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The Relation of Chlorine and Catalase Content of Milk to its Curd Tension*
T H E R E L A T I O N OF C H L O R I N E AND C A T A L A S E C O N T E N T OF M I L K TO I T S CURD T E N S I O N ~ E. G. HASTINGS AnD ARTHUI~ E R E K S O N
University of Wisconsin, Madison, Wisconsin, and Zakeshire-Marty Co., Division of The l~orde~ Co., Plymouth, Wisconsin
The type of curd obtained from milk with rennet has been studied by many in attempts to relate the nature of the curd to one or more of the properties of the milk. The reaction of the enzyme and the milk will v a r y from sample to sample in its speed, that is, in the time required for the rennet to cause visible curdling under standard conditions of temperature and concentration of enzyme. The physical properties of the coagulum will also vary from sample to sample. Most observations have been limited to the product of individual cows and also to relatively short periods. A field project on the manufacture of cheese presented an opportunity to study curdling properties and milk composition of each of six herds daily throughout a lactation period and the milk of each animal in each herd several times in the period. The animals of the six herds, totaling 157 milking cows, freshened in early spring and were dried off in early November. The resting time between lactation periods was thus longer than in herds in which production is maintained at a relatively constant level throughout the year. Firnmess of the curd produced under standard conditions of temperature and concentration of rennet, chlorine and catalase content of the sample, and also the reducing power of each sample toward methylene blue and toward resazurin were observed. The accumulated experience of m a n y has shown that the mass of reproducing bacteria of the milk is the chief reducing constituent of milk foward methylene blue and that the mass of growing bacteria and the mass of body cells in milk are the reducing agents toward resazurin. The action of each of these two agents on resazurin can be separately determined in some degree when the reducing power of the milk on this reagent is compared with the action on methylene blue. The reduction of resazurin can be divided into two phases: first, a change from the original slate gray color of the milk-resazurin mixture to a pink, and second, a change of the latter to white. The extent of the progress in each phase can be observed. I f the content of a milk in body cells (leucocytes) or bacteria is high, the time required for the first phase of the reduction of resazurin will be short. The answer as to which of the reducing agents is responsible for a color change noted with resazurin is supplied by comparing results of the two Received for publication September 25, 1943. * Published with the permission of the Director of the Wisconsin Agricultural Experiment Station. 337
338
E. G. HASTINGS AND AR.TItUR EREKSON
tests. I f t h e b a c t e r i a a r e t h e c h i e f cause of r e d u c t i o n in a n y s a m p l e , r e d u c t i o n t i m e s w i t h t h e two d y e s will be m u c h t h e same. I f , however, t h e m e t h y lene b l u e i n d i c a t e s p r e s e n c e of f e w b a c t e r i a , t h e n t h e r a p i d r e d u c t i o n of r e s a z u r i n to its p i n k f o r m is d u e to b o d y cells, t h e p r e s e n c e of w h i c h is i n d i c a t e d b y t h e h i g h c a t a l a s e c o n t e n t , since the b o d y cells a r e a p p a r e n t l y t h e source of t h e c a t a l a s e of milk. I t s o t h e r c o n s t i t u e n t s a r e d e v o i d of t h i s enzyme. T h e c h l o r i n e c o n t e n t of m i l k h i g h in c a t a l a s e will also be h i g h since blood s e r u m will also be e n t e r i n g t h e m i l k s y s t e m if cells a r e p a s s i n g f r o m t h e b l o o d s y s t e m i n t o t h e m i l k system. T h u s chlorine, c a t a l a s e a n d b o d y cells w i l l t e n d to v a r y t o g e t h e r in t h e m i l k of a n i n d i v i d u a l cow a n d these v a r i a t i o n s w i l l cause v a r i a t i o n s in r e d u c i n g p o w e r of the m i l k t o w a r d r e s a z u r i n . H i g h b a c t e r i a l c o n t e n t will t e n d to o b s c u r e t h e l a t t e r r e l a t i o n . T h e e n t r a n c e of b l o o d s e r u m i n t o the m i l k s y s t e m t e n d s to r a i s e t h e p H of t h e m i l k a n d i n c r e a s e t h e s o d i u m : c a l c i u m r a t i o , c h a n g e s t h a t a l t e r t h e TABLE 1 Theseason'shistoryoftheherdsstudied
May 9
Sept. 30
Herd Cows ]
t 2 3 4 5 6 Average
Oct. 24
I
i [ i ~ i
] h
Milk
Cows
No.
%
lbs.
%
34 33 27 21 24 18 157
100 100 100 100 100 100 100
1120 902 791 450 576 606 741
100 100 100 100 100 100 100
No.
°70
24 70 31 94 27 100 17 81 21 88 17 94 137 87
I
I
Milk lbs.
