PS-III-4

GENETICS OF RESISTANCE TO MASTITIS

Genetica de la resistencia a la mastitis

ROBERT H. MILLER*

UNITED STATES

M a s t i t i s is t e c h n i c a l l y d e f i n e d as a n i n f l a m m a t i o n of the m a m m a r y g l a n d . A s a p r a c t i c a l m a t t e r , it is e x p e c t e d t h a t c a u s a t i o n is b a c t e r i a l i n f e c t i o n of the g l a n d . A d d i t i o n a l l y , a s u b c l i n i c a l f o r m of m a s t i t i s is w i d e s p r e a d , in w h i c h i n f l a m m a t i o n is n o t o b v i o u s .

M a s t i t i s is a p r o b l e m in l i v e s t o c k o t h e r t h a n d a i r y c o w s b u t i n f o r m a t i o n on its e x t e n t in b e e f c o w s , s h e e p a n d p i g s is s c a n t . T a b l e 1 g i v e s r o u g h e s t i m a t e s of l o s s e s to t h e U . S . d a i r y i n d u s t r y , t o t a l l i n g $2 b i l l i o n a n n u a l l y . L o s s of m i l k d u e to d a m a g e d s e c r e t o r y t i s s u e is the m a j o r e c o n o m i c e f f e c t . O t h e r i m p o r t a n t l o s s e s a r e c o w s c u l l e d p r e m a t u r e l y , t r e a t m e n t c o s t s , a n d u n u s a b l e m i l k d u e to p r e s e n c e of a n t i b i o t i c s .

M a s t i t i s is c a u s e d by a w i d e v a r i e t y of o r g a n i s m s , e v e n i n c l u d i n g y e a s t s . T h e m i c r o o r g a n i s m s m o s t c o m m o n l y i n v o l v e d are S t r e p t o c o c c u s a g a l a c t i a e , S t a p h y l o c o c c u s a u r e u s , S t r e p t o c o c c u s d y s g a l a c t i a e , a n d S t r e p t o c o c c u s u b e r i s . A l s o o f t e n f o u n d a r e s o - c a l l e d e n v i r o n m e n t a l p a t h o g e n s s u c h as E. c o l i a n d K l e b s i e l l a s p e c i e s . A d d i t i o n a l l y , C o r y n e b a c t e r i u m b o v i s is o f t e n f o u n d , b u t the c o w s e e m s n o t be be u n f a v o r a b l y i m p a c t e d . S o m e p a t h o g e n s r e a d i l y e x i s t o u t s i d e the c o w ( c o l i f o r m ) b u t s o m e do not.

M a s t i t i s is d i f f i c u l t to s t u d y b e c a u s e w h e t h e r a c o w b e c o m e s i n f e c t e d e v i d e n t l y i n v o l v e s a c o m b i n a t i o n of e v e n t s a n d c o n d i t i o n s ; t i m i n g a l s o is i m p o r t a n t . P a t h o g e n s a r e g e n e r a l l y p a s s e d f r o m c o w - t o - c o w , b u t p r e s e n c e of t h e o r g a n i s m is n o t t h e o n l y r e q u i r e m e n t . I n t r i g u i n g l y , i n t r o d u c t i o n of p a t h o g e n s at t e a t e n d is b y n o m e a n s s u f f i c i e n t to i n d u c e i n f e c t i o n w i t h h i g h p r o b a b i l i t y .

F a c t o r s c o n d i t i o n i n g the l i k e l i h o o d of i n f e c t i o n m a y be c a t e g o r i z e d e i t h e r as e n v i r o n m e n t a l or as c o w - r e l a t e d . T h e e n v i r o n m e n t a l f a c t o r s r e l a t e to d e g r e e of e x p o s u r e to p a t h o g e n s , a n d a r e o f t e n a s s o c i a t e d w i t h h e r d m a n a g e m e n t . H e r d m a s t i t i s c o n t r o l r e g i m e is i m p o r t a n t -- s a n i t a t i o n , m i l k i n g m a c h i n e use, t h e r a p y p r a c t i c e s , a n d e x p o s u r e to i n f e c t e d h e r d m a t e s . S e a s o n is a l s o i m p o r t a n t -- i n f e c t i o n is m o r e p r o b a b l e d u r i n g s u m m e r in the U. S. C o w f a c t o r s a r e i n h e r e n t r e s i s t a n c e , a g e , s t a g e of l a c t a t i o n , a n d p h y s i o l o g i c a l s t a t e ( s t r e s s , n u t r i t i o n a l s t a t u s , e t c . ) .

N a t i o n a l s t a t i s t i c s o n m a s t i t i s a r e n o t a v a i l a b l e in t h e U . S . , b u t o n e c a n s t a t e t h a t the d i s e a s e is w i d e s p r e a d . F r e q u e n c y d e p e n d s o n t h e m e a s u r e a n d l e n g t h of t i m e a c o w is m o n i t o r e d . In a

* M i l k S e c r e t i o n and M a s t i t i s L a b o r a t o r y , A S I , U S D A , ARS, B e l t s v i l l e , M D 2 0 7 0 5 ( U . S . A . ) .

186

B r i t i s h s u r v e y of 501 h e r d s ( h e r d s w e r e s a m p l e d o n l y o n c e ) m a j o r p a t h o g e n s w e r e r e c o v e r e d in 9 9 . 8 % of h e r d s , 32% of c o w s , a n d 14.1% of q u a r t e r s . In o n c e - o n l y v i s i t s to 67 W i s c o n s i n h e r d s , S h o o k and M i l l e r ( 1 9 7 8 ) f o u n d p a t h o g e n s in 14 . 2 % of m i l k s a m p l e s ( p o o l e d u d d e r m i l k ) . In N o r w a y S o l b u (19 7 8 ) r e p o r t e d 1 5 . 6 % o f l a c t a t i o n s w e r e t r e a t e d f o r c l i n i c a l m a s t i t i s . C o m p a r a b l e f i g u r e s f r o m S w e d e n w e r e 7 . 9 6 % a n d 1 1 . 6 5 % in 2 b r e e d s ( P h i l i p s s o n et al., 1 9 8 0 ) . In a s u r v e y of 1 3 , 3 1 3 q u a r t e r s a m p l e s in 61 F i n n i s h h e r d s , L i n d s t r o m et a l . ( 1 9 8 1 ) r e p o r t e d b a c t e r i a l r e c o v e r y in 7.7% of s a m p l e s . O v e r 6 m o n t h s 2 3 . 6 % of c o w s w e r e i n f e c t e d . In a s u r v e y of 29 h e r d s in S w e d e n , B r o l u n d ( 1 9 8 1 ) c l a s s i f i e d 4 4 . 6 % o f m i l k s a m p l e s as i n f e c t e d , a n d 4 0 . 3 % as " l a t e n t " i n f e c t i o n s . In g e n e r a l , if o n e f o l l o w s a c o w o v e r a l i f e t i m e , f e w c o w s w i l l fail, to s h o w at l e a s t on e c l i n i c a l e p i s o d e .

A c o m p l i c a t i n g f a c t o r is t h a t c o w s b e c o m e m o r e s u s c e p t i b l e w i t h age. F r e q u e n c y of c l i n i c a l m a s t i t i s is at l e a s t t w i c e as g r e a t in m a t u r e c o w s as in 1st l a c t a t i o n s . D e t e c t i o n of u d d e r i n f e c t i o n is r a r e in h e i f e r s b e f o r e f i r s t c a l v i n g .

