReAeaAch Council o/) Canada IA gnate^ully appreciated. i v TABLE OF CONTENTS PAGE ABSTRACT i ACKNOWLEDGEMENTS i i i TABLE OF CONTENTS i v LIST OF TABLES V I LIST OF FIGURES v i i INTRODUCTION 1 REVIEW OF LITERATURE 3 a) A l a r m R e a c t i o n 3 b) R e s i s t a n c e o r A d a p t a t i o n Stage 3 c) Stage o f E x h a u s t i o n 5 PHYSIOLOGICAL RESPONSE TO HYPERCORTICALISM 8 PHYSIOLOGICAL RESPONSE TO CORTICOID INJECTION 9 ADRENAL CORTICAL INDUCED ALTERATIONS IN MUSCLE 9 ADRENAL CORTICAL CONTROL OF AVIAN METABOLISM 12 MATERIALS AND METHODS 15 P o u l t r y Source 15 S l a u g h t e r P r o c e d u r e 15 I n j e c t i o n P r o c e d u r e 15 Tenderness 16 1) I n t a c t muscle 16 2) E x c i s e d muscle 16 Chemical T e s t s 17 1) B l o o d g l u c o s e 17 2) T i s s u e g l y c o g e n 17 3) B l o o d c h o l e s t e r o l 17 4) pH 18 RESULTS AND DISCUSSION 19 E f f e c t o f I n j e c t i o n Method 19 S h o r t Term S t u d i e s 21 Long Term S t u d i e s 27 1) 5 Day s t u d y 27 2) 15 Day s t u d y 30 TABLE OF CONTENTS CONTINUED Shear t e s t i n g C h e m i c a l t e s t s B l o o d g l u c o s e T i s s u e g l y c o g e n P H B l o o d c h o l e s t e r o l SUMMARY AND CONCLUSIONS BIBLIOGRAPHY APPENDIX v i . LIST OF TABLES TABLE PAGE 1 Comparison of shear val u e s of P. Major muscle when c o r t i c o s t e r o n e was d i l u t e d w i t h d i s t i l l e d water o r p h y s i o l o g i c a l s a l i n e s o l u t i o n 19 2 Comparison of shear val u e s of P. Major muscle from u n i n j e c t e d b i r d s and b i r d s i n j e c t e d w i t h d i s t i l l e d water 20 3 E f f e c t o f c o r t i c o s t e r o n e i n j e c t i o n on shear v a l u e of P. Major muscle a t s e v e r a l i n t e r v a l s p o s t i n j e c t i o n 22 4 E f f e c t of c o r t i c o s t e r o n e i n j e c t i o n on blood glucose l e v e l s a t s e v e r a l time i n t e r v a l s post i n j e c t i o n 22 5 Comparison of shear v a l u e s of P. Major muscle from 6 and 8 week o l d b i r d s at s e v e r a l time i n t e r v a l s post i n j e c t i o n of c o r t i c o s t e r o n e 24 6 Comparison o f shear v a l u e s o f P. Major muscle w i t h s u b j e c t i v e e v a l u a t i o n of s t r e s s l e v e l of the b i r d 24 7 Shear val u e s of P. Major muscle from p l a c i d b i r d s over an 8 hour p e r i o d p o s t i n j e c t i o n of c o r t i c o s t e r o n e 25 8 Shear val u e s of P. Major muscle from m i l d l y e x c i t a b l e b i r d s over an 8 hour p e r i o d p o s t i n j e c t i o n o f c o r t i c o s t e r o n e 25 9 Shear val u e s of P. Major muscle from extremely e x c i t a b l e b i r d s over an 8 hour p e r i o d p o s t i n j e c t i o n of c o r t i c o s t e r o n e 26 10 U l t i m a t e pH of P. Major muscle from b r o i l e r s r e c e i v i n g d a i l y c o r t i c o s t e r o n e i n j e c t i o n s f o r 8 days and observed f o r a f u r t h e r 7 day recovery p e r i o d 3 5 11 Blood c h o l e s t e r o l l e v e l s of b r o i l e r s r e c e i v i n g d a i l y c o r t i c o s t e r o n e i n j e c t i o n s f o r 8 days and observed f o r a f u r t h e r 7 day recove r y p e r i o d 36 v i i . LIST OF FIGURES FIGURE PAGE Basic response to stress 6 Blood glucose l e v e l s of b r o i l e r s receiving d a i l y corticosterone injections over a 5 day period 28 Shear values of i n t a c t and excised P. Major muscle of b r o i l e r s receiving d a i l y corticosterone injections over a 5 day period 29 Shear value of excised and i n t a c t P. Major muscle of b r o i l e r s receiving d a i l y corticosterone i n j e c t i o n s for 8 days and observed for a further 7 days without i n j e c t i o n 31 Blood glucose l e v e l of b r o i l e r s receiving d a i l y corticosterone injections for 8 days and observed for a further 7 days recovery period 33 Tissue glycogen lev e l s of P. Major muscle from b r o i l e r s receiving d a i l y corticosterone injections for 8 days and observed for a further 7 day recovery period 34 1. INTRODUCTION The degree o f p o s t mortem t e n d e r i z a t i o n i n c h i c k e n muscle has been shown to be a f f e c t e d by the ante mortem p h y s i o l o g i c a l s t a t e of the c h i c k e n . S t r e s s f u l c o n d i t i o n s p r e s l a u g h t e r cause changes i n muscle c h e m i s t r y which have a d e l e t e r i o u s e f f e c t on meat q u a l i t y on p r o c e s s i n g . The a d r e n a l m e d u l l a r y hormone, e p i n e p h r i n e , has been i m p l i c a t e d as a m e d i a t o r between the s t i m u l a t i o n caused by s t r e s s and the c h e m i c a l r e s p o n s e i n the muscle t i s s u e , ( A b e r l e , 1968), (deFremery, 1963, 1966) . I t s most i m p o r t a n t m e t a b o l i c e f f e c t i s the p r o m o t i o n of g l y c o g e n o l y s i s i n muscle and l i v e r t i s s u e s r e s u l t i n g i n e l e v a t i o n of b l o o d g l u c o s e l e v e l s . T h i s a c t i o n tends to d e p l e t e the t i s s u e o f g l y c o g e n and A T P . Should s l a u g h t e r o c c u r a t t h i s p o i n t , p o s t mortem g l y c o l y s i s would p r o c e e d to a minimum e x t e n t r e s u l t i n g i n a r a p i d o n s e t o f r i g o r , a c o n d i t i o n known to cause a d e c r e a s e i n p o s t mortem t e n d e r i z a t i o n . I f the r e l e a s e or u t i l i z a t i o n of e p i n e p h r i n e c o u l d be m i n i m i z e d p r e s l a u g h t e r , t i s s u e g l y c o g e n o l y s i s would be d e c r e a s e d and p o s t mortem g l y c o l y s i s would p r o c e e d t o a •normal or e l e v a t e d e x t e n t , r e d u c i n g u l t i m a t e pH and f a c i l i -t a t i n g t e n d e r i z a t i o n . . The m e t a b o l i c e f f e c t o f e p i n e p h r i n e i s m o d i f i e d by the hormones o f the a d r e n a l c o r t e x , (Zimmerman, 1972) , (Brown, 1959). The g l u c o c o r t i c o i d s a c t to m a i n t a i n blood glucose and t i s s u e glycogen l e v e l s . An overdose of g l u c o c o r t i c o i d hormones has been shown to produce glycogen d e p o s i t s i n the l i v e r and to e l e v a t e blood glucose, (Greenman e t a l . 