S U C C E S S F U L D R Y R A T I O N S F O R U S E D U RI N G THE L A T E G R O W T H , M A IN T E N A N C E , AND R E P R O D U C T IV E P E R I O D S O F R A N C H - R A I S E D MINK By P A U L E. K IF E R A THESIS S u b m i t t e d to t h e S c h o o l of A d v a n c e d G r a d u a t e S t u d i e s of M i c h i g a n S t a t e U n i v e r s i t y of A g r i c u l t u r e a n d A p p l i e d S c i e n c e i n p a r t i a l f u l f i l l m e n t of t h e r e q u i r e m e n t s f o r t h e d e g r e e of D O CT O R OF PHILO SO PH Y D e p a r t m e n t of P o u l t r y H u s b a n d r y 1956 ProQuest Number: 10008661 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10008661 Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346 ABSTRACT E x p e r im e n ta l feeding t r i a l s , using n a tu ra l d a rk m in k , w e re conducted o v e r a tw o -y e a r perio d . T h e p u r p o s e of t h e s t u d y w a s t h e d e v e l o p m e n t of d r y r a t i o n s w h i c h w o u l d a l l o w n o r m a l p e r f o r m ­ a n c e d u rin g the l a te g ro w th , m a i n te n a n c e , a n d r e p r o d u c t i v e p e r i o d s (A u g u st 1 to M ay 1). A t o t a l of 380 m i n k w e r e u s e d i n t h e s e t r i a l s - - n i n e g r o u p s of 20 a d u l t a n d k i t m i n k d u r i n g t h e a n d t e n g r o u p s of 20 a d u l t a n d k i t m i n k d u r i n g th e The 1954-55 t r i a l s in d ic a te d that: 1954-55 t r i a l s , 1955-56 t r i a l s . (1) b a s e d o n a c o m p a r i s o n w i t h t h e p r e v i o u s y e a r ’s r e s u l t s , t h e l o n g - t i m e f e e d i n g of . d r y r a t i o n s h a d no d e l e t e r i o u s e f f e c t s ; (2) a n i n c r e a s e d e n e r g y l e v e l b y a d d i t i o n of f a t s e e m e d to b e d e s i r a b l e ; (3) t h e u s e of a n t i b i o t i c s ( p e n i c i l l i n and a u r e o m y c in in com bination) gave be n eficia l r e s u lts during late g ro w th and m a in te n a n c e , but was c o n tra in d ic a te d during re p ro d u c tio n ; (4) d r i e d b r e w e r s y e a s t a n d d r i e d t o r u l a y e a s t , e s p e c i a l l y i n s i m p l i ­ fie d r a t i o n s , gave good r e s u l t s w h e th er u s e d singly or in c o m b in a ­ tion; (5) s w i t c h i n g b r e d f e m a l e s f r o m d r y r a t i o n s to a " w e t ” r a t i o n ( c o n t a i n i n g f r e s h m e a t , f i s h , t r i p e , e t c . ) h a d no a p p a r e n t e f f e c t e i t h e r o n t o t a l n u m b e r of k i t s b o r n o r o n t h e n u m b e r of l o s s e s , a n d suggested that p ro p e rly fo rm u la te d d ry ra tio n s w ere adequate for supporting gestation. T h e 1 9 5 5 - 5 6 t r i a l s w e r e d e s i g n e d to e v a l u a t e f u r t h e r t h e r e ­ su lts obtained during 1954-55. E v i d e n c e o b t a i n e d s u g g e s t e d t h a t: (1) t h e l i m i t i n g f a c t o r i n d r y r a t i o n s p r e v i o u s l y u s e d w a s c h i e f l y energy; (2) w h e n c o m p a r e d to a r a t i o n i n w h i c h c r u d e c a s e i n w a s t h e c h i e f p r o t e i n s o u r c e , the a v a i l a b i l i t y of p r o t e i n f r o m d r i e d s o u r c e s w as not a c ritic a l and lim iting factor; (3) t h e v i t a m i n a n d m i n e r a l c o n c e n t r a t e s u s e d in the c o m p le x d ry ra tio n s E and B ) w ere not n e c e ssa ry (other than V ita m in s sin ce the d ry in g r e d ie n ts in s im p li- JL u f i e d d r y r a t i o n s a p p a r e n t l y s a t i s f i e d the m i n k 's r e q u i r e m e n t s f o r th ese nutrients; (4) a s p r e v i o u s l y o b s e r v e d , b r e w e r s d r i e d y e a s t a n d to ru la d r ie d y e a s t (singly o r in com bination) w e re su itab le f o r use a n d t o l e r a t e d b y t h e m i n k a t t h e l e v e l s u s e d (15 p e r c e n t ) ; (5) N a ­ t i o n a l R e s e a r c h C o u n c i l r e q u i r e m e n t s f o r m i n k a p p e a r to b e d i r e c t l y a p p l i c a b l e to m i n k f e d o n d r y r a t i o n s p r o v i d e d a l l o w a n c e i s m a d e f o r th e l o w e r d i g e s t i b i l i t y o f d r i e d i n g r e d i e n t s b y m i n k . O n t h e b a s i s of t h e e v i d e n c e p r e s e n t e d h e r e i n , i t i s f e l t t h a t d r y r a t i o n s co u ld be u s e d s a t i s f a c t o r i l y a n d e c o n o m i c a l ly d u rin g the p e r i o d s of l a t e g r o w t h , m a i n t e n a n c e , b r e e d i n g , a n d g e s t a t i o n ; i . e . , f r o m A u g u s t 1 u n t i l M a y 1. ACKNOWLEDGMENTS T h e a u t h o r w i s h e s to e x p r e s s h i s s i n c e r e a p p r e c i a t i o n to D r . P . J. S chaible f o r his g u id a n c e , a s s i s t a n c e , a n d e n c o u r a g e m e n t d u r ­ ing the t i m e th is w o r k w as co n d u cte d , a n d th ro u g h o u t o u r a s s o c i a t i o n . H e i s a l s o i n d e b t e d to P r o f e s s o r C. G. C a r d , r e t i r e d h e a d , D e p a r t m e n t of P o u l t r y H u s b a n d r y , P r o f e s s o r J , A. D a v i d s o n , a n d D r . H. C. Z i n d e l , h e a d , D e p a r t m e n t of P o u l t r y H u s b a n d r y , f o r t h e i r a s s i s t a n c e p r i o r to a n d d u r i n g t h e p e r i o d of t h i s s t u d y , a n d to D r . E . J . B e n n e , D e p a r t m e n t of A g r i c u l t u r a l C h e m i s t r y , f o r the a n a l y s e s of t h e e x p e r i m e n t a l r a t i o n s . S i n c e r e a c k n o w l e d g m e n t i s a l s o m a d e to th e B r e w e r s Yeast C ouncil a nd the Sulphite P u lp M a n u f a c t u r e r s ' R e s e a r c h L e a g u e fo r th e ir financial a s s is ta n c e in these studies. IV P a u l E. K if e r c a n d i d a t e f o r t h e d e g r e e of D o c t o r of P h i l o s o p h y - F i n a l e x a m i n a t i o n , A p r i l 24, 1956, 2 :3 0 p . m . , C o n f e r e n c e R o o m , P o u l t r y Building. D issertation: S u c c e s s fu l D ry R a tio n s f o r Use D u rin g the L a te G r o w t h , M a i n t e n a n c e , a n d R e p r o d u c t i v e P e r i o d s of R a n c h - R a i s e d M ink O u t l i n e of S t u d i e s : M a jo r Subject: A nim al N utrition M inor Subjects; P o u ltry N utrition, B io c h em istry B io g rap h ical Item s: B o r n , A u g u s t 16, 1924. U n d e r g r a d u a t e S t u d i e s , U n i v e r s i t y of P i t t s b u r g h , M ich ig an State C o lle g e, 1947-1950. G r a d u a t e S tu d ies, M ic h ig a n State U n i v e r s ity , 19 46- 1947; 19 51- 1956. E xperience: U. S. A r m y , 19 42- 1946, 1 950 - 1951. T e c h n i c i a n , D e p a r t m e n t of P o u l t r y H u s b a n d r y , M i c h i g a n State U n iv e r s ity , 1952-1955. G r a d u a t e R e s e a r c h A s s i s t a n t , D e p a r t m e n t of P o u l t r y H u s b a n d r y , M i c h i g a n S t a t e U n i v e r s i t y , 1 955- 1956. M e m b e r of: P o u ltry Science A s s o c ia tio n S o c i e t y of t h e S i g m a Xi A m e r i c a n A s s o c i a t i o n f o r t h e A d v a n c e m e n t of S c i e n c e v TABLE OF CONTENTS Page I N T R O D U C T I O N ...................................................................................................... I REVIEW OF L IT E R A T U R E 3 ........................................................................... T h e D i g e s t i v e T r a c t of t h e M i n k ...................................................... 3 ..................................................................................... 5 O b s e r v a t i o n s o n R a t e of F o o d P a s s a g e ........................................... 6 N u t r i t i v e R e q u i r e m e n t s .............................................................................. 7 D ig estib ility Studies S u m m a r y of N u trie n t R equirem ents Studies Involving D ry R a tio n s .............................................. 13 ............................................................. 13 G E N E R A L M A T E R IA L S AND M ETH O D S ............................................ 16 .............................................................................. 17 ................................................................................. 19 E v a l u a t i o n of R e s p o n s e .............................................................................. 20 D e s c r i p t i o n of R a t i o n s E xperim ental P e rio d s PR E S E N T A T IO N OF DATA The .......................................................................... 22 1954-55 F e e d in g T rials .............................................. 22 The 1955-56 F e e d in g T rials ................................................................ 51 G E N E R A L D I S C U S S I O N ..................................................................................... 73 S U M M A R Y A ND C O N C L U S I O N S ................................................................. 81 ........................................................................................ 83 L IT E R A T U R E CITED vi LIST OF TABLES TABLE Page 1. C o m p o s i t i o n of C o n t r o l R a t i o n , 2. C o m p o sitio n of E x p e r i m e n t a l R atio n s F e d a s P e l l e t s , 1954-55 25 C o m p o sitio n of E x p e r i m e n t a l R a tio n s F e d a s W et M a s h , 1954-55 26 P r o x i m a t e A n a l y s e s of t h e R a t i o n s F e d , 1954-55 27 M a i n t e n a n c e of A d u l t M a l e M i n k , A u g u s t 7, 1954, to D e c e m b e r 14, 1954 29 M a i n t e n a n c e of A d u l t F e m a l e M i n k , A u g u s t 7, 1954, to D e c e m b e r 14, 1954 30 L a t e G r o w t h of M a l e M i n k K i t s , A u g u s t 7, 1954 , to D e c e m b e r 14, 1954 31 L a t e G r o w t h of F e m a l e M i n k K i t s , A u g u s t 7, 195 4, t o D e c e m b e r 14, 1954 32 M a i n t e n a n c e of A d u l t M a l e M i n k , D e c e m b e r 14, 1954 , to M a r c h 5, 1955 ...................................................... 37 M a i n t e n a n c e of A d u l t F e m a l e M i n k , D e c e m ­ b e r 14, 19 54 , t o M a r c h 5, 1955 .............................................. 38 11. B re e d in g a nd W helping R e s u lts , Spring, 40 12. B r e a k d o w n of K i t M o r t a l i t y , S p r i n g , 1955 44 13. E a r l y G r o w t h of M i n k K i t s , S p r i n g , 1955 47 3. 4. 5. 6. 7. 8. 9. 10. vii 1954-55 24 1955 ............... TABLE 14. 15. Page C o m p a r i s o n of t h e R e p r o d u c t i v e P e r f o r m ­ a n c e of F e m a l e M i n k o n R a t i o n s A, B , a n d C f o r t h e Y e a r s 1954 a n d 1955 49 C o m p o s i t i o n of E x p e r i m e n t a l R a t i o n s f o r 1955-56 54 16. C o m p o s i t i o n of C o n t r o l R a t i o n s , 1 9 5 5 - 5 6 .......................... 57 17. P r o x i m a t e A n a l y s e s of t h e R a t i o n s F e d , A u g u s t 1, 1955, to D e c e m b e r 1, 1955 ............................... 58 P r o x i m a t e A n a l y s e s of t h e R a t i o n s F e d , D e c e m b e r 1, 1 9 55 , to M a r c h 1, 1956 59 L a t e G r o w t h R e s u l t s , A u g u s t 1, 195 5, to D e c e m b e r 1, 1955; F i v e K i t M a l e s p e r G r o u p ......................................................................................................... 60 L a t e G r o w t h R e s u l t s , A u g u s t 1, 195 5, to D e c e m b e r 1, 1955; S e v e n K i t F e m a l e s p e r G r o u p ......................................................................................................... 61 M a i n t e n a n c e R e s u l t s , A u g u s t 1, 195 5, to D e c e m b e r 1, 1955; Tw o A d u l t M a l e s p e r G r o u p ......................................................................................................... 63 M a i n t e n a n c e R e s u l t s , A u g u s t 1, 1955, to D e c e m b e r 1, 1955; S ix A d u l t F e m a l e s p e r G r o u p ......................................................................................................... 64 M a i n t e n a n c e R e s u l t s , D e c e m b e r 1, 1955, to M a r c h 1, 195 6 .............................................................................. 65 E s t i m a t e d C a l o r ic V alues f o r 1955-56 R a t i o n s ...................................................................................................... 75 18. 19. 20. 21. 22. 23. 24. viii INTRODUCTION T h e c o m m e r c i a l r a i s i n g of m i n k i n t h e U n i t e d S t a t e s h a s g r o w n to a s i z a b l e i n d u s t r y f r o m a b e g i n n i n g a b o u t 1866 w h e n w i l d m i n k w e r e f i r s t r a i s e d i n p e n s (15). N a t i o n a l B o a r d of F u r F a r m A s u r v e y c o n d u c te d by the O r g a n i z a t i o n s i n 1954 s h o w e d t h a t n e a r l y 3 , 0 0 0 r000 m i n k p e l t s of a l l t y p e s h a v i n g a t o t a l m a r k e t v a l u e i n e x c e s s of $ 6 5 , 0 0 0 , 0 0 0 w e r e p r o d u c e d t h a t y e a r (2). Fifty-nine p e r c e n t of t h a t c r o p w a s p r o d u c e d i n t h e m i d w e s t e r n s t a t e s of W i s ­ consin, M innesota, M ichigan, and Illinois. D u r i n g t h e g r o w t h of t h i s i n d u s t r y , p r a c t i c a l m i n k r a t i o n s h a v e b e e n c o m p o s e d c h i e f l y of c o m b i n a t i o n s of f r e s h h o r s e m e a t , packing p la n t b y - p r o d u c t s , a n d l i v e r with cooked c e r e a l s . In m o r e r e c e n t y e a r s , d u e to a d r o p i n t h e n u m b e r of a v a i l a b l e h o r s e s - i.e., fro m 1 0 , 0 8 7 , 0 0 0 o n f a r m s i n 1940 to 3 , 4 3 2 , 0 0 0 i n 1954 ( 1 ) - - m o r e r e l i a n c e h a s b e e n p l a c e d o n t h e u s e of f r e s h a n d f r o z e n f i s h ( b o th o c e a n a n d f r e s h - w a t e r v a r i e t i e s ) . E x c e p t f o r th e c e r e a l s , a l l of t h e s e i n g r e d i e n t s s h a r e t h e c o m m o n d i s a d v a n t a g e s of s e a s o n a l g l u t s a n d s h o r t a g e s , h i g h t r a n s ­ p o rtatio n costs (50 to 80 p e r c e n t of the m a t e r i a l i s w a t e r ) , e a s e of s p o i l a g e , a n d t h e n e e d f o r i n d i v i d u a l r a n c h e r s to b u i l d a n d m a i n t a i n 1 2 extensive grinding, m ixing, and r e f r ig e r a tio n fa c ilitie s. In addition, r i s i n g l a b o r c o s t s h a v e m a d e t h e d a i l y m i x i n g a n d f e e d i n g of a r a ­ t i o n c o m p o s e d of t h e s e i n g r e d i e n t s m o r e a n d m o r e e x p e n s i v e . T h e s e f a c t o r s , co u p led with the s u c c e s s a tta in e d in r a i s i n g o t h e r a n i m a l s o n d r y f e e d s , h a v e l e d to a t t e m p t s to d e v e l o p d r y r a t i o n s f o r m i n k w h i c h w o u l d b e c o m p o s e d of r e a d i l y a v a i l a b l e , e a s i ly s t o r e d , d r y i n g r e d i e n t s , and w hich could be fe d in a p e l l e t e d form . T h i s t h e s i s p r e s e n t s d a t a o b t a i n e d f r o m two y e a r s ' w o r k o n this p ro je c t. F o r m u l a t i o n s of s e v e r a l d r y r a t i o n s w h i c h h a v e p e r ­ f o r m e d s a t i s f a c t o r i l y d u r i n g t h e p e r i o d s of l a t e g r o w t h , m a i n t e n a n c e , b r e e d i n g , a n d g e s t a t i o n (including w helping) u n d e r the e x p e r i m e n t a l c o n d itio n s e x istin g a t the F u r A n im a l N u tr itio n P r o j e c t a t M ich ig an State U n iv e r s ity a r e d e s c r ib e d . S u p p le m e n ta ry o b se rv a tio n s on m a n a g e m e n t p r o b l e m s a n d a p p a r e n t n u t r i t i o n a l r e q u i r e m e n t s of m ink fe d such r a tio n s a r e included. REVIEW OF L IT E R A T U R E R e l a t i v e l y l i t t l e c o n t r o l l e d e x p e r i m e n t a l w o r k o n the n u t r i t i o n a l r e q u i r e m e n t s of m i n k h a s b e e n r e p o r t e d . B ased on available l i t e r a ­ t u r e a n d p r a c t i c a l i n f o r m a t i o n , the N a t i o n a l R e s e a r c h C o u n c i l ( h e r e i n ­ a fte r a b b re v ia te d as NRC) has published tentative n u trie n t s ta n d a rd s f o r m i n k (2,3). The s tu d ie s on which th e s e s t a n d a r d s a r e b a s e d , plus other re p o rts w here s u f f i c i e n t d a t a a r e p r e s e n t e d to j u s t i f y t h e c o n ­ c lu sio n s d raw n , a r e re v ie w e d in this sectio n . The D ig e stiv e T r a c t of t h e M i n k N o h i s t o l o g i c a l s t u d i e s of t h e d i g e s t i v e t r a c t of t h e m i n k h a v e been reported. The single a v a ila b le g r o s s a n a to m ic a l d e s c r i p t i o n p e rta in in g to t h e N o r t h A m e r i c a n m i n k (14) d e s c r i b e d t h e s t o m a c h a s w e i g h i n g 2.5 to 4.8 g m ( m e a n 3. 8 ± 0.8 g m ) , o r a b o u t 0.5 p e r c e n t of t h e b o d y weight. W h e n f u l l y d i s t e n d e d , th e s t o m a c h c o n t a i n e d 40 to 70 c c . (1 .3 3 to 2. 33 f l u i d o u n c e s ) of i n g e s t a . T h e se f i g u r e s w e re b a s e d on m e a s u r e m e n t s m a d e on s e v e n ty - s e v e n m ink ran g in g in body w eight from 400 to 1450 g m . 