496 NUTRITION OF FARM ANIMALS 



Eckles 1 has likewise determined partial energy balances of 

 ten milking cows for an entire year on rations just sufficient to 

 maintain their live weight. In these experiments the percentage 

 digestibility of the rations is computed for eight of the cows on 

 the basis of results obtained in digestion trials on five of the 

 animals, while the maintenance requirement of all but one of the 

 cows was determined in live weight experiments after the cows 

 were dried off, with the results reported in Chapter VIII (381). 



Estimating the metabolizable energy of the rations at 3.7 

 Therms per kilogram of digestible organic matter (753) and com- 

 puting the results, exactly as in Jordan's experiments, on the 

 assumption of no gain or loss by the body, the following values, 

 for the percentage utilization in milk production are obtained. 



TABLE 135. PERCENTAGE UTILIZATION OF METABOLIZABLE ENERGY IN 

 MILK PRODUCTION 



Cow No. 206 63.36 % 



Cow No. 304 67.60% 



Cow No. 400 66.90 % 



Cow No. 43 5 I -36% 



Cow No. 62 72.82% 



Cow No. 4 60.24% 



Cow No. 27 62.89% 



Cow No. 63 50.35 % 



Average 61.94% 



Haecker, 2 in discussing the results of extensive experiments 

 with the dairy herd of the Minnesota Experiment Station, has 

 compared the digestible nutrients of the feed and the solids of 

 the milk by reducing both to their carbohydrate equivalent. 3 

 Subtracting the estimated maintenance requirement from the 

 total carbohydrate equivalent (" nutriment ") of the feed, he 

 finds that of the remainder from 50.25 per cent to 66.22 per 

 cent was recovered in the milk, the general average for nine 

 years being 54.65 per cent, while the live weights of the cows 

 were in general maintained. This seems to indicate a decidedly 

 lower utilization of energy than that computed in Kellner's, 

 Jordan's and Eckles' experiments. It must be noted, however, 



1 Mo. Expt. Sta., Research Bui. 7. 



2 Minn. Expt. Sta., Bui. 140 (1914), p. 45. 



3 The fat of the feed is multiplied by the factor 2.2 and that of the milk by 2.25 

 and the product added to the carbohydrates and protein. The sums, which are 

 called " nutriment," are, of course, approximately proportional to the energy con- 

 tent of the milk and the metabolizable energy of the feed respectively. 