1961). However, the e f f e c t of g l u c o c o r -t i c o i d i n j e c t i o n on muscle glycogen and i t s r e l a t i o n to post mortem t e n d e r i z a t i o n has not been e l u c i d a t e d . T h i s r e s e a r c h was conducted to determine the e f f e c t of g l u c o c o r t i c o i d i n j e c t i o n on carbohydrate metabolism of muscle and l i v e r t i s s u e s and to observe any i n h i b i t i o n or m o d i f i c a t i o n of the s t r e s s r e a c t i o n by the g l u c o c o r t i c o i d s . REVIEW OF LITERATURE In 1936 Seyle proposed the General Adaptation Syndrome (GAS) as a theory on stress resistance and s u s c e p t i b i l i t y i n animals. Since t h i s time much research has been conducted to elucidate a physiological and biochemical basis for the reaction to, control of and adaptation to stress. Von Faber (1964) defined the general adaptation syndrome as "the sum of a l l non-specific responses to systematic stress" and indicated that i t evolves i n three d i s t i n c t phases: a) Alarm Reaction When the body i s exposed to damaging stressors, a series of physiological a l t e r a t i o n s occur which represent either shock or attempts of the organisms to defend i t s e l f against shock. The physiological manifestation of shock i s the release of epinephrine from the adrenal medulla which mediates the breakdown of l i v e r and muscle glycogen to glucose and l a c t i c acid. The p r i n c i p l e a l t e r a t i o n s that occur during counter shock are, increased release of adrenocorticotropic hormone (ACTH) from the anterior p i t u i t a r y and consequential release of c o r t i c a l steroids, (Briskey, 1966). C o r t i c a l steroids a f f e c t carbohydrate, f a t and protein metabolism along with water and e l e c t r o l y t e balance (Tepperman, 1968). b) Resistance or Adaptation Stage Adjustments made i n counter shock gain supremacy and the c a p a c i t y o f the organism to m a i n t a i n constancy bf the i n t e r n a l environment and n o r m a l i t y of b o d i l y f u n c t i o n s i n c r e a s e s (Sayers, 1950). As e a r l y as 1944, Swingle found adrenalectomized animals to be extremely s e n s i t i v e to the damaging e f f e c t s of a v a r i e t y of agents and environmental changes. He observed t h a t r e p l a c e -ment therapy would e i t h e r completely or p a r t i a l l y r e s t o r e normal r e s i s t a n c e . E l l i n g e r (1947) r e p o r t e d t h a t a d r e n a l c o r t i c a l e x t r a c t s i n c r e a s e d the s u r v i v a l of i r r a d i a t e d r a t s . F u r t h e r experimentation (Straube, 1949) c o u l d not c o n f i r m t h i s . A d renal c o r t i c a l e x t r a c t s were a l s o found to be o f no b e n e f i t i n i n c r e a s i n g the r e s i s t a n c e of man to a hot e n v i r o n -ment (Moriera e t a l . , 1945). Anoxia i s unique among s t r e s s e s i n r egard to the number of confirmed r e p o r t s of the t h e r a p e u t i c b e n e f i t of a d r e n a l c o r t i c a l e x t r a c t s . Thorn (1945) f i r s t demonstrated t h a t an e x t r a c t of beef a d r e n a l s reduced the m o r t a l i t y of i n t a c t r a t s exposed to low barometric p r e s s u r e . His o b s e r v a t i o n s were confirmed by Kottke (1948). A d a p t a t i o n to s t r e s s may f o l l o w i f s t r e s s i s f r e q u e n t or prolonged. Langley e t a l . (1942), showed t h a t t h e r e i s a marked i n c r e a s e i n the requirement of adrenalectomized animals f o r c o r t i c a l s t e r o i d s d u r i n g the i n i t i a l p e r i o d of exposure to low atmospheric p r e s s u r e but d e s p i t e c ontinued exposure the s t e r o i d requirement r e t u r n s to pre-exposure l e v e l s . c. Stage of Exhaustion In t h i s stage a c q u i r e d a d a p t a t i o n i s l o s t . Symptoms s i m i l a r to those i n the alarm r e a c t i o n appear and death ensues unless s t r e s s i s withdrawn. PHYSIOLOGICAL RESPONSE TO STRESS F i g u r e 1 o u t l i n e s the b a s i c p h y s i o l o g i c a l response to s t r e s s . In mammals and b i r d s the h y p o t h a l a m i c - p i t u i t a r y -a d r e n a l complex forms an important neuro-endocrine c h a i n i n the response to s t r e s s . The concept has been t h a t n e u r a l s t i m u l i reach the hypothalamus, an area l y i n g a t the f l o o r of the diencephalon or i n t e r b r a i n , which i s important i n the r e g u l a t i o n of temperature, a p p e t i t e and c a r d i o v a s c u l a r a c t i v i t y . These n e u r a l s t i m u l i are converted to a n e u r a l -humoral f a c t o r — c o r t i c o t r o p i n - r e l e a s i n g f a c t o r -- which then s t i m u l a t e s the. a n t e r i o r p i t u i t a r y to s e c r e t e the hormone a d r e n o c o r t i c o t r o p i n (ACTH). T h i s i n t u r n reaches the a d r e n a l gland v i a g e n e r a l c i r c u l a t i o n and causes an i n c r e a s e i n the s e c r e t i o n of s t e r o i d hormones. While t h i s c h a i n of events r e q u i r e s time to reach d e t e c t a b l e p r o p o r t i o n s , the immediate response of the body i s an e f f o r t to combat the o f f e n d i n g environment r a t h e r than to accommodate or a c c l i m a t e to i t . The responses are mediated by immediate s e c r e t i o n s of e p i n e p h r i n e or nor-e p i n e p h r i n e from medullary t i s s u e and are mechanisms which pro v i d e f o r i n c r e a s e d r e l e a s e of energy. In mammals the 6. STRESS STIMULI ^ HYPOTHALAMUS NERVE STIMULI ADRENAL CORTEX CHANGES IN CORTEX 1) i n c r e a s e d w e i g h t 2) c h o l e s t e r o l d e p l e t i o n 3) s u d a n o p h i l i a CORTICOIDS ADAPTATION REACTION . 1) l y m p h a t i c i n v o l u t i o n 2) b l o o d c e l l c o u n t 3) changes i n b l o o d c h e m i s t r y i o n s c h o l e s t e r o l n i t r o g e n o u s p r o d u c t s sugar 4) g a s t r o - i n t e s t i n a l u l c e r a t i o n 5) a n t i - i n f l a m m a t o r y a c t i o n 6) a n t i b o d y a c t i v i t y ADRENAL MEDULLA ^EPINEPHRINE FIGHT OR FLIGHT MECHANISM 1) i n c r e a s e d b l o o d sugar 2) v a s o c o n s t r i c t i o n 3) i n c r e a s e d r e s p i r a t o r y r a t e 4) i n c r e a s e d , muscle tone 5) i n c r e a s e d nerve s e n s i t i v i t y A f t e r H.S.. S i e g e l (1971) A d r e n a l , S t r e s s and the Environment. World's P o u l t r y S c i . J . 27(4) 327. FIGURE 1. B a s i c Response t o S t r e s s r e l e a s e of ACTH from the a n t e r i o r p i t u i t a r y i s . c o n t r o l l e d by a feedback system. When the c o r t i c a l s t e r o i d c o n c e n t r a t i o n , p a r t i c u l a r l y g l u c o c o r t i c o i d s , i n the c i r c u l a t i n g b l o o d i s e l e v a t e d , the c e n t r a l nervous system i n h i b i t s or d e l e t e s the process t h a t leads to s e c r e t i o n of ACTH, ( S i e g e l , 1971). However, the a d r e n a l c o r t e x o f b i r d s maintains some measure of a c t i v i t y a p a r t from p i t u i t a r y s t i m u l a t i o n and c o n t r o l , ( F r a n k e l , 1970)'. C a t a b o l i c processes are a c c e l e r a t e d d u r i n g s t r e s s and thus l e a d to a l o s s of l i v i n g substance throughout the body. T i s s u e s s h r i n k i n weight except f o r a d r e n a l c o r t i c a l t i s s u e which cont i n u e s to e n l a r g e and appears to be the o n l y t i s s u e to t h r i v e on s t r e s s . There i s no doubt t h a t the c o r t i c a l