94 



MAINTENANCE RATIONS OF FARM ANIMALS. 



It seems safe, therefore, to estimate 0.6 pound of crude protein or 0.5 

 pound true protein per 1,000 pounds live weight as representing in a 

 general wa} T the minimum protein requirement of mature cattle with a 

 probable range of 0.1 or 0.2 pound either way under varying conditions. 



For actual maintenance feeding it is probable that a somewhat 

 more liberal supply of protein than is indicated by these figures 

 would be advisable. Rations so poor in protein, if containing an 

 adequate amount of nonnitrogenous matter, would probably suffer a 

 loss through failure of the animal fully to digest the nonnitrogenous 

 matter. A somewhat narrower nutritive ratio could readily be 

 reached in practice in ordinary feeding without additional expense 

 and from the standpoint of digestibility would very likely be justified. 



SHEEP. 



While a considerable number of experiments with sheep are on 

 record in which approximate maintenance as a whole was observed, 

 at least so far as could be judged from the live weight, few of them 

 afford satisfactory data as to the minimum protein requirement. 

 For the immediate purpose of this discussion, only experiments in 

 which the nitrogen balance was actually determined are available, 

 mere maintenance of weight being too uncertain a criterion. 



A distinct difference between cattle and sheep, which affects the protein 

 requirement, lies in the greater demand for protein incident to the growth of 

 wool in the latter animals as compared with that of hair in the former. The 

 results of determinations by Armsby and Fries 1 on the same two steers in two 

 consecutive winters showed an average production of epidermal tissue, includ- 

 ing the growth of hair and the loss in brushings, equivalent to 0.19 gram nitro- 

 gen per day and 1.000 pounds live weight, which is equal to 0.0025 pound pro- 

 tein, an amount too small to materially affect our estimates of the maintenance 

 requirement. In the case of sheep, determinations of the growth of wool by 

 several investigators afford the following data regarding the average amount 

 of protein required for this purpose. The results have been computed per 

 1.000 pounds live weight for the sake of ready comparison : 



Protein contained in daily growth of toool per 1,000 pounds live weight. 



Pound. 



Henneberg, Kern, and Wattenberg 2 Mature sheep 0.132 



Henneberg, Kern, and Wattenberg 3 Lambs .143 



Weiske 4 Growing sheep .100 



Henneberg and Pfeiffer 5 Mature sheep . 149 



Pfeiffer and Kalb 6 Mature sheep . 150 



Average . 135 



Although, as the foregoing figures show, the protein requirements of sheep 

 for the growth of wool are considerably greater than those of cattle for the 



1 Bureau of Animal Industry, Bulletin 128. 

 - Journal fur Landwirtschaft, vol. 26, p. 549. 

 8 Ibid., vol. 28, p. 289. 



4 Landwirtschaftliche Jahrbiicher, vol. 9, p. 205. 



5 Journal fur Landwirtschaft, vol. 38, p. 215. 



6 Landwirtschaftliche Jahrbiicher, vol. 23, p. 175. 