4 T h e s m a l l i n t e s t i n e w a s d e s c r i b e d a s b e i n g d i v i d e d in to a d u o d e n u m h a v i n g a m e a n l e n g t h of 10.6 c m . w i t h a r a n g e of 7.4 to 13.9 c m . , a n d a j e j u n o - i l e u m h a v i n g a m e a n l e n g t h of 120 c m . w i t h a r a n g e of 93 to 150 c m . T h e r e w a s no c e c u m . colon, r e c t u m , and a n u s w as cm. The m e a n c o m b i n e d l e n g t h of t h e 10.1 c m . w i t h a r a n g e of 7.5 to 12.7 T hese m e a s u r e m e n t s r e p r e s e n t c o m b in ed data f r o m ranging fro m 106 m i n k 28.1 t o 42 .5 c m . i n b o d y l e n g t h . A l t h o u g h p o s t m o r t e m m e a s u r e m e n t s of e x c i s e d o r g a n s do n o t n e c e s s a r i l y r e f l e c t t h e d i m e n s i o n s of t h e s a m e o r g a n s d u r i n g l i f e , the a u t h o r s ta t e d th a t c o n s i s t e n t te c h n iq u e s w e r e e m p lo y e d in a n e f f o r t to e n s u r e a c o n s t a n t f a c t o r in m e a s u r i n g In t h e c a s e of t h e a b o v e m i n k , t h e r a t i o of i n t e s t i n a l t r a c t l e n g t h to b o d y l e n g t h r a n g e d f r o m of 3 . 9 7 : 1 . errors. 3 .6 0 : 1 to 4 .3 8 : 1 w i t h a m e a n r a t i o E a r l i e r t h e r a t i o of l e n g t h of d i g e s t i v e t r a c t to b o d y l e n g t h w a s r e p o r t e d a t 4:1 (22). M o r e r e c e n t l y W o o d (35) h a s r e p o r t e d t h e l e n g t h of t h e i n ­ t e s t i n e a s 4 6 . 8 i n c h e s w i t h a r a n g e of 43.5 to 5 1 .0 i n c h e s . These v a l u e s i n d i c a t e t h a t t h e i n t e s t i n e of t h e m i n k i s r o u g h l y o n e - h a l f t h e l e n g t h of t h a t of t h e a v e r a g e c a t , a n d o n e - f i f t h th e l e n g t h of t h a t of t h e a v e r a g e s m a l l dog. E s t i m a t e d v o l u m e of t h e e n t i r e i n t e s t i n e of th e m i n k w a s a p p r o x i m a t e l y tw o a n d o n e - t h i r d f l u i d o u n c e s , 5 c o m p a r e d to 20 f l u i d o u n c e s f o r t h e c a t a n d 250 f l u i d o u n c e s f o r t h e dog. T h e s e r e p o r t s d i d n o t i n c l u d e m e n t i o n of t h e a g e a n d s e x of the m in k stu d ied , b u t it a p p e a r s , on th is b a s i s , th a t the m a x i m u m c a p a c i t y of t h e s t o m a c h a n d i n t e s t i n e s of a n a v e r a g e m i n k w o u l d b e t h r e e to f o u r flu id o u n c e s . D ig estib ility Studies D i g e s t i b i l i t y s t u d i e s of t h e s t a r c h a n d c r u d e f i b e r i n b o t h r a w a nd cooked c e r e a l s have b e en r e p o r te d by B e r n a r d , Sm ith, and M a y n a r d (6). R a w p u r i f i e d c o r n s t a r c h w a s p o o r l y d i g e s t e d (54 p e r c e n t ) . S ta rc h fe d a s r a w yellow c o r n m e a l was s o m e w h a t m o r e d ig estib le (74 p e r c e n t ) , b u t p r o d u c e d l o o s e f e c e s , a n d p a r t i c l e s of c o r n w e r e o b s e r v e d in the e x c r e t a . S ta rc h fe d as ro lle d oats and ra w w heat m e a l w a s a p p a r e n t l y w e l l d i g e s t e d (87 p e r c e n t a n d 93 p e r c e n t ) , b u t t h e s e to o p r o d u c e d a s l i g h t s c o u r i n g i n s o m e a n i m a l s . C o o k e d s t a r c h , w h a t e v e r i t s s o u r c e , w a s d i g e s t e d 90 p e r c e n t o r b e t t e r , e v e n w h e n f e d a t a l e v e l of 45 to 50 p e r c e n t o n a d r y m a tte r basis. C r u d e f i b e r w a s f o u n d to be g e n e r a l l y n o n d i g e s t i b l e , a n d a m o u n t s of f i b e r h i g h e r t h a n 4 p e r c e n t r e s u l t e d i n u n p a l a t a b i l i t y . 6 W h e a t b r a n a t a 10 p e r c e n t l e v e l d e p r e s s e d t h e g e n e r a l d i g e s t i b i l i t y of t h e d i e t , b u t m o r e p a r t i c u l a r l y t h e s t a r c h f r a c t i o n . t h a t t h e l a x a t i v e e f f e c t of t h e b r a n w a s r e s p o n s i b l e . It w as thought O ther fib er s o u r c e s s t u d i e d h a d no e f f e c t e x c e p t b e e t p u l p , w h i c h w a s n o t t o l e r ­ a te d by m ink even a t a 1 p e r c e n t level. T h e a v e r a g e d i g e s t i b i l i t y of t h e c r u d e p r o t e i n p o r t i o n of th e a b o v e d i e t s , t h e c h i e f s o u r c e of w h i c h w a s r a w h o r s e m u s c l e , w a s 87 p e r c e n t . F a t s , a s e t h e r e x t r a c t , w e r e f o u n d to b e u n i f o r m l y highly d ig e stib le {93 p e r c e n t ) . O t h e r d ig e s t ib ilit y s tu d ie s have b e e n c o n c e r n e d chiefly with raw m e at products. G en era lly , raw m e a ts have b e en r e p o r te d as m o r e d i g e s t i b l e t h a n c o o k e d o r d r i e d p r o d u c t s - - ! . e . , r a w l i v e r , 93 p e r c e n t ; h o r s e m u s c l e , 86 p e r c e n t ; drying r e d u c e d the d ig e stib ility s p l e e n , 84 p e r c e n t . Cooking and to a b o u t 72 p e r c e n t (28). O b s e r v a t i o n s o n R a t e of F o o d P a s s a g e C o m p l e t e e l i m i n a t i o n of f o o d w i t h i n f i f t e e n h o u r s t i o n w a s r e p o r t e d (22). afterin g e s­ T h e a p p e a r a n c e of f e e d i n t h e f e c e s six h o u r s a f t e r i n g e s t i o n h a s a l s o b e e n r e p o r t e d (6). W o o d (3 5) , u s i n g s t a r v e d a n i m a l s , r e p o r t e d t h e r a t e of f o o d p a ssa g e as varying fro m o n e a n d o n e - h a l f to tw o h o u r s . A gain u s i n g s t a r v e d a n i m a l s , h e f o u n d t h a t t h e m i n k d e f e c a t e s w i t h i n 90 m i n u t e s a f t e r f e e d i n g , a n d t h a t f o o d t r a v e l s f r o m t h e m o u t h to t h e a n u s i n a p p r o x i m a t e l y 60 m i n u t e s . O n t h e b a s i s of t h e s e f i g u r e s , i t w a s s u g g e s t e d t h a t f e e d i n g , p a r t i c u l a r l y of y o u n g k i t s , b e a t f r e ­ q u e n t i n t e r v a l s ( a t l e a s t f o u r t i m e s d a i l y ) i n o r d e r to e n s u r e m a x i ­ m u m feed consu m p tio n and m a x im u m utilization. N utritive R eq u irem en ts P rotein. T h e f i r s t e s t i m a t e of t h e d i g e s t i b l e d r y p r o t e i n r e q u i r e m e n t of t h e a d u l t m i n k w a s m a d e b y S t i l l (29), who r e c o m ­ m e n d e d 22 g r a m s p e r m i n k p e r d a y . B a s e d o n t h e a d u l t m i n k ' s r e q u i r e m e n t of 0.9 o u n c e of r a w m e a t f o r n i t r o g e n e q u i l i b r i u m , S m i t h a n d L o o s l i (28) e s t i m a t e d t h e c r u d e p r o t e i n r e q u i r e m e n t to b e 25 g r a m s p e r d a y ( d r y b a s i s ) . T h i s w a s e s t i m a t e d to b e e q u i v a l e n t to 22 g r a m s of d i g e s t i b l e p r o ­ tein. T h e s a m e i n v e s t i g a t o r s f o u n d t h a t , i n t h e p r e s e n c e of a d e q u a t e c arb o h y d rate and fat, 10 g r a m s of d i g e s t i b l e p r o t e i n w o u l d m a i n t a i n n itro g e n e q u ilib r iu m in adult m ink. B a s s e t t (4) r e p o r t e d th e o p t i m u m p r o t e i n l e v e l of t h e r a t i o n f o r m i n k k i t g r o w t h to b e 28 to 34 p e r c e n t o n a d r y b a s i s . The N R C, citing u n p u b lish e d w ork by B a s s e t t , r e c o m m e n d s t h a t y o u n g m i n k k i t s b e t w e e n t h e a g e s of s e v e n a n d s i x t e e n w e e k s r e c e i v e a d i e t c o n t a i n i n g 22 to 26 p e r c e n t p r o t e i n ( d r y b a s i s ) . 8 G row ing m ink k its f r o m require s i x t e e n w e e k s of a g e to m a t u r i t y a p p e a r to 16 to 22 p e r c e n t p r o t e i n ( d r y b a s i s ) i n t h e i r d i e t . No r e c ­ o m m e n d e d l e v e l s f o r m a i n t e n a n c e a r e g i v e n (23). F at. T h e r e i s no a v a i l a b l e w o r k w h i c h p o i n t s o u t a s p e c i f i c fa t o r fatty a c id r e q u ir e m e n t fo r m ink. * B a s s e t t (4) s t a t e d t h a t f r e s h f a t c a n b e u s e d i n m i n k d i e t s a t l e v e l s of f r o m 5 to 30 p e r c e n t w i t h o u t h a r m . C arbohydrate. A s w i t h f a t , t h e r e h a v e b e e n no c r i t i c a l stud­ i e s m a d e w i t h r e s p e c t to the c a r b o h y d r a t e r e q u i r e m e n t s of m i n k . In p r a c t i c e , r a t i o n s a r e f o r m u l a t e d to c o n t a i n l e v e l s of h o r s e m e a t , fis h , p acking p la n t b y - p r o d u c t s , and li v e r , which e x p e rie n c e has s h o w n to g i v e s a t i s f a c t o r y r e s u l t s , a n d t h e r e m a i n d e r of t h e r a t i o n i s m a d e up of c o o k e d c e r e a l s . Tw o g e n e r a l t y p e s of c e r e a l m i x e s a r e c o m m e r c i a l l y a v a i l ­ able. "C ereal m ixes" a r e c o o k e d m i x t u r e s of c o r n , w h e a t , a n d r i c e i n t e n d e d f o r u s e a t l e v e l s up to 15 p e r c e n t of t h e r a t i o n , a n d contribute p r im a r i ly digestible c arb o h y d rate. "Supplem ented c e r e a l s " c o n t a i n , i n a d d i t i o n , o t h e r f e e d i n g r e d i e n t s to s u p p l y a d d i t i o n a l n u ­ t r i e n t s , a n d a r e i n t e n d e d f o r u s e a t l e v e l s up to 30 p e r c e n t of t h e ration. 9 T h e l e v e l of c e r e a l u s e d v a r i e s w i t h i n d i v i d u a l r a n c h e r s a n d w i t h t h e t i m e of t h e y e a r . These levels range fro m 10 to 20 p e r ­ c e n t d u r i n g th e b r e e d i n g a n d w h e l p i n g s e a s o n , a n d f r o m p e r c e n t t h r o u g h o u t t h e r e m a i n d e r of t h e y e a r E nergy. 10 to 35 (18). P a l m e r (24) a n d L o o s l i a n d S m i t h (22) r e p o r t e d a d a i l y c a l o r i c r e q u i r e m e n t of 120 to 130 c a l o r i e s , a n d H o d s o n a n d S m i t h (11), 124 c a l o r i e s p e r p o u n d o f b o d y w e i g h t f o r a d u l t m i n k . T h e l a t t e r valu e h a s b e e n a d o p te d by the NRC. V itam in. M o s t of t h e i n f o r m a t i o n r e l a t i v e to v i t a m i n r e q u i r e ­ m e n ts f o r m ink has co m e-b y inferen ce fr o m either previous studies on fo x e s o r stu d ie s on m in k w h e re p u r if ie d d ie ts w e r e u tiliz e d . B a s s e t t e t a l . (3) p o i n t e d o u t t h a t b o t h " g r o w i n g " a n d " p e l t ­ i n g " d i e t s f e d to m i n k , w h i c h u s u a l l y i n c l u d e v e g e t a b l e s a n d f r e s h l i v e r , c o n t a i n s u f f i c i e n t V i t a m i n A, a n d t h a t t h e a d d i t i o n of t h i s v i t a m i n o r of c a r o t e n e c o n c e n t r a t e s i s u n n e c e s s a r y . Some evidence w a s a l s o o b t a i n e d w h i c h i n d i c a t e d t h a t t h e c o n t e n t of V i t a m i n A in. t h e b l o o d s e r u m a n d l i v e r s of m i n k i n c r e a s e d w i t h t h e i n c r e a s e d i n t a k e of V i t a m i n A. A s c o r b i c a c i d a d d e d to t h e d i e t i n c r e a s e d th e V i t a m i n A c o n t e n t of t h e b l o o d s e r u m a n d l i v e r a n d a p p e a r e d to e x e r t a sp arin g action. 10 T h e N R C h a s a d o p t e d 780 I.U . of V i t a m i n A p e r p o u n d of f e e d (dry b a s i s ) b a s e d on e x p e r i m e n t a l w o rk w ith the fo x a s a t e n ­ tativ e a llo w an ce fo r the m ink. S m i t h a n d L o o s l i (28) r e p o r t e d t h a t a s e r i o u s V i t a m i n D d e ­ f i c i e n c y c o u l d n o t b e i n d u c e d d u r i n g t h e p e r i o d f r o m w e a n i n g to pelting. C a l c i u m a n d p h o s p h o r u s c o n t e n t of t h e b o n e s w a s r e d u c e d , how ever. B a s s e t t e t a l . (5) s u g g e s t t h a t , if t h e c a l c i u m - t o - p h o s p h o r u s r a t i o i s m a i n t a i n e d b e tw e e n 0.75:1.0 a n d 1.7:1.0, the V ita m in D r e ­ q u i r e m e n t i s p r o b a b l y l e s s t h a n 0.8 2 I. U . p e r g r a m of d r y f o o d . T h e N R C c o n c l u d e s t h a t " V i t a m i n D s u p p l e m e n t a t i o n of p r a c ­ tical fox and m ink diets th e re fo re does not a p p e a r n e c e s s a r y . " The c u r r e n t t r e n d t o w a r d s h o u s i n g m i n k i n s h e d s w h e r e a c c e s s to s u n ­ lig h t m ig h t be r e s t r i c t e d m a y r e s u l t in the n e e d f o r s o m e V ita m in D supplem entation. No d e fin itiv e s tu d ie s on V ita m in s E a n d K h a v e b e e n m a d e , a l t h o u g h b o t h v i t a m i n s a r e f r e q u e n t l y a d d e d to p r a c t i c a l r a t i o n s b y individual r a n c h e r s . V i t a m i n E is a d d e d to a i d i n the p r e v e n t i o n of " y e l l o w f a t " d i s e a s e , r e p o r t e d b y L a l o r e t a l . (19) a s b e i n g c a u s e d b y u n s a t u r a t e d fa tty a c id s p r e s e n t in h o r s e m e a t. The NRC s u g g e s t s t h a t 2 p e r c e n t 11 w h e a t g e r m m e a l o r t h e e q u i v a l e n t c o n c e n t r a t i o n of m i x e d t o c o p h e r o l a c e ta te s be added a s a prev en tiv e m e a s u re . V i t a m i n K i s a d d e d t o r a t i o n s b y i n d i v i d u a l r a n c h e r s to c o n ­ trol so-called " b le e d e rs ." No e x p e r i m e n t a l w o r k to j u s t i f y o r r e ­ fute this p ra c tic e h as b e en p e rfo rm e d . The te n ta tiv e a llo w a n c e s f o r the B v i t a m i n s - - t h i a m i n , r i b o ­ flavin, p an to th en ic acid, n iacin , py rid o x in e, and folic a c i d - - adopted b y t h e N R G w e r e a l l d e r i v e d f r o m p r e v i o u s w o r k w i t h f o x e s (26), a n d w i t h m i n k f e d p u r i f i e d d i e t s (25, 31). Loeschke e t a l . (20) o b t a i n e d a r e s p o n s e to V i t a m i n B u sin g a f o r c e - f e e d i n g technique on B -d eficien t m ink. w a s o b t a i n e d w i t h tw o a n d t h r e e m i c r o g r a m s of B Response p e r m ink p e r i day. by Ci T h e l a t t e r v a lu e h a s b e e n a d o p te d by the NRC a s a te n ta tiv e allow ance. Of t h e B v i t a m i n s , o n l y a t h i a m i n d e f i c i e n c y h a s b e e n o b ­ s e r v e d u n der p r a c tic a l r a n c h conditions. C e r t a i n s p e c i e s of f i s h f e d r a w to m i n k c a u s e a d e f i c i e n c y s y n d r o m e c a l l e d C h a s t e k p a r a l y ­ s i s (10 , 21). T h i s h a s b e e n s h o w n to r e s u l t f r o m d e s t r u c t i o n of t h i a m i n i n t h e d i e t b y th e e n z y m e t h i a m i n a s e . I n a c t i v a t i o n of th e e n z y m e b y c o o k i n g th e f i s h o r r a i s i n g t h e d i e t a r y l e v e l of t h i a m i n by su p p lem en tatio n have both given s a tisfa c to ry r e s u lts as control 12 m easures, F e e d in g the r a w f is h on a l te r n a t e days has a lso b e en used. S i m i l a r e n z y m a t i c d e s t r u c t i o n of p a n t o t h e n i c a c i d h a s b e e n s u g g e s te d by B o w n e s s known as (7) a s a p o s s i b l e c a u s e of a p e l t c o n d i t i o n ’'co tto n u n d e r f u r " or "cotton m in k ." The e n zy m e (s) i n v o l v e d h a v e n o t b e e n i d e n t i f i e d (8), n o r h a s f u r t h e r i n f o r m a t i o n b e e n published. M i n k do n o t a p p e a r to r e q u i r e a d i e t a r y s o u r c e of a s c o r b i c acid. B a s s e t t e t a l . (3) h a v e s h o w n , h o w e v e r , t h a t a n i n t e r r e l a t i o n ­ ship b e tw e e n a s c o r b i c a c i d and V ita m in A a p p a r e n tly e x is t s , with a d d e d d i e t a r y a s c o r b i c a c i d i n c r e a s i n g th e s t o r a g e of V i t a m i n A in the l i v e r . M ineral. B a s s e t t et al. (5) r e p o r t e d t h a t w h e n t h e r a t i o of c a l c i u m to p h o s p h o r u s w a s m a i n t a i n e d b e t w e e n 0 . 7 5 : 1 . 0 a n d 1 . 7 : 1 . 0 , t h e m i n i m u m c a l c i u m a n d p h o s p h o r u s r e q u i r e m e n t of the g r o w i n g m i n k w a s b e l o w 0.3 p e r c e n t of the d r y d i e t . T heir ex p erim en tal d i e t s u p p l i e d 0 ,8 2 I. U . of V i t a m i n D p e r g r a m of d r y f e e d , a n d t h i s a p p e a r e d to b e a d e q u a t e u n d e r n o r m a l c o n d i t i o n s . N o s t u d i e s o n o t h e r m i n e r a l r e q u i r e m e n t s of m i n k h a v e b e e n reported. 13 S u m m a r y of N u t r i e n t R e q u i r e m e n t s The NRC n u trie n t re q u ire m e n ts in p e rc e n ta g e or am ount p e r p o u n d of m o i s t u r e - f r e e f e e d a r e s u m m a r i z e d in the follow ing tab le (23): G row th M ature 7 to 16 16 w e e k s to ( m a i n t e weeks m aturity nance) E nergy* P ro te in , p e r cent Vita m in s V i t a m i n A , I. U. T hiam ine, mg Riboflavin, m g Pantothenic a c id r m g N icotinic acid , mg Pyridoxine, mg F o lic acid, m g M inerals Salt, p e r c e n t C alcium , p er cent P h o sp h o ru s, p er cent C a:P ratio 22 16 780 0.5 0.9 3.6 4.5 0.5 0.09 780 0.5 0.9 3.6 4.5 0.5 0.09 0.5 0.4 0.4 0.75:1.0 to 1 . 2 : 1 . 0 0.5 0.4 0.4 0.75:1.0 to 1 . 2 : 1 . 0 124 0.5 0.5 0.75:1.0 to 1 . 2 : 1 . 