s t e r o i d s are necessary to p r o t e c t a g a i n s t s t r e s s o r s and t h a t they are r e q u i r e d i n h i g h e r amounts d u r i n g s t r e s s , (Brown, 1959). Increased c e l l u l a r a c t i v i t y which accompanies homeostatic adjustments of the organisms to s t r e s s may be a t l e a s t p a r t i a l l y r e s p o n s i b l e f o r the p a r a l l e l i n c r e a s e i n the r a t e of u t i l i z a t i o n of c o r t i c a l hormones. Since h y p e r a c t i v i t y of the a d r e n a l c o r t e x i s an i n v a r i a b l e accompaniment of s t r e s s , c e r t a i n a l t e r a t i o n s i n m etabolic p a t t e r n c h a r a c t e r i s t i c s o f the a c t i o n of c o r t i c a l hormones are a l s o an i n v a r i a b l e accompaniment of s t r e s s . Evans (1935) showed t h a t the i n c r e a s e i n b l o o d sugar and l i v e r glycogen, which normally occurs a f t e r s t r e s s , does not occur i n the absence of a d r e n a l s . Lewis e t a l . (1942) continued t h i s study c o n f i r m i n g t h a t d u r i n g the i n i t i a l stage of s t r e s s there appears to be an i n c r e a s e d r a t e of u t i l i z a -t i o n of carbohydrate; blood glucose i s maintained w h i l e the s t o r e o f l i v e r glycogen i s reduced; w i t h time blood glucose and l i v e r glycogen r i s e t o g r e a t e r than normal c o n c e n t r a t i o n s , as c o r t i c a l s t e r o i d s , g l u c o c o r t i c o i d s , express themselves. Laiwrie, (1966) s t a l e s , t h a t i n the absence of a d r e n a l s , m i l d s t r e s s d e p l e t e s l i v e r glycogen and reduces b l o o d sugar below normal. The hyperglycemic r e a c t i o n of trauma f a i l s to occur i n the absence of a d r e n a l s , but a dose of a d r e n a l c o r t i c a l e x t r a c t , which does not e l e v a t e blood sugar of non-traumatized normal r a t s , r e s t o r e s the hyperglycemic trauma i n an adrenectomized r a t (Seyle, 1941). PHYSIOLOGICAL RESPONSE TO HYPERCORTICALISM A d i a b e t i c - l i k e s t a t e r e s u l t s from h y p e r c o r t i c a l i s m ; s i n c e one of the most c h a r a c t e r i s t i c a c t i o n s of the g l u c o -c o r t i c o i d s i s to i n h i b i t g lucose u t i l i z a t i o n by d i m i n i s h i n g glucose uptake by p e r i p h e r a l t i s s u e s (Sayer, 1950). Gluco-c o r t i c o i d overdose,: r e s u l t i n g from a d r e n a l c o r t i c a l hypertrophy i n an u n s t r e s s e d organism, can cause e x c e s s i v e d e p o s i t i o n o f l i v e r glycogen, b l o o d g l u c o s e e l e v a t i o n , p r o t e i n metabolism a l t e r a t i o n s and i n s u l i n s e n s i t i v i t y , (Tepperman, 1968). None of these symptoms appear i n a s t r e s s e d animal w i t h e l e v a t e d c o r t i c a l l e v e l s . 9. PHYSIOLOGICAL RESPONSE TO CORTICOID INJECTION C o r t i c a l s t e r o i d s may promote as w e l l as i n h i b i t g lucose u t i l i z a t i o n and produce anabolism as w e l l as c a t a b o l i s m depending upon the dose of the s t e r o i d and the t i s s u e needs. Von Faber, (1964) s t a t e s t h a t repeated c o r t i c a l s t e r o i d i n j e c t i o n s i n experimental animals produced numerous p h y s i o l o -g i c a l changes i n c l u d i n g lymphatic i n v o l u t i o n , changes i n l e u c o c y t e count, i n c r e a s e d b l o o d c i t r i c a c i d , r e t a r d a t i o n of growth, h y p e r l i p e m i a , h y p e r c h o l e s t e r e m i a , hyperglycemia and decreased a d r e n a l weight. Selye (1959) observed t h a t the a d m i n i s t r a t i o n of large' doses of g l u c o c o r t i c o i d s produced h y p e r t e n s i o n i n the r a t , c a t , guinea p i g , dog and monkey. Green, (194 8) observed the same i n humans and suggested the p o s s i b i l i t y o f a r r e s t i n g h y p e r t e n s i v e d i s e a s e e i t h e r by removing the adrenal gland or by n u l l i f y i n g i t s a c t i v i t y . ADRENAL CORTICAL INDUCED ALTERATIONS IN MUSCLE Research has shown t h a t a d r e n a l gland f u n c t i o n may be r e l a t e d to l a c t i c a c i d accumulation (Ludvigsen, 1957), tenderness (Addis e t a l . , 1965) and post mortem events i n p o r c i n e muscle, (Cassen et a l . , 1965). Ludvigsen suggested t h a t an imbalance of t r o p h i c hormones of the p i t u i t a r y (TSH, ACTH, STH) i s r e s p o n s i b l e f o r the a s s o c i a t i o n of m u s c u l a r i t y w i t h P a l e , S o f t , Exudative (PSE) muscle c o n d i t i o n . The data i n d i c a t e t h a t muscular animals w i t h PSE musculature may have d e f i c i e n c i e s i n a d r e n a l s t e r o i d p r o d u c t i o n i n 10. comparison with l e s s muscular animals w i t h q u a l i t a t i v e l y normal muscles. A f t e r f u r t h e r i n v e s t i g a t i o n Ludvigsen (1957) postu-l a t e d t h a t g l u c o c o r t i c o i d s i n s t r e s s - s u s c e p t i b l e animals were not of s u f f i c i e n t q u a n t i t y to ensure adequate c i r c u l a t o r y f u n c t i o n . S t r e s s - s u s c e p t i b l e p i g s were shown to have low l e v e l s of a d r e n a l s t e r o i d s and catecholamines e x c r e t e d i n t h e i r u r i n e compared to t h a t i n s t r e s s - r e s i s t a n t animals. Marple and Cassen, (1973b) observed an i n c r e a s e d m e t a b o l i c c l e a r a n c e of C o r t i s o l by s t r e s s - s u s c e p t i b l e p i g s . F u r t h e r evidence i n d i c a t e d an i n c r e a s e d p r o d u c t i o n (Topel, 1969), Weiss, 1971), and u t i l i z a t i o n (Marple and Cassen, 1973a) of g l u c o c o r t i c o i d s which l e a d to a b e r r a n t muscle metabolism of s t r e s s - s u s c e p t i b l e swine. Muscles of such animals were shown to have a lower c a p a c i t y f o r a e r o b i c muscle metabolism due to a h i g h percentage of white muscle f i b r e s and l a r g e r s i z e of white muscle f i b r e s . The s u g g e s t i o n of i n c r e a s e d p o t e n t i a l f o r anaerobic g l y c o l y s i s i s a l s o supported by r e p o r t s of s t r e s s - s u s c e p t i b l e swine having a more r a p i d accumulation of l a c t a t e i n muscle b i o p s y samples ( L i s t e r , 1970), and i n plasma a f t e r s t r e s s (Topel, 1969) and a more r a p i d consumption of C r e a t i n e Phosphate (CP) and Adenosine Triphosphate (ATP) i n muscle biopsy samples ( L i s t e r , 1970). Marple e t a l . , (1973a) e s t a b l i s h e d t h a t muscle from s t r e s s - s u s c e p t i b l e swine have l a r g e r f i b r e s and most l i k e l y a g r e a t e r mass of white anaerobic f i b r e / u n i t mass w i t h a lower c a p a c i t y f o r o x i d a t i v e metabolism but s i m i l a r c a p a c i t y to produce ATP by o x i d a t i v e p h o s p h o r y l a t