MILK 21 



are known where the addition of several "fresh" cows 

 to a small herd at the same time has reduced the fat per 

 cent, of the mixed milk below the standard formerly 

 maintained. In the last month of lactation, when the 

 secretion decreases rapidly, the proportion of solids 

 usually increases, especially the fat. At the same time, 

 the secretion reacts decidedly alkaline to litmus paper 

 and usually has a salty taste; sometimes it has an animal- 

 like odor and taste. Cows in this stage of lactation are 

 called "strippers." In exceptional cases the milk does 

 not show any noticeable change in chemical composition 

 during the entire period of lactation, while in rare cases 

 the per cent, of solids may decrease at the end of lacta- 

 tion. At different stages of the same milking the milk 

 also shows a regular and constant variation in composi- 

 tion, the first milk drawn containing a lower per cent, 

 of fat than the last or "end" milk. Incomplete milking 

 may lower the per cent, of fat, because the end milk is 

 much richer in fat than the first milk. 



Transitory and irregular variations in composition 

 may be observed in the milk of the same cow from day 

 to day, or even in the milk drawn at different milkings 

 on the same day. The fat content may show a difference 

 of as much as one per cent. These variations are attrib- 

 uted to change in the character of the feed, or in the time 

 of feeding and watering, change of milkers, the weather, 

 change of stable, and unusual occurrences (storms, stran- 

 gers, etc. ) . The quantity of milk secreted is also affected 

 by the same causes. While the feed has no pronounced 

 permanent effect on the composition of the milk, a change 

 from dry to green feed may cause a temporary increase 

 in the fat of from 0.5 to 1 per cent., while distillery slops 



