i 3 4 THE CHEMISTRY OF CATTLE FEEDING 



show that, in general, it is not expedient to restrict the supply 

 of protein to this theoretical minimum. In practice, it is usual 

 to feed larger quantities of protein to store animals, and the 

 following arguments have been adduced in support of the 

 custom. 



It is necessary to make allowance for the differences 

 between individual animals and for the variation in the 

 character and quality of the foods. The figure given above 

 no doubt represents a close approximation to the truth, but 

 it is not a mathematical certainty. 



The digestibility of the carbohydrates is reduced if the 

 proportion of protein is too small, especially if the ration 

 includes a large bulk of difficultly digestible materials. This 

 has been attributed to the fact that the digestive enzymes, 

 which are nitrogenous compounds, are formed from the protein, 

 and that larger quantities of the ferments are required for the 

 digestion of such materials. 



Each kind of animal requires a particular combination of 

 the amino-groups derived from the protein, to form its tissues, 

 and any groups which are not required are split off and 

 oxidised. As we have very little information regarding the 

 proximate composition of the different proteins of the foods 

 and practically none regarding the particular groups required 

 by the animals, it is advisable to make allowance for possible 

 waste in this way. 



The health of the animals is improved when they get more 

 than the theoretical minimum quantity of protein. This has 

 been denied on the strength of certain investigations carried 

 on for short periods ; but it has been found that when cattle 

 are kept for many months on very low nitrogenous rations 

 they lose their coats and exhibit a tendency to contract 

 disease and ailments of various kinds. On the other hand, 

 when they receive larger quantities of nitrogenous matter, 

 their respiration is quickened, circulation becomes more 

 vigorous, and body temperature a little higher. 



Deficiency of protein means starvation. A moderate 

 excess over and above the theoretical minimum is certainly 

 harmless and is probably beneficial. 