i o n . Eikelenboom and Van Den Bergh, (1971) suggested that muscle glycogenolysis w i l l be enhanced i n stress-susceptible swine i n an e f f o r t to produce ATP during periods of increased energy demand such as the stress response. During such a stress response the rapid u t i l i z a t i o n of epinephrine noted by Topel (1972) would also stimulate the rapid muscle glycogenolysis and g l y c o l y s i s noted by Sair (1970). S i m i l a r l y l i v e r glycogen would be converted to blood glucose by the action of epinephrine thus producing the increased blood . glucose c h a r a c t e r i s t i c of stress-susceptible pigs. Ultim-ately C o r t i s o l would be expected to stimulate l i v e r gluco-neogenesis to convert high l e v e l s of lactate produced by anaerobic muscle f i b r e mass to gluclose and to muscle and l i v e r glycogen, with the high rate of C o r t i s o l metabolism i n stress-susceptible pigs; t h i s conversion i s slow, (Marple and Cassen, 1973a). Russian workers (Nestorov et a l . , 1972) found an increase i n ACTH and 17-hydroxy co r t i c o s t e r o i d s (17-HCS) i n the blood of calves during transport. The l e v e l s of 17-HCS during an 8-hour rest period following transporation was main-tained at higher than normal values, while the content of glycogen i n the l i v e r and muscle attained and surpassed the i n i t i a l quantity. Analogous data was obtained for pigs. Effects of stress (simulated by an epinephrine i n j e c -tion) as loss of muscle e x t e n s i b i l i t y , low pH and ATP i n m u s c l e , i n r a b b i t s was demonstra ted by B e n d a l l (1962) to be overcome by an i n j e c t i o n o f c o r t i s o n e 2 0 hours b e f o r e the e p i n e p h r i n e i n j e c t i o n . T h i s was a l s o shown to o c c u r i n beef c a t t l e (Hendrik e t a l . , 1957) . However, P u r c h a s , (1970) s t a t e s t h a t g l u c o c o r t i c o i d s may be d e t r i m e n t a l to p o s t mortem muscle q u a l i t y , i f i n j e c t e d i n h i g h d o s e s . ADRENAL CORTICAL CONTROL OF AVIAN METABOLISM The a d r e n a l g l a n d i s n e c e s s a r y f o r c o n t i n u e d s u r v i v a l of the b i r d and death a f t e r a d r e n a l e c t o m y i s r a p i d , (Brown, 1958), (Leroy , 1954) . A d r e n a l e c t o m i z e d b i r d s can be m a i n t a i n e d i n an a p p a r e n t l y normal c o n d i t i o n by the a d m i n i s t r a t i o n o f a d r e n o c o r t i c a l e x t r a c t s or pure c r y s t a l l i n e c o r t i c o s t e r o i d s . A d m i n i s t r a t i o n o f a d r e n a l c o r t i c a l s t e r o i d s p r e v e n t e d t y p i c a l shock symptoms which appeared i n c o n t r o l , (Brown, 1958) . From t h e s e e x p e r i m e n t s , Brown (1958), c o n c l u d e d t h a t n o r m a l l y the a d r e n a l g l a n d s o f b i r d s , as w i t h mammals, r e l e a s e a d a p t i v e hormones which t e n d to c o u n t e r a c t shock produced by severe s t r e s s . More s p e c i f i c a l l y , the shock symptoms i n d u c e d by s t r e s s are c o u n t e r e d by the r e l e a s e o f ACTH from the p i t u i t a r y and the c o n s e q u e n t i a l r e l e a s e o f a d a p t i v e hormones from the a d r e n a l c o r t e x . I n c u b a t i o n o f White Leghorn c o c k e r e l a d r e n a l c o r t e x l e a d t o i d e n t i f i c a t i o n of c o r t i c o s t e r o n e , a l d o s t e r o n e and t e n t a t i v e i d e n t i f i c a t i o n o f s m a l l amount o f h y d r o c o r t i s o n e p r e s e n t , (de Roos, 1960) . A n a l y s i s o f f o w l plasma by P h i l l i p s et a l . (1957) indicated the primary adrenal s t e r o i d to be corticosterone followed by smaller amounts of hydrocortisone, cortisone and aldosterone. In vivo and i n v i t r o investiga-tions have shown that corticosterone i s the p r i n c i p l e free c o r t i c a l steroid i n chickens (Sandor, 1963; de Roos, I960,; Nagra, i960). Corticosterone was also established to be the p r i n c i p l e free c o r t i c o s t e r o i d i n turkey plasma (Brown, 1961) and the adrenal e f f l u e n t blood of the capon ( P h i l l i p s et a l . 1957) . Greenman (1961), found hydrocortisone and c o r t i c o -sterone to be of high glucocorticoid a c t i v i t y i n chickens and demonstrated that blood glucose and tissue glycogen showed marked increases with d a i l y hydrocortisone or corticosterone i n j e c t i o n s . Cortisone, possesses l i t t l e g l u c ocorticoid a c t i v i t y i n the b i r d . Stamler (1952) reported a f a i l u r e to induce hyperglycemia i n the chick with cortisone at doses which were e f f e c t i v e with hydrocortisone. Brown (1961) suggested that i t i s v a l i d to use plasma corticosterone concentrations as a measure of the severity of stress conditions i n the b i r d s . Degree of resistance to stress may be measured i n a number of ways, including mortality, maintenance of normal concentrations of metabolites in the body f l u i d s and maintenance or rate of restoration of i n d i v i d u a l functions. S u r g i c a l l y i n f l i c t e d stress was shown to cause an increase i n corticosterone concentration i n 14 . adrenal venous blood of cockerels (Nagra, 1963), (Frankel, 1967), pheasants (Nagra,' 1963) and ducks (Macchi, 1967). Cold stress increased corticosterone i n cockerels (Nagra, 1963), ducks (Boisin, 1967) and turkeys (Brown, 1961). However, continued exposure to high ambient temperatures for 4 weeks had l i t t l e e f f e c t on corticosterone concentra-tions. Chickens subject to stress imposed by muscle fatigue (Garren et a l . 1952), cold (Wolford, 1962), heat ( H i l l , 1961a,b,c) l i m i t a t i o n of feed and water (Conner, 1959), handling ( B e l l o f f et a l . 1963), immobilization (Newcomer, 1960) and crowding (Siegel, 1960) have been shown to e l i c i t a stress response and an adrenal c o r t i c a l reaction r e s u l t i n g i n hyperactivity of adrenals. I f stress i s not relieve d and hyperactivity of adrenal tissue i s prolonged, death w i l l r e s u l t . Terminal symptoms are muscular weakness, decreased blood glucose, decreased body temperature and convulsions (Brown, 1959). Brown (1973) demonstrated that turkeys which can adapt to stress conditions without i n i t i a t i n g the general adaptation syndrome or which at le a s t respond by a low release of adaptive hormones grow faster, convert feed more e f f i c i e n t l y , reproduce more e f f i c i e n t l y and are more re s i s t a n t to a wide variety of stress conditions. MATERIALS AND METHODS Poultry Source The chickens used i n t h i s study were commercial b r o i l e r s obtained from a l o c a l processing plant and maintained in range houses on the U.B.C. Poultry Farm. The birds were 6 or 8 weeks of age when obtained. The birds were subjected to experimental