ENERGY VALUES OF RATIONS FOR FARM ANIMALS. 17 



mals — such, for example, as the 2 to 3-year-old steers which are com- 

 monly fattened in the corn belt — probably 3.25 therms of net energy 

 per poimd of gain in live weight is a fair allowance, although more 

 appears to be often used in practice. As yet no corresponding data are 

 available for the fattening of growing animals, as, for example, in the 

 production of the so-called baby beef. It is not probable, however, 

 that any larger amount of protein is required in such fattening than 

 in feeding simply for normal growth, so that the additional feed 

 given for fattening may, from this point of view, consist largely of 

 nonnitrogenous material; that is, carbohydrates and fats. It is to be 

 noted, however, that an excess of these materials in the ration tends 

 to cause less perfect digestion and also that a moderate proportion 

 of the more nitrogenous concentrates seems to promote the con- 

 sumption of heavy rations. Kellner recommends that at least 1 

 pound of digestible protein be supplied in the ration for each 8 to 10 

 pounds of carbohydrates and fat. 



REQUIREMENTS FOR MILK PRODUCTION. 



Of all forms of animal production that of milk is perhaps the most 

 variable and most influenced in its amount by the feed supply. The 

 energy relations of milk production have not been very fully investi- 

 gated. Tentatively, however, it seems safe to estimate that the pro- 

 duction of 1 pound of average milk, containing about 13 per cent of 

 total solids and 4 per cent of fat, will require approximately 0.27 therm 

 of net energy value in the feed. Naturally this amount would vary 

 with the quality of the milk, milk rich in fat and in total solids requir- 

 ing more than milk containing more water or a lower percentage 

 of fat. 



The matter of the protein requirements for milk production has 

 not been altogether cleared up. It seems to have been pretty well 

 demonstrated that, for a time at least, a moderate milk production 

 may be kept up on a supply of protein only slightly exceeding that 

 found in the milk produced (of course, in addition to the maintenance 

 requirement). In the case of average milk, this would call for about 

 0.032 pound of digestible protein for each pound of milk. It has not 

 been demonstrated, however, that a cow can keep this up indefinitely. 

 Furthermore, for the production of liberal yields of milk more protein 

 seems to be required, or at least to be advantageous. 



Tentatively, the requirements of digestible true protein and of 

 net energy for the production of 1 pound of milk may be formulated 

 as follows. 