C u r r e n t m e t h o d s of m a s t i t i s c o n t r o l in t h e U.S. a r e b o t h s a n i t a t i o n a n d t h e r a p y . D a i r y m e n a r e r e c o m m e n d e d to s a n i t i z e m i l k i n g e q u i p m e n t a f t e r e a c h m i l k i n g a n d to d i p e a c h c o w ' s t e a t s in a d i s i n f e c t a n t s o l u t i o n a f t e r m i l k i n g . A n t i b i o t i c t h e r a p y is w i d e s p r e a d , e s p e c i a l l y in the U.S. w h e r e d a i r y m e n c a n e a s i l y o b t a i n a n t i b i o t i c s . It is r e c o m m e n d e d t h a t c o w s w i t h c u r r e n t or r e c e n t c l i n i c a l m a s t i t i s be t r e a t e d w i t h a n t i b i o t i c at t h e t i m e of d r y i n g off. In s o m e a r e a s d a i r y m e n a p p l y a n t i b i o t i c to a l l c o w s as t h e y go dr y. T h e l a s t r e s o r t of c o n t r o l is to c u l l i n f e c t e d c o w s (as m u s t o f t e n be d o n e s i n c e c e r t a i n o r g a n i s m s c a n n o t b e o v e r c o m e by a n t i b i o t i c s ) . A n o t h e r f i e l d p r o g r a m is the m o n t h l y c o u n t i n g of s o m a t i c c e l l c o n c e n t r a t i o n of p o o l e d u d d e r m i l k of i n d i v i d u a l cows.

W h i l e m a n y d a i r y m e n r e d u c e d i s e a s e f r e q u e n c y to a l o w l e v e l by t h e s e p r a c t i c e s , I a m n o t a w a r e of a n y d e f i n i t i v e r e p o r t s of r a p i d l y d e c l i n i n g m a s t i t i s r a t e s in n a t i o n a l p o p u l a t i o n s . T h e r e are a d d i t i o n a l d r a w b a c k s to t h e s e c o n t r o l m e t h o d s : (1) m i l ks u p p l i e s c a n b e c o n t a m i n a t e d b y r e s i d u e s (2) o v e r - u s e of a n t i b i o t i c s m a y l e a d to r e s i s t a n t s t r a i n s ( c u r r e n t c u r e r a t e s are g e n e r a l l y n o t v e r y h i g h ) (3) f a r m e r s m u s t c o n s t a n t l y r e p e a t r o u t i n e a c t i o n s .

I m m u n i z a t i o n a g a i n s t m a s t i t i s h a s p r o v e d to be a n i n t r a c t a b l e p r o b l e m , a l t h o u g h i m m u n e r e s p o n s e is s u r e l y an i m p o r t a n t d e f e n s e m e c h a n i s m . O n e r e a s o n is the w i d e v a r i e t y o f c a u s a t i v e o r g a n i s m s . S u c c e s s f u l i m m u n i z a t i o n a g a i n s t o n e s p e c i e s is n o t l i k e l y to be r e w a r d i n g , e x c e p t f o r s p e c i e s u n r e s p o n s i v e to a n t i b i o t i c s . T h e r e is on e v i e w t h a t s a y s if one t y p e of o r g a n i s m is r e m o v e d in a s u s c e p t i b l e co w, it w i l l be r e p l a c e d b y a n o t h e r .

T h e s e f a c t o r s s u g g e s t the p o s s i b i l i t y a n d v a l u e of g e n e t i c c o n t r o l . H o w e v e r , s e a r c h f o r b e t t e r c o n t r o l m e a s u r e s s h o u l d r e c e i v e m a j o r a t t e n t i o n ; a p r o m i s i n g d e v i c e is n o w b e i n g e v a l u a t e d at B e l t s v i l l e ( P a a p e et a l ., 1981 ) .

187

T a b l e 1. T o t a l A n n u a l L o s s e s D u e to M a s t i t i s in U.S . A .

S o u r c eL o s s e s

( M i l l i o n s )

D e c r e a s e d M i l k P r o d u c t i o n $ 1 , 3 8 6D i s c a r d e d M i l k 220V e t e r i n a r y C o s t s 34D r u g C o s t s 65I n c r e a s e d L a b o r 39D e c r e a s e d S a l e V a l u e of Cows 97I n c r e a s e d R e p l a c e m e n t Co s t s 159

T O T A L $ 2 , 0 0 0

T a b l e 2. H e r i t a b i l i t y E s t i m a t e s for B a c t e r i o l o g i c a l Tes t s .

TestS o u r c e E s t i m a t e

B a c t e r i o l o g i c a l

M e a s u r e

S c h m i d t § V a n V l e c k .20 No. q u a r t e r s w i t h S. ag.■ It .10 No. q u a r t e r s w i t h o t h e r p a t h o g e n s .

1! .05 No. q u a r t e r s w i t h all p a t h o g e n s .

W i l t o n et a l . - .01 S. ag. 1st l a c t a t i o n .II .02 5. ag. 2nd l a c t a t i o n .II .00 S. ag. 3 r d l a c t a t i o n .

N o n - 5. ag. 1st l a c t a t i o n .ft .01If .01 N o n 5. ag. 2nd l a c t a t i o n .II .05 N o n 5. ag. 3rd l a c t a t i o n .II .00 No. q u a r t e r s all p a t h o g e n s ,

1st l a c t a t i o n .II .05 No. q u a r t e r s all p a t h o g e n s ,

2nd l a c t a t i o n .II . 11 No. q u a r t e r s all p a t h o g e n s ,

3 r d l a c t a t i o n .Y o u n g et a l . .18 S c o r e b a s e d on n a t u r e of

p a t h o g e n .

188

D e f e n s e M e c h a n i s m s

If c o w s d i f f e r in t h e i r a b i l i t y to r e s i s t i n f e c t i o n , t h e s e d i f f e r e n c e s m u s t t r a c e to o n e or m o r e d e f e n s e m e c h a n i s m s . T e a t d e f e n s e s are : (1) t e a t s p h i n c t e r ( m u s c u l a t u r e at t e a t o r i f i c e w h i c h e x c l u d e s o r g a n i s m e n t r y ) (2) t e a t c a n a l l i n i n g ( k e r a t i n m a t e r i a l w i t h a n t i - b a c t e r i a l p r o p e r t i e s ) . O n c e the p a t h o g e n g a i n s e n t r y to t h e m a m m a r y g l a n d , it b e c o m e s s u b j e c t to p h a g o c y t o s i s by p o l y m o r p h o n u c l e a r l e u k o c y t e s (PMN). F i n a l l y , b a c t e r i a w i t h i n the g l a n d s t i m u l a t e v a r i o u s c e l l - m e d i a t e d (CMI) a n d h u m o r a l i m m u n e r e s p o n s e s .

L i t t l e is k n o w n of t h e i n h e r i t a n c e of t h e s e m e c h a n i s m s . S t a v i k o v a a n d L o j d a ( 1 9 5 7 ) r e p o r t e d g e n e t i c v a r i a t i o n in the c o m p o s i t i o n of t e a t c a n a l k e r a t i n . P a a p e et a l . ( 1 9 7 8 ) r e p o r t e d s u b s t a n t i a l c o w d i f f e r e n c e s in the a b i l i t y of t h e i r m i l k to s u p p o r t p h a g o c y t o s i s . U n f o r t u n a t e l y , b a s i c k n o w l e d g e of g e n e t i c a n d o t h e r a s p e c t s of i m m u n e r e s p o n s e a g a i n s t m a s t i t i s is s c a n t . F r o m r e s u l t s w i t h l a b o r a t o r y m a m m a l s , w e k n o w t h a t q u a l i t a t i v e a n d q u a n t i t a t i v e a s p e c t s of b o t h C M I a n d h o m o r a l i m m u n e r e s p o n s e a r e u n d e r g e n e t i c c o n t r o l . B h a t i n a n d G a n g u l i ( 1 9 7 5 ) r e p o r t e d t h a t v a r i o u s b r e e d s a n d t h e i r c r o s s e s d i d n o t d i f f e r in b l o o d c o n c e n t r a t i o n s of the v a r i o u s i m m u n o g l o b u l i n (Ig) c l a s s e s . Lie ( 1 9 7 8 ) r e p o r t e d h e r i t a b i l i t i e s of .26 and .54 for Ig l e v e l s in b o v i n e b l o o d .