treatments either within 48 hours of transport or a f t e r 5-7 days acclimatization depending upon the requirements of the experiment. Slaughter Procedure Birds were placed i n a metal funnel, which r e s t r i c t e d wing and leg movement, and were exsanguinated by an outside neck cut and allowed to bleed f r e e l y . Blood was co l l e c t e d at th i s time. Carcasses were then placed i n ice to c h i l l . In j ect ion Pro c edure In an i n i t i a l experiment corticosterone (4-pregnen-l l B , 21 Diol-3, 20-dione*) was dissolved i n physiological saline and in d i s t i l l e d water to determine optimum s o l u b i l i t y and to determine i f any s i g n i f i c a n t change i n 'muscle shear value was caused by either d i l u e n t. In subsequent tests 2 ml of a 5 mg/ml corticosterone i n d i s t i l l e d water s l u r r y was injected. Birds were injected intramuscularly i n the majorum peronaeus * Schwartz/Mann, Orangeburg, N.Y. longus. When repeated inj e c t i o n s were given, consecutive injections were given i n alternate legs. Some control birds were injected with 2 ml d i s t i l l e d water to compare with uninjected controls. A l l subsequent control birds were uninjected. Tenderness 1) Intact muscle For shear testing carcasses'.• were c h i l l e d overnight i n ice slush placed i n a cold room at 4°C. The P e c t o r a l i s Major was then excised and placed between metal plates for cooking. The plates held the muscle at a constant thickness of 6 mm. The muscles were then immersed i n b o i l i n g water for 10 minutes, cooled i n cold water for 5 minutes and released from between the plates. The cooked muscle was then cut into s t r i p s 4 cm wide at random orientation to the muscle f i b r e . Shear was measured on an Allo-Kramer shear press with a 250 pound proving ring and a single blade shear attachment. Range was set at 20. 2) Excised muscle Muscle was excised from the b i r d immediately after death, to allow shortening without s k e l e t a l r e s t r i c t i o n s , and c h i l l e d overnight i n an ice s l u r r y placed i n a cold room at 4°C. Cooking procedure and shear measurement was as previously described for i n t a c t muscle. Chemical Tests 1) Blood glucose Blood was c o l l e c t e d a t the time o f e x s a n g u i n a t i o n , i n a t e s t tube c o n t a i n i n g 20 mg potassium o x a l a t e and 2 5 mg sodium f l u o r i d e . These chemicals prevent c o a g u l a t i o n and i n h i b i t g l y c o l y t i c a c t i v i t y i n blood samples. Glucose was measured i n whole, d e p r o t e i n a t e d blood u s i n g the g l u c o s t a t * method (Washko, 1961), an enzymatic method f o r the determina-t i o n of g l u c o s e . O p t i c a l d e n s i t y was measured at 420 nm w i t h a Beckman DB spectrophotometer. 2) T i s s u e glycogen Muscle and l i v e r t i s s u e s were removed from the b i r d immediately a f t e r death. Samples were p l a c e d i n an a l k a l i n e s o l u t i o n i n a b o i l i n g water bath, w i t h i n 20 minutes of death, to d i g e s t . L i v e r and muscle glycogen were determined by the method of Roe and D a i l e y (1966), an anthrone method f o r carbohydrate d e t e r m i n a t i o n . O p t i c a l d e n s i t y was r e c o r d e d a t 62 0 nm w i t h a Beckman DB spectrophotometer. 3) Blood c h o l e s t e r o l Blood c h o l e s t e r o l was determined by the method of * Worthington Biochemical Corp., F r e e h o l d , N.J. •9 Z l a t k i s e t a l . ( 1 9 5 3 ) . O p t i c a l d e n s i t y w a s m e a s u r e d w i t h a B e c k m a n D B s p e c t r o p h o t o m e t e r a t 5 6 0 n m . 4 ) p H T h e P e c t o r a l i s M a j o r m u s c l e w a s e x c i s e d a t d e a t h a n d c h i l l e d o v e r n i g h t . 2 0 g o f m u s c l e t i s s u e w a s h o m o g e n i z e d w i t h 4 0 m l o f w a t e r i n a W a r i n g B l e n d e r f o r 5 m i n . p H w a s d e t e r m i n e d w i t h a F i s h e r A c c u m e t , M o d e l 2 3 0 p H M e t e r . RESULTS AND DISCUSSION E f f e c t of Injection Method When an i n j e c t i o n i s made into a l i v i n g animal, i t should be made i n such a way that tissue trauma i s kept to a minimum and that c e l l u l a r environment i s not d r a s t i c a l l y altered. A preliminary study was c a r r i e d out to determine a favourable diluent for the corticosterone both with respect to s o l u b i l i t y i n i n j e c t i o n solution and absorption i n the muscle tissue when injected. Greenman (1961) reported favourable r e s u l t s when corticosterone was injected as a s l u r r y with physiological s a l i n e . Saline solution was used to prevent osmotic shock i n the muscle tissue which may be promoted i f d i s t i l l e d water was used as a diluent. However, Table 1 indicates that there was no s i g n i f i c a n t difference i n shear values of p e c t o r a l i s major, when corticosterone was injected as a s l u r r y i n physiological saline or d i s t i l l e d water TABLE 1. COMPARISON OF SHEAR VALUES OF P. MAJOR MUSCLE WHEN CORTICOSTERONE WAS DILUTED WITH DISTILLED WATER OR PHYSIOLOGICAL SALINE SOLUTION Hours* D i s t i l l e d Water Saline T Value df T-calc.** Shear~Value 0 15.88 16.00 .521 90 1.99 4 14.67 14.14 .511 83 1.99 8 11.10 10.52 .592 54 2.02 * Hours post i n j e c t i o n ** P < .05 20, T e s t s were c a r r i e d out on c o n t r o l b i r d s which were i n j e c t e d w i t h p h y s i o l o g i c a l s a l i n e or d i s t i l l e d water o n l y , as w e l l as a t two time i n t e r v a l s p o s t i n j e c t i o n , on b i r d s t h a t r e c e i v e d c o r t i c o s t e r o n e . These r e s u l t s i n d i c a t e t h a t osmotic shock was n o n - s i g n i f i c a n t and t h a t a b s o r p t i o n of the c o r t i c o s t e r o n e was not dependent on a s a l i n e environment. In subsequent s t u d i e s c o r t i c o s t e r o n e was i n j e c t e d as a thoroughly mixed s l u r r y i n d i s t i l l e d water, due to s i m p l i c i t y of the method. To t e s t the v a l i d i t y o f u s i n g u n i n j e c t e d c o n t r o l b i r d s , an experiment was c a r r i e d out to compare shear v a l u e s of u n i n j e c t e d b i r d s w i t h those of b i r d s i n j e c t e d w i t h d i s t i l l e d water. Table 2 i n d i c a t e s t h a t no s i g n i f i c a n t d i f f e r e n c e was found. T h e r e f o r e , c o n t r o l b i r d s i n a l l subsequent s t u d i e s were u n i n j e c t e d . In these p r e l i m i n a r y s t u d i e s a s i g n i f i c a n t d i f f e r e n c e i n shear value was used as an i n d i c a t i o n of g e n e r a l a l t e r a t i o n s i n the muscle induced by the treatment. Chemical t e s t s would i n d i c a t e o n l y very s p e c i f i c m e t a b o l i c changes and would not r e f l e c t an o v e r a l l a l t e r a t i o n i n