576 446 569 235 497 360 447
% 60 49 72 52 86 57 60
Cows No. 20 31 25 14 21 15 126
% 60 91 92 66 88 83 80
~/[ilk lbs.
o/
364 324 387 242 314 258 315
3 3 4 5 5 4 4
s p e e d of r e a c t i o n of m i l k w i t h r e n n e t a n d also the p r o p e r t i e s of the coagulum. I t seems p r o b a b l e t h a t t h e p r e s e n c e of a n i n f l a m m a t o r y p r o c e s s in t h e u d d e r causes a d e c r e a s e in t h e p e r c e n t a g e of casein f r o m t h a t n o r m a l f o r the a n i m a l a n d c h a n g e s its q u a l i t y in such a m a n n e r t h a t c u r d l i n g w i t h r e n n e t is r e t a r d e d a n d t h e firmness of t h e c u r d is d e c r e a s e d f r o m t h a t n o r m a l f o r t h e a n i m a l . I t is also to be r e m e m b e r e d t h a t t h e c u r d s f o r m e d in t h e nfilk of d i f f e r e n t cows b y r e n n e t w i l l v a r y i n p h y s i c a l p r o p e r t i e s d u e to t h e g e n e t i c p a t t e r n of t h e a n i m a l . I n t h i s case the f o u r q u a r t e r s of the u d d e r s h o u l d p r o d u c e m i l k s h o w i n g t h e same t y p e of c o a g u l u m , while in t h e case of a n i n f l a m m a t o r y p r o c e s s the n a t u r e of the c o a g u l u m n o t e d in the p r o d u c t of t h e affected q u a r t e r or q u a r t e r s w o u l d differ f r o m t h a t of the n o r m a l q u a r t e r . T h i s s t u d y is one of t h e r e l a t i o n of m a s t i t i s to t h e q u a l i t y of m i l k a n d to t h e q u a l i t y of the cheese m a d e t h e r e f r o m . T h e d i s c u s s i o n is b a s e d w h o l l y on c o m p a r a t i v e values, so it does n o t seem essential to d e s c r i b e i n d e t a i l t h e m e t h o d s used. The p r o p e r t y of the c u r d o b s e r v e d was firmness or tension. The seasonal r e c o r d of the h e r d s is p r e s e n t e d in t a b l e 1.
339
CHLORINE AND CATALASE CONTENT OF MILK
The curd tension of the entire q u a n t i t y of milk produced in 24 hours was noted once or twice each week throughout the season. Readings were made 30 and 40 minutes a f t e r the rennet was added to the milk. The relative values were the same in either case. Only those noted a f t e r 30 minutes are given in table 2. The p r o d u c t of herd 4 is m a r k e d l y different in curd tension f r o m that of the other herds. I n the detailed s t u d y of each herd it seemed that the clearest picture of the relation of mastitis to curd tension and to other items of interest would be obtained by comparing animals that in May produced milk of a curd tension of 5 or below with animals that during the same period produced milk having a curd tension of 40 or above. One point of interest is the relation of c u r d tension to persiste.nce in production. The data are presented in table 3. The significance of the data is only indicative on account of the limited n u m ber of animals in each herd. TABLE 2
Average curd tension by months of herd milk Herd May Sune ,~uly August September October Average
]3 9 10 4 5 12 8.8
17 9 12 6 7 14 10.8
18 6 5 5 4 12 8.3
22 13 14 11 16 20 16.0
12 3 4 2 2 10 5.5
14 4 8 4 5 9 7.3
The entire comparison m a y be thus expressed. Twenty-five cows that produced milk of a curd tension of 5 or below in May gave in late September 53.1 per cent as much milk as in May. T w e n t y - f o u r cows that ~n May produced milk with a curd tension of 40 or above gave in September 65.0 per cent as much milk as in May. The observations conform with what one would expect in showing that mastitis is a factor in persistence of production in a n y lactation period. CURD TENSION IN" RELATION TO CI~:LORINE AN"D CATALASE CONTENT
The relationship of curd tension to chlorine and catalase content of milk was also studied, using only the extreme cases, i.e., those with a curd tension of 5 or below and those with a curd tension of 40 or above. The j u d g m e n t as to the members of the intermediate group would be questionable, hence the use of the extremes rather t h a n the entire n u m b e r of cows in the six herds. The catalase content of the milks was determined by collecting the total amount of oxygen set free f r o m an excess of hydrogen peroxide b y a q u a n t i t y of the milk and expressing it in terms of percentage of the quantity of milk
340