A b a s i c q u a n d a r y in s t u d y of g e n e t i c r e s i s t a n c e is t h a t the a n i m a l p o s s e s s e s a c e r t a i n i n h e r e n t a b i l i t y to r e s i s t i n f e c t i o n b e f o r e e x p o s u r e to t h e p a t h o g e n . O n e c a n e s t a b l i s h as a g o a l the a b i l i t y to d e t e c t or to m e a s u r e this i n h e r e n t r e s i s t a n c e c a p a b i l i t y b e f o r e e x p o s u r e . T h i s is a n o t h e r w a y to s a y t h a t w e w o u l d l i k e to k n o w the g e n o t y p e f o r r e s i s t a n c e (or the g e n o t y p e s f o r the v a r i o u s r e s i s t a n c e m e c h a n i s m s ) .

T h e l i t e r a t u r e c o n t a i n s n u m e r o u s r e p o r t s of i n v e s t i g a t i o n s of " m a r k e r s " of r e s i s t a n c e ( e n z y m e s , u s u a l l y ) , b u t w e a r e far a w a y f r o m d e t e c t i n g r e s i s t a n c e c a p a b i l i t y . In p r a c t i c e , we f a l l b a c k u p o n r e t r o s p e c t i v e s t u d i e s of d a t a in w h i c h c e r t a i n a n i m a l s b e c a m e i n f e c t e d a n d o t h e r s d i d not. U s u a l l y we h a v e l i t t l e or no idea of w h a t r i s k or e x p o s u r e an a n i m a l e x p e r i e n c e d .

It is t h e o r e t i c a l l y p o s s i b l e to e s t i m a t e g e n e t i c d i f f e r e n c e s a m o n g c o w s in a b i l i t y to r e s i s t by e x p e r i m e n t a l l y s u b j e c t i n g e a c h a n i m a l to a u n i f o r m a p p l i c a t i o n of l i v e p a t h o g e n s i n t o the u d d e r , a n d o b s e v i n g w h e t h e r i n f e c t i o n o c c u r s . In d a i r y c a t t l e w h e r e g e n e t i c i m p r o v e m e n t is m a i n l y t h r o u g h sire s e l e c t i o n , o n e w o u l d h a v e to a s s e m b l e p r o g e n y of m a n y b u l l s in o n e l o c a t i o n to c o n d u c t s u c h an e v a l u a t i o n . T h e r e p o r t of G r o o t e n h u i s J[1976) is the o n l y k n o w n a t t e m p t of t h i s k i n d ( o n l y 2 p r o g e n y g r o u p s ) .

U l t i m a t e l y , o n e m u s t s e l e c t a m e a s u r e of m a s t i t i s w h i c h c a n be u s e d in a m i l k r e c o r d i n g s y s t e m , p r e f e r a b l y b a s e d o n a n a l y s i s of m i l k s a m p l e s . F r o m s u c h d e t e r m i n a t i o n s o n e m u s t j u d g e w h e t h e r the c o w w a s i n f e c t e d or n o t , k n o w i n g l i t t l e or n o t h i n g a b o u t e x p o s u r e to p a t h o g e n s .

189

A l t e r n a t i v e M e a s u r e s of M a s t i t i s

T h e m o s t d e s i r a b l e f i e l d m e a s u r e of m a s t i t i s is the t e s t i n g ot a s e p t i c a l l y c o l l e c t e d m i l k s a m p l e s for b a c t e r i a l p r e s e n c e .I d e a l l y , t h i s w o u l d be b y q u a r t e r , s i n c e e a c h q u a r t e r m a y h a v e a d i f f e r e n t s t a t u s ( a l t h o u g h m o s t i n f e c t e d c o w s h a v e o n l y o n e q u a r t e r a f f e c t e d ) . T h e d r a w b a c k to b a c t e r i o l o g i c d e t e r m i n a t i o n s is that c o l l e c t i n g s a m p l e s for b a c t e r i a l a n a l y s i s b y f a r m e r s or m i l k r e c o r d i n g p e r s o n n e l is n o t v e r y f e a s i b l e . In c o m m o n w i t h a n y t e s t l i n k e d to m i l k r e c o r d i n g , m o s t i n f e c t i o n s a r e l i k e l y to be m i s s e d b y o n c e - m o n t h l y s a m p l i n g , s i n c e an i n f e c t i o n m a y a r i s e a n d t h e n be o v e r c o m e w i t h i n a 3 0 - d a y i n t e r v a l .

L a r g e s t u d i e s of b a c t e r i o l o g y a r e r a r e ( a l l c o w s m u s t be s a m p l e d , n o t j u s t s u s p e c t s ) . T a b l e 2 g i v e s r e s u l t s f r o m t h r e e s t u d i e s ; a v e r a g e of t h e s e p o o l e d e s t i m a t e s f r o m t h e s e r e p o r t s is a b o u t 0 . 1 0 , w i t h a r a n g e of -.01 to .20. T h u s , the h e r i t a b i l i t y is le ss t h a n h a l f t h a t of l a c t a t i o n m i l k y i e l d (.20 to .25).

T h e s e c o n d m o s t d e s i r a b l e c r i t e r i o n of i n f e c t i o n is the r e c o r d i n g of e a c h c l i n i c a l c a s e ( t r e a t m e n t ) of m a s t i t i s . T a b l e 3 g i v e s h e r i t a b i l i t i e s b a s e d on c l i n i c a l d a t a f r o m 12 r e p o r t s . T h e r a n g e of e s t i m a t e s is f r o m -.03 to .50; t a k i n g o n e c o m b i n e d e s t i m a t e f r o m e a c h s t u d y , t h e a v e r a g e is .12. T h e r e f o r e , h e r i t a b i l i t i e s of b a c t e r i o l o g i c a l a n d c l i n i c a l c r i t e r i a of m a s t i t i s a r e q u i t e s i m i l a r . O n e m i g h t h a v e e x p e c t e d t h a t b a c t e r i o l o g i c a l r e s u l t s w o u l d h a v e a h i g h e r h e r i t a b i l i t y t h a n c l i n i c a l , i n a s m u c h as t h e f o r m e r d e t e c t s s u b c l i n i c a l i n f e c t i o n s , w h i c h a r e t h e m a j o r i t y of c a s e s ( G i e s e c k e , 197 9 ) . Y o u n g et al. ( I 9 6 0 ) r e p o r t e d a low (. 29) g e n e t i c c o r r e l a t i o n b e t w e e n c l i n i c a l f r e q u e n c y a n d b a c t e r i o l o g y .

T h e d r a w b a c k to u s i n g a c l i n i c a l m e a s u r e is t h a t it is d i f f i c u l t to g e t f a r m e r s to r o u t i n e l y r e c o r d t r e a t m e n t s , p a r t i c u l a r l y in l a r g e h e r d s . H o w e v e r , t h e s t r u c t u r e o f d i s e a s e c o n t r o l w o r k in some c o u n t r i e s m a k e s t h e r e c o r d i n g of c l i n i c a l m a s t i t i s f e a s i b l e . S o l b u (19 7 8 ) d e s c r i b e d a N o r w e g i a n p r o g r a m in w h i c h v e t e r i n a r i a n s r e c o r d all m a s t i t i s t r e a t m e n t s . R e p o r t s are c o l l e c t e d , c o m p u t e r i z e d a n d b u l l p r o g e n y g r o u p s a r e e v a l u a t e d for f r e q u e n c y of c l i n i c a l m a s t i t i s . It w i l l b e i n t e r e s t i n g to see w h e t h e r t h i s p r o g r a m b r i n g s a b o u t r e d u c t i o n in d i s e a s e f r e q u e n c y t h r o u g h s e l e c t i o n . P e r h a p s s i m i l a r p r o g r a m s c o u l d be i n s t i t u t e d in o t h e r c o u n t r i e s w h e r e o n l y v e t e r i n a r i a n s a d m i n i s t e r a n t i b i o t i c s .

