GENERAL PROBLEMS IN DAIRY HUSBANDRY 347 



other milking produce milk containing 6 per ct. of fat or over. The 

 fluctation in the composition of the milk from the same cow is thus 

 much greater than has often been assumed. 



White and Judkins of the Connecticut (Storrs) Station 18 point out 

 that due to the variations in percentages of both fat and solids-not-fat in 

 the milk of different cows, it is essential when the milk is to be sold on 

 a city market to strain the milk from all the cows into a large can or 

 tank where it can be thoroly mixed before bottling or putting in small 

 cans. Otherwise the milk in some of the containers may fall below the 

 legal standards for fat or solids-not-fat. 



553. First and last drawn milk. The first milk drawn from the udder 

 is very poor in fat, each succeeding portion increasing in richness. 

 In a trial by Van Slyke at the New York (Geneva) Station 19 the first 

 portion of milk drawn from a Guernsey cow contained but 0.76 per ct 

 fat ; the second, 2.60 per ct. ; the third, 5.35 per ct. ; and the last, 9.80 

 per ct. The percentages of casein and albumin vary but little, decreas- 

 ing slightly as the milk becomes richer in fat. 



554. Effect of period between milkings. When the intervals of time 

 between milkings are unequal, cows generally yield a smaller amount 

 of milk after the shorter period, but this milk is slightly richer in fat 

 and total solids. For this reason the evening milk is usually richer 

 than that drawn in the morning. Where the intervals are equal there 

 is no regular difference in quality with cows milked twice a day. 

 When they are milked 3 times daily the mid-day milking is usually 

 the richest. 20 



555. Effect of age. The annual yield of both milk and fat by a cow 

 normally increases from the first lactation until she is mature. The maxi- 

 mum yield is usually reached at from 7 to 9 years of age. On account 

 of this, the requirements of milk or fat production by the various breed 

 associations for entry of cows into the advanced registry increases with 

 the age of the cow until maturity is reached. 



From a study of all the data bearing on the effect of age of the cow 

 on the yield and fat content of milk Eckles 21 concludes: 



"A dairy cow on the average as a 2-yr.-old may be expected to pro- 

 duce about 70 per ct. ; as a 3-yr.-old around 80 per ct. ; and as a 4-yr.-old 

 about 90 per ct. of the milk and butter fat she will produce under the 

 same treatment when mature. 



"Probably the majority of dairy cattle are rejected from the herd on 

 account of failure to breed, or from udder trouble before the effect of 

 advancing years can be observed to any marked extent. It is a fact 

 often observed that a cow may make her best record when 10 or 11 years 

 old, altho as a rule she does her best rather earlier. If a dairy cow 



M Conn. (Storrs) Bui. 94. 



19 Jour. Am. Chem. Soc., 30, p. 1173.. 



^Eckles and Shaw, U. S. D. A., Bur. Anim. Indus., Bui. 157. 



'"Dairy Cattle and Milk Production, p. 153. 



