BUREAU OF ANIMAL INDUSTRY. 119 



CLEANING MILKING MACHINES. 



During investigations relative to- the cleaning and sterilizing oi 

 milking machines 291 samples of machine-drawn milk were taken 

 for bacterial counts. The results show that the heat method of 

 sterilization is so far the most efficient and practicable. Of all 

 samples taken from machines properly sterilized by the heat method, 

 the average bacterial count was 11,200. The use of this method 

 caused great reductions in the bacterial content of milk produced 

 on a number of farms where tests were made. Experiments with 

 the salt-and-chlorin solution indicated that for cleaning milking ma- 

 chines this solution was no more effective than the plain chlorin 

 solution. A set of simple instructions in the use of the heat method 

 was sent out in circular letters to health officers and through the 

 press. 



OTHER ACTIVITIES. 



Field observations on the use of metal tanks for transporting 

 milk on railroads and motor trucks have led to the following con- 

 clusions : Metal tanks on railway .flat cars can be used successfully 

 in transporting milk and partially condensed milk, especially when 

 full-tank shipments are made. Pick-up shipments of milk have 

 not proved desirable so far. Metal tanks mounted on motor trucks 

 or horse-drawn vehicles are in successful use. More thorough meth- 

 ods of cleaning tanks and greater care in selecting sizes and tj'pes 

 to fit the work to be done are recommended. 



A study of the bacterial counts in cream and skim milk after sepa- 

 rating centrifugally indicated that these counts approximated closely 

 the original count of the whole milk. 



A tabulation of data from 180 tests showed that there were 338 

 per cent more bacteria in fresh milk produced with unsterile uten- 

 sils than in milk produced in sterilized utensils. After standing 

 for 24 hours at 60° F. the count was 630 per cent greater for milk 

 in unsterile utensils. Other tests showed that where steam was not 

 available thorough washing caused a marked reduction in bacterial 

 counts. 



The experiments in connection with the effect of silages on the 

 flavor and odor of milk were coKipleted and a manuscript on this 

 subject was prepared for publication. It was found that relatively 

 heavy feedings of silage could be fed to cows one hour after milking 

 without affecting the milk. Silage odors and flavors were absorbed 

 largely through the body of the cow rather than from the air. Aera- 

 tion of the milk while still warm reduced or eliminated silage flavors 

 and odors. Green alfalfa fed in relatively large quantities one 

 hour before milking gave marked odors and flavors to milk, but 

 when as much as 30 pounds was fed after milking there was practi- 

 cally no effect on the milk from the next milking. 



Experiments on the whipping quality of cream were concluded 

 and a manuscript reporting the work was prepared for publication. 

 Age, richness, and low temperature at time of whipping were found 

 to be essential to good Avhipping quality. 



The results of experiments on the feathering of cream in coffee, 

 completed last year, were tabulated, and a manuscript has been pre- 

 pared for publication. 



2.5684— AGR 1923 9 



