12 THE CONTAMINATION OF MILK. 



Feeding. The dust in the air occasioned by the feeding of 

 grain and hay, during the milking, increases the bacterial con- 

 tent of the milk drawn during the feeding by about one-third 

 of that of cows milked when not feeding, other conditions be- 

 ing alike. The feeding of dry corn stover, immediately before 

 milking, also increases the contamination to about threefold 

 of that occurring without such source of dust in the air (60). 



Feeding hay during the milking period is a common practice 

 by no means necessary. Cows accustomed to at least eating 

 grain at that time require considerable training before they 

 will patiently wait until after milking for their feed. Delay 

 in feeding in some cases undoubtedly adds some extra trouble 

 to the attendants, but is practiced in the best dairies. 



Certain feeds are highly objectionable because of their effect 

 upon the cow. Brewers' grains, distillers' grains, and sugar- 

 beet pulp are a cheap source of feed in certain localities, and 

 they are fed in great quantity long after attaining an advanced 

 stage of fermentation. The result is a chronic diarrhea in 

 the cows and conditions in the stable that prevent the drawing 

 of clean milk. It is not at all unlikely that milk from cows 

 almost exclusively fed on such highly fermented food, would 

 contain substances not found in the milk of cows consuming 

 wholesome feed. On the other hand, the use of limited quan- 

 tities of beet pulp and the like, when fresh and combined with 

 a properly balanced ration, seems to cause no trouble. These 

 products, when dried, are unobjectionable (37). 



Special milking rooms. Efforts to reduce bacterial contam- 

 ination to the minimum have, in some dairies, led to the con- 

 struction of a milking room apart from the general stable where 

 better aseptic conditions might be maintained. Such construc- 

 tion as to permit sterilization of the walls, floor and ceiling, 

 together with the absence of the contaminating features of 

 feeding and manure, offered hope of reducing bacterial contam- 

 ination. Such rooms are necessarily small and a few cows at 

 a time are admitted. Results have been disappointing, for the 

 movements of the cattle dislodge the dust from the hair and 

 result in a higher bacterial content of the air than in the general 

 stable where the cattle stand quietly. An open shed in a pas- 