E. G. H A S T I N G S AND A R T H U R E R E K S O N
TABLE 3 The relationship of curd tension to persistence in production
Curd tension Herd 1 3 cows 3 cows Herd 2 9 cows 3 cows Herd 3 5 cows 3 cows Herd 4
On Sept. 25 produced of the May 8 yield Per cent
0 COWS 6 cows
Herd 5 7 cows 2 cows Herd 6 1 cow 7 cows
5 or
tess 40 or more
24.7 68.0
5 o r less 40 or more
42 50.0
5 o r less 40 or more
74 60
5 o r less 40 or more
65
5 o r less 40 or more
92 100
5 o r less 40 or more
33 48
used, t h u s i f 10 cc. of m i l k set f r e e 10 cc. of o x y g e n its catalase v a l u e w o u l d be 100. T h e v a l u e s g i v e n i n t a b l e 4 a r e t h e a v e r a g e of all o b s e r v a t i o n s d u r i n g t h e e n t i r e p e r i o d of o b s e r v a t i o n . T h e r e l a t i o n of h i g h c h l o r i n e a n d c a t a l a s e c o n t e n t to low c u r d t e n s i o n is to be n o t e d in each h e r d e x c e p t h e r d 5. S i n c e t h e r e c o r d of this h e r d differs so m a r k e d l y f r o m t h a t of the o t h e r five herds, t h e d e t a i l e d d a t a a r e p r e s e n t e d i n ta b l e 5. H e r d 5 c o n t a i n e d m a n y cows prod u c i n g m i l k o f l o w c u r d t e n s i o n w i t h no e v i d e n c e of u d d e r t r o u b l e as s h o w n by t h e c h l o r i n e a n d c a t a l a s e c o n t e n t of t h e milk. I t has long b e e n k n o w n t h a t some cows n o r m a l l y p r o d u c e s o f t - c u r d milk, w h i l e i n o t h e r s t h e c h a n g e d c o m p o s i t i o n of t h e m i l k is d u e to a d i s t u r b a n c e in t h e p h y s i o l o g y of the TABLE 4 The catalase and chlorine content of herd milk of low and high curd tension in May
Curd tension Herd
5 or less
40 or more
Chlorine
Catalase
% 0.169 0.170 0.146
% 145 97 52
0.114 0.184
18 59
i
Chlorine % 0.117 0.125 0.128 0.117 0.130 0.121
Cata]ase % 34 38 15 26 10 22
CHLORINE AND CATALASE CONTENT OF MILK
341
u d d e r . A s f a r as. th e w r i t e r s know, this is t h e first i n s t a n c e o f a h e r d o f a p p a r e n t l y n o r m a l cows p r o d u c i n g m i l k of low c u r d t e n s i o n or s o f t - c u r d milk. T h e h e r d s s t u d i e d consist l a r g e l y , if n o t w h o l l y , of t h e i r o w n p r o g e n y ;. t h e g e n e t i c f a c t o r r e s p o n s i b l e f o r s o f t - c u r d m i l k m a y t h u s be b r o u g h t to a t t e n t i o n i n a d e g r e e n o t p r o b a b l e in a h e r d m a i n t a i n e d b y p u r c h a s e . TABLE 5 The eatalase and vhlorine vontent of the mill~ of individual cows of low and high curd tension in herd 5
Cow
tensionCUrd Chlorine
Catalase I Cow
tensionCUrd Chlorine
Catalase
1
May 9, 1941 23
O
0.114
[
17
I
1 5 12
63 48 42
0.135 0.122 0.133
10 14 6
48
0.088
2
1 2 4 5 11
42 52 65 43 40
0.087 0.082 0.101 0.086 0.098
17 2
17 24
44 43
0.103 0.103
33
65 52 50 42
0.081 0.062 0.097 0.106
5 14 13 36
May 26 1941 6 13 14 15 18 19 22 23 25 27
0.085 0.102 0.091 0.097 0.091 0.093 0.101 0.083 0.092 0.089
7
2
15
4 28 4 17 5 10 6 35 July 21, 1941
6 7 14 15 18 22 23 27
0.082 0.100 0.102 0.079 0.103 0.103 0.099
12 3 6 50 10 9 7 18
14
9
Aug. 7, 1941 6 7 14 15 18 22 23 27
0.079 0.066 0.086 0.100 0.107 0.087 0.084 0.090
21 10 18 69 17 39 30 47
17 24
T h e r e s a z u r i n t e s t s w e r e o b s e r v e d a t t h e e n d o f e a c h h o u r f o r five h o u r s , a n d a n u m b e r g i v e n to each s a m p l e at each o b s e r v a t i o n . A low n u m b e r , 1, f o r e x a m p l e , i n d i c a t e s t h a t l i t t l e c h a n g e i n t h e color of t h e d y e was n o t i c e d
342
E. G. HASTINGS AND ARTHUR EREiKSON TABLE 6 The relationship of resazurin reduction after 1 hour incubation to curd tension, chlorine and catala~e content of mill~
Herd
Curd tension
Cows
5 or less 40 or more 5 or less 40 or more 5 or less 40 or more 5 or less 40 or more 5 or less 40 or more 5 or less 40 or more
10 15 3 6 3 0 7 1 3 2 6
Chlorine
Catalase
0.169 0.117 0.170 0.125 0.146 0.128
145 34 97 38 52 15
4.0 '2.0 3.5 1.0 1.6 1.0
0.117 0.114 0.130 0.184 0.121
26 17 10 59 22
1.5 1.0 1.3 4.0 1.5
6
Resazurin
