FACTORS THAT AFFECT COMPOSITION OF MILK 59 



1 ; and of the ten-day interval between the succeeding periods, 

 the first three or four days were taken for changing rations, 

 leaving six or seven days of the new ration before the beginning 

 of the period. 



' ' Each period lasted twenty-one days. The cows were weighed 

 on three successive days every two weeks during the experiment. 

 Variations in weights were no greater than usually appear in 

 live weights of such animals, and did not surely indicate either 

 gain or loss." 



The results which were obtained as to percentage composition 

 of milk were as follows : 



"1. Quality of milk, so far as measured by its percentage of 

 fat, was changed by feed to a much greater degree than was 

 quantity. Two-thirds of the increase in average gross yield 

 of butter-fat was due to improved quality of the milk, and only 

 one-third to increased milk flow. 



"2. Sugar-meal produced .58 Ib. more butter-fat a 100 pounds 

 of milk than did corn- and cob-meal ; this difference is 17 per cent 

 of the amount of fat in 100 Ib. of milk produced by corn- and 

 cob-meal. 



"3. Sugar-meal produced .73 Ib., more total solids a 100 

 pounds of milk than did corn- and cob-meal ; this difference is 

 6 per cent of the solids in 100 Ib. of milk produced by corn- and 

 cob-meal. 



"4. As compared with corn- and cob-meal, sugar-meal in- 

 creased the ratio of fat to 'solids not fat' in 100 Ib. of milk, 

 from 396 a 1000 of 'solids not fat/ to 457 a 1000 of 'solids 

 not fat ' an increase of over 15 per cent." 

 Effect of under- and over-feeding. 



The influence of under-feeding and liberal feeding was studied 

 by Wing during a period of four years. A herd of twenty-one 

 cows was selected when they had been normally underfed by the 

 owner. 



" A record of the production of the herd in milk and fat was 