muscle c h a r a c t e r i s t i c s . TABLE 2. COMPARISON OF SHEAR VALUES OF P. MAJOR MUSCLE FROM UNINJECTED BIRDS AND BIRDS INJECTED WITH DISTILLED WATER Treatment Shear Value** T Value • df T - c a l c . * I n j e c t e d U n i n j e c t e d 15.88 16.56 .455 90 1.99 * T - c a l c u l a t e d f o r a t w o - t a i l e d T - t e s t a t P < .05 ** Shear val u e s are an average of s e v e r a l v a l u e s . Short Term Studies Glucocorticoids are not released immediately upon stress but act to increase resistance by inducing metabolic alt e r a t i o n s only after stress has continued for a time. In the event that glucocorticoids were present at the onset of stress, as when injected, they would i n i t i a t e the general adaptation syndrome.and thus modify the catabolic e f f e c t of stress-induced epinephrine on glycogen and ATP reserves. Metabolic a l t e r a t i o n s of stress should be decreased or modified i f glucocorticoid i n j e c t i o n were used to increase the resistance to the stress of slaughter and a favourable e f f e c t on meat quality should r e s u l t . Table 3 indicates the e f f e c t of corticosterone injections on muscle tenderness at several time in t e r v a l s post i n j e c t i o n . No s i g n i f i c a n t e f f e c t of the i n j e c t i o n i s noted u n t i l 6 hours at which time the shear values increase from those of the c o n t r o l . This i s a r e s u l t of the continu-ous absorption of the corticosterone from the injected muscle. In an excited b i r d , as one that has received an i n j e c t i o n i n the previous few hours, the corticosterone i s u t i l i z e d to overcome the stress of handling and i n j e c t i o n , and i s incorporated into the body metabolism, i n i t i a t i n g the GAS to restore homeostatic conditions. As the stress subsides the continuing absorption of corticosterone from the injected muscle creates an overdose i n the b i r d . In an unstressed TABLE 3. EFFECT OF CORTICOSTERONE INJECTION ON SHEAR VALUE OF P. MAJOR MUSCLE AT SEVERAL INTERVALS POST INJECTION Hours* Shear Value T Value df T-calc.** 0 12.25 2 11.66 .588 70 1.99 4 12.81 .575 70 1.99 6 16.69 4.68 76 1.99 8 16.27 3.66 70 1.99 * Hours post i n j e c t i o n ** P < .05 animal corticosterone overdose i s reported by L i s t e r (1970) to induce increased c e l l u l a r a c t i v i t y and depletion of ATP which at slaughter w i l l ultimately lead to a rapid onset of r i g o r mortis and post mortem toughening of muscle t i s s u e . Results of blood glucose tests indicated i n Table 4 confirm that corticosterone has been absorbed and i s e l i c i t i n g an e f f e c t at 2 hours post i n j e c t i o n . This i s further evidence that the lack of a s i g n i f i c a n t difference i n shear values at 2 and 4 hours post i n j e c t i o n i s not merely due to. a lag i n corticosterone absorption. TABLE 4. EFFECT OF CORTICOSTERONE INJECTION ON BLOOD GLUCOSE LEVELS AT SEVERAL TIME INTERVALS POST INJECTION Hours* Blood Glucose T Value df T-calc.** mg % 0 268 2 325 2.87 10 2.23 4 367 4.67 10 2.23 6 373 2.89 14 2.15 8 337 3.14 14 2.15 * Hours post i n j e c t i o n ** P < .05 B l o o d g l u c o s e l e v e l s i n c r e a s e s t e a d i l y o v e r the 8 hour p o s t i n j e c t i o n p e r i o d . T h i s i s c o n s i s t e n t w i t h the r e s u l t s o f S i e g e l e t a l . (1960) who i n j e c t e d ACTH, a c o r t i c o s t e r o n e p o t e n t i a t o r , i n t o c h i c k e n s , and r e f l e c t s t h e a c t i o n o f c o r t i c o s t e r o n e i n i n h i b i t i n g c e l l u l a r u ptake and u t i l i z a t i o n o f g l u c o s e . T a ble 5 i n d i c a t e s a comparison o f shear v a l u e s o f P. Major muscle from 6 week-old b r o i l e r s and 8 week-old b r o i l e r s a f t e r b o t h have r e c e i v e d c o r t i c o s t e r o n e i n j e c t i o n s . A c o n s i s t e n t d i f f e r e n c e i n shear v a l u e i s o b s e r v e d . The f a c t t h a t t h e shear v a l u e s were c o n s i s t e n t l y d i f f e r e n t i n d i c a t e s t h a t the d i f f e r e n c e was due t o an age and w e i g h t e f f e c t r a t h e r t h a n t o an e f f e c t o f t h e d i f f e r e n c e i n t h e p h y s i o l o g i c a l h a n d l i n g and e f f e c t o f t h e c o r t i c o s t e r o n e i n j e c t i o n . The e f f e c t o f age on t e n d e r n e s s o f p o u l t r y muscle has been w e l l e s t a b l i s h e d by May e t a l . (1962). They found a c o r r e s p o n d i n g i n c r e a s e i n shear v a l u e w i t h i n c r e a s e d age o f t h e c h i c k e n . I t i s l i k e l y t h a t t h e r e i s l i t t l e s i g n i f i c a n t p h y s i o l o g i c a l change i n the m e t a b o l i s m o f c o r t i c o s t e r o n e w i t h i n the two week p e r i o d . The g r e a t e s t d i f f e r e n c e i n t r e a t m e n t e f f e c t was found between b i r d s o f d i f f e r e n t s t r e s s l e v e l . S t r e s s l e v e l was s u b j e c t i v e l y e v a l u a t e d w i t h r e s p e c t t o t h e b i r d s r e a c t i o n t o a p e r s o n e n t e r i n g the range house, and t h e i r r e s p o n s e t o h a n d l i n g . The shear v a l u e s o f the P. M a j o r from the c o n t r o l 24 . TABLE 5. COMPARISON OF SHEAR VALUES OF P. MAJOR MUSCLE FROM 6 AND 8 WEEK OLD BIRDS AT SEVERAL TIME INTERVALS POST INJECTION OF CORTICOSTERONE. SHEAR VALUE Hours* 6 Weeks old 8 weeks old 0 14.93 16.16 2 13.98 15.56 4 13.67 15.72 6 12.61 15.68 8 12.29 15.36 * Hours post i n j e c t i o n birds confirmed the subjective observations. Table 6 indicates an increase i n shear value of the P. Major muscle from the control birds with a corresponding increase i n the l e v e l of stress. Table 7 indicates treatment re s u l t s of very p l a c i d b i r d s . The birds did not bunch up i n a corner of the house, did not flap about when handled and showed no sign of stress on i n j e c t i o n . Shear values increased immediately on i n j e c t i o n and remained elevated throughout the 8 hour post i n j e c t i o n period. I t may be explained that, as no stress was e l i c i t e d i n the birds, corticosterone absorbed even at 2 hours post i n j e c t i o n produced a metabolic overdose r e s u l t i n g i n hyper-tension and a post mortem toughening of muscle ti s s u e . TABLE 6. COMPARISON OF SHEAR VALUES OF P. MAJOR MUSCLE WITH SUBJECTIVE EVALUATION OF STRESS LEVEL OF THE BIRD. Stress Level Shear Value Pla c i d 10.88 Mil d l y excitable 16.16 Extremely excitable 16.20 25. TABLE 7. SHEAR VALUES OF P. MAJOR MUSCLE FROM PLACID BIRDS OVER AN 8 HOUR PERIOD POST INJECTION OF CORTICO-STERONE . Hours* Shear Value T Value df T-calc.