JS'ew York Aguicultukal Experiment Station. 15 



believed that this figure represents fairly the digestibility of 

 rations made up in part of silage and containing a fair propor- 

 tion of high-class grains. A widening of the nutritive ratios 

 ajtpeared to render rations less digestible, especially the protein. 

 The marked changes in protein content and in fat content of 

 rations did not produce noticeable changes in the character or 

 composition of the milk. In the former test, during 59 days, 

 18.4 lbs. of fat was formed in the milk which could not have 

 had its source in food fat or food protein and could hardly have 

 been drawn from the cow's body fat as she increased in weight 

 33 lbs; in the same time. In the second test Cow 12 in 74 

 days produced 39 lbs. of fat similarly unaccounted for, with 

 a body gain of 15 lbs., and Cow 2 in 4 days, 1^ lbs. These 

 amounts of fat must have come from the carbohydrates in the 

 food. 



A lessening of protein supply in the food did not produce a 

 corresponding decrease of protein in the milk solids, but caused 

 --a marked lessening of protein decomposition in the body. Calo- 

 rimeter determinations show that the heat value of urine bears 

 no constant relation to its nitrogen content, and also prove that 

 the formula used in computing heat energy of urine, Nx5.343 

 Cal., is greatly in error, actual results being from 3 to 4 times 

 as large as calculated by this formula. The energy value of 

 nutrients as given by Rubner — protein and carbohydrates each 

 4.1 Cal. and fats 9.3 Cal.^ — appear to be fully high enough for 

 herbivora, even when the loss due to escape of unoxidized gases, 

 methane chielly, is not considered. 



Over 40 per ct. of the available energy value of the rations 

 was used for maintenance, over 30 per ct. reappeared in the 

 milk solids, leaving a balance of from one-fifth to one-fourth of 

 the ration. The logical conclusion is that this balance, in jjart 

 at least, sustains the work of milk secretion. 



77/c immediate effect on milk foiv of chauf/cs in the composition of 

 the ration. — A large number (nearly 1,000) of the individual 

 records from a daily herd have been averaged according to 

 dilferent relations in the constituents of the food to show the 