at t h a t p e r i o d of o b s e r v a t i o n , w h il e a h i g h n u m b e r i n d i c a t e d m u c h g r e a t e r r e d u c t i o n at t h e p e r i o d of o b s e r v a t i o n . Thus, 1 a t t h e f o u r t h h o u r m e a n s a m i l k v e r y low in b a c t e r i a l c o n t e n t a n d in cells, w h i l e 5 at t h e first h o u r m e a n s a m i l k h i g h in b a c t e r i a or i n b o d y cells, or in both. T h e a n s w e r as to w h i c h is g i v e n b y th e m e t h y l e n e blue test. T h e m i l k s in q u e s t i o n w e r e cons t a n t l y so low in b a c t e r i a t h a t a r a p i d r e d u c t i o n w i t h r e s a z u r i n m a y be used as a n e v i d e n c e of h i g h c o n t e n t in b o d y cells. I t t h u s seems p r o p e r to use the a v e r a g e s of the r e s a z u r i n r e a d i n g of t h e two classes of c o w s - - t h o s e prod u c i n g m i l k of a c u r d t e n s i o n of 5 or below a n d those s h o w i n g a t e n s i o n of 40 or above. T a b l e 6 p r e s e n t s t h e a v e r a g e r e a d i n g of t h e r e s a z u r i n test at t h e en d of t h e first h o u r f o r th e two g r o u p s of cows in each of t h e six h e r d s on a p a r t i c u l a r d a y in May. T h e e x p e c t e d r e l a t i o n b e t w e e n h i g h c h l o r i n e a n d catalase c o n t e n t a n d r a p i d r e d u c t i o n of r e s a z u r i n is sh o w n in each h e r d e x c e p t 5, in w h i c h the m o r e r a p i d r e d u c t i o n was n o t e d in t h e h i g h t e n s i o n g r o u p of cows. T h e n u m b e r of cows i n each g r o u p of t h i s h e r d was so sm al l t h a t the figures can be o n l y s u g g e s t iv e . T h e smallness of t h e g r o u p s r e p r e s e n t i n g the e x t r e m e h i g h a n d low v a l u e s i n d i c a t e s t h a t the h e r d consists l a r g e l y of n o r m a l animals. TABLE 7 The relationship of catalasc content of milk to the rapidity of reduction of resazurin
Herd
Average catalase content
Average reading in resazurin test, 1 hr.
56 65 48 29 25 48
3.0 3.2 2.5 1.9 1.4 2.7
C H L O R I N E A N D CATALASE C O N T E N T
OP MILK
343
The relationship between the average catalase content of the entire amount of milk delivered at the factory to the average reading of the resazurin test at the end of the first hour for each herd is shown in table 7. The relationship between catalase content and reducing power toward resazurin is clearly evident f r o m the data, which also show t h a t herd 5 is the only one of the six that can be considered as producing normal milk, since the milk of cows with healthy udders should not exceed 25 in its c a t a l a s e value. Indeed, the value 20 is most frequently found in the literature on the subject, and in the experience of the writers some herds will consistently produce milk that will not exceed this value. The same is true of most first lactation cows. The cause of the condition noted in herds 1, 2, 3 and 6 cannot be stated with certainty. F r o m the few observations made as to the presence of streptococci ix the milk of individual cows, one is inclined to consider them as the p r i m e disturbing agent. The observations of the senior author indicate that herds in similar condition are to be found in all areas. I t is hoped that the incidence of such herds is not as high as in the six studied, for they cannot serve as the foundation of a successful f a r m or of a successful cheese industry. Some p r o g r a m of herd m a n a g e m e n t should be developed through the use of which such herds can be placed on a more normal base. SUMMARY
The tension of the curd produced u n d e r s t a n d a r d conditions in the 24-hour product of each of six herds was noted f r e q u e n t l y throughout a period of six months. The p r o d u c t of one herd (No. 4) had an average curd tension a p p r o x i m a t e l y twice as great as that of the other five herds and is believed to represent what one would expect to obtain f r o m a group of cows with healthy udders. The low curd tension of f o u r of the remaining five herds is believed to be due to the high incidence of chronic mastitis in these herds, since the p r o d u c t thereof was abnormally high in catalase and in chlorine. The low curd tension noted in the product of the remaining herd (No. 5) is believed due to the genetic p a t t e r n of the members of the herd since the chlorine and catalase content of its p r o d u c t was normal. The record of the four herds indicates them to be agents of low value for the production of milk both f r o m the standpoint of q u a n t i t y and quality of milk.