A t h i r d m e a s u r e of m a s t i t i s is s o m a t i c c e l l c o n c e n t r a t i o n (SCC) in m i l k . U s e of SCC (or i n d i r e c t t e s t s ) is g r o w i n g ; in the U.S. m i l k r e c o r d i n g p r o g r a m , s o m e 1.5 m i l l i o n c o w s are n o w t e s t e d for S C C m o n t h l y ( s a m e c o m p o s i t e m i l k s a m p l e u s e d for m i l k c o m p o s i t i o n t e s t s ) . T h e r a t i o n a l e for S C C t e s t i n g is t h a t c e l l c o n c e n t r a t i o n r i s e s m a r k e d l y w i t h the o n s e t of i n f e c t i o n , p a r t i c u l a r l y in the i n f l a m m a t o r y p h a s e . S t a t e m e n t s a b o u t S C C v a l u e s m u s t a l w a y s be c o n t i n g e n t u p o n the c o n d i t i o n s of s a m p l i n g , s i n c e v a r i a t i o n is g r e a t ( l o g t r a n s f o r m a t i o n s are u s u a l l y m a d e ) . N a t z k e et al. ( 1 9 7 2 ) r e p o r t e d t h a t c o m p o s i t e m i l k f r o m c o w s w i t h n o b a c t e r i a p r e s e n t

190

Table 3. Heritability Estimates for Clinical Cases.

Source Estimate Measure UsedO'Bleness et al. .05 (0,1) clinicalAf if i .12 (0,1) clinical--4 lactationsWilton et al. - .03 (0,1) clinical 1st lactation

II .05 " 2nd lactationII .02 " 3rd lactationII .02 No. quarters clinical, 1st

lactationII .11 No. quarters clinical, 2nd

lactationII .00 No. quarters clinical, 3rd

lactationYoung et al . .06 °/o months clinically

affectedRendel § Sundberg

It.04 (0,1) clinical, 1st lactation.19 (0,1) clinical, 2nd lactation" .23 (0,1) clinical, 3rd lactation

Legates § Grinnells .27 (0,1) clinicalGaunya § Mather .07 Lactation number 1st

clinical caseIt .14 (0,1) clinical, 1st 2 lact.

Lush .38 (0,1) clinical (up to 8 yrs)Solbu .03 (0,1) clinicalLindstrom § Syvajarvi .00 Clinical score, 1st lactation

II .03 Clinical score, 1st 2 lact.II .06 Clinical score, 2nd lactationII .02 Clinical score, 3rd lactation

Hibbitt et al. .50 (0,1) clinical, 1st lactationII .07 (0,1) clinical, 2nd lactation

Philipsson et al. .04 (0,1) clinical, SR breedIt .01 (0,1) clinical, SL breed

Table 4. Heritability Estimates for Cell Count Measures.

Source Estimate MeasureAf if i .37 Cell count -- 4th lactationAfifi .14 Cell count -- 1st lactationYoung et al. .38 Mean log cell countRenner 6 Kosmack .26 Log cell count -- 1st lactationDuysings et al. .03 Log cell count -- breed 1Duysings et al. .30 Log cell count -- breed 2Probst et al. .22 CMT scoreAlrawi et al. .37 Coded CMT, test 1, 1st lactationAlrawi et al. .26 Coded CMT, test 9, 1st lactationAlrawi et al. .11 Coded CMT, test 1, 4th lactationAlrawi et al. .25 Coded CMT, test 9, 4th lactationSethar et al. .05 Log somatic cells , 2 yearsSethar et al. .07 Log somatic cells , 3 yearsSethar et al. .08 Log somatic cells , 4 yearsSethar et al. .09 Log somatic cells , 5 yearsSethar et al . .10 Log somatic cells , 5 yearsKing et al. .07 Average CMT, 1st lactationKing et al. .11 Average CMT, 2nd lactationKing et al. .10 Average CMT, 3rd lactationKing et al. .00 Average CMT, 4th lactationKing et al. .14 Average CMT, 5th lactationPhilipsson et al. .13 Log cell count on test day

191

c o n t a i n e d 2 1 4 , 0 0 0 c e l l s / m l . M a n y of t h e s e c e l l s h a v e l o s t t h e i r f u n c t i o n , as t h e y d e t e r i o r a t e in 1-2 d a y s a f t e r l e a v i n g t h e b l o o d . T h i s l e v e l m a y r i s e into the m i l l i o n s w i t h i n f e c t i o n .

T a b l e 4 g i v e s h e r i t a b i l i t y e s t i m a t e s of v a r i o u s c e l l c o u n t m e a s u r e s f r o m n i n e s t u d i e s . E s t i m a t e s w e r e f r o m z e r o to .38, w i t h a n a v e r a g e ( o n e p o o l e d e s t i m a t e p e r s t u d y ) of a b o u t .20. T h i s is n e a r l y t w i c e t h e c o m p a r a b l e r e s u l t s f o r b a c t e r i o l o g i c a l a n d c l i n i c a l m e a s u r e s . B e f o r e c o n c l u d i n g t h a t S C C is the m a s t i t i s t r a i t to u s e in t h e f i e l d , some f u r t h e r e x a m i n a t i o n of the i n t e r p r e t a t i o n of SCC is r e q u i r e d .

C h i e f a m o n g t h e p r o b l e m s of i n t e r p r e t a t i o n is t h a t m a n y f a c t o r s c a u s e S C C f r o m m i l k s a m p l e s to va r y . W h i l e i n f e c t i o n s t a t u s of the g l a n d is a s s u m e d to be of p r i m a r y i m p o r t a n c e , M i l l e r a n d S c h u l t z e ( 1 9 8 1 ) e n u m e r a t e d the f o l l o w i n g a d d i t i o n a l f a c t o r s : (1) v a r i a t i o na m o n g c o w s in t h e i r n o r m a l l e v e l s in t h e a b s e n c e of i n f e c t i o n (2) o r g a n i s m t y p e (3) age of c o w (4) s t a g e of l a c t a t i o n (5) s e a s o n (6) m a n a g e m e n t ( m i l k i n g m a c h i n e s , m i l k i n g p r a c t i c e s , h o u s i n g ) (7) p h y s i o l o g i c a l s t a t e (8) e r r o r s a s s o c i a t e d w i t h c o u n t i n g (9) s a m p l i n g t e c h n i q u e .

A d d i t i o n a l l y , i n t e r p r e t a t i o n of c e l l c o u n t s is h a m p e r e d b y the f a c t t h a t m a n y c e l l t y p e s are i n v o l v e d . T a b l e 5 g i v e s f r e q u e n c i e s of 5 c e l l t y p e s f o u n d in m i l k f r o m u n i n f e c t e d u d d e r s (Lee et al.,1 9 8 0 ) . T h e m a c r o p h a g e s h a v e n o r m a l r o l e s in s e e k i n g out d a m a g e d b o d y t i s s u e d e b r i s a n d f o r e i g n m a t t e r . W h e n i n f e c t i o n o c c u r s , a s h i f t in c e l l t y p e t a k e s p l a c e w i t h P M N ' s i n v o l v e d in p h a g o c y t o s i s m i g r a t i n g f r o m t h e b l o o d d u r i n g t h e i n f l a m m a t o r y p h a s e . T h i s s u g g e s t s a t e s t for c e l l t y p e s m i g h t be m o r e s e n s i t i v e t h a n t o t a l c e l l n u m b e r . M o r e i m p o r t a n t l y , c o n s i d e r a t i o n of c e l l t y p e s a n d t h e i r r o l e s m a k e s it c l e a r that S C C at all t i m e s r e f l e c t s p r e s e n c e of c e l l s a c t i v e in d e f e n s e s ( m a c r o p h a g e s , P M N ) . In s e l e c t i o n o n e p r e s u m a b l y w o u l d aim to l o w e r SCC. H o w e v e r , f r o m t h e s t a n d p o i n t of d e f e n s e , an i n c r e a s e d n u m b e r of t h e p h a g o c y t i c c e l l s is d e s i r a b l e . T h e r e are m a n y r e p o r t s s h o w i n g t h a t h i g h e r c e l l c o u n t d e c r e a s e s r a t e of i n f e c t i o n to s u b s e q u e n t e x p o s u r e ( S c h a l m et a l ., 1971; P o u t r e l a n d L e r o n d e l l e , 1978; S c h a l m et al., 1 9 7 6 ) . T h i s s u g g e s t s o n e m u s t b e v e r y c a r e f u l n o t to d i s c r i m i n a t e a g a i n s t c o w s or p r o g e n i e s w i t h h i g h e r n o r m a l c o u n t s . S i r e s e l e c t i o n is l a r g e l y o n f i r s t l a c t a t i o n s w h e r e m a s t i t i s i n f e c t i o n r a t e is low.