** 0 10.88 2 13.43 3.63 158 1.96 4 14 .58 6 .20 147 1.96 6 13.06 3.00 155 1.96 8 11.86 1.60 167 1.96 * Hours post i n j e c t i o n ** P < .05 Table 8 indicates shear values of P. Major muscle from mildly excitable b i r d s , for an 8 hour period post i n j e c t i o n of corticosterone. No s i g n i f i c a n t changes were observed i n shear value. Birds were not stressed to the extent that the corticosterone would be immediately and rapidly u t i l i z e d a f f e c t i n g a tenderization of muscle tissue when com-pared to the control, nor were they so p l a c i d that c o r t i c o s -terone was never required. The injected corticosterone would enter into the metabolism, be u t i l i z e d and never constitute an overdose, nor produce deleterious e f f e c t s on muscle q u a l i t y . TABLE 8. SHEAR VALUES OF P. MAJOR MUSCLE FROM MILDLY EXCITABLE BIRDS OVER AN 8 HOUR PERIOD POST INJECTION OF CORTI-COSTERONE. Hours* Shear Value T Value df T-calc.** 0 16.16 2 15.56 1.240 79 1.99 4 15.72 1.23 67 1.99 6 15.68 1.29 70 1.99 8 15.36 1.57 68 1.99 * Hours post i n j e c t i o n ** P < .05 26, In comparison, Table 3 a l s o i n d i c a t e s shear v a l u e s obtained from m i l d l y e x c i t a b l e b i r d s . In t h i s case t h e r e was a s i g n i f i c a n t d i f f e r e n c e i n shear value a t 6 and 8 hours post i n j e c t i o n . V a r i a b i l i t y i n shear v a l u e s as a f f e c t e d by c o r t i c o s t e r o n e i n j e c t i o n i s the g r e a t e s t i n the m i l d l y e x c i t a b l e b i r d s due to p h y s i o l o g i c a l v a r i a b i l i t y and e r r o r i n s u b j e c t i v e judgement. When extremely e x c i t a b l e b i r d s r e c e i v e d a c o r t i -c osterone i n j e c t i o n s , marked changes i n shear v a l u e s o c c u r r e d , as shown i n Table 9. There was a s i g n i f i c a n t decrease i n shear v a l u e s f o r c o r t i c o s t e r o n e t r e a t e d b i r d s a t a l l times post i n j e c t i o n . C o r t i c o s t e r o n e i n j e c t i o n appears to have r e l i e v e d s t r e s s symptoms and i n i t i a t e d a more r a p i d r e t u r n to homeostatic c o n d i t i o n s of c e l l u l a r a c t i v i t y and carbo-hydrate metabolism.. TABLE 9. SHEAR VALUES OF P. MAJOR MUSCLE FROM EXTREMELY EXCITABLE BIRDS OVER AN 8 HOUR PERIOD POST INJECTION OF CORTICOSTERONE. Hours * Shear Value T Value df T - c a l c . * * 0 16.20 2 13.69 2.41 139 1.96 4 14.45 1.98 174 1.96 6 14.77 2.08 174 1.96 8 10.77 5.91 145 1.96 * Hours post i n j e c t i o n ** P < .05 When treatment e f f e c t was to be compared a l l b i r d s were ob t a i n e d a t the same time as t h i s study was conducted over an 18 month p e r i o d and environmental c o n d i t i o n s i n the range house v a r i e d . The main v a r i a b l e was temperature which ranged from 4 5°F to 85°F. Due to t h i s v a r i a b i l i t y f u r t h e r comparisons beyond those t h a t are made may not be v a l i d . Long Term S t u d i e s On a long term b a s i s , h y p e r c o r t i c a l i s m m o d i f i e s carbohydrate metabolism, p a r t i c u l a r l y g lucose m o b i l i z a t i o n and glycogen d e p o s i t i o n i n the t i s s u e . 1) 5 Day study D a i l y c o r t i c o s t e r o n e i n j e c t i o n s were found to i n c r e a s e blood glucose l e v e l s (Figure 2). T h i s i s c o n s i s t e n t with the r e s u l t s o f S i e g e l (1962) and r e f l e c t s the a b i l i t y o f c o r t i c o s t e r o n e to i n h i b i t c e l l u l a r uptake of g l u c o s e . To i n d i c a t e gross changes i n muscle metabolism over the 5 day p e r i o d of c o r t i c o s t e r o n e i n j e c t i o n , a study of muscle tenderness was conducted. Shear v a l u e s f o r both e x c i s e d and i n t a c t P. Major muscles are d i s p l a y e d i n F i g u r e 3. E x c i s e d muscle showed a much more pronounced e f f e c t of the treatment on shear v a l u e s probably because muscle s h o r t e n i n g i s not c o n t r o l l e d or m o d i f i e d by s k e l e t a l attachments. In the e x c i s e d t i s s u e a dramatic decrease i n shear v a l u e was recorded 24 hours a f t e r the f i r s t i n j e c t i o n . T h i s i s not apparent i n the i n t a c t t i s s u e . T h i s marked decrease i n shear v a l u e s may be the r e s u l t of the m o d i f i c a t i o n of s t r e s s induced post mortem changes i n muscle t i s s u e , as decreased pH and ATP l e v e l , by the i n j e c t e d c o r t i c o s t e r o n e . F o l l o w i n g FIGURE 3. Shear v a l u e s of i n t a c t and e x c i s e d P. Major muscle of b r o i l e r s r e c e i v i n g d a i l y c o r t i c o s t e r o n e i n j e c t i o n s over a 5 day p e r i o d . t h i s i n i t i a l 24 hour p e r i o d , homeostatic adjustments decrease the s i g n i f i c a n c e of the c o r t i c o s t e r o n e e f f e c t , shear v a l u e s proceeding t o the c o n t r o l l e v e l . The i n t a c t muscle w i t h the m o d i fying i n f l u e n c e of s k e l e t a l r e s t r i c t i o n merely f l u c -t u a tes n o n - s i g n i f i c a n t l y about the c o n t r o l v a l u e d u r i n g the 5 day p e r i o d . 2) 15 Day study A 15 day study was c a r r i e d out to c o n f i r m the e f f e c t of d a i l y c o r t i c o s t e r o n e i n j e c t i o n found i n the 5 day study and to observe changes d u r i n g the r e c o v e r y p e r i o d f o l l o w i n g c e s s a t i o n o f d a i l y i n j e c t i o n . B i r d s were i n j e c t e d d a i l y f o r 8 days and were observed f o r a f u r t h e r 7 day rec o v e r y p e r i o d . Shear t e s t i n g ; A marked decrease i n shear value i s seen i n e x c i s e d muscle, a f t e r i n i t i a l i n j e c t i o n , f o l l o w e d by a r e t u r n to more normal shear v a l u e s (Figure 4 ) . T h i s e f f e c t was a l s o seen i n F i g u r e 3. Shear v a l u e s f o r i n t a c t t i s s u e a g a i n f l u c t u a t e d n o n - s i g n i f i c a n t l y about the c o n t r o l l i n e on c e s s a t i o n of i n j e c t i o n . A l a g i n homeostatic a d j u s t -ment produces a temporary h y p o c o r t i c a l i s m a f t e r day 8, det e c t e d as an i n c r e a s e i n s t r e s s symptoms and an u l t i m a t e s i g n i f i c a n t i n c r e a s e i n shear v a l u e s i n both e x c i s e d and i n t a c t t i s s u e . T h i s i s i n accord w i t h the f i n d i n g s of Zimmerman e t a l . , (1972a, 1972b) who r e p o r t e d t h a t p h y s i o -l o g i c a l l e v e l s of c o r t i c o s t e r o n e suppressed n o n - s t r e s s , and s t r e s s induced p i t u i t a r y - a d r e n a l f u n c t i o n i n r a t s . A f t e r the FIGURE 4. Shear v a l u e s of e x c i s e d and i n t a c t P. Major muscle o f b r o i l e r s r e c e i v i n g d a i l y c o r t i c o s t e r o n e i n j e c t i o n s f o r 8 days and obse r v e d f o r a f u r t h e r 7 d a y s , w i t h o u t i n j e c t i o n . o — e x c i s e d • i n t ac t i n i t i a l reaction to cessation of corticosterone i