0 ^ C a l o r i e s p e r pound bod y w eight. Studies Involving D ry R a tio n s T r a v i s e t a l . (30) r e p o r t e d a n i n i t i a l a t t e m p t a t t h e f o r m u l a ­ t i o n of a c o m p l e t e l y d r y r a t i o n f o r m i n k . R esu lts obtained fr o m f e e d i n g t r i a l s o n s i x a d u l t a n d f i f t e e n k i t m i n k s h o w e d t h a t the d ie t e m p lo y e d w a s in a d e q u a te f o r p r o m o tin g g ro w th in young m in k 14 (10 to 12 w e e k s of a g e a t t h e s t a r t of t h e e x p e r i m e n t ) , b u t d i d a p ­ p e a r to m a i n t a i n b o d y w e i g h t i n a d u l t s o v e r a p e r i o d of 111 d a y s . T h e p r i n c i p a l d e f e c t of t h e d i e t w a s s h o w n to b e c o n c e r n e d w i t h p r o t e i n a n d s p e c ific a lly w ith the a m in o a c id s m e th io n in e , ly s i n e , and tryptophane. H o w e v e r , i t w a s n o t d e t e r m i n e d w h e t h e r o n l y on e of t h e a m i n o a c i d s o r a p a i r of t h e m w a s i n v o l v e d . H o w e l l ( 1 2 , 13) a l s o r e p o r t e d l i m i t e d s u c c e s s w i t h d r y r a ­ tions. G ro w th and re p ro d u c tio n w e re s u b n o rm a l when a n im a ls w e re fe d solely on the d ry r a tio n s . T h e s h o r t c o m i n g s of t h e r a t i o n s w e r e t h o u g h t to b e d u e to a p r o t e i n o r a m i n o a c i d d e f i c i e n c y r a t h e r t h a n to a v i t a m i n d e f i c i e n c y . M ethionine, ly s in e , a n d try p to p h a n e did not a p p e a r to b e i n v o l v e d . B oth T r a v is and Howell r e p o r t e d p a la ta b ility an d d ig e stib ility of d r y r a t i o n s a s b e i n g l i m i t i n g f a c t o r s i n t h e s u c c e s s f u l u s e of these rations. K if e r and Schaible w e re fe d in p e lle te d f o r m . (16, 17) d e s c r i b e d t h r e e d r y r a t i o n s w h i c h T h e s e r a tio n s , while not p e r m itti n g a s l a r g e w e i g h t g a i n s a s th e c o n t r o l r a t i o n d u r i n g l a t e g r o w t h , a p p e a r e d to b e adeq u ate in all o th e r w ay s. fa c to ry fo r m aintenance. All of t h e d r y r a t i o n s w e r e satis­ P a l a t a b i l i t y d i d n o t a p p e a r to b e a f a c t o r a s n o i n s t a n c e s of f e e d r e f u s a l w e r e n o t e d . All d i e t s w e r e c o n s u m e d 15 r e a d i l y if a d e q u a t e w a t e r w a s a v a i l a b l e . D uring fre e z in g w e a th e r, l a c k of w a t e r a p p e a r e d to b e a l i m i t i n g f a c t o r . B r e e d i n g p e r f o r m a n c e of m i n k f e d d r y p e l l e t e d r a t i o n s f o r a p e r i o d of s e v e n m o n t h s p r i o r to t h e s t a r t of t h e b r e e d i n g s e a s o n w a s s u p e r i o r to t h a t of m i n k f e d a c o n t r o l r a t i o n of a t y p e u s e d com m ercially. All d r y r a t i o n s s u p p o r te d n o r m a l g e s t a t i o n an d w h e lp ­ ing. N o n e of t h e d r y r a t i o n s a l l o w e d s a t i s f a c t o r y e a r l y g r o w t h (0 to 10 w e e k s of a g e ) of m i n k k i t s e v e n w h e n p a r t i a l l y s u p p l e ­ m e n t e d by fe e d in g the c o n tro l ra tio n . F a i l u r e of t h e m i n k k i t s to g r o w n o r m a l l y a p p e a r e d to b e r e l a t e d to i n a d e q u a t e l a c t a t i o n b y t h e fem ale. T h e m a t e r i a l r e p o r t e d i n t h i s t h e s i s i s a c o n t i n u a t i o n of these studies. G E N E R A L M A T E R IA L S AND M ETHODS T h e m i n k used, i n t h e s e e x p e r i m e n t s w e r e a l l f r o m t h e s t o c k of n a t u r a l d a r k m i n k m a i n t a i n e d b y t h e F u r A n i m a l N u t r i t i o n P r o j ­ e c t a t M ic h ig a n State U n iv e r s ity . The o rig in a l a n im a ls w e re donated to t h e p r o j e c t i n 1949 b y m e m b e r s of t h e M i c h i g a n F u r B r e e d e r s A ssociation. I n A u g u s t , 19 53 , th e K e l l o g g F e e d R e s e a r c h F a r m , H ic k o ry C o r n e r s , M ichigan, donated seventy m ink k its. g r o u p s of m i n k w e r e s u b s e q u e n t l y i n t e r b r e d . T h e tw o T h e p r e s e n t s t o c k is not highly in b r e d , a n d a p p a r e n tly is slightly s m a l l e r in o v e r - a l l body s iz e an d body w eight than the highly s e le c te d m in k r a i s e d on c o m ­ m e rc ia l ranches. P e l t q u a l i t y of t h e a v a i l a b l e a n i m a l s a l s o a p p e a r s to b e l o w e r t h a n t h a t of c o m m e r c i a l l y r a i s e d m i n k . Due to the r e l a t i v e l y f e w m i n k m a i n t a i n e d i n t h e p a s t , no s e l e c t i o n f o r p e l t q u a l i t y h a s b e e n possible. Since s i m i l a r a n i m a l s w e r e u s e d in a ll c o m p a r i s o n s in th is s tu d y , and p e lt quality is l a r g e l y d e t e r m i n e d by h e r e d ity , this f a c t o r w a s n o t c o n s i d e r e d to o i m p o r t a n t f o r t h e p u r p o s e s of t h i s study. T h e a n i m a l s w e r e k e p t o u t of d o o r s t h r o u g h o u t t h e y e a r i n i n d i v i d u a l c a g e s of u n i f o r m s i z e , c o v e r e d to p r o v i d e s o m e p r o t e c t i o n 16 17 from the e le m e n ts . E a c h cage w as equipped with a w a te r cup, fe e d d o o r , and nestbox. W here p ellets w e re fed, each cage contained a tin cup w hich s e r v e d a s a f e e d e r. N o rm a l ra n c h conditions w ere f o l l o w e d w h e r e v e r p o s s i b l e , t h e c h i e f d i f f e r e n c e b e i n g t h e l a c k of o p e n - s i d e d s h e d s w h ich a r e i n r e l a t i v e l y c o m m o n u s e on c o m m e r c i a l ranch es . D e s c r i p t i o n of R a t i o n s T h e c o n t r o l r a t i o n ( Mw e t M r a t i o n ) u s e d i n t h e s e e x p e r i m e n t s w as m i x e d r p la c e d in p la s tic bags containing a p p ro x im a te ly enough f o r one d a y ls fe e d in g , and f r o z e n a t the K ellogg F e e d R e s e a r c h F a r m , H ickory C o r n e r s , M ichigan. T h i s r a t i o n w a s i n t e n d e d to b e s l i g h t l y b e tte r than those fed c o m m e rc ia lly . D u r i n g th e c o u r s e of t h e e x ­ p e r i m e n t s t h e f o r m u l a t i o n of t h e r a t i o n v a r i e d o c c a s i o n a l l y i n t h e t y p e of f i s h i n c l u d e d , a s i s p r o b a b l y t r u e w i t h m o s t c o m m e r c i a l rations. T h i s v a r i a t i o n w a s u n a v o i d a b l e d u e to s e a s o n a l f l u c t u a t i o n s i n a v a i l a b i l i t y of v a r i o u s t y p e s of f i s h . A ll d ry r a t i o n s (about 7 p e r c e n t m o is tu r e ) w e re m ix e d in an u p r ig h t m i x e r a t the p o u ltr y plant. These ra tio n s w ere then fed e ith e r as a wet m a s h o r , m o r e often, a s a d ry p ellet. 18 W hen f e d a s a w et m a s h , the d r y f e e d was m ix e d with w a te r to f o r m a v e r y t h i c k g r u e l . This w e t m i x w as th e n p l a c e d on the f e e d d o o r f o r t h e m i n k to c o n s u m e . W h en f e d a s a p e l l e t , th e m i x e d d r y f e e d w as t a k e n to a f e e d m anufacturer pelleting. (Valley C ity M illing C o m p a n y , P o r t l a n d , M ichigan) f o r P e l l e t i n g w a s so m a n a g e d t h a t only the holding ta n k , p e lle t m ill, c o o le r, a n d bagging eq u ip m en t w e re used. A ls o , the f i r s t f e w p o u n d s of p e l l e t s m a d e f r o m e a c h r a t i o n m i x w e r e d i s ­ carded. T h i s e l i m i n a t e d m o s t of t h e p o s s i b i l i t y of i n t r o d u c i n g a n y e x t r a n e o u s f e e d i n g r e d i e n t s into the e x p e r i m e n t a l m i x e s . P ellet s i z e w a s 3 / 1 6 in c h ( d i a m e t e r ) by a b o u t 3 / 8 in c h (length). A l l r a t i o n s w e r e f e d d a i l y (in t h e l a t e a f t e r n o o n ) e x c e p t d u r ­ ing t h e l a c t a t i o n p e r i o d o f t h e f e m a l e a n d t h e p e r i o d of e a r l y g r o w t h of t h e m i n k k i t s . D uring th e se p e rio d s a n additional feeding was s u p p lie d i n the m o r n i n g . A l l r a t i o n s w e r e f e d i n e x c e s s of th e a m o u n t a n a n i m a l would n o r m a l l y c o n s u m e b e tw e e n fe e d in g s. W ate r was constantly available. In o r d e r to i n s u r e a d e q u a t e w a te r f o r m in k re c e iv in g d ry ra tio n s during fre e z in g w e a th e r, an a u to m a tic , in te rm itte n t, w aterin g s y ste m w as developed and installed. This s y s t e m , p r o t e c t e d f r o m f r e e z i n g b y t h e u s e of h e a t i n g c a b l e s w i t h i n t h e s u p p l y p i p e a n d c o n t r o l l e d b y a t i m e c l o c k , e n a b l e d th e a n i m a l s to d r i n k e v e r y h o u r if d e s i r e d , w i n t e r o r s u m m e r . 19 E xperim ental P e rio d s E x p e rim e n ta l feeding tr i a ls w e re s t a r t e d on o r about A u g u st 1 a n d t h e p e r f o r m a n c e of t h e a n i m a l s w a s f o l l o w e d t h r o u g h o u t t h e s e periods: 1. D ecem ber. L ate grow th. T h i s p e r i o d r a n f r o m A u g u s t 1 to m i d - T h is e n c o m p a s s e s the ti m e w hen m in k k i t s a r e f i n i s h ­ in g t h e i r g r o w t h a n d w h e n t h e i r f u r i s p r i m i n g . In a c o m m e r c i a l o p e r a t i o n a ll m i n k e x c e p t b r e e d i n g s to c k w ould be p e l t e d a t the end of t h i s p e r i o d . 2. M aintenance. This t e r m D e c e m b e r until e a r ly M arch . c o v e r s the p e r i o d f r o m m id - F o r adult m ink held o v e r fo r long­ t i m e s t u d i e s of t h e e f f e c t s of d r y r a t i o n s , t h e e n t i r e y e a r w a s c o n ­ s i d e r e d t o b e a m a i n t e n a n c e p e r i o d w i t h t h e e x c e p t i o n of t h e b r e e d ­ ing s e a s o n f o r m a l e s a n d t h e b r e e d i n g season and subsequent period of g e s t a t i o n , w h e l p i n g , a n d l a c t a t i o n f o r f e m a l e s . 3. B re e d in g , g e sta tio n , w helping, a n d la ctatio n . F o r ranch- r a i s e d m i n k t h e b r e e d i n g s e a s o n i s r o u g h l y t h e m o n t h of M a r c h . G e sta tio n la s ts a p p ro x im a te ly seven weeks fro m t h e d a t e of t h e f i n a l m a t i n g , a l t h o u g h t h e l e n g t h of g e s t a t i o n m a y v a r y f r o m f o r t y to s e v e n ty d a y s with individual f e m a l e s . d u r i n g t h e f i r s t tw o w e e k s of M a y . F e m a l e s u su ally w helped T h e v a r i a t i o n i n l e n g t h of zo g e s ta tio n r e s u l t e d in a n o c c a s io n a l l i t t e r being w helped in la te A p ril o r late M ay, M ink k its a r e e n t i r e l y d e p e n d e n t o n t h e m i l k of t h e f e m a l e d u rin g the f i r s t fo u r w eeks a fte r b irth . 4. E a r l y g r o w t h of m i n k k i t s . T h i s w a s c o n s i d e r e d to b e t h e p e r i o d f r o m t h e d a t e of b i r t h u n t i l t h e k i t s w e r e e i g h t to t e n w e e k s of a g e , o r a b o u t A u g u s t 1. A f t e r f o u r w e e k s of a g e , t h e k its u su ally c o n s u m e d the r a t i o n o ffered . W h en the k i t s w e r e eig h t w e e k s of a g e , t h e f e m a l e w a s s e p a r a t e d f r o m t h e l i t t e r . The l i t t e r w a s t h e n s p l i t i n t o g r o u p s of o n e , t w o , o r t h r e e , a n d r e m a i n e d t h u s f o r a n a d d i t i o n a l w e e k o r s o u n t i l t h e s u c c e e d i n g s e t of f e e d i n g t r i a l s was started . In t h i s t h e s i s the t e r m 11k i t 1f i s u s e d to d e s c r i b e a n y m i n k l e s s t h a n s i x a n d o n e - h a l f m o n t h s of a g e . The t e r m " a d u l t " is u s e d f o r t h o s e o v e r s i x a n d o n e - h a l f m o n t h s of a g e . E v a l u a t i o n of R e s p o n s e R e s p o n s e of the a n i m a l s to t h e d i e t a r y t r e a t m e n t s w a s e v a l ­ u a t e d p r i m a r i l y i n t e r m s of g a i n s i n w e i g h t . All a n i m a l s w e re w e i g h e d w e e k l y d u r i n g t h e e a r l y p a r t of t h e f e e d i n g t r i a l s . D uring t h e l a t t e r p a r t of g r o w t h a n d d u r i n g m a i n t e n a n c e , w e i g h i n g , u s i n g a b e a m -ty p e b a la n c e , w as on a biw eekly b a s is . W eights w e re r e c o r d e d 21 to t h e n e a r e s t 10 g r a m s . I n c le m e n t w e a th e r o c c a s io n a lly f o r c e d the s h i f t i n g o r c a n c e l l a t i o n of t h e a c t u a l d a t e of w e i g h i n g . B re e d in g and re p ro d u c tiv e p e r f o r m a n c e w e re both ev alu ated a n d c o n s i d e r e d i m p o r t a n t a lth o u g h it w as f e l t th a t the n u m b e r s i n ­ v o l v e d w e r e t o o s m a l l to r e f l e c t m o r e t h a n a g e n e r a l i n d i c a t i o n of t h e q u a l i t y of t h e r a t i o n s . O b s e r v a t i o n s w e r e a l s o m a d e on m o r t a l i t y , g e n e r a l h e a lth , a n d a p p e a r a n c e of t h e a n i m a l s . All m in k th a t died w e re n e c r o p s i e d a n d , w h e n p o s s i b l e , t h e c a u s e of d e a t h d e t e r m i n e d . O t h e r s p e c ific p r o c e d u r e s follow ed w ill be outlined in c o n n e c ­ tio n with the fe e d in g t r i a l s c o n c e rn e d . PR ES EN TA T IO N O F DATA The 1954-55 F e e d in g T r i a l s Procedure, The e x p e rim e n ta l w ork fo r 1954-55 w as divided into two p h a s e s . T h e f i r s t p h a s e r e p r e s e n t e d a c o n t i n u a t i o n of p r e v i o u s l y r e ­ p o r t e d s t u d i e s w i t h d r y r a t i o n s (16, 17). T h i s w a s d e s i g n e d to s t u d y th e r e s u l t s , if a n y , of l o n g - c o n t i n u e d f e e d i n g of d r y r a t i o n s to m i n k . The sec o n d p h a se w as e x p lo ra to ry in n a tu re , and was a n a t ­ te m p t at: (a) s i m p l i f i c a t i o n of t h e e x i s t i n g r a t i o n s b y r e m o v a l of m o s t supplem ents; (b) e x a m i n a t i o n of t h e e f f e c t s of i n c r e a s i n g t h e e n e r g y l e v e l of t h e r a t i o n ; a n d (c) m e a s u r i n g t h e v a l u e of i n c l u d i n g antib io tics in a d ry ratio n . A n i m a l s w e r e a l l o t t e d to t h e e x p e r i m e n t a l g r o u p s i n two w a y s . The c o n t r o l g r o u p a n d d r y - r a t i o n g r o u p s A, B , and C w e r e s e l e c t e d f r o m t h o s e m i n k (a n d t h e i r o f f s p r i n g ) w h i c h h a d p r e v i o u s l y r e c e i v e d t h e r a t i o n s to b e f e d . T h e b e s t of t h e a d u l t s a n d the l a r g e s t of t h e k i t s w e n t i n t o t h e s e f o u r g r o u p s . Each group con­ tain ed th re e a d u lt m a le s , five k it m a l e s , five adult f e m a le s , and seven kit fe m a les. 22 23 The re m a in in g adults and kits w e re allo tte d at ra n d o m by age a n d s e x to t h e f i v e r e m a i n i n g r a t i o n g r o u p s . These groups each c o n tain ed five ad u lt m a le s , six kit m a le s , six adult f e m a le s , and t h r e e k i t f e m a l e s , e x c e p t i n g r a t i o n g r o u p s F a n d H. I n a d d i t i o n to the above a d u lts , g ro u p s F and H co n tain ed five k it m a l e s and f o u r kit fe m a le s . The v a r ia tio n in r a tio n F r e s u l t e d f r o m an e r r o r in sexing a n anim al; t h e v a r i a t i o n i n H w a s n e c e s s i t a t e d b y th e s e x of the av ailab le k its . T h e c o n s t i t u e n t s of t h e v a r i o u s r a t i o n s a r e g i v e n i n T a b l e s 1, 2, a n d 3. P r o x i m a t e a n a l y s e s of t h e r a t i o n s a r e g i v e n i n T a b l e 4. R a t i o n s A , B , a n d C o f f e r a d i r e c t c o m p a r i s o n of t o r u l a d r i e d y e a s t , b r e w e r s d r i e d y e a s t , a n d no d r i e d y e a s t (an e q u i v a l e n t a m o u n t of soybean o i l m e a l r e p l a c e d t h e d r i e d y e a s t ) i n a c o m p l e x t y p e of d ry p elleted ration. T h ese ra tio n s w e re slightly m odified f r o m the c o m p le x d r y r a t i o n s fed the p re v io u s y e a r . R a t i o n s D, E , a n d F a f f o r d a s i m i l a r c o m p a r i s o n i n a l e s s c o m p l e x t y p e of d r y r a t i o n . In r a t i o n G the e n e r g y c o n te n t w as r a i s e d by the in c lu s io n of 4 p e r c e n t f a t (i n t h e f o r m of r e f i n e d c o t t o n s e e d o i l ) . The p r o t e i n l e v e l w as a l s o r a i s e d so th a t the r a t i o n a p p r o x i m a t e d the c o n tro l r a t i o n w i t h r e s p e c t to c r u d e p r o t e i n l e v e l . l o w e r t h a n t h a t of t h e c o n t r o l r a t i o n . The c r u d e f a t l e v e l w as 24 TABLE 1 C O M P O S IT IO N O F C O N T R O L R A T IO N , 1954-5 5 Ingredients H orse m eat ........................................................................ 50 a F i s h , o c e a n ............................................................................................... 15 m T r i.p e b ............................................................................................................. 15 L iver andbone Percentage ............................................................................................................. 5 Q C e re a l m ix, supplem ented ......................................................... 15 G round haddock ra c k s. ■L R e p l a c e d M a y 1, 1955, w i t h D r u m P a k ( W i l s o n a n d C o . , C hicago, Illinois). CK e l l o g g , s M in k R a t i o n - - n o m e a t no. 1001. 