In a d d i t i o n , s t u d i e s s h o w t h a t S C C d i s t r i b u t i o n s of i n f e c t e d a n d u n i n f e c t e d c o w s o v e r l a p . S h o o k a n d M i l l e r ( 1 9 7 8 ) a n d L i n d s t r o m and S y v a j a r v i (19 8 1 ) f o u n d r a t h e r h i g h e r r o r r a t e s in c l a s s i f y i n g s i n g l e m i l k s a m p l e s as i n f e c t e d or u n i n f e c t e d . T h i s is n o t s u r p r i s i n g w h e n one c o n s i d e r s that n u m b e r of q u a r t e r s i n f e c t e d a n d s p e c i e s of o r g a n i s m s p r e s e n t v a r y g r e a t l y a m o n g c o m p o s i t e m i l k s f r o m i n f e c t e d c o w s . S p e c i e s h a v e v a r y i n g i m p a c t s o n SCC.

W h i l e S C C s h o u l d b e v i e w e d c a u t i o u s l y as a n i n d i c a t o r of m a s t i t i s , i n f o r m a t i o n on m i l k r e c o r d e d c o w s m a y h a v e o t h e r us e s . E l e v a t e d c e l l c o u n t s a r e g e n e r a l l y a s s o c i a t e d w i t h p o o r m a n a g e m e n t a n d s t r e s s u p o n the c o w ( G i e s e c k e , 1 9 7 9 ) . T h e r e is g r o w i n g

192

i n d i c a t i o n t h a t e l e v a t e d S C C is a s s o c i a t e d w i t h l o w e r m i l k y i e l d ( r e g a r d l e s s of m a s t i t i s ) , so t h a t c e l l c o u n t s m a y be u s e f u l as m a n a g e m e n t i n d i c a t o r s . V a r i a t i o n in SCC a m o n g q u a r t e r s w o u l d be a m u c h m o r e s e n s i t i v e m a s t i t i s c r i t e r i o n .

S C C is a n a t t r a c t i v e f i e l d t e s t b e c a u s e it is e a s i l y a d d e d to m i l k r e c o r d i n g . H o w e v e r , m a n y o t h e r e l e m e n t s of m i l k m a y be i n d i c a t o r s of m a s t i t i s . In the f o l l o w i n g w e b r i e f l y e n u m e r a t e t h o s e t h a t h a v e r e c e i v e d m o s t a t t e n t i o n . F o r a d d i t i o n a l d e t a i l s , see K i t c h e n ( 1 9 8 1 ) . M i l k L i p i d s : S o m e r e p o r t s i n d i c a t e r e d u c e dt r i g l y c e r i d e p e r c e n t a g e due to i n f e c t i o n , b u t t h i s c a n be o v e r s h a d o w e d b y t h e g r e a t e r r e d u c t i o n in t o t a l m i l k y i e l d . M i l k P r ^ e r n s : T o t a l m i l k p r o t e i n c o n c e n t r a t i o n c h a n g e s l i t t l e d u e toi n f e c t i o n , b u t p r o t e i n s s y n t h e s i z e d in t h e g l a n d d e c r e a s e , w h i l e b l o o d - o r i g i n p r o t e i n s i n c r e a s e . In p a r t i c u l a r , b o v i n e s e r u m a l b u m i n r i s e s m a r k e d l y a f t e r i n f e c t i o n (0.2 to 20 m g / m l ) . H o w e v e r , B S A d e t e r m i n a t i o n is t e d i o u s . L a c t o s e : m a m m a r y g l a n d i n f e c t i o n r e s u l t s in t i s s u e d a m a g e a n d l e s s l a c t o s e b i o s y n t h e s i s . T h i s , in tu r n , i n f l u e n c e s the d r o p in t o t a l v o l u m e of m i l k s e c r e t e d . S o m e r e p o r t s ( R e n n e r , 1 9 8 0 ) s u g g e s t l a c t o s e as a n a l t e r n a t i v e to S C C as a m a s t i t i s i n d i c a t o r . C u r r e n t t e c h n o l o g y p e r m i t s r a p i d a n d e c o n o m i c l a c t o s e a n a l y s i s . I o n i c C o m p o s i t i o n : M a s t i t i s c a u s e si n c r e a s e s in N a a n d C l a n d a d e c r e a s e in K in m i l k ; c h a n g e s in Ca, Mg a n d P a r e s l i g h t . A s s o c i a t e d w i t h t h e s e c h a n g e s is m e a s u r e m e n t of e l e c t r i c a l c o n d u c t i v i t y of m i l k . L i n z e l l a n d P e a k e r ( 1 9 7 5 ) r e p o r t e d t h a t 98% of i n f e c t e d q u a r t e r s c o u l d be d e t e c t e d by c o n t i n u o u s m o n i t o r i n g of c o n d u c t i v i t y . F u t u r e m i l k i n g s y s t e m s m a y p e r m i t a u t o m a t i c d e t e c t i o n of c o n d u c t i v i t y at m i l k i n g time.

E n z y m e C h a n g e sB e c a u s e of t h e s p e c i f i c r o l e s of e n z y m e s , t h e i r m e a s u r e m e n t

o f f e r s p o s s i b i l i t i e s f o r d e t e c t i n g p a t h o l o g i c a l r e s u l t s of m a m m a r y g l a n d i n f e c t i o n . C a t a l a s e : C a t a l a s e m o n i t o r i n g h a s b e e n u s e d tot e s t for m a s t i t i s m i l k for s o m e time, but h a s n o t s u p p l a n t e d S C C as a p r i m a r y t e s t . C o r r e l a t i o n w i t h S C C is 0.7. O x i d a s e s /R e d u c t a s e s : A f e w s t u d i e s h a v e g i v e n m i x e d r e s u l t s as to theu s e f u l n e s s of s u c h e n z y m e s . L a c t a t e D e h y d r o g e n a s e : T h e r e a r el a r g e i n c r e a s e s in L D H a f t e r i n f e c t i o n ^ p r e s u m a b l y d u e in p a r t to

T a b l e 5. T y p e s of C e l l s F o u n d in N o r m a l M i l k .