n j e c t i o n s , homeostasis ensures that metabolism returns to a normal condition and shear values proceed to that of the control birds. Alterations of shear values as a r e s u l t of c o r t i -costerone inj e c t i o n s are not as d e f i n i t i v e as are the re s u l t s of s p e c i f i c chemical t e s t s . Shear value r e f l e c t s the sum of a l l changes i n muscle metabolism induced by corticosterone and not the r e s u l t of any one detectable change. Conclusions made on the basis of alt e r a t i o n s i n shear value are only possible with reference to re s u l t s of s p e c i f i c chemical t e s t s . Chemical t e s t s : Blood glucose. Figure 5 indicates blood glucose leve l s during the 15 day study: As previously noted, d a i l y injections caused an elevation i n blood glucose l e v e l s . When injections were discontinued glucose rapi d l y decreased as would be expected i n a hypocortical condition. C e l l u l a r deprivation of glucose during c o r t i c a l steroid i n j e c t i o n produces a marked c e l l u l a r glucose deficiency that i s ra p i d l y corrected on discontinuing i n j e c t i o n s , producing a hypoglycemic condition i n the blood. Progress to a normal glycemic condition followed as expected. Tissue glycogen. Figure 6 indicates tissue glycogen le v e l s during this 15 day study. Glycogen content increased with corticosterone i n j e c t i o n as corticosterone acted to FIGURE 5.. B l o o d g l u c o s e l e v e l o f b r o i l e r s r e c e i v i n g d a i l y c o r t i c o s t e r o n e i n j e c t i o n s f o r 0 days and observed f o r a f u r t h e r 7 day r e c o v e r y p e r i o d . 3.5. modify the t i s s u e glycogen d e p l e t i o n e f f e c t of e p i n e p h r i n e . The gluconeogenic a c t i v i t y o f c o r t i c o s t e r o n e i s w e l l docu-mented. Gluconeogenesis i s an i n v o l v e d m e t a b o l i c p r o c e s s , i n c l u d i n g many i n t e r m e d i a t e s t e p s . T h e r e f o r e , response a t c e s s a t i o n of i n j e c t i o n i s not immediate. pH. With the i n c r e a s e noted i n muscle glycogen a decrease i n u l t i m a t e pH i s expected. At death anaerobic, post mortem g l y c o l y s i s a c t s to metabolize t i s s u e glycogen to l a c t i c a c i d , d e c r e a s i n g the u l t i m a t e pH. Table 10 i l l u s t r a t e s t h i s pH d e c l i n e . Blood c h o l e s t e r o l . C h o l e s t e r o l i s the b a s i c p r e -c u r s o r f o r the b i o s y n t h e s i s of c o r t i c a l s t e r o i d s . With d a i l y i n j e c t i o n s of c o r t i c o s t e r o i d s the ad r e n a l c o r t e x i s spared of producing them, w i t h a r e s u l t i n g decrease i n uptake of blood c h o l e s t e r o l , i n c r e a s i n g c i r c u l a t i n g l e v e l s . Table 11 i l l u s t r a t e s t h i s e f f e c t . TABLE 10. ULTIMATE pH OF P. MAJOR MUSCLE FROM BROILERS RECEIVING DAILY CORTICOSTERONE INJECTIONS FOR 8 DAYS AND OBSERVED FOR A FURTHER 7 DAY RECOVERY PERIOD. Day pH* 0 5.79 8 5.57 10 5.40 . . Values are an average o f those from 4 b i r d s . TABLE 11. BLOOD CHOLESTEROL LEVELS OF BROILERS RECEIVING DAILY CORTICOSTERONE INJECTIONS FOR 8 DAYS AND OBSERVED FOR A FURTHER 7 DAY RECOVERY PERIOD. Day Blood C h o l e s t e r o l * mg % 0 115 8 275 15 120 * Values are an average o f those determined f o r 4 b i r d s . 37. SUMMARY AND CONCLUSIONS I n j e c t e d c o r t i c o s t e r o n e d i d express an e f f e c t on carbohydrate metabolism and muscle tenderness o f b r o i l e r s . Short term s t u d i e s conducted over an 8 hour p e r i o d i n d i c a t e d an e l e v a t i o n i n blood glucose from 2-8 hours p o s t -i n j e c t i o n . E f f e c t on P. Major muscle tenderness was found to be dependent on the p r e - i n j e c t i o n s t r e s s l e v e l of the b i r d . When p l a c i d b i r d s were i n j e c t e d w i t h c o r t i c o s t e r o n e shear v a l u e s i n c r e a s e d immediately and remained s i g n i f i c a n t l y higher than the c o n t r o l over the 8 hour p e r i o d . M i l d l y e x c i t a b l e b i r d s d i s p l a y e d no s i g n i f i c a n t change i n shear v a l u e . Extremely e x c i t a b l e b i r d s i n d i c a t e d a marked decrease i n shear v a l u e s a t 2-8 hours p o s t - i n j e c t i o n . Long term s t u d i e s i n d i c a t e d a decrease i n shear value upon i n i t i a l i n j e c t i o n , homeostatic adjustments to r e t u r n muscle to a normal metabolic c o n d i t i o n d u r i n g continued i n j e c t i o n s and a marked i n c r e a s e i n shear v a l u e s a t the c e s s a t i o n o f i n j e c t i o n s . Blood g l u c o s e , t i s s u e glycogen and blood c h o l e s t e r o l l e v e l s s i m i l a r l y i n c r e a s e d to the c e s s a -t i o n of i n j e c t i o n s and then decreased r a p i d l y , u l t i m a t e l y r e t u r n i n g t o those l e v e l s found i n the c o n t r o l b i r d s . U l t i m a t e pH of the pos t mortem t i s s u e decreased w i t h d a i l y c o r t i c o s t e r o n e i n j e c t i o n s . As proposed, c o r t i c o s t e r o n e i n j e c t i o n s d i d o f f s e t the s t r e s s r e a c t i o n i n t h a t i t m o d i f i e d s t r e s s induced m e t a b o l i c changes i n the muscle and r e s u l t e d i n a decrease 38, in shear value of some post mortem muscle. It appears from the re s u l t s of the short term studies, that the e f f e c t of intramuscular corticosterone i n j e c t i o n i s dependent on the physiological state of the b i r d and i t s state of resistance to environmental stressors at the time of in j e c t i o n . Long term studies indicated the a b i l i t y of homeo-s t a t i c adjustments to overcome physiological a l t e r a t i o n s induced by corticosterone i n j e c t i o n and return the muscle to a r e l a t i v e l y normal condition. 39. BIBLIOGRAPHY 1. Aberle, E.D, and R.A. Merkel. (1968). Physical and bio-chemical properties of porcine muscle as affected by exogenous epinephrine and prednisolone. J . Food S c i . 33; 43. 2. 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APPENDIX I Parameters of Subjective Evaluation of Stress Level of Birds STRESS S T R E S S L E V E L Pl a c i d Mildly Excitable Extremely Excitable A person entering range house Head movement remained s i t t i n g Walked away from person Rapidly moved to furthest corner of house Continued presence of person Got up and walked about Bunched i n the corner Fought to get in corner-most position Person handling other birds Walked about Moved into tighter bunch some fig h t i n g Fought w i l d l y sat on each other i n corner Being handled Flapped wings Flapped wings Flapped w i l d l y , a few times continuously writhing body and occasionally and pecking, pecked 

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