274 EXPERIMENT STATION RECORD, 



ual herds of cows, such as are coruiuon in dairy regious of New York State, the 

 fat varied froui 2.90 to 5.50 per ceut, the total proteins from 2.31 to 3.71 per 

 cent, the casein from 1.70 to 3.02 per cent, and the albumin from 0.41 to 0.97 

 per cent. (3) In the case of milk consisting of a mixture of the milk of many 

 different herds of cows, the fat varied from 3.04 to 4.60 per cent, total proteins 

 from 2.53 to 3.76 per ceut, casein from 1.93 to 3 per cent, and albumin 

 from 0.47 to 0.88 per ceut. 



Conditions affecting variations of fat and proteins in milk. — The following 

 conditions are considered as of special prominence: (1) Individuality, (2) 

 breed, (3) stage of lactation, (4) food, (5) season, (6) time and manner of 

 milking, including fractional milkiugs, milk from different quarters of udder, 

 and relative order of milking a quarter of udder. 



Conditions affecting the relation of fat to total proteins and to casein in 

 milk. — (1) The breeds studied fall into two general groups; in one case, the 

 ratio of fat to proteins is relatively high (Guei'nsey and Jersey) ; iu the other, 

 relatively lower. Individuals of the same breed may vary considerably in this 

 respect. (2) The ratio of fat to proteins is very uniform through the lactation 

 period until about the ninth month, when the total i)roteins increase quite rap- 

 Idly in relation to fat. The ratio of fat to casein is very uniform throughout the 

 entire period of lactation, there being a slight increase of casein iu relation to 

 fat about the ninth month, (3) Variations in composition of milk due to man- 

 ner of milking affect the fat more or less extensively but the proteins very 

 little. 



Conditions affecting the relation of casein to albumin. — Albumin in milk 

 varies quite widely in relation to casein. The relation varies (1) with different 

 breetls, (2) with different individuals of the same breed, (3) with time and 

 manner of milking, (4) the relation is quite uniform during the first eight 

 or nine mouths of lactation, after which the albumin increases relatively more 

 than the casein. 



Methods of calculating casein and total proteins in normal milk. — In the case 

 of herd milk containing 3 to 4.50 per cent of fat, the following formula for cal- 

 culating the amount of casein has been found to give, in most cases, quite satis- 

 factory results : 



(F-3) X 0.4 + 2.1 = percentage of casein in milk (F equals number repre- 

 senting percentage of fat in milk). Total proteins in milk can be roughly 

 estimated by the following modification of the preceding foi-mula : 

 (P''-3) X 0.4 + 2.8 = percentage of proteins in milk. 



The relation of fat and casein in milk to yield of cheese. — In milk of avei'age 

 composition (3,6 to 3,8 per cent of fat) the yield of fresh cheese from 100 lbs. 

 of milk may be ascertained by multiplying the number representing the per- 

 centage of fat in milk by 2.7. The yield of cheese may be calculated more 

 closely for milks containing fat below 3.6 or above 3.8 per cent, wheu the per- 

 centage of both fat and of casein in milk is known, as follows: (Casein X 2.5) -\- 

 (Fat X 1.1) = pounds of fresh cheese made from 100 lbs. of milk. 



The relation of fat and casein in milk to composition and quality of cheese. — 

 Cheese made from milk in which fat is high relative to casein is superior in 

 quality to cheese made from milk in which fat is low relative to casein. Skim- 

 milk cheese, whole-milk cheese and cream cheese owe their difference in quality 

 to the difference in relation of fat to casein in milk. 



The relation of fat to jiroteins in milk as a basis for detecting skimmed milk 

 and skimmed-milk cheese. — In the case of herd milk as commonly found iu New 

 York State, the milk is open to the suspicion of being skimmed when the per- 

 centage of fat is less than that of proteins. Cheese of the Cheddar type which 



