120 AISTNUAL EEPORTS OF DEPARTMENT OF AGRICULTURE. 



DAIRY RESEARCH LABORATORIES. 



KUTRITION .OF DAIRY COWS. 



The feeding exi^eriments on the effect of rations low in calcium 

 and phosphorus are still under way and are giving positive results. 

 The cows on a low-phosphorus ration did not eat enough to supply 

 total nutrients required, and a phosphorus supplement had little 

 or no effect on the milk yield. The cows on a low-calcium ration 

 ate more than enough to supply their requirements for both protein 

 and total nutrients, but the milk yield of those giving more than 

 25 pounds of milk a day fell off rapidly. Cows on the same ration 

 supplemented with half a pound of ground limestone daily showed 

 a much less rapid drop in milk yield. 



Cows on a ration of grain, alfalfa hay, and corn silage, which 

 contained about the same quantities of protein and total nutrients 

 as a timothy -hay ration, maintained their milk yield somewhat better 

 than those which had the timothy-hay ration with the limestone 

 supplement. There is some indication that the calcium deficiency 

 has some effect on the reproductive function, and the evidence on 

 this point is being carefully followed. 



BACTEEIOLOGY AND CHEMISTRY OF MILK. 



The characteristics of several species of the streptococci which 

 may occur in milk have been determined with considerable accuracy 

 by the study of a large number of cultures from definite sources. 

 This and some other research work is too technical for detailed 

 description in this report. 



It has been definitely established that the accessory substances 

 which promote the growth of bacteria are not identical with 

 vitamins, at least in the ordinary acceptance of the term. Methods 

 which remove the water-soluble vitamin from yeast extract do not 

 affect its ability to promote the growth of bacteria. 



The stimulating effect of fats and oils is not confined to those 

 of vegetable or animal sources but is true also of mineral oils even 

 wdien present in extremely small traces. 



On account of a proposal to sliip milk at high temperatures an 

 investigation has been begun on the nature of the bacteria which 

 grow at temperatures between 40° and 70° C. In 6 hours at 60° C. 

 there is a slight increase in bacteria, but in 24 hours the number 

 reaches fnillions. • 



The very general use of chlorin compounds to sterilize dairy 

 utensils has suggested that these may be used as a preservative for 

 milk. A test has been devised by which it is possible to detect 1 

 part of chlorin in 50,000 parts of milk. 



The value of the alcohol test in detecting abnormal milk has been 

 demonstrated. Milk which reacted to the alcohol test and which 

 had an abnormally low coagulating temperature when evaporated 

 Avas traced to cows which had been fed moldy or decayed silage. 



MANUFACTURE OF WHOLE MILK AND CREAM PRODUCTS. 



Ice CREAM. — The influence of the composition of the mix on palata- 

 bility of ice cream has been studied by selling ice creani to a con- 



