144 Testing Milk and Its Products. 



and the milk sugar and ash content increases but little 

 (about .69 per cent.) within the range given. 



6. A test of only one milking may give a very erro- 

 neous impression of the average quality of a certain 

 cow's milk. A composite sample (see 179) taken from 

 four or more successive milkings will represent the 

 average quality of the milk which a cow produces at 

 the time of sampling. 



161. The variations that may occur in testing the 

 milk of single cows, are illustrated by the following fig- 

 ures obtained in an experiment made at the Illinois ex- 

 periment station, 1 in which the milk of each of six cows 

 was weighed and analyzed daily during the whole period 

 of lactation. Among the cows were pure-bred Jerseys, 

 Shorthorns and Holsteins, the cows being from three to 

 eight years of age and varying in weight from 850 to 

 1350 Ibs. During a period of two months of the year 2 

 the cows were fed a heavy grain ration consisting of 

 twelve Ibs. of corn and cob meal, six Ibs. of wheat bran, 

 and six Ibs. of linseed meal, per day per head. This sys- 

 tem of feeding was tried for the purpose of increasing, 

 if possible, the richness of the milk. The influence of this 

 heavy grain feed, as well as that of the first pasture 

 grass feed, on the quality and the quantity of the milk 

 produced is shown in the following table, which gives 

 the complete average data for one of the cows (No. 3). 

 The records of the other cows are given in the publica- 

 tion referred to ; they were similar to the one here given 

 in so far as variations in quality are concerned. 



1 Bulletin 24. 

 a See 175. 