C e l l T y p e R a n g e ( P e r C e n t )

N e u t r o p h i l s (PMN) 0-11

L y m p h o c y t e s 1 0 - 2 7

M a c r o p h a g e s 6 6 - 6 8

E p i t h e l i a l ( d u c t a l ) 0-7

M i s c e l l a n e o u s 1

193

d a m a g e d u d d e r p a r e n c h y m a a n d d i s i n t e g r a t i o n of l e u k o c y t e s . T h e r e is a s h i f t in i s o e n z y m e p a t t e r n al s o . K i t c h e n ( 1 9 8 1 ) h a s p r o p o s e d L D H m o n i t o r i n g b y " c o w - s i d e " t e s t s . L i p a s e : S t u d i e s o f l i p a s ea c t i v i t y in n o r m a l and m a s t i t i c m i l k s h a v e g i v e n m i x e d r e s u l t s , as h a v e t h o s e of P h o s p h a t a s e s . G l y c o s i d a s e s : K i t c h e n ( 1 9 8 1 )s u g g e s t e d t h a t o n e ( N A G - a s e ) c o u l d be u s e d r o u t i n e l y in m a s t i t i s m o n i t o r i n g , s i n c e it i n c r e a s e s d u r i n g i n f e c t i o n d u e to r e l e a s e of c y t o p l a s m i c m a t e r i a l f r o m d a m a g e d m a m m a r y g l a n d s e c r e t o r y c e l l s .

O t h e r s u b s t a n c e s m e n t i o n e d in t h e l i t e r a t u r e as m a s t i t i s i n d i c a t o r s a r e l a c t o f e r r i n ( S m i t h a n d S c h a n b a c h e r , 1 9 7 6 ) ; l y s o z y m e ( S e n f t et a l ., 1980); a n d l a c t o p e r o x i d a s e ( K o r h o n e n , 1 9 8 0 ) . S e n f t et al. , 1 9 8 0 r e p o r t e d h e r i t a b i l i t i e s of l a c t o f e r r i n a n d l y s o z y m e of .40 a n d .13, r e s p e c t i v e l y .

C o n c l u s ions

W h e t h e r d a i r y c a t t l e s h o u l d be s e l e c t e d f o r i n c r e a s e d m a s t i t i s r e s i s t a n c e is a la r g e a n d c o m p l e x q u e s t i o n . E v i d e n c e is that h e r i t a b i l i t y r a n g e s f r o m 0 . 1 0 to 0 . 2 0 , d e p e n d i n g u p o n the m e a s u r e u s e d . B r e e d d i f f e r e n c e s a l s o a p p e a r to e x i s t ( L i n d s t r o m , 1980; P h i l i p s s o n et al., 1979; R e n d e l a n d S u n d b e r g , 1 9 6 2 ) . T h u s , s o m e g e n e t i c c h a n g e a p p e a r s p o s s i b l e .

M a s t i t i s l o s s e s are g r e a t e n o u g h to j u s t i f y a p r o g r a m that w o u l d d e c r e a s e i n f e c t i o n w i t h o u t r e q u i r i n g l a r g e o u t l a y s or d r a s t i c c h a n g e s in m i l k r e c o r d i n g . A d d i t i o n a l l y , m a s t i t i s is a c h r o n i c d i s e a s e , c o n d i t i o n e d by m a n y f a c t o r s . C u r r e n t c o n t r o l m e t h o d s r e q u i r e c o n s t a n t r e p e t i t i v e a c t i o n s of d a i r y m e n . S o m e m e t h o d s ( a n t i b i o t i c s ) m a y be d e c r e a s i n g in e f f e c t i v e n e s s . It is s o b e r i n g , h o w e v e r , to r e c o g n i z e that g e n e t i c c h a n g e s in the p a t h o g e n s c a n o c c u r f o r m o r e q u i c k l y t h a n in the b o v i n e h o s t . P r o b a b l y w e s h o u l d n o t r e l y t o o h e a v i l y on a n y one c o n t r o l m e a s u r e .

It is n o t c l e a r w h a t is h a p p e n i n g to r e s i s t a n c e a b i l i t y at p r e s e n t . O n a p o p u l a t i o n b a s i s , p r e v a l e n c e of m a s t i t i s d o e s n o t a p p e a r to b e d e c r e a s i n g a n y w h e r e . C u r r e n t g e n e t i c s e l e c t i o n in d a i r y c a t t l e is p r i m a r i l y on l a c t a t i o n m i l k y i e l d . F e a r h a s b e e n e x p r e s s e d t h a t h i g h m i l k y i e l d l o w e r s r e s i s t a n c e a n d that, t h e r e f o r e , m a s t i t i s f r e q u e n c y is i n c r e a s e d d u e to s e l e c t i o n . C o r r e l a t i o n s t u d i e s s u g g e s t o n l y s m a l l r e l a t i o n s h i p s ; t h e s e are s u b j e c t to b i a s due to d e c r e a s e d m i l k y i e l d a f t e r i n f e c t i o n o c c u r s . A s t u d y of m a s t i t i s d i f f e r e n c e s r e s u l t i n g f r o m m i l k s e l e c t i o n i n d i c a t e d no c h a n g e ( M i l l e r et al., 1 9 8 1 ) . O n e m i g h t a s k w h e t h e r n a t u r a l s e l e c t i o n h a s i n c r e a s e d m a s t i t i s r e s i s t a n c e . S p e c i f i c r e s i s t a n c e is n o t l i k e l y to h a v e b e e n a s t r o n g f o r c e . M a s t i t i s is r a r e l y f a t a l , o c c u r s m o s t f r e q u e n t l y in lat e r l a c t a t i o n s , a n d at l e a s t one q u a r t e r w o u l d l i k e l y r e t a i n l a c t a t i o n a l f u n c t i o n .

W e n e e d m u c h m o r e w o r k b e f o r e r a t i o n a l s e l e c t i o n p l a n s c a n be d e v i s e d fo r p r a c t i c a l u s e w h e r e c o m p l e t e c l i n i c a l i n f o r m a t i o n is u n a v a i l a b l e . T h e p r i n c i p a l d i f f i c u l t y is t h e l a c k of a m e a s u r e w h i c h is a s a t i s f a c t o r y i n d i c a t o r of m a s t i t i s a n d a l s o c o n v e n i e n t l y a d a p t e d to f i e l d use.

194

T h e l o g i c a l s o l u t i o n is to f i n d a m e a s u r e w h i c h m e s h e s to the s t r u c t u r e of m i l k r e c o r d i n g . O n e r e a s o n s o m a t i c c e l l c o u n t is a t t r a c t i v e is t h a t it r e q u i r e s o n l y a n o t h e r m a c h i n e a n a l y s i s of m i l k s a m p l e s a l r e a d y a v a i l a b l e in m i l k r e c o r d i n g . W h i l e we n e e d m o r e r e s e a r c h on t h e i n t e r p r e t a t i o n a n d u s e of SCC, its d r a w b a c k s a r e c l e a r : (1) d i s t r i b u t i o n s of i n f e c t e d a n d u n i n f e c t e d c o w so v e r l a p s u b s t a n t i a l l y (2) h i g h e r s o m a t i c c e l l c o n c e n t r a t i o n in c o w s p r e - i n f e c t i o n 'is d e s i r a b l e (3) S C C is a f f e c t e d by m a n y f a c t o r s o t h e r t h a n m a s t i t i s -- n o t a b l y c o w m a n a g e m e n t . S C C m a y be u s e f u l in i d e n t i f y i n g w i t h i n - h e r d m a n a g e m e n t v a r i a t i o n s .

F u t u r e r e s e a r c h s h o u l d be d i r e c t e d t o w a r d d e v e l o p i n g a b a t t e r y of t e s t s w h i c h c a n be c o n d u c t e d on a m a s s b a s i s o n m i l k r e c o r d i n g s a m p l e s . S u c h t e s t s m a y i n c l u d e l a c t o s e , e n z y m e s ( s u c h as LDH,N A G , e t c . ) , as w e l l as SCC. W h i l e g e n e t i c a p p l i c a t i o n s do n o t n e c e s s a r i l y r e q u i r e a c r i t e r i o n of the s a m e p r e c i s i o n as for m a s t i t i s m a n a g e m e n t d e c i s i o n s , w e s h o u l d c o n t i n u e to s e a r c h f o r o n e c r i t e r i o n w h i c h m e e t s b o t h n e e d s .