University of Wisconsin, Madison, Wisconsin, and Zakeshire-Marty Co., Division of The l~orde~ Co., Plymouth, Wisconsin
The type of curd obtained from milk with rennet has been studied by many in attempts to relate the nature of the curd to one or more of the properties of the milk. The reaction of the enzyme and the milk will v a r y from sample to sample in its speed, that is, in the time required for the rennet to cause visible curdling under standard conditions of temperature and concentration of enzyme. The physical properties of the coagulum will also vary from sample to sample. Most observations have been limited to the product of individual cows and also to relatively short periods. A field project on the manufacture of cheese presented an opportunity to study curdling properties and milk composition of each of six herds daily throughout a lactation period and the milk of each animal in each herd several times in the period. The animals of the six herds, totaling 157 milking cows, freshened in early spring and were dried off in early November. The resting time between lactation periods was thus longer than in herds in which production is maintained at a relatively constant level throughout the year. Firnmess of the curd produced under standard conditions of temperature and concentration of rennet, chlorine and catalase content of the sample, and also the reducing power of each sample toward methylene blue and toward resazurin were observed. The accumulated experience of m a n y has shown that the mass of reproducing bacteria of the milk is the chief reducing constituent of milk foward methylene blue and that the mass of growing bacteria and the mass of body cells in milk are the reducing agents toward resazurin. The action of each of these two agents on resazurin can be separately determined in some degree when the reducing power of the milk on this reagent is compared with the action on methylene blue. The reduction of resazurin can be divided into two phases: first, a change from the original slate gray color of the milk-resazurin mixture to a pink, and second, a change of the latter to white. The extent of the progress in each phase can be observed. I f the content of a milk in body cells (leucocytes) or bacteria is high, the time required for the first phase of the reduction of resazurin will be short. The answer as to which of the reducing agents is responsible for a color change noted with resazurin is supplied by comparing results of the two Received for publication September 25, 1943. * Published with the permission of the Director of the Wisconsin Agricultural Experiment Station. 337
338
E. G. HASTINGS AND AR.TItUR EREKSON
tests. I f t h e b a c t e r i a a r e t h e c h i e f cause of r e d u c t i o n in a n y s a m p l e , r e d u c t i o n t i m e s w i t h t h e two d y e s will be m u c h t h e same. I f , however, t h e m e t h y lene b l u e i n d i c a t e s p r e s e n c e of f e w b a c t e r i a , t h e n t h e r a p i d r e d u c t i o n of r e s a z u r i n to its p i n k f o r m is d u e to b o d y cells, t h e p r e s e n c e of w h i c h is i n d i c a t e d b y t h e h i g h c a t a l a s e c o n t e n t , since the b o d y cells a r e a p p a r e n t l y t h e source of t h e c a t a l a s e of milk. I t s o t h e r c o n s t i t u e n t s a r e d e v o i d of t h i s enzyme. T h e c h l o r i n e c o n t e n t of m i l k h i g h in c a t a l a s e will also be h i g h since blood s e r u m will also be e n t e r i n g t h e m i l k s y s t e m if cells a r e p a s s i n g f r o m t h e b l o o d s y s t e m i n t o t h e m i l k system. T h u s chlorine, c a t a l a s e a n d b o d y cells w i l l t e n d to v a r y t o g e t h e r in t h e m i l k of a n i n d i v i d u a l cow a n d these v a r i a t i o n s w i l l cause v a r i a t i o n s in r e d u c i n g p o w e r of the m i l k t o w a r d r e s a z u r i n . H i g h b a c t e r i a l c o n t e n t will t e n d to o b s c u r e t h e l a t t e r r e l a t i o n . T h e e n t r a n c e of b l o o d s e r u m i n t o the m i l k s y s t e m t e n d s to r a i s e t h e p H of t h e m i l k a n d i n c r e a s e t h e s o d i u m : c a l c i u m r a t i o , c h a n g e s t h a t a l t e r t h e TABLE 1 Theseason'shistoryoftheherdsstudied
May 9
Sept. 30
Herd Cows ]
t 2 3 4 5 6 Average
Oct. 24
I
i [ i ~ i
] h
Milk
Cows
No.
%
lbs.
%
34 33 27 21 24 18 157
100 100 100 100 100 100 100
1120 902 791 450 576 606 741
100 100 100 100 100 100 100
No.
°70
24 70 31 94 27 100 17 81 21 88 17 94 137 87
I
I
Milk lbs.