25 TABLE 2 COMPOSITION OF E X P E R IM E N T A L RATIONS F E D AS P E L L E T S , 1 9 5 4 - 5 5 Ration Ingredients A B C Percent a C e r e a l m i x ................................................ D r i e d y e a s t , t o r u l a .............................. D r i e d y e a s t , b r e w e r s ........................ S o y b e a n o i l m e a l (50% p r o t e i n ) . . F i s h m e a l (55% p r o t e i n ) * 3 ................. H e r r i n g m e a l (70% p r o t e i n ) 0 . . . M e a t s c r a p s (65% p r o t e i n ) ............. L i v e r m e a l ^ ................................................ F i s h s o l u b l e s e ......................................... S k i m m i l k , d r i e d .................................. D r i e d s o l u b l e b l o o d ^ ........................... C h o l i n e c h l o r i d e ( 2 5 % ) ........................ V i t a m i n m i x § ............................................ T e r r a m y c i n T M - 5 .................................. 39.5 15 10 10 5 5 5 5 2 2 0.8 0.2 0.2 39.5 15 10 10 5 5 5 5 2 2 0.8 0.2 0.2 Per V ita m in A (10,000 U S P u n i t s / g m ) V i t a m i n D (3 , 0 0 0 IC u n i t s / g m ) . . V i t a m i n E ( 2 0 , 0 0 0 I U / l b ) ................. MnSC>4 ( f e e d i n g g r a d e ) ........................ F o l i c a c i d ( 3 % ) ......................................... V itam in ................................................ 5 1 gm 45 g m 20 g m 10 g m 5 gm 2.5 m g 39 .5 25 10 5 5 5 5 2 2 0.8 0.2 0.2 100 P o u n d s 5 1 gm 45 g m 20 g m 10 g m 5 gm 2.5 m g 5 1 gm 45 g m 20 g m 10 g m 5 gm 2.5 m g a M i n k M i x n o . 1007, K e l l o g g C o m p a n y , B a t t l e C r e e k , M i c h . ^ V i t a p r o i l 7 5 -A , M ain e M a r i n e P r o d u c t s , In c ., P o r t l a n d , Me. CR e p l a c e d b y 5 p e r c e n t S e a h o r s e F i s h F l o u r ( M a i n e M a r i n e P r o d u c t s , I n c . , P o r t l a n d , M a i n e ) i n N o v e m b e r , 1954. ^ R i t a l i v e r , I m p e r i a l P r o d u c t s Co., W a d s w o rth , Illin o is. 6P h i l i p R . P a r k C o . , S a n P e d r o , C a l i f o r n i a . f R e p l a c e d b y 2 p e r c e n t of t h e c e r e a l m i x i n N o v e m b e r , 1954. gF o r t a f e e d 2 -4 9 C , L e d e r l e L a b o r a t o r i e s , P e a r l R i v e r , New York. 26 TABLE 3 C O M P O S IT IO N O F E X P E R I M E N T A L RATIONS F E D AS W E T MASH, 1954-55 Ration Ingredients D E F G H 19.15 2 2 .9 5 7.5 7.5 7.5 7.5 P e rc ent C ereal m ixa . . . D ried yeast, b r e w e r s .............. D ried yeast, t o r u l a ................. S o y b e a n o il m e a l (50% p r o t e i n ) .............. F i s h m e a l (55% protein)^ . . . . F i s h m e a l (60% protein)0 . . . . M eat scraps (65% p r o t e i n ) Liverm eal^- . . . Skim m ilk , d r ie d C o t t o n s e e d o il P ro ca in e peni­ c i l l i n (4 g m / l b ) e A u r e o m y c i n HC1 (3 .6 g m / l b ) . . . 23.2 23 .2 33 .2 15 15 20 20 25 20 20 20 20 20 20 20 10 10 10 10 10 5 3 3 - 5 3 3 - 5 3 3 - 5 3 3 4 5 3 3 - _ _ 0.05 - - 0.2 - Per V itam in B j2 • • • V itam in E . . . . 2.5 m g 2.5 m g 100 P o u n d s 2.5 m g 2,5 m g 23 g m 2.5 m g a M i n k M i x N o . 1007, K e l l o g g C o . , B a t t l e C r e e k , M i c h i g a n . ^ V i t a p r o i l 7 5 - A , M a i n e M a r i n e P r o d u c t s , I n c . , P o r t l a n d , Me CS e a h o r s e F i s h F l o u r , M a i n e M a r i n e P r o d u c t s , I n c . , P o r t ­ land, M aine. dR i t a l i v e r , I m p e r i a l P r o d u c t s C o . , W a d s w o r t h , I l l i n o i s . e E q u i v a l e n t to 2 . 4 g m of P e n i c i l l i n G p e r p o u n d . 27 TABLE 4 P R O X IM A T E A N A LY SES O F THE RATIONS F E D > 1954-55 (all v a l u e s in p e r c e n t a g e s ) M ois­ ture C rude Pro­ tein Crude Fat Control " w e t 11 . . 6 5 .5 0 15. 90 5 .9 0 1.00 C ontrol nair-d ry b a s i s ,,a . 5.61 42.90 15 .9 0 A ................. 5.71 39.06 B ................. 5 .6 8 C ................. D R ation Crude N .F.E . Fiber Ash Ca P 7.70 4 .0 0 1.15 0.69 2.70 20.80 10. 80 3 .1 0 1.90 6.00 2.5 7 3 7 .8 4 8 .8 2 1.08 1.10 3 8 .3 8 5.12 2 .4 8 39.76 8.58 1.02 1.13 5 .5 3 38.94 4 .6 8 2.59 39.36 8 .9 0 1.10 1.04 ................. 5 .5 4 4 3 .9 4 5.50 2 .2 6 32.82 9.94 1.44 1.38 E ................. 5.67 4 6 .2 5 6.5 6 2.04 29.05 10.43 1.56 1.38 F ................. 5.78 44.56 5. 87 1.94 31.56 10.29 1.60 1.30 G ................. 5 .2 0 49.94 11 .8 6 1.79 20.99 10.22 1.32 1.34 H ................. 5.7 5 46.38 5.6 7 2 .1 6 29.54 10.5 0 1.55 1.42 a C alculated values. 28 A n t i b i o t i c s , p e n i c i l l i n , a n d a u r e o m y c i n , w e r e a d d e d to r a t i o n H to s t u d y t h e i r e f f e c t o n l a t e g r o w t h , m a i n t e n a n c e , a n d r e p r o d u c t i o n . R a tio n s A, B , a n d C w e re fed as p e lle ts . G, and H w e re fe d a s a wet m a sh . R a t i o n s D, E , F , Mixing a n d fe e d in g p r a c t i c e s p re v io u s ly d e s c r ib e d w e re followed. F e e d i n g t r i a l s w e r e s t a r t e d o n A u g u s t 7, 1954, a n d , w i t h t h e e x c e p t i o n s n o t e d l a t e r , w e r e c o n t i n u e d u n t i l a p p r o x i m a t e l y M a y 1, 1955. A ll a n i m a l s w e re w eighed biw eekly, R e s u lts an d discussion. w eather perm itting. D u e to t h e s e l e c t i o n p r a c t i c e d in t h e a l l o t m e n t of m i n k t o t h e r a t i o n g r o u p s a n d t h e f a c t t h a t two d i f f e r e n t m e t h o d s of f e e d i n g t h e d r y r a t i o n s w e r e u s e d , w e i g h t g a i n s a s r e c o r d e d i n t h e t a b l e s a r e n o t w h o l l y i n d i c a t i v e of the v a l u e a n d s u c c e s s of t h e i n d i v i d u a l d r y r a t i o n s . su lts obtained N o r c a n the r e ­ co m p ared d irectly and in d iscrim inately among groups. R a t i o n g r o u p s A, B r a n d C , w h i c h w e r e f e d a s p e l l e t s * c a n be c o m p a r e d w ith one a n o th e r . S i m i l a r l y , r a t i o n g r o u p s D, E , F , G , a n d H, w h i c h w e r e f e d a s w e t m a s h e s , a r e c o m p a r a b l e . L a te grow th. T a b l e s 5, 6, 7, a n d 8 s u m m a r i z e t h e r e s u l t s o b t a i n e d d u r i n g t h e p e r i o d f r o m A u g u s t 7, 195 4, to D e c e m b e r 14, 1954. D u rin g t h i s p e r i o d , w hich e n c o m p a s s e s both the la te g ro w th 29 TABLE 5 M A I N T E N A N C E O F A D U L T M A L E M IN K , A U G U S T 7, 1954, TO D E C E M B E R 14, 1954 ( a ll w e i g h t s i n g r a m s ) R ation G roup No. per G roup C ontrol At S tart At F inish A vg. G ain M or­ tal­ ity Avg. Wt. Range in W eight Avg. Wt. Rang e in W eight 3 1230 1160-1280 1743 1680-1840 513 0 A 3 990 840-1090 1013 920-1080 23 0 B 3 1133 1040-1270 1227 1050-1510 94 0 C 3 1083 830-1330 1313 1250-1390 230 0 D 5 944 750-1370 1123 820-1670 179 1 E 5 900 690-1020 1052 820-1350 152 0 F 5 846 7 0 0 - 950 1078 840-1230 232 1 G 5 830 720-1000 1114 890-1220 284 0 H 5 994 710-1500 1196 980-1630 202 0 30 TABLE 6 M A I N T E N A N C E O F A D U L T F E M A L E M I N K , A U G U S T 7, 1954, TO D E C E M B E R 14, 1954 ( a ll w e i g h t s i n g r a m s ) R ation G roup No. per G roup C ontrol At S tart At F inish Avg. G ain M or­ tal­ ity Avg. W t. Range in W eight Avg. Wt. Range in W eight 5 662 550-760 824 740-940 162 0 A 5 532 460-650 613 560-680 81 1 B 5 566 550-600 616 470-690 50 0 C 5 582 530-610 738 700-770 156 0 D 6 582 520-660 684 630-720 102 1 E 6 645 580-810 743 590-940 98 0 F 6 637 570-690 768 520-890 131 0 G 6 625 510-750 740 520-880 115 0 H 6 625 490-760 780 650-880 155 1 31 TABLE 7 L A T E G R O W T H O F M A L E M IN K K I T S , A U G U S T 7, 1954, TO D E C E M B E R 14, 1954 (all w e ig h ts in g r a m s ) R a t+•i o n G roup d Noper At S tart At Finish —----------------------------------------Avg. Range Avg. Range W t. in W eight W t. in W eight a Gain Mor ■ tal- C ontrol 5 1110 1020-1250 1528 1250-1730 418 0 A 5 590 3 2 0 - 840 770 550-1140 180 1 B 5 756 6 3 0 - 880 942 710-1140 186 0 C 5 928 840-1050 1346 1120-1570 418 0 D 6 802 5 9 0 - 870 942 670-1070 140 1 E 6 745 66 0 - 880 1100 990-1260 355 1 i F 5 798 6 6 0 - 890 1000 920-1110 202 2 G 6 710 5 7 0 - 900 1042 960-1180 322 0 H 5 726 4 8 0 - 890 1074 910-1250 348 0 Avg 32 TABLE 8 L A T E G R O W T H O F F E M A L E M IN K K I T S , A U G U S T 7, 1954, TO D E C E M B E R 14, 1954 ( a ll w e i g h t s i n g r a m s ) R ation G roup No. per G roup C ontrol At S tart At F in ish Avg. G ain M or­ tal­ i ty Avg. W t. Range in W eight Avg. Wt. Range in W eight 7 733 660-800 874 830-1020 141 0 A 7 466 340-560 544 3 8 0 - 650 78 0 B 7 563 480-630 664 5 8 0 - 750 101 0 C 7 564 480-620 729 6 2 0 - 890 165 0 D 3 543 490-600 630 5 9 0 - 670 87 1 E 3 570 500-620 687 6 0 0 - 780 117 0 • F 4 547 530-590 765 7 3 0 - 800 218 2 G 3 547 530-570 687 6 4 0 - 760 140 0 H 4 593 550-680 680 5 3 0 - 800 87 0 33 of t h e m i n k k i t s a n d m a i n t e n a n c e of a d u l t s , a l l r a t i o n s p e r m i t t e d w eight gains. T h e c o n t r o l r a t i o n w a s s u p e r i o r to all d r y r a t i o n s f o r the l a t e g r o w t h p e r i o d if f i n a l w e i g h t s a r e u s e d a s t h e c r i t e r i o n . The l a r g e d iffe re n c e in both s ta rtin g w eights and final w eights am ong g r o u p s i s c h i e f l y t h e r e s u l t of t h e u n a v o i d a b l e s t u n t i n g of t h e m i n k k its w hich w e re fe d on d ry r a t i o n s d u rin g the p r e v io u s c r i t i c a l e arly grow th p erio d . E x p e r i m e n t s h a d sh o w n th a t the d r y r a t i o n s t h e n i n u s e w e r e u n s u i t a b l e d u r i n g l a c t a t i o n a n d e a r l y g r o w t h (17). H o w e v e r , w i t h r e s p e c t t o w e i g h t g a i n s , s e v e r a l of t h e d r y r a t i o n s ( e . g . , C, E , G , a n d H) p e r m i t t e d g a i n s b y t h e k i t s n e a r l y c o m p a r a b l e to t h o s e o b t a i n e d f r o m f e e d i n g t h e c o n t r o l r a t i o n . W e ig h t g a in s by the a d u lt a n im a ls r e p r e s e n t p r i m a r i l y f a t d e p o s i t i o n , a n d a r e r o u g h l y i n d i c a t i v e of t h e a m o u n t of e n e r g y a v a i l a b l e to t h e a d u l t s a f t e r m a i n t e n a n c e r e q u i r e m e n t s a r e ' m e t . < In t h i s r e s p e c t , t h e c o n t r o l r a t i o n w a s a p p a r e n t l y s u p p l y i n g t h e l a r g e s t a m o u n t of e n e r g y i n e x c e s s of m a i n t e n a n c e r e q u i r e m e n t s . Of d r y r a t i o n s A , B , a n d C , t h e l a r g e s t w e i g h t g a i n s a m o n g a d u l t s w e r e b y t h o s e a n i m a l s o n r a t i o n C. a lm o s t identical re s u lts. R ations A and B gave Th e a d u l t m a l e s o n r a t i o n B w e r e s l i g h t l y h e a v i e r t h a n t h o s e o n r a t i o n A a t t h e e n d of t h e p e r i o d , b u t w e r e a l s o s lig h tly h e a v i e r a t the s t a r t . 34 T h e p r o x i m a t e a n a l y s e s of t h e s e t h r e e d r y r a t i o n s ( T a b l e 4) show them to be n e a r ly id e n tic al. T h e d i f f e r e n c e s i n r a t e of g a i n o b t a i n e d m a y b e a s c r i b e d to a g r e a t e r a v a i l a b i l i t y of t h e n u t r i e n t s i n s o y b e a n o i l m e a l c o m p a r e d to t h e a v a i l a b i l i t y of t h e n u t r i e n t s i n the two ty p e s of d r i e d y e a s t fed. T h e d r i e d y e a s t s a p p e a r to b e s im ila r in th is re s p e c t. A m o n g th e k i t s on d ie ts A, B , a n d C, the a b o v e r e s u l t s w e r e n e a rly duplicated. The c o n tro l r a t i o n p r o d u c e d the l a r g e s t k its a t t h e e n d of t h i s p e r i o d . R a tio n C w as the next m o s t e ffe ctiv e, a llo w ­ i n g a n a v e r a g e g a i n i d e n t i c a l w i t h t h a t of th e m a l e k i t s o n t h e c o n ­ t r o l r a t i o n a n d a s lig h tly g r e a t e r a v e r a g e g a in f o r the f e m a l e k i t s . A g a in , the r a t i o n s containing d r ie d y e a s t did not give a s good g ro w th r e s p o n s e s a s t h e o t h e r two r a t i o n s , b u t w e r e s i m i l a r to e a c h o t h e r . I n r a t i o n g r o u p s D, E , F , G , a n d H t h e a d u l t s a n d k i t s w e r e a l l o t t e d a t r a n d o m a t t h e b e g i n n i n g of t h e t r i a l . A d u lts o n th e s e r a t i o n s had n e a r l y the s a m e s ta r t i n g w eights; t h u s t h e f i n i s h i n g w e i g h t s a n d a v e r a g e g a i n s of t h e s e a d u l t s g i v e s o m e i n d i c a t i o n of t h e r e l a t i v e v a l u e of t h e r a t i o n s . Those adults w h ich r e c e i v e d r a t i o n G m a d e the g r e a t e s t w eight g a in s. These g a i n s p r o b a b l y r e f l e c t e d t h e h i g h e r e n e r g y c o n t e n t of t h a t r a t i o n w hich c o n tain ed a d d ed fat. 35 K i t s o n t h e s e r a t i o n s r e s p o n d e d to t h e t r e a t m e n t s i n a f a s h i o n s i m i l a r to t h e a d u l t s ; h o w e v e r , s o m e g r o w t h a s w e l l a s f a t t e n i n g w as involved. R a tio n s E, G, an d H allow ed b e t t e r w eight g a in s and the a n i m a l s w e r e b e t t e r in o v e r - a l l a p p e a r a n c e . R atio n F allow ed r e la t i v e l y good w eight g a in s, b u t the a n im a ls a p p e a re d m o r e n e rv o u s and did not e a t r e a d ily . R a t i o n D a llo w e d the l o w e s t g a in s in w e ig h t (fo r m a l e s ) a n d the a n i m a l s w e r e p o o r e s t i n g e n e r a l a p ­ pearance. M o r t a l i t y a m o n g a n i m a l s on the v a r i o u s t r e a t m e n t s w as s p o r ­ a d i c a n d d i s p l a y e d no p a t t e r n t h a t c o u l d b e a t t r i b u t e d to d i e t a r y t r e a t m e n t s a t the tim e . c a l c u l u s , one ; A m ong the m o r t a lit y c a u s e s w ere: urinary i n f e c t i o n r e s u l t i n g f r o m d e c a y e d t e e t h , o ne ; no d e m o n ­ s t r a b l e c a u s e , e i g h t ; a n d o n e a n i m a l (on r a t i o n D) w h e r e t h e o n l y g r o s s l e s i o n w a s a f a t t y m e t a m o r p h o s i s of t h e l i v e r . A t t h e e n d of t h i s f e e d i n g p e r i o d , t h e p o o r e r a n i m a l s w e r e rem oved fro m w ere: each g ro up and pelted. The c r i t e r i a f o r r e m o v a l (a) w e i g h t a t t h e e n d of t h e p e r i o d ( m a l e s u n d e r a n d f e m a l e s u n d e r 600 g r a m s ) ; 1000 g r a m s (b ) p e lt d e fe cts (m ink which had ch ew ed o r o th e r w is e d a m a g e d t h e ir pelts); (c) p h y s i c a l f a u l t s (e.g., d e ca y e d teeth). S i n c e t h e s e m i n k w e r e c u l l e d f o r t h e p u r p o s e of h e r d i m p r o v e ­ m e n t, it w a s f e lt th a t any data on p e lt value would not be in d ic a tiv e 36 of n u t r i t i o n a l t r e a t m e n t and. no a t t e m p t w a s m a d e t o o b t a i n s u c h d a t a . In g e n e r a l , t h e p e l t s of t h e a n i m a l s a p p e a r e d s i m i l a r a n d no a b n o r ­ m a l it ie s w e re noted. The r e m a in in g m in k w e re k e p t a s b re e d in g stock, and w ere con tin u ed th ro u g h the w in ter on th e ir re s p e c tiv e ra tio n s . M aintenance. D a t a p e r t a i n i n g to p e r f o r m a n c e of the m i n k f r o m D e c e m b e r 15, 195 4, u n t i l M a r c h 5, 1955 (the b e g i n n i n g of t h e breeding season), a re r e c o r d e d i n T a b l e s 9 a n d 10. Th e m i n k on d r y r a t i o n s w e r e a llo w e d f e e d ad lib. d u rin g the m a i n t e n a n c e p e r i o d a n d , in g e n e r a l , the r e s u l t s d u rin g t h i s p e r i o d w ere satisfactory. The g ain s a n d l o s s e s in a v e r a g e w eig h ts a s r e c o r d e d in T a b l e s 9 a n d 10 a r e c h i e f l y d u e to n o r m a l f l u c t u a t i o n s i n b o d y w eight. T h e a n i m a l s r e m a i n e d o u t of d o o r s t h r o u g h o u t t h e p e r i o d a n d w e r e s u b j e c t to t h e s t r e s s e s of t h e w i n t e r w e a t h e r . Individual w e i g h t r e c o r d s d u r i n g t h i s p e r i o d i n d i c a t e t h a t v a r i a t i o n s of 20 to 50 g r a m s i n b o d y w e i g h t a r e a n o r m a l o c c u r r e n c e . The m in k on the c o n tro l r a tio n w e re r e s t r i c t e d slig h tly in f o o d i n ta k e d u r in g th is p e r i o d in a n e ffo rt to lo w e r t h e i r body w e ig h t p r i o r to t h e b r e e d i n g m e rc ia l ranches. season. This is a n o rm a l p ra c tic e on c o m ­ E x p e r i e n c e h a s s h o w n t h a t f a t m i n k f a i l to b r e e d a n d r e p r o d u c e a s well a s th in n e r a n im a ls . 37 TABLE 9 M A I N T E N A N C E O F A D U L T M A L E M IN K , D E C E M B E R TO M A R C H 5, 1955 (a ll w e i g h t s i n g r a m s ) R a tion Group No. per Group C ontrol At Start 14, 1954, A t F ini sh Avg. G ain M or­ tal­ ity Avg. Wt. Range in W eight Avg. Wt. Range in W eight 6 1609 1250-1840 1485 1190-2060 -124 0 A 4 1045 920-1140 1163 1020-1310 118 0 B 6 1152 970-1510 1293 1130-1620 141 0 C 8 1334 1120-1570 1397 1210-1680 63 1 E 8 1123 990-1350 1299 1070-1590 176 0 F 4 1080 970-1160 1050 790-1240 -30 0 G 10 1093 960-1180 1246 930-1490 153 0 D to H a 5 1026 960-1090 1135 1060-1210 109 3 H 7 1203 1050-1630 1363 1160-1780 160 0 ■ a R atio n D d isco n tin u ed in J a n u a r y , 1955. 