W e h a v e s a i d l i t t l e of the g e n e t i c s o f i m m u n e r e s p o n s e r e l a t i v e to b o v i n e m a s t i t i s , s i m p l y b e c a u s e n o t h i n g is k n o w n . P r e s e n t l y , i m m u n o l o g i c a l w o r k m u s t f o c u s on s t u d i e s of b a s i c p r o c e s s e s i n v o l v e d in i m m u n e r e s p o n s e to m a s t i t i s , as for e x a m p l e r e l a t i v e i m p o r t a n c e o f h o r m o n a l a n d c e l l - m e d i a t e d i m m u n i t y ; r o l e s of the d i f f e r e n t c l a s s e s of i m m u n o g l o b u l i n s ; a n t i g e n i c d i f f e r e n c e s a m o n g p a t h o g e n i c s p e c i e s , etc. O n c e t h e s e q u e s t i o n s a r e c l a r i f i e d , o n e m i g h t b e g i n to i d e n t i f y g e n o t y p e s w i t h d i f f e r i n g i m m u n e r e s p o n s e c o m p e t e n c e fo r r e s i s t a n c e to m a s t i t i s . D o u b t l e s s we w i l l f i n d t h a t d a i r y c a t t l e h a v e s i m i l a r p a t t e r n s of g e n e t i c c o n t r o l of i m m u n e r e s p o n s i v e n e s s as t h o s e i d e n t i f i e d in o t h e r s p e c i e s . O n e w o u l d r e q u i r e s i m p l e t e s t s ( " G e n e t i c M a r k e r s " ) to i d e n t i f y g e n o t y p e s , s i n c e b r e e d i n g e x p e r i m e n t s w i l l n o t be v e r y p r a c t i c a l . P e r h a p s the b u r g e o n i n g m o n o c l o n a l a n t i b o d y t e c h n o l o g y w i l l p r o v i d e s u c h t e s t s .

S U M M A R Y

M a s t i t i s is t h e m o s t e c o n o m i c a l l y s e r i o u s d i s e a s e in m o d e r n d a i r y c a t t l e p r o d u c t i o n , c a u s i n g an e s t i m a t e d $ 2 , 0 0 0 , 0 0 0 , 0 0 0 a n n u a l l o s s in t h e U.S . H e r i t a b i l i t y e s t i m a t e s r a n g e f r o m .10 to .20 for a l t e r n a t i v e m e a s u r e s of m a s t i t i s , i n d i c a t i n g t h e o r e t i c a l p o s s i b i l i t i e s to s e l e c t for i n c r e a s e d r e s i s t a n c e . A m a j o r o b s t a c l e is l a c k of a f i e l d c r i t e r i o n of m a s t i t i s w h i c h is a l s o of s a t i s f a c t o r y a c c u r a c y f o r , g e n e r a l u s e in m a s t i t i s c o n t r o l .

RESUMELa m a m m i t e e s t la m a l a d i e la p l u s c o u t e u s e d a n s la p r o d u c t i o n

l a i t i ^ r e . C e t t e m a l a d i e a b o u t i t a un d e b i t de d e u x t r i l l i o n d o l l a r s t o u s les ans A u x f c t a t s - U n i s . L ' e s t i m a t i o n d e 1 ' h e r i t a b i l i t e p a r c o u r t de .10 a .20 p o u r les m e s u r e s a l t e r n a t i v e s de la m a m m i t e et e l l e i n d i q u e u n e p o s s i b i l i t e t h e o r i q u e c h o i s i r p o u r la r e s i s t a n c e a u g m e n t e e . U n e o b s t a c l e m a j e u r e e s t la m a n q u e d ' u n e d i a g n o s e de la m a m m i t e q u i p e u t e t r e u t i l i s S e s u r la f e r m e , et a u s s i une d i a g n o s e , q u i e s t d ' u n e p r e c i s i o n s a t i s f a i s a n t e p o u r l ' u s a g e g e n e r a l d a n s la r e d u c t i o n de la m a m m i t e .

195

Ref e r e n c e s

Afifi, Y. A. 1967. Ge n e t i c a l and some e n v i r o n m e n t a l influences a f f e c t i n g the level of leukocyte counts in the m i l k of cows. M e d e d e l i n g e n L a n d b o u w h o g e s c h o o l , Wagen i n g e n , N e t h e r l a n d s , 67-11.

A l r a w i , A. A., E. J. Poliak, and R. C. Laben. 1979. Genetic a n a l y s i s of C a l i f o r n i a M a s t i t i s Test records. J. D a i r y Sci. 62: 1115 -1 12 4.

Bhatin, K. L. and N. C. Ganguli. 1975. I m m u n o g l o b u l i n s of blo o d and m i l k of Ind i a n pure and c r o ssbred cattle. Ind. J. Da i r y Sci.28: 297-299.

Br olund, L. 1981. The dia g n o s t i c value of cell c o u n t s in b o v i n e milk. Proc. EAAP, 32nd A n n u a l Meeting, Zagreb, Y u g o s l a v i a .

D u y sings, P. M. J., L. J. H o o ghiemstra, and R. D. Politiek. 1979. M i l k cel l co unt in first lactations of p r o g e n y gro u p s of A. I. bulls. Z. Tierz. Z u c h t . biol. 96: 48-55.

Ga unya, W. S. and R. D. Mather. 1962. H e r i t a b i l i t y of res i s t a n c e to b o v i n e m a s titis. J. Da i r y Sci. 45: 1577.

Giese ck e, W. H. 1979. Bovine mastitis. Tech. Comm. No. 151,Dept, of Ag ri c. Tech. Services. R e p u b l i c of So u t h Africa, p. 28.

G r o o t e n h u i s , G. 1976. The dif f e r e n c e in h e r e d i t a r y s u s c e p t i b i l i t y to thre e m a s t i t i s agents b e t w e e n two d a u g h t e r groups. Tijdschr. D i ergeneesk, 101, 14.

Hibb it t, K., A. Hill, M. Williams, and K. Bunch. 1980. Factors a f f e c t i n g the r e s i s t a n c e of the m a m m a r y gla n d to i n f e c t i o n and the i n f luence of the sire on the s u s c e p t i b i l i t y of his d a u g h t e r s to m a s titis. Proc. Conf. on Resi s t a n c e F a c t o r s and G e n e t i c A s p e c t s of M a s t i t i s Cont rol, Jablonna, Poland, p. 114-129.

King, G. J., H. D. Norman, and R. L. Powell. 1976. H e r i t a b i l i t y e s t i m a t e s of CMT scores. J. Dairy Sci. 59: 130 (Abstr.).

Ki tchen, B. 1981. Bovine mastitis: m i l k c o m p o s i t i o n a l changesand r e l a t e d d i a g n o s t i c tests. J. Dai r y Res. 48: 167-188.

Ko rhonen, H. 1980. P o t ential rate of the l a c t o p e r o x i d a s e s y s t e m L P / S C N - / H 2O 2 in m a s titis resistance. Proc. Conf. on R e s i s t a n c e F a c t o r s and G e n e t i c Aspects of Masti t i s Control. Jablonna, Poland, pp. 323-339.

Lee, C. S., F. B. P. W o o d i n g and P. Kemp. 1980. Iden t i f i c a t i o n , prop e r t i e s , and d i fferential counts of cell p o p u l a t i o n using e l e c t r o n m i c r o s c o p y of dry cow secretions, c o l o s t r u m and m i l k from normal cows. J. Dairy Res. 47: 39-50.Legat es , J. E. and C. D. Grinnells. 1952. G e n e t i c r e l a t i o n s h i p s in r e s i t a n c e to m a s t i t i s in dairy cattle. J. D a i r y Sci. 35: 829-833.

Lie, 0. 1978. Genetic var i a t i o n s in some immune c h a r a c t e r s intest i n g s t a t i o n bulls. Proc. 29th Ann. M e e ting, E u r o p e a n Assoc. Anim. Prod., Stockholm, Sweden, June 5-7.