576 446 569 235 497 360 447
% 60 49 72 52 86 57 60
Cows No. 20 31 25 14 21 15 126
% 60 91 92 66 88 83 80
~/[ilk lbs.
o/
364 324 387 242 314 258 315
3 3 4 5 5 4 4
s p e e d of r e a c t i o n of m i l k w i t h r e n n e t a n d also the p r o p e r t i e s of the coagulum. I t seems p r o b a b l e t h a t t h e p r e s e n c e of a n i n f l a m m a t o r y p r o c e s s in t h e u d d e r causes a d e c r e a s e in t h e p e r c e n t a g e of casein f r o m t h a t n o r m a l f o r the a n i m a l a n d c h a n g e s its q u a l i t y in such a m a n n e r t h a t c u r d l i n g w i t h r e n n e t is r e t a r d e d a n d t h e firmness of t h e c u r d is d e c r e a s e d f r o m t h a t n o r m a l f o r t h e a n i m a l . I t is also to be r e m e m b e r e d t h a t t h e c u r d s f o r m e d in t h e nfilk of d i f f e r e n t cows b y r e n n e t w i l l v a r y i n p h y s i c a l p r o p e r t i e s d u e to t h e g e n e t i c p a t t e r n of t h e a n i m a l . I n t h i s case the f o u r q u a r t e r s of the u d d e r s h o u l d p r o d u c e m i l k s h o w i n g t h e same t y p e of c o a g u l u m , while in t h e case of a n i n f l a m m a t o r y p r o c e s s the n a t u r e of the c o a g u l u m n o t e d in the p r o d u c t of t h e affected q u a r t e r or q u a r t e r s w o u l d differ f r o m t h a t of the n o r m a l q u a r t e r . T h i s s t u d y is one of t h e r e l a t i o n of m a s t i t i s to t h e q u a l i t y of m i l k a n d to t h e q u a l i t y of the cheese m a d e t h e r e f r o m . T h e d i s c u s s i o n is b a s e d w h o l l y on c o m p a r a t i v e values, so it does n o t seem essential to d e s c r i b e i n d e t a i l t h e m e t h o d s used. The p r o p e r t y of the c u r d o b s e r v e d was firmness or tension. The seasonal r e c o r d of the h e r d s is p r e s e n t e d in t a b l e 1.
339
CHLORINE AND CATALASE CONTENT OF MILK
The curd tension of the entire q u a n t i t y of milk produced in 24 hours was noted once or twice each week throughout the season. Readings were made 30 and 40 minutes a f t e r the rennet was added to the milk. The relative values were the same in either case. Only those noted a f t e r 30 minutes are given in table 2. The p r o d u c t of herd 4 is m a r k e d l y different in curd tension f r o m that of the other herds. I n the detailed s t u d y of each herd it seemed that the clearest picture of the relation of mastitis to curd tension and to other items of interest would be obtained by comparing animals that in May produced milk of a curd tension of 5 or below with animals that during the same period produced milk having a curd tension of 40 or above. One point of interest is the relation of c u r d tension to persiste.nce in production. The data are presented in table 3. The significance of the data is only indicative on account of the limited n u m ber of animals in each herd. TABLE 2
Average curd tension by months of herd milk Herd May Sune ,~uly August September October Average
]3 9 10 4 5 12 8.8
17 9 12 6 7 14 10.8
18 6 5 5 4 12 8.3
22 13 14 11 16 20 16.0
12 3 4 2 2 10 5.5
14 4 8 4 5 9 7.3
The entire comparison m a y be thus expressed. Twenty-five cows that produced milk of a curd tension of 5 or below in May gave in late September 53.1 per cent as much milk as in May. T w e n t y - f o u r cows that ~n May produced milk with a curd tension of 40 or above gave in September 65.0 per cent as much milk as in May. The observations conform with what one would expect in showing that mastitis is a factor in persistence of production in a n y lactation period. CURD TENSION IN" RELATION TO CI~:LORINE AN"D CATALASE CONTENT
The relationship of curd tension to chlorine and catalase content of milk was also studied, using only the extreme cases, i.e., those with a curd tension of 5 or below and those with a curd tension of 40 or above. The j u d g m e n t as to the members of the intermediate group would be questionable, hence the use of the extremes rather t h a n the entire n u m b e r of cows in the six herds. The catalase content of the milks was determined by collecting the total amount of oxygen set free f r o m an excess of hydrogen peroxide b y a q u a n t i t y of the milk and expressing it in terms of percentage of the quantity of milk
340