38 TABLE 10 M A I N T E N A N C E O F A D U L T F E M A L E M IN K , D E C E M B E R 1954, TO M A R C H 5, 1955 (all w e ig h ts in g r a m s ) R ation G roup No. per G roup C ontrol At Start At F in is h 14, Avg. Gain M or­ tal­ ity Avg. Wt. Range in W eight Avg. Wt. Rang e in W eight 1Z 853 740-1020 843 760-1000 - 10 0 A 7 616 550- 680 662 5 7 0 - 730 46 0 B 12 644 4 7 0 - 750 704 6 2 0 - 790 60 0 C 12 733 6 2 0 - 890 739 630-1000 6 0 E 8 741 6 0 0 - 940 733 6 3 0 - 840 -8 0 F 7 802 7 3 0 - 890 789 7 1 0 - 890 -13 0 G 7 771 6 4 0 - 880 771 6 4 0 - 92*0 0 0 D to H a 6 667 590- 720 677 6 1 0 - 720 10 0 H 7 773 6 1 0 - 880 724 650- -49 0 a R a t i o n D d i s c o n t i n u e d i n J a n u a r y , 1955. 790 39 The chief sig n ifican t o b s e rv a tio n during this p e rio d was r e ­ l a t e d to m o r t a l i t y . T h r e e m a l e s on r a t i o n D died in e a r l y J a n u a r y . U p o n n e c r o p s y , a l l s h o w e d a s i m i l a r s e v e r e f a t t y c h a n g e of t h e l i v e r and kidneys. The single s i m i l a r c a s e o b s e r v e d d u rin g the p re c e d in g p e r io d w as a lso f r o m this g roup. A s the m in k w e re n e e d e d f o r b r e e d i n g s to c k , r a t i o n D w a s a b r u p tly d is c o n tin u e d a n d the su rv iv in g m a l e s a n d f e m a l e s t r a n s f e r r e d to r a t i o n H. T h e c a u s e of t h e o t h e r l o s s d u r i n g t h i s p e r i o d (a m a l e o n r a t i o n C.) c o u l d n o t b e d e m o n s t r a t e d . B reeding, gestation, and w h e l p i n g T a b l e 11 s u m m a r i z e s r e s u l t s o b ta in e d d u rin g b r e e d in g a n d w helping. B reed in g p e rfo rm a n c e was s a tisfa c to ry on all ra tio n s. m in k which r e c e iv e d d r y diets b r e d m o r e re a d ily . Th e This m ay have b e e n d u e to t h e i r b e i n g s l i g h t l y t h i n n e r t h a n t h e c o n t r o l g r o u p . T h e m a j o r i t y of t h e b r e e d i n g s w e r e m a d e w i t h i n g r o u p s ; i s , both m a le an d f e m a l e w e re r e c e iv in g the s a m e ra tio n . that H ow ever, n e a r t h e e n d of t h e b r e e d i n g s e a s o n t h e m o r e a g g r e s s i v e m a l e s w e r e u s e d i n d i s c r i m i n a t e l y i n o r d e r to s e c u r e a s m a n y m a t i n g s a s p o s s i b l e . A fte r the b re e d in g s e a s o n , a g r o u p of e i g h t f e m a l e s w a s s e ­ l e c t e d f r o m am o n g th o s e b r e d f e m a l e s which ha d r e c e i v e d d ry r a tio n s f o r the p re v io u s seven m onths. T hese f e m a le s w e re sw itched 40 TABLE 11 B R E E D I N G AND W H E L P I N G R E S U L T S , S P R I N G , 1955 No. of F e m a l e s R ation G roup C o n t r o l ............................................................ ............. D r y r a t i o n to c o n t r o l A vail­ able B red 11 9 7 8 7 6a 3 ........................................ W helped A ......................................................................... ............. 7 B ....................................................................................... 12 C ......................................................................... ............. 10 9a 6 E ...................................................................... ............. 8 b 8 6 F ......................................................................... ............. 6 6a 2 G ...................................................................... ............. 7 7 7 ......................................................... ............. 6 6a 2 ...................................................................... ............. 7 6a 2 D to H H 12 a 9 One b r e d f e m a l e r e m o v e d a n d p l a c e d o n c o n t r o l r a t i o n o n A p r i l 6 , 1955. b Two b r e d f e m a l e s r e m o v e d a n d p l a c e d o n c o n t r o l r a t i o n o n A p r i l 6 , 1955. c Table 12 g i v e s a b r e a k d o w n of m o r t a l i t y f i g u r e s . 41 TABLE G e s ta tio n (days) ---------------— —— ----Avg. Range in Length Avg. L ength 11 ( C o n t i n u e d ) N o . of K i t s —------------------------------------------At L i v e d to B irth 8 W eeks K it A verage p e r W helping F em ale — —----------------— At At 8 B irth W eeks 45 .5 41-57 33 8 25 4.7 1.1 45 .9 44-50 35 22 13 5.0 3.1 46.3 43-52 11 9 2 3 .6 3.0 4 8 .4 43-55 27 15 12 3.0 1.6 47 .3 45-50 29 25 4 4.8 4.1 45.0 43-51 24 20 4 4.0 3.3 48 .0 45-51 7 1 6 3.5 0.5 4 7 .9 41-54 46 31 15 6.5 4.4 44. 5 44-45 10 7 3 5.0 3.5 47 .0 46-48 6 4 2 3.0 2. 0 42 a b r u p t l y to t h e c o n t r o l r a t i o n o n A p r i l 6 , 1955 , a n d s u b s e q u e n t l y re c e iv e d that ra tio n . T h i s t r a n s f e r w a s to s e r v e two p u r p o s e s . F i r s t , it w as an a t t e m p t to f i n d o u t if a n y h a r m f u l e f f e c t s w o u l d r e s u l t f r o m a d i e t change a t that tim e . Second, though the n u m b e r s w e r e s m a l l , it w a s h o p e d t h a t t h i s w o u l d g i v e a n i n d i c a t i o n of th e a d e q u a c y of t h e dry rations for supporting gestation. The kits r e s u ltin g f r o m f i r s t two w e e k s i n M a y . a r e included in T able the m a t i n g s w e r e b o r n d u rin g the T h e r a n g e a n d a v e r a g e l e n g t h of g e s t a t i o n 11. No e v i d e n c e w a s o b t a i n e d to s u g g e s t t h a t a n y r a t i o n t r e a t ­ m e n t i n f l u e n c e d t h e l e n g t h of g e s t a t i o n . N o r d i d t h e c h a n g i n g of the d i e t of t h e e i g h t f e m a l e s f r o m a d r y r a t i o n to t h e c o n t r o l r a t i o n have any effect. T h e n u m b e r of k i t s b o r n a n d s u b s e q u e n t l o s s e s a r e a l s o r e ­ c o rd e d in Table 11. K i t m o r t a l i t y i s b r o k e n d o w n a n d r e l a t e d to t im e a f t e r b i r t h in Table 12. O n l y two d r y r a t i o n s g a v e a n y i n d i c a t i o n of f a i l u r e to s u p p o r t gestation. D u e to t h e f a c t t h a t t h e n u m b e r of f e m a l e s i n v o l v e d i s s m a l l , t h e v a l i d i t y of t h e r e s u l t s i n t h e s e tw o c a s e s i s q u e s t i o n a b l e b u t s h o u ld be p o in te d out. 43 R a t i o n F , w h i c h h a d b e e n o nl y p a r t i a l l y s a t i s f a c t o r y d u r i n g th e l a t e g r o w t h p e r i o d , a l s o g a v e u n s a t i s f a c t o r y r e p r o d u c t i v e p e r ­ form ance. R a t i o n H, w h i c h c o n t a i n e d a n t i b i o t i c s , a l s o g a v e i n f e r i o r resu lts. All o th e r d ry r a tio n s supported g estatio n adequately. m o s t s a t i s f a c t o r y d r y r a t i o n w a s r a t i o n G. The T h is w as the only r a t io n in w hich all f e m a l e s b r e d and p ro d u c e d k its , and it a lso p ro d u c e d the h i g h e s t k it a v e r a g e both a t b i r t h and a t e ig h t w eek s a f t e r w a r d s . A t b i r t h , t h e d r y r a t i o n s a s a g r o u p p r o d u c e d a n a v e r a g e of 4.1 k i t s p e r w h e l p i n g f e m a l e (4.4 w h e n r a t i o n g r o u p s F a n d H w e r e e x c l u d e d ) , c o m p a r e d to 4.85 f o r t h e two g r o u p s i n w h i c h t h e f e m a l e s re c e iv e d the co n tro l ratio n . A t e i g h t w e e k s , t h e a v e r a g e w a s 2 .8 k i t s p e r w h e l p i n g f e m a l e f o r a l l d r y r a t i o n s (3.3 w h e n r a t i o n g r o u p s F a n d H w e r e e x c l u d e d ) , c o m p a r e d to 2.1 f o r t h e f e m a l e s r e c e i v i n g th e c o n t r o l r a t i o n . K it m o rta lity . The f e m a l e s w e r e o b s e r v e d da ily s t a r t i n g a w e e k b e f o r e the f i r s t l i t t e r s w e r e e x p e c te d a n d continuing until the k i t s w e r e e i g h t w e e k s of a g e . N e s t b o x e s w e r e o p e n e d a t the t i m e of e a c h o b s e r v a t i o n , a n d th e i n t e r i o r c a r e f u l l y e x a m i n e d . No e v i ­ d e n c e w a s o b t a i n e d d u r i n g t h i s p e r i o d to g i v e a n y s u p p o r t to th e w i d e l y - h e l d t h e o r y t h a t f e m a l e m i n k w i l l k i l l a n d e a t t h e i r you ng when disturbed. 44 TABLE 12 BREAKDOW N OF K IT M O R T A L IT Y , SPRING, N o. of K its Counted at B irth Total N o . of Kits Died No. of Kits Dead at B irth C o n t r o l .............. 33 25 D r y r a t i o n to c o n t r o l .............. 35 A ........................... B R ation G roup 1955 N o. of K i t s D i e d an d Day D ied (d a y s f o l l o w i n g b i r t h ) 1 2 3 4 5 ° ver 5 3 10 4 1 0 1 6 13 1 9 3 0 0 0 0 11 2 0 2 0 0 0 0 0 ............................ 27 12 3 3 3 1 0 1 1 C ........................... 29 4 0 1 3 0 0 0 0 E ............................ 24 4 1 1 1 0 0 0 1 F ........................... 7 6 6 0 0 0 0 0 0 G ........................... 46 15 3 5 3 0 0 0 4 .............. 10 3 0 3 0 0 0 0 0 ........................... 6 2 2 0 0 0 0 0 0 D to H H 45 L o s s e s of m i n k k i t s c o n f o r m e d t o t h e p a t t e r n o b s e r v e d th e p r e v i o u s y e a r (17). T h e m a j o r i t y of t h e l o s s e s o c c u r r e d e i t h e r a t b i r t h o r i n t h e f i r s t two d a y s s u b s e q u e n t t h e r e t o . w ere L ater lo sses s c a t t e r e d , a n d i t i s b e l i e v e d t h e y c o u l d b e a t t r i b u t e d to t h r e e causes. These w ere: (a) c e s s a t i o n of l a c t a t i o n b y th e f e m a l e b e ­ f o r e t h e k i t s w e r e o l d e n o u g h to c o n s u m e the r e g u l a r f e e d ; (b) d e a t h of r u n t s ; a n d (c) a n o c c a s i o n a l k i t t h a t w a s k i l l e d i n a f i g h t w i t h its litte r m a te s. E a r l y g r o w t h of k i t s . D u rin g the p r e v io u s s p r i n g (1 954 ), e v id e n c e w as o b ta in e d which in d ic a te d th a t the d r y r a tio n s th e n in u se, while su itab le fo r la te g ro w th , m a in te n a n c e , b re e d in g , and g e s ­ tation, w e re inadequate fo r supporting la c ta tio n and e arly kit grow th, stunting m o s t k its involved. F o r w ork planned for 1 9 5 5-56, it w as d e c id e d that the k i t s should have a u n ifo rm n u tritio n a l b ackground. fem ales w ere To t h i s e n d , a l l s w i t c h e d to t h e c o n t r o l r a t i o n a s t h e y w h e l p e d , a n d t h e y a n d t h e i r o f f s p r i n g r e c e i v e d th e c o n t r o l r a t i o n u n t i l t h e n e x t s e t of f e e d i n g t r i a l s w a s s t a r t e d o n A u g u s t 1. K i t s w e r e w e i g h e d w e e k l y , s t a r t i n g w h e n t h e y w e r e on e w e e k of a g e ( e . g . , a n y l i t t e r s b o r n o n S u n d a y w e r e w e i g h e d f o r t h e f i r s t tim e on the follo w in g Sunday an d e a c h Sunday t h e r e a f t e r until they 46 w ere e i g h t w e e k s old ). both sex es w e re p re s e n t. L i t t e r s w e r e w e ig h ed as a g r o u p e v e n though T h e p u r p o s e of the w e i g h i n g d u r i n g t h i s p e r i o d w a s o n l y to d e t e r m i n e if t h e y w e r e g r o w i n g s a t i s f a c t o r i l y . T h e s e w e ig h ts a r e g iv e n in T able 13. The w e ig h t d i f f e r e n c e s b e ­ t w e e n t h e t w o g r o u p s a r e d u e to t h e v a r i a t i o n i n s e x r a t i o . The NRC s ta t e s th a t m a le m in k k its weigh on a n a v e r a g e 318 g r a m s a t s e v e n w e e k s of a g e , f e m a l e m i n k k i t s 272 g r a m s . C o m p a r i s o n of t h e o b s e r v e d w e i g h t s w i t h t h o s e r e p o r t e d b y th e N R C i n d i c a t e s t h a t th e k i t s w e r e n o r m a l i n s i z e a t s e v e n w e e k s of a g e . S u m m a r y of 1 9 5 4 - 5 5 t r i a l s . As p o in te d out e a r l i e r , the r a ­ t i o n g r o u p s w e r e n o t e x a c t l y c o m p a r a b l e w i t h one a n o t h e r du e to s o m e v a r i a t i o n i n t h e s e l e c t i o n of a n i m a l s , i n the n u m b e r of a d u l t a n d k i t m i n k w i t h i n g r o u p s , a n d i n t h e m e t h o d of f e e d i n g the d r y rations. factors H o w ev e r, when all a v a ila b le data w e re c o n s id e re d , c e r ta in sto o d out a n d could be c o n s id e r e d useful f o r planning fu tu re work. Of t h e d r y r a t i o n s f e d a s p e l l e t s ( r a t i o n s A , B , a n d C), r a ­ t io n C g a v e the b e s t o v e r - a l l r e s u l t s . S i n c e t h i s p a r t of the e x p e r i ­ m e n t a l w o r k w a s a c o n t i n u a t i o n of p r e v i o u s l y r e p o r t e d w o r k (16, 17), a c o m p a r i s o n of p r e s e n t d a t a w i t h the p r e v i o u s y e a r s ' r e s u l t s should 47 TABLE 13 E A R L Y G R O W T H O F MINK K I T S , S P R I N G , 1955 ( a ll w e i g h t s i n g r a m s ) A ge in W ee k s A v g . W e i g h t of K its f r o m a C ontrol G roups A v g . W e i g h t of K its f r o m Dry R ation G roups^ 1 26.9 27 .8 2 52.3 53 .4 3 8 7 .8 79.4 4 130.5 106 .8 5 196.9 14 5. 8 6 2 9 8 .5 237.1 7 398.0 344.9 8 482.0 4 2 6 .2 Si N ineteen m ales; eleven fe m a le s. F o rty -fiv e m ales; sixty-six fem ales. 48 i n d i c a t e w h e t h e r l o n g - t e r m f e e d i n g of d r y r a t i o n s m i g h t b e s a t i s f a c ­ t o r y o r not. T h e a b i l i t y of a r a t i o n to s u p p o r t r e p r o d u c t i o n w o u l d b e t h e m o s t c ritic a l test. Table 14 c o m p a r e s r e p r o d u c t i o n d a t a f o r the s a m e ra tio n s fo r a tw o -y ear period. It is evident that, th ro u g h two s u c c e s s i v e r e p r o d u c t i v e s e a s o n s , the k it a v e r a g e p e r w helping fe m a le re m a in e d rela tiv e ly constant. T h i s w o u l d a p p e a r to i n d i c a t e t h a t t h e s e p a r t i c u l a r d r y r a t i o n s h a d no u n d e s i r a b l e e f f e c t s w h e n u s ed continuously f r o m e i g h t to t w e l v e w e e k s of a g e u n t i l w h e l p i n g . On th e c o n t r a r y , it would in d ic a te th a t d ry r a tio n s could be d e e m e d s a t i s f a c t o r y as m e a s u r e d by this c r ite r io n . A s i m i l a r c o m p a r i s o n f o r la te g r o w th would be d e s i r a b l e , but, f d u e to v a r i o u s d e l a y s , t h e p r e v i o u s y e a r ' d t r i a l s ( 1 9 5 3 - 5 4 ) w e r e n o t s ta r te d until la t e r in that y e a r. Hence, su ch a c o m p a r i s o n would n o t be v a l i d . T h e s e c o n d p h a s e of t h i s e x p e r i m e n t d e a l t w i t h s i m p l i f i c a t i o n of t h e e x i s t i n g d r y r a t i o n s . From a c o n s i d e r a t i o n of the a v a i l a b l e i n f o r m a t i o n , t h e f o l l o w i n g p o i n t s a p p e a r to b e w o r t h y of f u r t h e r study. A n i n c r e a s e d e n e r g y l e v e l i n the d r y r a t i o n s b y a d d i t i o n of f a t s e e m s to b e i n d i c a t e d . R atio n G gave good r e s u l t s during la te 49 TABLE 14 COM PARISO N O P THE R E P R O D U C T IV E P E R F O R M A N C E OF F E M A L E M IN K ON R A T I O N S A , B , A N D C F O R T H E Y E A R S 1 9 5 4 a A ND 1955 Ration Item A B C 1954 1955 1954 1955 7 10 12 10 10 6 6b 10 12b 6 9b 4 3 6 9 6 6 A t b i r t h .............................. 14 11 23 27 32 29 D i e d ..................................... 2 2 7 12 7 4 12 9 16 15 25 25 1954 1955 A v a i l a b l e ........................... 7 B r e d ...................................... W h e l p e d ............................... N u m b e r of f e m a l e s : N u m b e r of k i t s : L i v e d to 8 w e e k s . . . K it a v e ra g e p er whelping fe m a le: At b i r t h . . . * ................. 3.5 3.6 3.8 3.0 5.3 4.8 At 8 w eeks .................... 3.0 3.0 2.7 1.6 4.1 4.1 a i 9 5 4 d a t a r e p o r t e d b y K i f e r a n d S c h a i b l e (17). b O ne b r e d f e m a l e t r a n s f e r r e d to c o n t r o l r a t i o n ( s e e t e x t ) . 