REPORT OF THE DEPARTMENT OF 
ANIMAL HUSBANDKY. 
tee tOOD “SOURCE “OF MILK FAT;~ WITH 
STUDIES ON THE NUTRITION 
OF MILCH COWS.* 
W. H. JORDAN, C. G. JENTER AND F. D. FULLER. 
The tests herein reported are in continuation of one given in 
Bulletin 132 relating to the food source of milk fats. The 
conclusion reached in that experiment, that part, at least, of 
the milk fat comes from the carbohydrates, is confirmed; and 
other facts relating to metabolism and utilization of food by 
milch cows are brought out. | 
Three cows were used: Cow 12 fed a fat-poor ration in which 
the protein supply was gradually decreased from 2.6 lbs. daily 
to 1.6 lbs. and then gradually restored to the maximum, with 
accompanying increase and decrease in carbohydrates so that 
the digestible dry matter of the ration was kept fairly uniform; 
Cow 10 fed a ration with normal supply of fat at first which 
was gradually increased to 1.4 lbs. daily, then gradually restored 
to the normal; Cow 2 fed the herd ration having a nutritive 
ratio about 1:5.6. These rations were quite varied in character 
and contained some fat-extracted foods; yet showed a quite 
uniform digestibility of about 70 per ct. of the dry matter. It 
is 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 
appeared to render rations less digestible, especially the pro- 
tein. The marked changes in protein content and in fat content 
of rations did not produce noticeable changes in the character 

*A reprint of Bulletin No. 197. 