E. G. H A S T I N G S AND A R T H U R E R E K S O N
TABLE 3 The relationship of curd tension to persistence in production
Curd tension Herd 1 3 cows 3 cows Herd 2 9 cows 3 cows Herd 3 5 cows 3 cows Herd 4
On Sept. 25 produced of the May 8 yield Per cent
0 COWS 6 cows
Herd 5 7 cows 2 cows Herd 6 1 cow 7 cows
5 or
tess 40 or more
24.7 68.0
5 o r less 40 or more
42 50.0
5 o r less 40 or more
74 60
5 o r less 40 or more
65
5 o r less 40 or more
92 100
5 o r less 40 or more
33 48
used, t h u s i f 10 cc. of m i l k set f r e e 10 cc. of o x y g e n its catalase v a l u e w o u l d be 100. T h e v a l u e s g i v e n i n t a b l e 4 a r e t h e a v e r a g e of all o b s e r v a t i o n s d u r i n g t h e e n t i r e p e r i o d of o b s e r v a t i o n . T h e r e l a t i o n of h i g h c h l o r i n e a n d c a t a l a s e c o n t e n t to low c u r d t e n s i o n is to be n o t e d in each h e r d e x c e p t h e r d 5. S i n c e t h e r e c o r d of this h e r d differs so m a r k e d l y f r o m t h a t of the o t h e r five herds, t h e d e t a i l e d d a t a a r e p r e s e n t e d i n ta b l e 5. H e r d 5 c o n t a i n e d m a n y cows prod u c i n g m i l k o f l o w c u r d t e n s i o n w i t h no e v i d e n c e of u d d e r t r o u b l e as s h o w n by t h e c h l o r i n e a n d c a t a l a s e c o n t e n t of t h e milk. I t has long b e e n k n o w n t h a t some cows n o r m a l l y p r o d u c e s o f t - c u r d milk, w h i l e i n o t h e r s t h e c h a n g e d c o m p o s i t i o n of t h e m i l k is d u e to a d i s t u r b a n c e in t h e p h y s i o l o g y of the TABLE 4 The catalase and chlorine content of herd milk of low and high curd tension in May
Curd tension Herd
5 or less
40 or more
Chlorine
Catalase
% 0.169 0.170 0.146
% 145 97 52
0.114 0.184
18 59
i
Chlorine % 0.117 0.125 0.128 0.117 0.130 0.121
Cata]ase % 34 38 15 26 10 22
CHLORINE AND CATALASE CONTENT OF MILK
341
u d d e r . A s f a r as. th e w r i t e r s know, this is t h e first i n s t a n c e o f a h e r d o f a p p a r e n t l y n o r m a l cows p r o d u c i n g m i l k of low c u r d t e n s i o n or s o f t - c u r d milk. T h e h e r d s s t u d i e d consist l a r g e l y , if n o t w h o l l y , of t h e i r o w n p r o g e n y ;. t h e g e n e t i c f a c t o r r e s p o n s i b l e f o r s o f t - c u r d m i l k m a y t h u s be b r o u g h t to a t t e n t i o n i n a d e g r e e n o t p r o b a b l e in a h e r d m a i n t a i n e d b y p u r c h a s e . TABLE 5 The eatalase and vhlorine vontent of the mill~ of individual cows of low and high curd tension in herd 5
Cow
tensionCUrd Chlorine
Catalase I Cow
tensionCUrd Chlorine
Catalase
1
May 9, 1941 23
O
0.114
[
17
I
1 5 12
63 48 42
0.135 0.122 0.133
10 14 6
48
0.088
2
1 2 4 5 11
42 52 65 43 40
0.087 0.082 0.101 0.086 0.098
17 2
17 24
44 43
0.103 0.103
33
65 52 50 42
0.081 0.062 0.097 0.106
5 14 13 36
May 26 1941 6 13 14 15 18 19 22 23 25 27
0.085 0.102 0.091 0.097 0.091 0.093 0.101 0.083 0.092 0.089
7
2
15
4 28 4 17 5 10 6 35 July 21, 1941
6 7 14 15 18 22 23 27
0.082 0.100 0.102 0.079 0.103 0.103 0.099
12 3 6 50 10 9 7 18
14
9
Aug. 7, 1941 6 7 14 15 18 22 23 27
0.079 0.066 0.086 0.100 0.107 0.087 0.084 0.090
21 10 18 69 17 39 30 47
17 24
T h e r e s a z u r i n t e s t s w e r e o b s e r v e d a t t h e e n d o f e a c h h o u r f o r five h o u r s , a n d a n u m b e r g i v e n to each s a m p l e at each o b s e r v a t i o n . A low n u m b e r , 1, f o r e x a m p l e , i n d i c a t e s t h a t l i t t l e c h a n g e i n t h e color of t h e d y e was n o t i c e d
342
E. G. HASTINGS AND ARTHUR EREiKSON TABLE 6 The relationship of resazurin reduction after 1 hour incubation to curd tension, chlorine and catala~e content of mill~
Herd
Curd tension
Cows
5 or less 40 or more 5 or less 40 or more 5 or less 40 or more 5 or less 40 or more 5 or less 40 or more 5 or less 40 or more
10 15 3 6 3 0 7 1 3 2 6
Chlorine
Catalase
0.169 0.117 0.170 0.125 0.146 0.128
145 34 97 38 52 15
4.0 '2.0 3.5 1.0 1.6 1.0
0.117 0.114 0.130 0.184 0.121
26 17 10 59 22
1.5 1.0 1.3 4.0 1.5
6
Resazurin