196

Lindstrom, U. B., H. Kenttaraies, J. Arstila, and R. Tuovila. 1981. Usefulness of cell counts in predicting bovine mastitis. Acta Agric. Scand. 31: 199-203.

Lindstrom, U. B. and J. Syvajarvi. 1980. Breeding for mastitis resistance in ca ttle--practical possibilities. Proc. C o n f . on Resistance Factors and Genetic Aspects of Mastitis Control.Jablonna, Poland, pp. 130-147.

Linzell, J. L. and M. P e a k e r . 1975. Efficacy of the m e a surement ofthe el ectrical c o n ductivity of milk for the detection of subclinical mastitis in cows: detection of infected cows at a sinele visitBrit. Vet. J. 131: 447.

Lush, J. L. 1950. Inheritance of susceptibility to mastitis. J. Dairy Sci. 33: 121.

Miller, R. H., R. E. Pearson, M. F. Rothschild, and L. A. Fulton. 1981. Com p a r i s o n of single- and multiple-trait selected sires. Response in mastitis traits. J. Dairy Sci. 64: 832-837.

Miller, R. H. and W. D. Schultze. 1981. Genetic resistance to mastitis. Proc. 20th Annual Meeting, National Mastitis Council. Washington, D.C., p. 51-78.

Natzke, R. P., R. W. Everett and D. S. Postle. 1972. Normal milk and somatic cell counts. J. Milk and Food Tech. 35: 261-263.

0'B l e n e s s , G. V., L. D. VanVleck, and C. R. Henderson. 1960. He ri ta bi lities of some type appraisal traits and their genetic ph en otypic co rr elations with production. J. Dairy Sci. 43- 1490-1498.

Paape, M. J., R. E. Pearson and W. D. Schultze. 1978. Sources of variat io n in the ability of milk to support phagocytosis and of pol ymorphonuclear leukocytes to phagocytose S t aphylcoccus aureus Am. J. Vet. Res. 39: 1907-1910. --------------------------

Paape, M. J., W. D. Schultze, A. J. Guidry, W. M. Kortum, and B. T. Weinland. 1981. Effect of an intramammary p o lyethylene device on the co ncentration of leukocytes and immunoglobulins in milk and on the leukocyte response to Escherichia coli endotoxin and challenge exposure with S t a p h y l o c o c c us a u r e u s . Am. J. Vet. Res. 42: 774-783.Philipsson, J., E . P e r s s o n , U. Andersson, L. Brolund, and H. Funke. 1978. Gen et ic aspects on breeding for mastitis resistance.Symp os iu m on Bovine Mastitis, Grub bei Munchen, May 30-31, 1978.

Philipsson, J., B. Thafvelin, and J. H e d e b r o - V e l a n d e r . 1980.Genetic studies on disease recordings in first lactation cows of Swedish dairy breeds. Acta Agric. Scand. 30: 327-335.

P o u t r e l , B. and C. Lerondelle. 1978. Induced staphylococcal infections in the bovine mammary gland. Ann. Rech. Vet. 9: 119.

Probst, A., J. Behringer and F. Kiermeier. 1968. Predisposing factors in mastitis. III. Genetic factors in udder health. Zuc htu ngskunde 40: 248-253.

Rendel, J. and T. Sundberg. 1962. Factors influencing the type and incidence of mas ti tis in Swedish dairy cattle. Acta Vet. Scand. 3:

197

R e n ner, E. 1980. M a s t i t i s control by l a c t o s e d e t e r m i n a t i o n in milk. Proc. Conf. on R e s i s t a n c e F a c t o r s and G e n e t i c A s p e c t s of M a s t i t i s C o n t r o l . Jablonna, Poland, pp. 56-66.

Re nner, E. and Kosmack, U. 1976. G e n e t i s c h e a s p e k t e zum a u f t r e t e n von s e k r e t i o n s s t o r u n g e n b e i m rind. Z u c h t u n g s k u n d e 48: 10-21.

Sch al m, 0. W. E. J. C a r r o l l and N. C. Jain. 1971. Bovine M a s t i t i s . Lea a n d Febiger, Phila., Pa.

Sc ha lm , 0. W., J. Lasmanis and N. C. Jain. 1976. C o n v e r s i o n of c h r o n i c s t a p h y l o c o c c a l m a s t i t i s to ac u t e g a n g r e n o u s m a s t i t i s after n e u t r o p e n i a in bl o o d and bone m a r r o w c a u s e d by an e q u i n e a n t i - b o v i n e le u k o c y t e serum. Am. J. Vet. Res. 37: 885.

Schm id t, G. H. and L. D. V a n Vleck. 1965. H e r i t a b i l i t y es t i m a t e s of u d d e r d i s e a s e as m e a s u r e d by v a r i o u s tests a n d th e i r r e l a t i o n s h i p to ea ch ot her and to m i l k yield, age, and m i l k i n g times. J. D a i r y Sci. 48: 51-55.Senft, B., F. Meyer, and P. E r h a r d t . 1980. G e n e t i c a s p e c t s of theb a c t e r i o s t a t i c acting whey p r o t e i n s l a c t o f e r r i n and lysoszyme.Proc. Conf. on R e s i s t a n c e Fact o r s and G e n e t i c A s p e c t s of M a s t i t i s Con trol. J a b l o n n a , Poland, pp. 340-357.

Set ha r, M. S. B. to. Kennedy, A. K. W. Tong, J. E. Moxley, and B. R. Dow ne y. 1979. G e n etic and e n v i r o n m e n t a l f a c t o r s a f f e c t i n g test day s o m atic cell c o u n t s in H o l steins. J. D a i r y Sci. 62 (Suppl. 1):148. (Abs tr .)Shook, G. E. and R. H. Miller. 1978. J o i n t f r e q u e n c y d i s t r i b u t i o n of s o m a t i c cell c o n c e n t r a t i o n s (SCC) and p r e s e n c e or a b s e n c e of ud d e r p a t h o g e n s in milk. J. Da i r y Sci. 61 (Suppl. 1): 92-93( A b s t r .)Sm ith, K. L. and F. L. Schanb a c h e r . 1976. L a c t o f e r r i n as a factor of r e s i s t a n c e to i n f ection of the b o v i n e m a m m a r y gland. Am. J. Vet. Res. 170: 1224-1227.

So lbu, H. 1978. Breeding for i m p roved d i s e a s e r e s i s t a n c e , w i t h s p e cial e m p h a s i s on a pr a c t i c a l m e t h o d of c o l l e c t i n g data. P r o c - 29 th Ann. M e e t i n g , E u r o p e a n Assoc, for An i m . Prod., S t o ckholm, Sw eden. J u n e 5-7.

S t a v i k o v a , M. and L. Lojda. 1957. E f f e c t of g e n o t y p e on lipid c o m p o s i t i o n of the bovine teat canal lact o s e b u m . D a i r y Sci. Abstr. 38 (5338).W i l son, C. D. and M. S. Richards. 1980. A sur v e y of m a s t i t i s in the B r i t i s h da i r y herd. Vet. Rec. 106: 431-435.

Wilton, J. W., L. D. Van Vleck, R. W. E v e r e t t , R. S. G u t h r i e and S. J. R o b e r t s . 1972. G e n etic and e n v i r o n m e n t a l a s p e c t s of udder infe c t i o n s . J. Dairy Sci. 55: 183-193.

Young, C. W., J. E. Legates and J. G. Lecce. I960. G e n e t i c and p h e n t o y p i c r e l a t i o n s h i p s b e t w e e n c l i n i c a l m a s t i t i s , l a b o r a t o r y c r i teria, and udder height. J. D a i r y Sci. 43. 54.

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E05-GENETICS OF RESISTANCE TO MASTITISROBERT H. MILLER