50 g r o w t h a n d m a i n t e n a n c e , a n d , a l t h o u g h t h e n u m b e r of f e m a l e s i n v o l v e d w as s m a ll, re p ro d u c tiv e p e rf o r m a n c e was a lso encouraging. T h e u s e o f a n t i b i o t i c s ( i n r a t i o n H) g a v e b e n e f i c i a l r e s u l t s during late g row th and m ain ten an ce. a lm o s t inhibited. R ep ro d u ctio n , how ever, was It should be r e c a l l e d that this ra tio n c o n tain ed both p e n icillin and a u re o m y c in . T h e u s e of a s i n g l e a n t i b i o t i c a n d a t a l o w e r l e v e l m i g h t not h a v e h ad e i t h e r effect. F u r t h e r study w o u l d b e n e e d e d to a s c e r t a i n s p e c i f i c v a l u e s a n d e f f e c t s . A l t h o u g h s o y b e a n o i l m e a l i n a c o m p l e x t y p e of r a t i o n ( r a ­ t i o n C) g a v e g o o d r e s u l t s , a s i m p l i f i e d r a t i o n ( r a t i o n F ) c o n t a i n i n g the s a m e l e v e l of s o y b e a n o i l m e a l w a s n o t s a t i s f a c t o r y f o r g r o w t h , m a i n t e n a n c e , o r r e p r o d u c t i o n , e v e n t h o u g h p r o x i m a t e a n a l y s e s of t h e two r a t i o n s w e r e s i m i l a r w i t h r e s p e c t to n u t r i e n t c o n t e n t a n d energy level. The s i m p l e r of the tw o r a t i o n s ( r a t i o n F ) m i g h t h a v e b e e n s o m e w h a t d e fic ie n t in the B - c o m p le x v ita m in s or unknown factors. T h i s m i g h t e x p l a i n t h e n e r v o u s n e s s of th e a n i m a l s a n d subsequent poor p erform ance. D ried b re w e rs y e a s t and d r i e d to ru la y e a s t, e s p e c ia lly in s im p lif ie d r a t i o n s , gave good r e s u l t s w h e th e r u s e d singly o r in c o m ­ bination. The l o s s e s a m o n g m in k on r a t i o n D m a y have b e e n c a u s e d b y f a u l t y f e e d i n g r e d i e n t s , a n d s h o u l d n o t b e c o n s t r u e d (o n t h e b a s i s 51 of t h i s e v i d e n c e ) a s i n d i c a t i n g s o m e f a i l u r e o n t h e p a r t of th e d r i e d yeast. T h e h e a v y k i t l o s s e s on t h e c o n t r o l r a t i o n ( t w e n t y - f i v e o u t of t h i r t y - t h r e e k i t s ) a r e b e l i e v e d to h a v e b e e n c a u s e d b y h o t w e a t h e r . S e v e r a l c o m p l e t e l i t t e r s w e r e l o s t i n t h e e a r l y p a r t of M a y , 1955, during a n u n sea so n ab le hot spell. m a l e s in the c o n t r o l g r o u p . T hese l i t t e r s w e re all f r o m f e ­ N o l i t t e r s w e r e b o r n to f e m a l e s o n o th er ra tio n s during that p a r tic u la r p erio d . T hese l o s s e s should not be c o n s id e r e d a s re s u ltin g f r o m faulty nutrition. S w i t c h i n g b r e d f e m a l e s f r o m a v a r i e t y of d r y r a t i o n s to t h e c o n t r o l r a t i o n h a d n o a p p a r e n t e f f e c t e i t h e r o n t o t a l n u m b e r of k i t s b o r n o r o n t h e n u m b e r of l o s s e s . w e r e s m a l l b u t the r e s u l t s H e r e a g a in the n u m b e r s involved s u g g e s t t h a t the b e t t e r d r y r a t i o n s w e r e a d e q u a t e f o r s u p p o r t i n g g e s t a t i o n a n d t h a t t h e u s e of p r o p e r l y f o r m u ­ l a t e d d r y r a t i o n s until w helping is f e a s i b l e . T his would in d ic a te th a t the u s e fu l p e r i o d f o r p r e s e n t d ry r a tio n s extends f r o m A ugust u n t i l M a y , o r f o r n i n e m o n t h s o u t of t h e y e a r . The P rocedure. 1955-56 F eed in g T rials T h e e n c o u r a g i n g r e s u l t s o b t a i n e d f r o m th e p r e ­ v i o u s y e a r ' s w o r k s u g g e s t e d t h a t th e d e v e l o p m e n t of a d r y r a t i o n w hich would allow n o r m a l late g ro w th an d m a in te n a n c e was definitely 52 w ithin r e a c h . T h e r e f o r e i t w a s d e c i d e d to c o n c e n t r a t e t h e e x p e r i ­ m ental w ork for M arch 1. 1 9 5 5 - 5 6 p r i m a r i l y o n t h e p e r i o d f r o m A u g u s t 1 to T h i s p e r i o d c o v e r s b o t h l a t e g r o w t h of k i t s a n d m a i n t e ­ n a n c e of a d u l t s p r i o r to a n d d u r i n g t h e t i m e w h e n t h e y a r e n o r m a l l y c o n d itio n e d f o r the b r e e d in g s e a s o n . I n c r e a s i n g t h e e n e r g y l e v e l a n d p o s s i b l y p a l a t a b i l i t y of a d r y ration b y m e a n s of a d d e d f a t a p p e a r e d to b e th e m o s t p r o m i s i n g l i n e of a tta c k .The m o r e s u c c e s s f u l r a tio n s fe d the p re v io u s y e a r w e re m o d i f i e d b y s u b s t i t u t i n g 4 p e r c e n t f a t a t t h e e x p e n s e of the c e r e a l com ponent. In som e ra tio n s 6 p e rc e n t added fat was used. R efined c o tto n s e e d oil w a s u s e d b e c a u s e it w a s e a s ily p r o c u r e d , n o t b e c a u s e i t w a s t h o u g h t to h a v e a n y s p e c i a l v i r t u e s b e y o n d e n e r g y . lik e ly o t h e r f a t s would h a v e done a s w ell. w ere also m ade. R atio n 55-1: V ery O ther m in o r m odifications A b r i e f d e s c r i p t i o n of t h e r a t i o n s f e d f o l l o w s : This ra tio n w as c a r r ie d o v er p ra c tic a lly unchanged fro m the p re v io u s y e a r when it was fed as r a tio n C and was i n t e n d e d to s e r v e a s a d r y c o n t r o l r a t i o n . T h e two p r e v i o u s y e a r s i t h a d c o n s i s t e n t l y g i v e n th e b e s t r e s u l t s during late grow th, m aintenance, and reproduction. R a tio n 55-2: This w as the r a tio n fe d a s r a t i o n E the p re c e d in g y e a r , b u t with 4 p e r c e n t f a t added. R atio n 55-3: T h i s w a s t h e r a t i o n f e d a s r a t i o n D th e p r e c e d i n g y e a r , b u t with 4 p e r c e n t f a t ad d ed . 53 R ations 5 5 -4 and 55-5: T h e s e w e r e t h e r a t i o n s f e d a s A a n d B the p r e c e d i n g y e a r w i t h t h e e n e r g y l e v e l r a i s e d b y the a d d i t i o n of 4 p e r c e n t f a t . R atio n 55-6: T h i s w a s s i m i l a r to r a t i o n G f r o m th e p r e c e d i n g y e a r . T h e p r o t e i n l e v e l w a s l o w e r e d s l i g h t l y a n d th e a m o u n t of a d d e d f a t i n c r e a s e d f r o m R atio n 5 5-7: 4 p e r c e n t to 6 p e r c e n t . T h i s r a t i o n w a s f o r m u l a t e d to m e e t N R C s t a n d a r d s w i t h r e s p e c t to p r o t e i n a n d v i t a m i n r e q u i r e m e n t s , a n d c o n t a i n e d no a d d e d f a t . To c o m p e n s a t e f o r t h e l o w e r d i g e s t i b i l i t y of d r i e d i n g r e d i e n t s b y m i n k , t h e N R C a l l o w a n c e s w e r e i n c r e a s e d b y 25 p e r c e n t . R ation 5 5 - 8 : T h is w as id e n tic a l w ith 5 5 -7 e x c e p t th a t w a s a d d e d to i n s u r e t h a t t h e r a t i o n would 6 percent fat m eet or exceed re c o m m e n d e d energy levels. R ation 55-9: This co n tain ed c ru d e c a s e i n and had 6 p e r c en t .added fat. as the chief p r o t e i n s o u r c e It w as hoped th a t this r a t i o n 1 w o u l d g i v e a n i n d i c a t i o n a s to w h e t h e r o r n o t p r o te in availability was a lim iting fa c to r. F o r t h e 1 9 5 5 - 5 6 f e e d i n g t r i a l s a l l d r y r a t i o n s w e r e f e d in pellet fo rm s o t h a t t h e r e w o u l d b e no v a r i a t i o n i n t h e t e x t u r e of t h e r a t i o n o r in the fe e d in g m e th o d . is g iv en in Table 15. T h e c o m p o s i t i o n of the d r y r a t i o n s 54 TABLE 15 COMPOSITION O F E X P E R IM E N T A L R A TIO N S F O R 1955-56 R ation N um ber Ingredients 55-2 55-1 Percent a C e r e a l m i x ............................................................... D r i e d y e a s t , t o r u l a ........................................... ' , D r i e d y e a s t , b r e w e r s ........................................ S o y b e a n o il m e a l (50% p r o t e i n ) .................... F i s h m e a l (55% p r o t e i n )^3 ................................. M e a t s c r a p s (65% p r o t e i n ) .............................. F i s h m e a l (60% p r o t e i n ) c .................................. L i v e r m e a l ^ - ............................................................... S k i m m i l k , d r i e d .................................................. C o t t o n s e e d o i l ......................................................... F i s h s o l u b l e s ............................................................ C r u d e c a s e i n ............................................................ C h o l i n e C h l o r i d e (25%) ..................................... V i t a m i n m i x e ............................................................ T e r r a m y c i n T M - 5 .................................................. . . . . . . . . 41.1 . . . . . . . . 25 .0 10. 0 5.0 5. 0 . . . . 2. 0 . . . . 5.0 . . . . 0.8 . . . . . . . . Per V i t a m i n A ( 1 0,0 00 U S P u n i t s / g m ) . V i t a m i n D (3, 000 IC u n i t s / g m ) .................... V i t a m i n E (20 ,0 00 I U / l b ) . . . . MnSC>4 ( f e e d in g g r a d e ) ................. V i t a m i n B j 2 ................................. a C ereal m ix num ber 19.15 15.0 20.0 20.0 5. 0 10. 0 3.0 3 .0 4 .0 - 100 P o u n d s _ 23 g m 4 .8 m g 1007, K e l l o g g C o . , B a t t l e C r e e k , M i c h . V itap ro il 75-A, M aine M a rin e P r o d u c t s , Inc., P o r t l a n d , Me. c S eah o rse F i s h F l o u r , M aine M arin e P r o d u c t s , Inc., P o r tla n d , M aine. 55 TABLE 15 ( C o n t i n u e d ) R ation N um ber 55-3 55-4 55- 6 55 - 5 55-8 55-7 55-9 Percent 37.8 15.0 19.15 15.0 20 . 0 20. 0 5.0 10.0 3.0 3.0 4 .0 - 10. 0 15.0 5 .0 5. 0 5 .0 2.0 4.0 - - 37.8 17.15 7.5 7.5 20. 0 20. 0 5.0 10.0 3.0 3.0 6.0 - 15.0 10. 0 15.0 5 .0 5.0 5 .0 2. 0 4.0 _ _ 0.8 0.2 0. 8 0.2 _ 51 .5 5.0 5.0 10.0 10.0 5.0 10.0 3.0 - - 45.5 5.0 5.0 10.0 10.0 5.0 10.0 3.0 6.0 - - - - Per - 23 g m - 4.8 m g 5 1 gm 45 g m 23 g m 10 g m 2.5 m g - - 10.0 - 6.0 25.0 - “ _ _ 37.3 5.0 5.0 10.0 5 1 gm 45 g m 23 g m 10 g m 2.5 m g - 100 P o u n d s - - 23 g m 4.8 m g 8 gm 20 g m 20 g m 10 g m 2.0 m g 8 gm 20 g m 20 g m 10 g m 2.0 m g 8 gm 20 g m 20 g m 10 g m 4.8 m g d R i t a l i v e r , I m p e r i a l P r o d u c t s Co., W ad sw o rth , Illinois. e F o r t a f e e d 2 -4 9 C , L e d e r l e L a b o r a t o r i e s , P e a r l R i v e r , New Y ork. 56 The co n tro l ra n c h -ty p e in p r e v io u s y e a r s . ponent. Mw e t M r a t i o n w a s s i m i l a r to t h a t u s e d A gain th e r e w as s o m e v a r i a t i o n in the f is h c o m ­ D u r i n g t h e m a i n t e n a n c e p e r i o d ( J a n u a r y to M a r c h ) th e c e r e a l com ponent was in c re a s e d fro m 15 to 30 p e r c e n t . T h i s w a s do ne to a i d i n w e i g h t c o n t r o l d u r i n g t h e c o n d i t i o n i n g p e r i o d p r i o r to th e breeding season. F o r m u l a t i o n of b o t h of t h e s e r a t i o n s i s P r o x i m a t e a n a l y s e s of a l l in Table ra tio n s a r e given in T ables 16. 17 a n d 18. M ink w e r e a l l o t t e d r a n d o m l y by a g e an d s ex into te n e x p e r i ­ m ental groups. m ales, E a c h g r o u p c o n t a i n e d two a d u l t m a l e s , f i v e k i t six adult fe m a le s , and seven kit fe m a le s . At the beginning of t h i s e x p e r i m e n t ( A u g u s t 1, 1955) a l l k i t s w e r e t e n to t w e l v e w e e k s of a g e . O b s e r v a t i o n s of r e s p o n s e t o t h e r a t i o n s w e r e c o n t i n u e d u n t i l M a r c h 1, 195 6. As in p r e v io u s t r i a l s , weighing was biw eekly and w e i g h t s w e r e r e c o r d e d to t h e n e a r e s t t e n g r a m s . All o th e r p r o c e d u r e s follow ed have b e en p re v io u s ly d e sc rib e d . R e s u lts and d iscu ssio n . Tables 19 a n d 20 s u m m a r i z e the d a ta o b ta in e d f r o m l a t e g r o w t h s tu d ie s on k it m a l e s an d f e m a l e s d u r i n g t h e p e r i o d f r o m A u g u s t 1, 1955, u n t i l D e c e m b e r D ata c o n c e r n e d with m a in te n a n c e 1, 1955. s tu d ie s on a d u lts f o r the s a m e 57 TABLE 16 C O M P O S IT IO N O F C O N T R O L RATIONS, 1955-5 6 (a ll v a l u e s i n p e r c e n t a g e s ) Ingredients A u g u s t , 1955, to J a n u a r y , 1956 J a n u a r y , 1956, to M a r c h , 1956 H o r s e m e a t w i t h b o n e ............. , , 50 21-2/3 Fish ................................................ 15 21-2/3 Tripe ............................................... 15 21-2/3 Liver ................................................ 5 5 15 15 Cooked c e r e a l Cooked c e r e a l b c ........................... ........................... . . . 15 . a The f i s h c o m p o n e n t was g ro u n d haddock r a c k s during A u g u s t a n d S e p t e m b e r , 1955, a n d o c e a n w h i t i n g t h e r e a f t e r . ^ K e l l o g g ' s M i n k R a t i o n No. CK e l l o g g ' s M i n k M i x N o . 1001 ( s u p p l e m e n t e d c e r e a l m i x ) . 1007 ( c e r e a l m i x ) . f 58 TABLE 17 P R O X I M A T E ANA LY SES O F THE RATIONS F E D , AUGUST 1955, T O D E C E M B E R 1, 1955 (all v a l u e s i n p e r c e n t a g e s ) M ois­ ture Crude Pro­ tein Ether Ex­ tract Crude Fiber C o n t r o l ’' a s f e d 1,a .............. 6 4 .4 9 14.25 8.13 0.91 8.77 Control " a i r d ry b a s i s "k . 8 .2 6 3 6 .7 7 20. 9 8 2.35 55-1 ................. 9.5 4 30 .8 1 4.68 5 5 - 2 ................. 8.55 42.50 5 5 - 3 ................. 8 .6 0 5 5 - 4 ................. R ation Ca P 3.45 0. 88 0.57 22.6 3 8. 90 2.28 1.48 3.08 42.56 9.33 1.52 1.11 10.24 2. 02 2 6 .2 8 10.41 1.63 1.42 42.1 3 10. 22 1.98 27.22 9.85 1.54 1.41 8 .3 7 3 4 .6 3 9.88 2.5 0 36.21 8.41 1.22 1.17 5 5 - 5 ................. 8.18 33.88 9.5 9 2.45 37.4 9 8.41 1.23 1.19 5 5 - 6 ................. 7.98 41. 63 11.94 2. 07 2 6 .5 4 9.84 1.49 1.36 5 5 - 7 ................. 8 .4 4 32.00 6.13 2.63 4 2 .6 8 8. 12 1.15 1.13 5 5 - 8 ................. 7 .9 2 30.13 11.36 2 .4 6 40 .4 2 7.71 1.20 1.13 5 5 - 9 ................. 8.02 42 .1 3 9.43 1.91 32.9 5 5 .66 0.5 6 0. 88 a This c o n tro l r a t i o n was fed through C alculated values. NFE Ash 1, Ja n u a ry 12, 1956. 59 TABLE 18 P R O X IM A T E A N A LY SES OF THE RATIONS F E D , D E C E M B E R 1955, TO M A R C H 1, 1956 ( a ll v a l u e s i n p e r c e n t a g e s ) R ation M ois­ ture Crude Pro­ tein E ther Ex­ tra c t C rude F iber NFE Ash Ca 1, P C ontrol n as f e d , , a .............. 68.3 0 9 .7 8 5.2 4 1.08 13.60 2. 00 0.321 0.321 C o n tro l lla i r d r y b a s i s 11^ . 6.69 2 8 .7 5 15.41 3.1 8 39.98 5. 88 0.944 0.944 5 5 - 4 ................. 6.8 7 34.31 9. 84 2.53 38.60 7.85 1.19 1.15 55-5 ................. 6.70 35.38 9.73 2.4 8 3 7 .9 0 7.81 1.14 1.15 5 5 - 6 ................. 6.55 43.44 11. 87 2. 00 26.1 3 10.01 1.55 1.39 5 5 - 7 ................. 6,63 31.50 5 .5 0 2.65 4 6 .1 0 7.62 1.07 1.11 a This c o n tro l r a tio n was fed a fte r J a n u a ry C alculated values. 12, 1956. 60 TABLE 19 L A T E G R O W T H R E S U L T S , A U G U S T 1, 1955, TO D E C E M B E R 1, 1955; F I V E K I T M A L E S P E R G R O U P ( a ll w e i g h t s i n g r a m s ) At S t a r t R ation Group At F in is h Avg. Gain Avg. Wt . Range in W eight Avg. Wt. Range in W eight C ontrol 902 750-1020 1254 950-1550 352 55-1 764 6 2 0 - 870 788 7 1 0 - 870 24 55-2 -810 590-1060 1034 850-1260 224 55-3 740 60 0 - 850 938 650-1260 198 55-4 820 670-1070 1142 870-1460 322 55-5 820 680-1000 1044 900-1510 224 55-6 868 780-1000 1226 1040-1460 358 55-7 802 7 0 0 - 890 1050 890-1200 248 55-8 758 5 9 0 - 860 1048 760-1290 290 55 _9 758 6 1 0 - 950 1184 910-1450 426 M or­ tal­ ity 61 T A B L E 20 L A T E G R O W T H R E S U L T S , A U G U S T 1, 1955, TO D E C E M B E R 1955; S E V E N K I T F E M A L E S P E R G R O U P (all w e ig h ts i n g r a m s ) At Start R ation G roup Avg. W t. Range in W eight At F in i s h Avg. W t. Range in W eight Avg. G ain C ontrol 719 630-840 806 700-1020 87 55-1 591 510-700 574 5 2 0 - 650 -17 561 470-660 644 560- 690 83 55-3 531 460-580 660 5 4 0 - 790 129 55-4 549 470-600 684 5 5 0 - 840 135 55-5 537 420-640 623 5 6 0 - 750 86 55-6 580 530-650 694 6 2 0 - 750 114 55_7 577 490-670 660 5 7 0 - 780 83 55_8 591 510-670 703 6 2 0 - 860 112 55-9 621 520-690 751 650- 830 130 55-2 • 1, M or­ tal­ ity 0 62 p e r i o d a r e p r e s e n t e d i n T a b l e s 21 a n d 22. Th e i n f o r m a t i o n i n T a b l e 23 r e l a t e s to t h e m a i n t e n a n c e of a d u l t m i n k f o r t h e p e r i o d from Decem ber 1, 1955, u n t i l M a r c h L a t e g r o w t h of m i n k k i t s . 1, 1956. W i t h th e e x c e p t i o n of r a t i o n 5 5 - 1 , a ll d r y r a t i o n s p e r m i t t e d g r o w th by the k its d u rin g the e x p e r i m e n t a l period. R a t i o n 5 5 -1 w as a c c i d e n t a l l y c o m b in e d with a n u n d e t e r m in e d a m o u n t of p o u l t r y f e e d w hile b e in g p e l l e t e d a t the f e e d m i l l . This s u b s e q u e n t l y t u r n e d o u t to b e a f o r t u i t o u s a c c i d e n t s i n c e t h e d a t a o b t a i n e d a p p e a r t o i n d i c a t e a l o w e r l i m i t of n u t r i e n t l e v e l s a l t h o u g h p o o r palatab ility m ight have b een a fa c to r. The ra tio n , a s fed, b a r e l y a l l o w e d m a i n t e n a n c e of a d u l t m i n k d u r i n g t h i s p e r i o d , a n d p e r m i t t e d e s s e n t i a l l y no g r o w t h b y t h e m i n k k i t s . T h e o t h e r r a t i o n s g a v e r e l a t i v e l y u n if o r m r e s u l t s , with r a t io n s 5 5 - 4 , 5 5 - 6 , a n d 5 5 - 9 s t a n d i n g o u t w h e n c o m p a r e d to t h e c o n t r o l r a ­ tion. A n a l y s i s of v a r i a n c e b a s e d o n th e i n d i v i d u a l w e i g h t g a i n s m a d e by th e m i n k k i t s d u rin g th is p e r i o d gave the r e s u l t s p r e s e n t e d on page 66. R a t io n 55-1 w as not in c lu d e d in the a n a l y s i s sin ce it w a s o b v i o u s f r o m t h e d a t a t h a t t h e s e a n i m a l s d i d n o t b e l o n g i n th e s a m e p o p u la tio n with the o th e r s . 