at t h a t p e r i o d of o b s e r v a t i o n , w h il e a h i g h n u m b e r i n d i c a t e d m u c h g r e a t e r r e d u c t i o n at t h e p e r i o d of o b s e r v a t i o n . Thus, 1 a t t h e f o u r t h h o u r m e a n s a m i l k v e r y low in b a c t e r i a l c o n t e n t a n d in cells, w h i l e 5 at t h e first h o u r m e a n s a m i l k h i g h in b a c t e r i a or i n b o d y cells, or in both. T h e a n s w e r as to w h i c h is g i v e n b y th e m e t h y l e n e blue test. T h e m i l k s in q u e s t i o n w e r e cons t a n t l y so low in b a c t e r i a t h a t a r a p i d r e d u c t i o n w i t h r e s a z u r i n m a y be used as a n e v i d e n c e of h i g h c o n t e n t in b o d y cells. I t t h u s seems p r o p e r to use the a v e r a g e s of the r e s a z u r i n r e a d i n g of t h e two classes of c o w s - - t h o s e prod u c i n g m i l k of a c u r d t e n s i o n of 5 or below a n d those s h o w i n g a t e n s i o n of 40 or above. T a b l e 6 p r e s e n t s t h e a v e r a g e r e a d i n g of t h e r e s a z u r i n test at t h e en d of t h e first h o u r f o r th e two g r o u p s of cows in each of t h e six h e r d s on a p a r t i c u l a r d a y in May. T h e e x p e c t e d r e l a t i o n b e t w e e n h i g h c h l o r i n e a n d catalase c o n t e n t a n d r a p i d r e d u c t i o n of r e s a z u r i n is sh o w n in each h e r d e x c e p t 5, in w h i c h the m o r e r a p i d r e d u c t i o n was n o t e d in t h e h i g h t e n s i o n g r o u p of cows. T h e n u m b e r of cows i n each g r o u p of t h i s h e r d was so sm al l t h a t the figures can be o n l y s u g g e s t iv e . T h e smallness of t h e g r o u p s r e p r e s e n t i n g the e x t r e m e h i g h a n d low v a l u e s i n d i c a t e s t h a t the h e r d consists l a r g e l y of n o r m a l animals. TABLE 7 The relationship of catalasc content of milk to the rapidity of reduction of resazurin
Herd
Average catalase content
Average reading in resazurin test, 1 hr.
56 65 48 29 25 48
3.0 3.2 2.5 1.9 1.4 2.7
C H L O R I N E A N D CATALASE C O N T E N T
OP MILK
343
The relationship between the average catalase content of the entire amount of milk delivered at the factory to the average reading of the resazurin test at the end of the first hour for each herd is shown in table 7. The relationship between catalase content and reducing power toward resazurin is clearly evident f r o m the data, which also show t h a t herd 5 is the only one of the six that can be considered as producing normal milk, since the milk of cows with healthy udders should not exceed 25 in its c a t a l a s e value. Indeed, the value 20 is most frequently found in the literature on the subject, and in the experience of the writers some herds will consistently produce milk that will not exceed this value. The same is true of most first lactation cows. The cause of the condition noted in herds 1, 2, 3 and 6 cannot be stated with certainty. F r o m the few observations made as to the presence of streptococci ix the milk of individual cows, one is inclined to consider them as the p r i m e disturbing agent. The observations of the senior author indicate that herds in similar condition are to be found in all areas. I t is hoped that the incidence of such herds is not as high as in the six studied, for they cannot serve as the foundation of a successful f a r m or of a successful cheese industry. Some p r o g r a m of herd m a n a g e m e n t should be developed through the use of which such herds can be placed on a more normal base. SUMMARY
The tension of the curd produced u n d e r s t a n d a r d conditions in the 24-hour product of each of six herds was noted f r e q u e n t l y throughout a period of six months. The p r o d u c t of one herd (No. 4) had an average curd tension a p p r o x i m a t e l y twice as great as that of the other five herds and is believed to represent what one would expect to obtain f r o m a group of cows with healthy udders. The low curd tension of f o u r of the remaining five herds is believed to be due to the high incidence of chronic mastitis in these herds, since the p r o d u c t thereof was abnormally high in catalase and in chlorine. The low curd tension noted in the product of the remaining herd (No. 5) is believed due to the genetic p a t t e r n of the members of the herd since the chlorine and catalase content of its p r o d u c t was normal. The record of the four herds indicates them to be agents of low value for the production of milk both f r o m the standpoint of q u a n t i t y and quality of milk.