114 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



shown that tliis organism is not patliogenic and can be safely usec^ in 

 such work. 



Studios on tlie transportation of milk and tlie effect of different 

 methods of refrigeration (hiring transportation have been contiinied, 

 and various types of milk cans have been tested in experimental 

 shipments. 



DAIRY RESEARCH LABORATORIES. 



NUTRITION EXPERIMENTS. 



Nutrition experiments with daiiy cattle have continued to show 

 the beneficial effect of increasing the calcium and phosphorus content 

 of the ration. This is especially true of cows fed according to com- 

 monly accepted feeding standards, and indicates that such cows are 

 probably not getting sufficient quantities of bone-building material. 

 Ex[)erimcnts on the changes produced in the blood of cows by chang- 

 ing the alkalinity of the ration show that the response of cows to such 

 change differs in several respects from that of omnivorous and car- 

 nivorous animals. Silage fed in large amounts acts as an acid- 

 producing feed. This is contrary' to what would be expected from its 

 ash content, and is a fact which may have considerable practical im- 

 portance. Tt has also been demonstrated that the amino acids of the 

 blood are the precursors of the milk proteiins. 



BACTERIOLOGY. 



The work on the sporogenes test for the quality of milk has been 

 .completed, and it has been shown that if a sufficiently large quantity 

 of milk is tested from each sample there is some relation between 

 this test and the conditions under which the milk was produced. 

 The test will at best differentiate onl}' between extremes in methods 

 of production. 



A butter cultuns which is widely used commercially has been found 

 to consist of two tj'pes of streptococcus; one which ])roduces a high 

 acid in milk, and a sharp flavor, with but little volatile acid; and 

 another producing less total acid but considerable volatile acid. 

 When they are grown together in milk the volatile acid is increased 

 and the flavor of the culture is greatly improved. The isolation of 

 the second type w^as made possible by the use of a new milk-powder 

 agar. This medium gives high counts with milk anc[ makes possible 

 a qualitative as well as quantitative count. 



Preliminarj^ work on the sterilization of dairy utensils by dry 

 heat has shown that spores can not be destroj^ed on soldered tin in this 

 way, but very satisfactory reductions in bacteria can be obtained in 

 bacily contaminated cans by exposure at comparatively low tempera- 

 tures and for short periods. 



Some bacteriological work of a nature too technical to be described 

 in this report has been carried on, and the results of some of it have 

 been published. 



ICE CREAM. 



Experiments indicate that " sandiness " in commercial ice cream is 

 .due to crystallization of the lactose and that it is influenced by the 