63 T A B L E 21 M A I N T E N A N C E R E S U L T S , A U G U S T 1, 1955, TO D E C E M B E R 1, 1955; TWO A D U L T M A L E S P E R G R O U P (a ll w e i g h t s i n g r a m s ) At S ta r t R ation Group At F inish Av g. Gain Avg. Wt. Range in W eight Avg. W t. Range in W eight 950 9 4 0 - 960 1140 1020-1260 190 55-1 1005 990-1020 1050 990-1110 45 55-2 1155 970-1340 1305 1120-1500 150 55-3 1210 1200-1220 1545 1510-1580 335 55-4 1110 1080-1140 1305 1230-1380 195 55-5 935 9 2 0 - 950 980 9 8 0 - 980 45 55_6 955 9 3 0 - 980 1115 1020-1210 160 55-7 1105 1080-1130 1300 1290-1310 195 55-8 1025 950-1100 1245 55-9 1085 1000-1170 1275 C ontrol ' 1150-1340 1120-1430 220 190 M or­ tal­ ity 64 T A B L E 22 M A I N T E N A N C E R E S U L T S , A U G U S T 1, 1955, TO D E C E M B E R 1955; SIX A D U L T F E M A L E S P E R G R O U P (a ll w e i g h t s i n g r a m s ) R ation G roup At S t a r t — --------------------------------Avg. Range W t. in W eight At F i n i s h —-—----- —--------Avg. Range Wt. in W eight 1, A vg . G ain M or­ tal­ ity C ontrol 630 540-710 810 730-920 180 0 55-1 562 540-580 582 540-620 20 0 55-2 578 530-660 654 540-710 76 0 55-3 533 510-560 590 490-660 57 0 55-4 612 540-690 698 590-790 86 0 55-5 582 560-610 647 560-740 65 0 55-6 602 490-730 693 640-860 91 0 55_7 610 550-660 692 580-860 82 0 55_8 5 78 510-700 677 590-810 99 0 5 5_9 665 530-730 733 640-810 68 0 65 T A B L E 23 M A I N T E N A N C E R E S U L T S , D E C E M B E R 1, 1955, TO M A R C H 1, 1956 (all w e ig h ts in g r a m s ) At Start R ation G roup Avg. W t. At F i n is h Range in W eight Avg. Wt . Range in W eight A vg. Gain M or­ tal­ ity Seven M ales C ontrol 1379 1 1 9 0 - 1580 1299 1 190-1440 -80 0 55-4 1246 1110-1460 1374 1 190- 1500 128 0 55-5 1190 980-1510 1224 950-1310 34 0 55-6 1194 1020-1460 1309 1090-1640 115 0 55-7 1203 1010-1310 1261 1080-1390 58 0 Seventeen F e m a le s Control 768 610-1020 779 6 1 0 - 950 11 0 55-4 699 5 9 0 - 840 721 52 0 - 830 22 0 55-5 681 5 9 0 - 830 705 5 4 0 - 820 24 0 55-6 723 5 7 0 - 860 727 61 0 - 910 4 0 55-7 686 570- 680 5 8 0 - 800 -6 0 860 66 S o u r c e of V a r i a t i o n D e g r e e s of Freedom Mean Square F o r K it M ales T o t a l ................................................................ T reatm ents E rror ............................................................. 44 8 2 9 ,2 5 9 36 18,782 F = 1.55 (F a t 5% l e v e l = 2.21) F o r K it F e m a le s T o t a l ................................................................ T reatm ents 62 ............................................... 8 3,412 E r r o r ............................................................. 54 4, 2 7 6 F = 0 . 7 9 8 (F a t 5% l e v e l = 2.11) The F r a t i o s i n d i c a t e t h a t th e v a r i a t i o n s a m o n g th e g r o u p s a r e p r o b a b l y d u e to c h a n c e . T h e s t a r t i n g w e i g h t s of b o t h t h e m a l e a n d f e m a l e m i n k k i t s (T ables 19 a n d 2 0 ) , e v e n t h o u g h t h e y w e r e s o r t e d a t r a n d o m a t t h e b e g i n n i n g of t h e t r i a l , s h o w e d c o n s i d e r a b l e v a r i a t i o n . As a c h e c k to s e e w h e t h e r t h i s v a r i a t i o n w a s b e y o n d t h e n o r m a l r a n g e , a f u r ­ t h e r a n a l y s i s of v a r i a n c e w a s c a r r i e d o u t u s i n g t h e i n d i v i d u a l startin g w eights. 67 T h e r e s u l t s of t h i s a n a l y s i s f o r m a l e m i n k k i t s w e r e : S o u r c e of V a r i a t i o n D e g r e e s of Freedom Mean Square T o t a l ........................... G roups E rror ........................... 140 ............................................ 155 F = 0 . 9 0 3 (F a t 5% l e v e l = 2.2 1) T h e r e s u l t s ( F = 0.9 0 3 ) i n d i c a t e t h a t t h e v a r i a t i o n s i n s t a r t ­ in g w e i g h t s of m a l e m i n k k i t s w e r e due to c h a n c e , a n d t h a t the a n a l y s i s b a s e d on w eight g ain s w a s valid. T h e r e s u l t s of a s i m i l a r a n a l y s i s f o r f e m a l e m i n k k i t s w e r e : , , S o u r c e of V a r i a t i o n D e g r e e s of _ . Freedom T o t a l ............................................................. 62 G roups Mean Square ...................................................... 8 231 E r r o r .......................................................... 54 37 F = 6 . 2 5 * * (F a t 1% l e v e l = 2.85) T h is a n a l y s i s in d ic a te d th a t t h e r e w as a highly sig nificant d i f f e r e n c e a m o n g t h e s t a r t i n g w e i g h t s of t h e f e m a l e m i n k k i t s . T h e r e f o r e , a c o v a r i a n c e a n a l y s i s of s t a r t i n g w e i g h t (x) b y f i n i s h i n g 68 w e i g h t (y) w a s m a d e to s e e if t h i s d i f f e r e n c e i n s t a r t i n g w e i g h t s h a d a s i g n i f i c a n t e ffe c t on the fin is h in g w eig h ts. S o u r c e of V ariation E rror S u m s of S q u a r e s and P r o d u c ts d .f. E r r o r s of Estim ate Sx2 Sxy Sy2 S.S. d.f. 62 3852 3441 5819 2745 61 .............. 8 1844 1686 1799 ................. 54 2008 1755 4020 2486 53 46.9 268 8 89.3 T o t a l s ................. G roups These re s u lts were: »“ ( 0 00 11 This F ra tio M.S. (F a t 5% l e v e l = 2.12; ) s h o w s t h a t t h e r e w e r e no s i g n i f i c a n t d i f f e r e n c e s a s f a r a s the f e m a l e s w e r e c o n c e r n e d w hen the s ta r ti n g w eights w e r e a d ju s t e d f o r d iff e r e n t individual in itial w eights. T h u s , the a n a l y s i s b a s e d on w e ig h t g a in s w a s v alid. O n t h e b a s i s of t h i s e x p e r i m e n t , i t a p p e a r s t h a t f o r l a t e g r o w t h No f k i t s s e v e r a l of t h e d r y r a t i o n s a r e a d e q u a t e . M a i n t e n a n c e of a d u l t s . by the a d u lt m a l e s an d f e m a l e s All d r y r a t i o n s p e r m i t t e d w eig h t g a in s (again excluding ra tio n 55-1) during t h e p e r i o d f r o m A u g u s t 1 to D e c e m b e r 1, 1955. A possible excep­ t i o n a p p e a r s i n t h e g a i n s r e c o r d e d f o r m a l e s on r a t i o n 5 5 - 5 . 69 H o w e v e r , t h e p e r f o r m a n c e of f e m a l e s o n t h i s r a t i o n w a s c o m p a r a b l e to t h a t of th o s e f e m a l e s o n the o t h e r d r y r a t i o n s . It t h a t t h e p e r f o r m a n c e of t h e two a d u l t m a l e s o n r a t i o n s e e m s probable 55-5 was atypical. D u rin g the w in te r m a in te n a n c e p e r i o d (fro m D e c e m b e r 1, 1955, to M a r c h 1, 1956) f o u r d r y r a t i o n s ( 5 5 - 4 , 5 5 - 5 , 5 5 - 6 , a n d 5 5 - 7 ) a n d the co n tro l r a tio n w e re fed. R a t io n s 5 5 -4 a n d 5 5 -5 w e r e continued b e c a u s e they o ffe re d a d i r e c t c o m p a r i s o n of t h e two t y p e s of d r i e d y e a s t p r e v i o u s l y s t u d i e d . R a t i o n 5 5 -6 w as c o n tin u e d b e c a u s e it w as the d ry r a tio n w hich, in t h e o p i n i o n of t h e p r e s e n t i n v e s t i g a t o r , g a v e t h e b e s t r e s u l t s w i t h k i t s a n d a d u l t s d u r i n g the p r e c e d i n g p e r i o d . R a tio n 5 5 -7 , which was s e t up t o m e e t N R C s t a n d a r d s , w a s c o n t i n u e d a l s o , a n d w a s c h o s e n i n s t e a d of 5 5 - 8 b e c a u s e t h e a d d e d f a t i n 5 5 - 8 g a v e no apparent bene­ fits . T h e s i z e of t h e e x p e r i m e n t a l g r o u p s w a s i n c r e a s e d to s e v e n m ales and seventeen fe m a le s. of t h e b e t t e r a n i m a l s f r o m T h is w as done by the r a n d o m a d d itio n th e g r o u p s w h i c h w e r e to b e d i s c o n t i n u e d . All r a t i o n s a llo w e d n o r m a l m a i n t e n a n c e d u rin g th is p e rio d . A fter Jan u a ry 1, 19 56 , t h e m i n k o n t h e c o n t r o l r a t i o n w e r e r e s t r i c t e d i n t h e i r f o o d i n t a k e to c o n t r o l t h e i r w e i g h t . In F e b r u a r y 70 i t b e c a m e n e c e s s a r y to l i m i t th e i n t a k e of a n u m b e r of a n i m a l s on t h e v a r i o u s d r y r a t i o n s a s t h e y w e r e a l s o g e t t i n g too f a t . T h i s , p e r h a p s , i s the m o s t s i g n i f i c a n t s t a t e m e n t t h a t c a n be m a d e c o n c e r n i n g t h e v a l u e of t h e d r y r a t i o n s f o r m a i n t e n a n c e . In e s s e n c e , the d r y r a t i o n s w e r e supplying m o r e n u tr i e n ts th a n n e c e s ­ s a r y a n d the m in k w e r e c o n s u m i n g m o r e than they n e e d e d f o r m a i n ­ tenance p u rp o se s. M ortality. D u r i n g t h e p e r i o d A u g u s t 1, 1955, to D e c e m b e r 195 5, o n l y tw o a n i m a l s d i e d . 55-1, 1, T h e se w e re both k it f e m a l e s on r a tio n B oth d ie d d u rin g the f i r s t p ro lo n g e d cold spell. N ecropsy s h o w e d no g r o s s l e s i o n s , a n d d e a t h w a s a t t r i b u t e d to i n a b i l i t y b y these anim als ( w h i c h w e r e o n a m a r g i n a l r a t i o n ) to w i t h s t a n d the s t r e s s of the cold w e a th e r . D u r i n g t h e p e r i o d D e c e m b e r 1, 1955, to M a r c h 1, 1956, on e fem ale (on r a t i o n 5 5 - 7 ) d i e d . N e cro p sy showed g e n e ra l em aciatio n a n d s e v e r a l m in u te s to n e s ( m i c r o c o n c r e ti o n s ) in e a c h kidney. No o t h e r g r o s s l e s i o n s w e r e noted. S u m m a r y of t h e 1955-56 t r i a l s . Th e a p p a r e n t s u c c e s s of a l l d r y r a t i o n s f e d ( e x c l u d i n g 5 5 - 1 ) w o u l d s e e m to i n d i c a t e t h a t the l i m ­ iting f a c t o r in r a t i o n s p r e v io u s ly u s e d was chiefly e n erg y . 71 T h e u s e of c r u d e c a s e i n a s a p r o t e i n s o u r c e i n r a t i o n 5 5 - 9 ga v e b e t t e r r e s u l t s than s e v e r a l r a t i o n s , notably 55-7, 55-5, 55-3, and 55-2. The f a c t th a t the re m a in in g d ry r a tio n s w e re as s u c c e s s ­ f u l a s r a t i o n 5 5 - 9 a n d t h e c o n t r o l r a t i o n w o u l d a p p e a r to s u g g e s t t h a t a v a i l a b i l i t y of p r o t e i n f r o m d r i e d s o u r c e s (i.e., f is h m e a l s , s o y b e a n oil m e a l , e tc.) w as not a c r i t i c a l and lim itin g f a c t o r , and th a t the m in k c a n utilize p r o te in s in this f o r m . T h e s u c c e s s f u l u s e of a s i m p l i f i e d t y p e of d r y r a t i o n ( e . g . , r a t i o n 5 5 -6 ) s u g g e s t s th a t the v ita m in and m i n e r a l c o n c e n tr a te s u s e d in the o t h e r d r y r a t i o n s (other than V ita m in s E and necessary. w ere n°t D r y i n g r e d i e n t s (if r e a s o n a b l y f r e s h ) s e e m to b e a b l e to s a t i s f y the m i n k 's v it a m in a n d m i n e r a l r e q u i r e m e n t s und er n o r ­ m a l conditions. A d i r e c t c o m p a r i s o n of d r i e d y e a s t s ( t o r u l a a n d b r e w e r s ) in b o t h a c o m p l e x t y p e of d r y r a t i o n ( 5 5 - 4 a n d 5 5 - 5 ) a n d i n a s i m p l i ­ f i e d t y p e of d r y r a t i o n ( 5 5 - 2 a n d 5 5 - 3 ) i n d i c a t e s t h a t b o t h t y p e s of y e a s t s w e r e s u i t a b l e f o r u s e a n d w e r e t o l e r a t e d b y t h e m i n k a t th e l e v e l s u s e d (15 p e r c e n t ) . D r i e d y e a s t w a s n e c e s s a r y to th e s u c c e s s f u l p e r f o r m a n c e of t h e s i m p l i f i e d d i e t s . is not possible, due to other Although a d ir e c t c o m p a r is o n variations in ration com position, it should be po in ted out th at the m o r e su c c e ss fu l d ry ra tio n s co n ­ t a i n e d a c o m b i n a t i o n of t h e d r i e d y e a s t s . 72 N R C r e q u i r e m e n t s f o r m i n k a s p u b l i s h e d a p p e a r to b e d i r e c t l y a p p l i c a b l e to m i n k f e d o n d r y r a t i o n s p r o v i d e d a l l o w a n c e i s m a d e f o r t h e l o w e r d i g e s t i b i l i t y of d r i e d i n g r e d i e n t s b y m i n k . The d ry r a tio n s a s r e p o r t e d have given s a tis fa c to ry r e s u lts during the e x p e r im e n t a l p e r io d s studied. O n t h e b a s i s of t h i s w o r k t h e r e s e e m s t o b e l i t t l e d o u b t t h a t d r y r a t i o n s c o u l d b e u s e d to f e e d m i n k f o r t h e p e r i o d A u g u s t 1 t o M a r c h 1. G E N E R A L DISCU SSION T h e m a j o r i t y of t h e d r y r a t i o n s w h i c h w e r e u s e d i n the 1 9 5 5 - 5 6 t r i a l s w e r e s u c c e s s f u l in sup p o rtin g both la te grow th and m a in te n a n c e m in k u n d e r the e x p e r im e n t a l conditions. Since, in m o s t in s ta n c e s , th e c h ief d if f e r e n c e b e t w e e n the r a t i o n s u s e d i n 1954-55 and in 1955-56 w a s t h e a d d i t i o n of f a t , i t s e e m s p r o b a b l e t h a t f a t a n d / o r e n e r g y c o n ­ t e n t h a s b e e n the l i m it in g f a c t o r in p r e v i o u s d ry r a t i o n s . T h e d r y r a t i o n s u s e d ( r e f e r r i n g to t h e 1 9 5 5 - 5 6 r a t i o n s ) w e r e m a r k e d l y s i m i l a r i n r e s p e c t to m o i s t u r e , c r u d e f i b e r , a n d a s h c o n ­ tent. The ch ief d i f f e r e n c e s w e r e in p r o t e i n , f a t, a n d n i t r o g e n - f r e e e x t r a c t (N FE) le v e ls . E x c l u d i n g r a t i o n 5 5 - 1 , c r u d e p r o t e i n c o n t e n t of th e 1 9 5 5 - 5 6 r a t i o n s v a r i e d f r o m a l o w of 30 p e r c e n t i n r a t i o n 5 5 - 8 to a h i g h of s l i g h t l y o v e r 42 p e r c e n t i n r a t i o n s 5 5 - 2 , 5 5 - 3 , a n d 5 5 - 9 . Crude fat c o n t e n t v a r i e d f r o m a l o w of 6 p e r c e n t i n r a t i o n 5 5 - 7 to a h i g h of nearly 12 p e r c e n t i n r a t i o n 5 5 - 6 . represents N F E c o n t e n t , w h i c h f o r the m i n k e s s e n t i a l l y the d ig e s t ib le o r p o te n tia lly d ig e s t ib le c a r b o ­ h y d r a te f r a c t i o n , v a r ie d equally widely f r o m 5 5 - 2 to 42 p e r c e n t i n r a t i o n 5 5 - 7 . 73 26 p e r c e n t i n r a t i o n This wide v a r i a t i o n in d ic a te s th a t 74 t h e m i n k c a n u t i l i z e n u t r i e n t s f r o m a v a r i e t y of s o u r c e s a n d i n a v a r i e t y of c o m b i n a t i o n s . E s t i m a t e s of b o t h t h e t o t a l c a l o r i c c o n t e n t a n d the d i g e s t i b l e c a l o r i c c o n t e n t of t h e 1 9 5 5 - 5 6 r a t i o n s a r e s h o w n i n T a b l e 24. Th e f i g u r e s w e r e e s t i m a t e d f r o m t h e p r o x i m a t e a n a l y s e s of th e r a t i o n s u s i n g t h e e m p i r i c a l v a l u e s of f o u r c a l o r i e s p e r g r a m f o r p r o t e i n a n d c a r b o h y d r a t e ( N F E o n ly w a s c o n s i d e r e d ; c r u d e f i b e r w h i c h i s p r a c t i c a l l y in d i g e s t i b l e by the m in k w as ig n o re d ) a n d nine c a l o r i e s p e r g ra m f o r fat. I n b o t h th e d r y a n d c o n t r o l r a t i o n s , N F E a n d f a t w e r e c o n s i d e r e d to b e 90 p e r c e n t d i g e s i b l e . P r o t e i n i n the d r y r a ­ t i o n s w a s c o n s i d e r e d t o b e 70 p e r c e n t d i g e s t i b l e ; i n t h e c o n t r o l r a t i o n s , 85 p e r c e n t d i g e s t i b l e . T h u s th e f i g u r e s r e p o r t e d a r e a l s o a n e s t i m a t e of t h e t o t a l c a l o r i e s a v a i l a b l e to t h e m i n k . dry rations A l l of the s u p p l i e d a p p r o x i m a t e l y 300 c a l o r i e s p e r 100 g r a m s , w h e re a s both co n tro l ra tio n s 100 g r a m s o n a n " a i r - d r y " s u p p l i e d a n e x c e s s of 350 c a l o r i e s p e r basis. T h i s i n d i c a t e s t h a t t h e u s e of h i g h e r l e v e l s of f a t i n a d r y r a t i o n m i g h t b e b e n e f i c i a l d u r i n g th e l a t e g r o w t h p e r i o d . The f a c t th a t in r a t i o n 5 5 -7 the e n e r g y was supplied chiefly b y d i g e s t i b l e c a r b o h y d r a t e w o u l d s e e m to i n d i c a t e t h a t t h e e n e r g y l e v e l r a t h e r th a n th e f a t l e v e l w as the m o r e c r i t i c a l f a c t o r . 75 T A B L E 24 E S T IM A T E D CALORIC V ALU ES F O R 1955-56 RATIONS E nergy Level Total C alories per Pound Total C alories p e r 100 G ram s D igestible Calories p e r 100 Gram s C alories0 Protein . . . , 1948 429 379 10.2 C o n tro l Bb . . . , 1866 411 365 12,6 5 5 - 2 ........................ 1662 3 66 295 6.9 5 5 - 3 ........................ 1662 366 293 7.0 5 5 - 4 ........................ 1698 374 309 8.8 5 5 - 5 ........................ 1698 374 309 9.1 5 5 - 6 ........................ 1743 384 312 7.4 55-7 . . . . . . . . 1607 354 294 9.2 5 5 - 8 .................... 1721 379 317 10.6 5 5 - 9 ....................... 1730 381 310 7.4 R ation C ontrol A a R a t i o n f e d f r o m A u g u s t , 1955, to J a n u a r y , 195 6. b R ation fed f r o m J a n u a r y , 1956, to M a r c h , CD i g e s t i b l e c a l o r i e s p e r protein. 1956. 