..A STUDY OF RATIONS FED TO MILCH COWS. 59 
In the thirty-two tests of actual feeding practice the average 
ration per cow per day supplied from 1.15 to 2.70 pounds, 
averaging 2.0 pounds, of digestible protein; while the range of 
fuel values was from 21,150 to 35,150, averaging 28,250 cal- 
ories. The nutritive ratios of these rations ranged from 1: 4.5 
Porm t,.4, AVelaging 1: 7:0. 
To illustrate the apparent effects of larger and smaller quan- 
tities of protein these thirty-two tests have been divided into 
two groups. The first group includes all herds receiving two 
pounds or less of digestible protein per cow per day; the second 
group, those receiving more than two pounds of digestible pro- 
tein. In the first group of sixteen tests, including sixteen 
herds and 226 cows, the digestible protein per cow per day 
ranged from 1.3 pounds to 2.0 pounds, with an average of 1.62 
pounds. ‘The nutritive ratios ranged from 1:6.0 to 1:11.3, 
with an average of 1:8.1. In the second group (including 
sixteen herds and 227 cows) the digestible protein ranged from 
2.1 to 2.7 pounds per cow per day, with an average of 2.32 
pounds. The nutritive ratios ranged from 1:4.5 to 1:7.3, 
averaging 1:5.9. All but one of the first group were very 
wide, while most of the second group might be regarded as 
moderately narrow, ten out of sixteen being below 1:6.0. 
The results obtained with these two groups are easily com- 
pared with each other in respect to feeding, milk production, 
and profit, as shown in the table on the page following. 
In thirteen of the thirty-two cases just mentioned the tests 
were repeated with new rations containing an increase of pro- 
tein. [he number of cows in the thirteen herds ranged from 
eight to fifteen, the whole number being 156. The second test 
with each herd included the same cows as were used in the 
first test. These second tests, with the larger amounts of pro- 
tein and the narrower nutritive ratios, were made from two 
to four weeks later than the first test with the wide ration. 
Owing to advance in the period of lactation the milk flow and 
amount of butter-fat would naturally be less than in the first 
tests. Only eleven of these comparative tests are included in 
the following discussion for reasons explained on page 42. 
The thirteen comparative tests with narrow rations were 
made with the same herds as the thirteen tests with the wider 
ration. 