100 g r a m s d i v i d e d b y p e r c e n t 76 H o w e v e r , t h e s m a l l c a p a c i t y of t h e d i g e s t i v e t r a c t of t h e m i n k s u g ­ g e s t s t h a t u s e of f a t m i g h t b e a m o r e e f f i c i e n t m e a n s of s u p p l y i n g energy. The c a lo rie :p ro te in ra tio s ( T a b l e s 24) i n d i c a t e , i n g e n e r a l , th a t the r a t i o n s w hich allo w ed l e s s g a in s had a n a r r o w e r ra tio and a r e a f u r t h e r i n d i c a t i o n t h a t th e u s e of a d d i t i o n a l e n e r g y in the f o r m of a d d e d f a t m ig h t be b e n e fic ia l. The f e w e r c a l o r i e s th a t the r a ti o n c o n t a i n s p e r u n i t of p r o t e i n , t h e l e s s t h e a b i l i t y of the a n i m a l to s to re body fat. S i n c e m o s t r a n c h e r s p r e f e r to h a v e t h e i r a n i m a l s e x c e s s i v e l y f a t a t p e l t i n g t i m e , t h e a d d i t i o n of f a t to g i v e a w i d e r c a l o r i e : p r o t e i n ra tio would be a d v a n ta g e o u s f r o m a p r a c tic a l v ie w ­ point. B e s i d e s e n e r g y , t h e a d d i t i o n of f a t s u p p l i e s two o t h e r f a c t o r s , t h e e f f e c t s of w h i c h c a n n o t b e m e a s u r e d d i r e c t l y . These a re satiety and p alatability. S a t i e t y w o u l d b e v a l u a b l e i n t h a t the m i n k w o u ld " f e e l f u l l " longer and thus be m o re satisfied and le s s nervous. T h i s w ould t e n d to e l i m i n a t e n e r v o u s r u n n i n g b y t h e m i n k w h i c h b u r n s up e n e r g y th at m ig h t b e t t e r be u sed f o r g row th and fattening. I n c r e a s e d p a l a t a b i l i t y w o u l d r e s u l t i n i n c r e a s e d a c c e p t a n c e of a d ry f e e d by the m in k . I n g e n e r a l , t h i s d o e s n o t a p p e a r to h a v e b een a lim itin g f a c to r in th ese tr i a ls . O n ly two of th e r a t i o n s 77 reported h ere ( r a t i o n F of t h e 1 9 5 4 - 5 5 t r i a l s a n d r a t i o n 5 5 - 1 of the 1 9 5 5 - 5 6 t r i a l s ) a p p e a r e d to b e u n p a l a t a b l e to th e m i n k . The a n i m a l s rec eiv in g th e se ratio n s ate sparingly and w asted a considerable p o r ­ t i o n of e a c h da y*s f e e d i n g . O th e r r a t i o n s w e re well a c c e p te d a s f a r a s could be d e te rm in e d . M e n t i o n of f e e d c o n s u m p t i o n h a s p u r p o s e l y b e e n o m i t t e d until this point. The m i n k in v o lv e d in th e s e t r i a l s w e re r a i s e d u n d e r c o n d i t i o n s w h i c h s i m u l a t e d p r a c t i c a l o n e s i n o r d e r t h a t a ny r e s u lts ob tain ed m ig h t be a s d irectly applicable as possible. A n a c c u r a t e m e a s u r e m e n t of d a i l y f e e d c o n s u m p t i o n w a s not m a d e . H o w e v e r , c a l c u l a t i o n s f r o m the t o t a l a m o u n t of t h e d r y r a t i o n s u s e d o v e r a p e r i o d of s e v e r a l m o n t h s i n d i c a t e d t h a t a m i x e d g r o u p of m a l e s m ately (seven) and f e m a le s (thirteen) co n su m ed a p p ro x i­ 100 g r a m s p e r m i n k i n a 2 4 - h o u r p e r i o d . individual m a le s O b s e r v a t io n s on s h o w e d c o n s u m p t i o n to b e a s h i g h a s 150 g r a m s o r m o r e in a 2 4 -h o u r p e rio d ; individual f e m a le s as little a s 50 g r a m s in a 2 4 -h o u r p eriod. A l s o , t h e a m o u n t of f e e d c o n s u m e d v a r i e d with the w e a th e r an d w as usually d e p r e s s e d in hot w e ath e r a n d i n c r e a s e d i n c o l d w e a t h e r (if a d e q u a t e w a t e r w a s a v a i l a b l e ) . These e s t i m a t e s of d a i l y f e e d c o n s u m p t i o n ( i . e . , 50 to 100 g r a m s f o r a f e m a l e a n d 100 to 150 g r a m s f o r a m a l e ) a n d the e s t i m a t e s of d i g e s t i b l e c a l o r i e s s u p p l i e d b y th e d r y r a t i o n s (T a b l e 78 24) i n d i c a t e t h a t t h e d r y r a t i o n s w e r e s u p p l y i n g e n e r g y to th e a d u l t s i n a m o u n t s r o u g h l y e q u i v a l e n t to t h e m a i n t e n a n c e r e q u i r e m e n t e s t a b ­ l i s h e d b y t h e N R C (124 c a l o r i e s p e r p o u n d of b o d y w e i g h t d a il y ) . T h e f a c t t h a t k i t m i n k o n t h e s e r a t i o n s g r e w n o r m a l l y d u r i n g th e l a t e g r o w t h p e r i o d w ould in d ic a te th a t the a m o u n t s supplied w e re a d e q u a te f o r g ro w th a s well. M o r e a c c u r a t e e s t i m a t e s would r e ­ q u i r e d e t a i l e d i n f o r m a t i o n on th e d i g e s t i v e c a p a b i l i t i e s of t h e m i n k beyond that c u rre n tly available. S o m e i n d i c a t i o n of t h e s u c c e s s of the c u r r e n t d r y r a t i o n s is a l s o s u p p lie d by the f a c t th at, during the e x p e r im e n t a l p e r io d s cov­ e r i n g t w o y e a r s , t h e r e w a s a l m o s t a c o m p l e t e l a c k of m o r t a l i t y f r o m nutritional cau ses. N o n e of th e s o - c a l l e d " n u t r i t i o n a l d i s e a s e s " w hich plague c o m m e r c i a l r a n c h e r s ap p ea re d . F o r e x a m p l e , o n ly o n e a n i m a l d i e d a s a r e s u l t of a u r i n a r y c a l c u l u s ; no l o s s e s w e r e incurred from "yellow f a t" (a c o n d i t i o n a s c r i b e d to th e f e e d i n g of r a n c i d o r h i g h l y u n s a t u r a t e d f a t s i n th e die t); a n d " w e t b e l l y " (in­ c o n t i n e n c e ) w a s o b s e r v e d o n l y i n f r e q u e n t l y a n d f o r o n ly s h o r t p e ­ riods. Yet in c o m m e r c i a l o p e ra tio n s th e se t h r e e conditions cause e x p e n s i v e l o s s e s a n n u a l l y (9). I n a d d i t i o n , i n d i c a t i o n s of v i t a m i n a n d / o r m i n e r a l d e f i c i e n c i e s o t h e r t h a n the p o s s i b l e m u l t i p l e B v i t a m i n d e f i c i e n c y s u g g e s t e d i n t h e c a s e of r a t i o n F ( 1 9 5 4 - 155) w ere not observed. 79 M a n a g e m en t p ro b le m s have also been m inim al. T h e o nl y s e r i o u s p r o b l e m h a s b e e n t h a t of s u p p l y i n g a d e q u a t e w a t e r to m i n k re c e iv in g d ry ra tio n s during fre e z in g w eath er. This has b e e n solved b y t h e u s e of t h e a u t o m a t i c w a t e r i n g s y s t e m d e s c r i b e d e a r l i e r . F o r c u r r e n t d r y r a t i o n s ( e . g . , r a t i o n 5 5 - 6 ) the i n g r e d i e n t c o s t i s a b o u t e i g h t to n i n e c e n t s a p o u n d . The only a d d itio n a l c o s t b e f o r e t h e r a t i o n c o u l d b e f e d w o u l d b e on e f o r m i x i n g , p e l l e t i n g , and transportation. T h i s w o u l d b e a p p r o x i m a t e l y o n e to two c e n t s a pound (including b a g s). In g red ien t c o sts fo r a typical ran ch -ty p e n w e t M r a t i o n w o u l d r u n f r o m f i v e to e i g h t c e n t s a p o u n d . To t h i s m u s t b e a d d e d b o th r e f r i g e r a t i o n c o s ts and a daily l a b o r c h a rg e f o r t h e m i x i n g of t h e r a t i o n . T h u s , a t t h e t i m e of f e e d i n g , th e two t y p e s of r a t i o n s a r e r o u g h l y e q u a l i n p r i c e . T a k i n g i n t o c o n s i d e r a t i o n the f a c t t h a t a t l e a s t t w i c e a s m u c h of th e " w e t " r a t i o n m u s t b e f e d p e r m i n k p e r d a y s u g g e s t s t h a t t h e p r o p e r u s e of d r y r a t i o n s d u r i n g t h e l a t e g r o w t h a n d m a i n t e n a n c e p e r i o d s w o u l d r e s u l t i n a s a v i n g on f e e d c o s t s f o r the a v e r a g e r a n c h e r . F o r e x a m p l e , f e e d c o s t p e r d a y f o r a m i n k c o n s u m i n g 100 g r a m s of a d r y r a t i o n c o s t i n g e i g h t c e n t s a p o u n d w o u ld be a p p r o x i ­ m a t e l y tw o c e n t s . S u p p l y i n g a n e q u i v a l e n t a m o u n t of d r y m a t t e r v i a a " w e t 11 r a t i o n w o u l d r e q u i r e 300 g r a m s of f e e d . Feed cost 80 p e r d a y f o r a m i n k c o n s u m i n g 300 g r a m s of a " w e t " ra tio n costing s ix c e n ts a pound would be about fo u r c e n ts, T h e i n i t i a l p r o b l e m h a s b e e n to f i n d a r a t i o n w h i c h w ou ld su p p o rt ad eq u ately late grow th and m aintenance. The r a t i o n s a s f o r m u l a t e d w e r e n o t d e s i g n e d to b e c r i t i c a l b u t r a t h e r to i n s u r e s u p p l y of a l l of t h e e s s e n t i a l n u t r i e n t s i n a b u n d a n c e . As such they do n o t i n d i c a t e m i n i m a l l e v e l s , a n d i t s e e m s p r o b a b l e t h a t t h e y do n o t su p p ly o p tim a l l e v e l s n o r sh o u ld the le v e ls su pplied b e i n t e r ­ p r e te d a s indicating such. F u r t h e r s t u d y w il l b e n e e d e d b e f o r e specific n u trie n t le v els can be established. P r o b a b l e a r e a s of g r e a t e s t v a l u e i n t h i s r e s p e c t w o u l d b e i n v e s t i g a t i o n of t h e r e q u i r e m e n t s of t h e m i n k f o r s p e c i f i c a m i n o a c i d s , s t u d i e s of t h e o p t i m u m f a t l e v e l s f o r d r y r a t i o n s , a n d s t u d i e s of s p e c i f i c v i t a m i n a n d m i n e r a l r e q u i r e m e n t s of m i n k f e d d r y r a t i o n s . S t u d i e s in . b a s i c p h y s i o l o g y , r e l a t i n g p a r t i c u l a r l y to the f u n c t i o n i n g o f t h e d i g e s t i v e t r a c t of t h e m i n k , m i g h t a l s o l e a d to f u t u r e s i m p l i ­ f i c a t i o n of t h e e x i s t i n g d r y r a t i o n s . S U M M A R Y AND C O N C L U S IO N S E x p e r i m e n t a l feeding t r i a l s , using n a tu ra l d ark m ink, w ere conducted over a tw o -y e a r period. T h e p u r p o s e of the s t u d y w a s t h e d e v e l o p m e n t of d r y r a t i o n s w h i c h w o u l d a l l o w n o r m a l p e r f o r m ­ a n c e d u rin g the la te g ro w th , m a in te n a n c e , and r e p r o d u c tiv e p e rio d s ( A u g u s t 1 t o M a y 1). A t o t a l of 380 m i n k w e r e u s e d i n t h e s e t r i a l s ; n i n e g r o u p s of 20 a d u l t a n d k i t m i n k d u r i n g t h e 1 9 5 4 - 5 5 t r i a l s , a n d t e n g r o u p s o f 20 a d u l t a n d k i t m i n k d u r i n g t h e 1 9 5 5 - 5 6 t r i a l s . T h e f o l l o w i n g c o n c l u s i o n s a r e b a s e d o n th e m a t e r i a l p r e s e n t e d h e r e i n , a n d a r e , of c o u r s e , a p p l i c a b l e o n l y to t h e e x p e r i m e n t a l a n i ­ m a l s u s e d a n d u n d e r the e x p e r im e n t a l conditions which p r e v a ile d a t t h e t i m e of t h i s s t u d y . 1. T h e d r y r a t i o n s u s e d .i n t h e 1955-56 t r i a l s w e re s a t i s ­ f a c t o r y . d u r i n g t h e p e r i o d of l a t e g r o w t h a n d m a i n t e n a n c e ; i . e . , f r o m A u g u s t 1 to M a r c h 1. 2. E v id e n c e w as p r e s e n t e d which showed that d ry ra tio n s w e r e a d e q u a te f o r u s e d u rin g b r e e d in g and g e s ta tio n , thus extending t h e u s e f u l p e r i o d f o r s u c h r a t i o n s to a p p r o x i m a t e l y M a y 1. 3. I n c r e a s i n g t h e e n e r g y l e v e l of th e d r y r a t i o n s by th e i n ­ c l u s i o n of f a t i n t h e f o r m of r e f i n e d c o t t o n s e e d o il g a v e b e n e f i c i a l 81 82 r e s u l t s , and s u g g e s ts th a t en erg y m ight have b e en a lim iting fa c to r in p re v io u s d ry ra tio n s . 4. A v a i l a b i l i t y of p r o t e i n f r o m d r i e d s o u r c e s w a s n o t a l i m ­ iting f a c t o r . 5. The v ita m in and m i n e r a l c o n c e n tr a te s u sed (other than V itam ins E and 6. d i d n o t a p p e a r to b e n e c e s s a r y . T h e u s e of a n t i b i o t i c s i n a d r y r a t i o n g a v e b e n e f i c i a l r e s u l t s d u r i n g l a t e g r o w t h a n d m a i n t e n a n c e , b u t , a t the l e v e l s u s e d (2. 4 g r a m s of p e n i c i l l i n p e r ton; 14 g r a m s of a u r e o m y c i n p e r to n ) , a p p e a r e d to h a v e a n i n h i b i t o r y e f f e c t o n r e p r o d u c t i o n . 7. No d iffe re n c e s w e re noted b e t w e e n th e two t y p e s of dried y e a s t (b r e w e r s and to ru la ) studied, e ith e r in c o m p le x or sim plified t y p e s of d r y r a t i o n s . Singly o r i n c o m b in a tio n they w e r e well a c ­ c e p te d by the m ink. 8. N R C a l l o w a n c e s a s p u b l i s h e d a p p e a r e d to b e d i r e c t l y a p ­ p lic a b le f o r u se w ith d ry r a tio n s when allow ance was m a d e f o r the l o w e r d i g e s t i b i l i t y of d r y r a t i o n s . 9. T h e n e e d f o r a n d s u g g e s t i o n s p e r t i n e n t to f u r t h e r s t u d y w e r e p o in te d out. L IT E R A T U R E CITED 1. A g ric u ltu ra l S tatistics, ington. '1 9 5 4 . 2. Anonymous. '54 f a c t s and f ig u r e s . 12-13. 1955. 3. B a s s e t t , C. F . , J . K. L o o s l i , a n d F . W i l k e . The V itam in A r e ­ q u i r e m e n t f o r g r o w t h of f o x e s a n d m i n k s a s i n f l u e n c e d by a sc o rb ic acid and potatoes. J. N u t r i t i o n . 35:62963 8. 1948. 4. 5. 1954. U. S. D e p t , of A g r i c u l t u r e . Am. F u r B reeder. W ash­ 28(9): B a s s e t t , C. F . P r a c t i c a l e c o n o m ie s in feeding m in k k its. N at. F u r N ew s. 12 :1 6. 1949. B a s s e t t , C. F . , L . E . H a r r i s , a n d C. F , W i l k e . E f f e c t of v a r i ­ o u s l e v e l s of c a l c i u m , p h o s p h o r u s a n d V i t a m i n D i n t a k e on bone grow th. II. M i n k s . J. N u tritio n . 44:433-442. 1951. 6 . B e r n a r d , R . , S. E . S m i t h , a n d L . A. M a y n a r d . D i g e s t i o n of c e r e a l s b y m i n k a n d f o x e s w i t h s p e c i a l r e f e r e n c e to s ta r c h and crude fiber. C o rn e ll Vet. 32:29-36. 1942. 7. B o w n e ss, E. R . H ow to p r o d u c e q u a l i t y f u r a n d g o o d s i z e i n m ink. B l a c k F o x M a g . a n d M od . M i n k B r e e d e r . 38(6): 28. 19 5 4 a . 8. B o w n e s s, E. R. 9. G o r h a m , J . R . , a n d H. J . G r i f f i t h s . D i s e a s e s a n d P a r a s i t e s of M inks. U. S. D e p t , of A g r . F a r m e r ' s B u l l e t i n No. 2050. 1952. 10. G r e e n , R . G . , W. E . C a r l s o n , a n d C. A. E v a n s . A d e f i c i e n c y d i s e a s e i n f o x e s p r o d u c e d b y f e e d i n g f i s h . B^ a v i t a m i n ­ o s i s a n a l o g o u s to W e r n i c k e ' s d i s e a s e of m a n . J. N u t r i­ tion. 21:243-256. 1941. P e r s o n a l com m unication. 83 1954b. 84 11. H o d s o n , A. Z . , a n d S. E . S m i t h . E s tim a te d m aintenance energy r e q u i r e m e n t s of f o x e s a n d m i n k s . F u r T r a d e J . of C a n ­ ada. 19(6): 12. 1942. 12. H o w e l l , R . E . A n u t r i t i o n a l s t u d y of r a n c h r a i s e d m i n k . Un­ p u b l i s h e d M. S. T h e s i s . M ic h ig a n State C ollege. 1952. 108 n u m b , l e a v e s . 13. How ell, R. 14. K a i n e r , R . A. T h e g r o s s a n a t o m y of t h e d i g e s t i v e s y s t e m the m in k . A m . J . of V e t. R e s . 15:82-97. 1954. E. U npublished data. 1953. of 15. K e l l o g g , C . E . , C. F . B a s s e t t , a n d R. K. E n d e r s . M ink R a i s ­ i n g . U. S. D e p t , of A g r i c u l t u r e . C i r c u l a r 801. 1954. 16. K if e r , P a u l E ., an d P . J . Schaible. D ry diets fo r r a n c h - r a i s e d m i n k . I. Suitability fo r la te grow th and m aintenance. M t c h . A g r . E x p . Sta. Q u a r t . B u i . 37:593-598. 1955a. 17. K ife r, P a u l E . r and P . J. Schaible. D ry diets for r a n c h - r a i s e d m ink. II. E f fe c t on b r e e d in g , w helping, an d e a r ly g ro w th of k i t s . M i c h . A g r . E x p . S ta . Q u a r t . B u i. 3 8 : 1 2 9 - 138. 1 95 5b. 18. K if e r , P a u l E ., and P . J. Schaible. S e c t . IV. N u t r i t i o n a n d Feeding. T h e B l u e B l o o k of F u r F a r m i n g . Editorial S erv ices Company. M ilw aukee. 1956. 19. L a l o r , R . J . , W . L . L e o s c h k e , a n d C. A. E l v e h j e m . in m ink. J. N utrition. 45:183-188. 1951. Yellow fa t 20. L e o s c h k e , W. L . , R . J . L a l o r , a n d C. A. E l v e h j e m . m i n B ^ 2 r e q u i r e m e n t of m i n k . J. N u t r i t i o n . 1953. The V i t a ­ 49:541-548. 21. L o n g , J . B . , a n d J . N. S ha w . C h a s t e k p a r a l y s i s p r o d u c e d in O r e g o n m i n k a n d f o x e s by t h e f e e d i n g of f r e s h f r o z e n s m e l t . N o r t h A m . Vet. 24:234-237. 1943. 22. L o o s l i , J . K . , a n d S. E. S m i t h . N u t r i t i o n a l e x p e r i m e n t s with foxes and m inks. Am. Fur B reeder. 12(7):6. 1940. 85 23. N u trie n t R e q u ire m e n ts fo r D om estic A nim als. VII. N u t r i e n t re q u ire m e n ts fo r foxes and m inks. National R e s e a r c h Council. W ashington. 1954. 24. P a l m e r , L . S. D i e t e t i c s a n d i t s r e l a t i o n to f u r p r o d u c t i o n . and F u r F a r m e r . 1:18. 1928. 25. S c h a e f e r , A. E . , C. K,. W h i t e h a i r , a n d C. A. E l v e h j e m . 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N utri­ t i o n a l d e f i c i e n c i e s i n m i n k w i t h s p e c i a l r e f e r e n c e to h e m o r r h a g i c g a s t r o e n t e r i t i s , " y e llo w f a t ," and a n e m ia . J. A m . Yet. Med. A s s o c . 1 15(868):54-58. 19 4 9. 35. W o o d , A. J . T i m e of p a s s a g e of f o o d i n m i n k . M ag. a n d Mod. Mink B r e e d e r . 3 8 ( 9 ) :1 2 . Black Fox 1956.