622 NUTRITION OF FARM ANIMALS 



for the organisms and so stimulating their multiplication and 

 activity, and the fact that readily soluble nitrogenous materials 

 like amino acids or ammonium salts seem to be particularly 

 effective is quite in harmony with this view. The action of 

 nitrogenous materials in stopping the excretion of undigested 

 starch, on this view, would be explained as due to an increase 

 .of the proportion fermented, leaving less to be acted on by the 

 digestive juices of the intestines. 



727. Effect of addition of protein. It was shown in the 

 last paragraph that rations containing a large portion of car- 

 bohydrates and therefore relatively deficient in protein, i.e., 

 those having a wide nutritive ratio, are likely to show an im- 

 paired digestibility, especially by ruminants. Correcting this 

 condition by increasing the protein content of such rations tends, 

 as would be expected, to increase their digestibility. 



Trials have been macle by several investigators of the effect of 

 the addition of nearly pure protein (wheat gluten with 78 per 

 cent of crude protein, or fish meal with 96 per cent of crude 

 protein in the organic matter) to a basal ration. In general, 

 such an addition has had little effect on the digestibility of the 

 protein of the basal ration, but in several experiments on rumi- 

 nants an increased digestibility of crude fiber, and, in some cases 

 of the nitrogen-free extract, has been observed, especially, with 

 basal rations poor in protein. In other instances, however, 

 particularly when the deficiency in protein was less marked, 

 this effect has been either slight or entirely absent and the 

 same is true of such experiments on swine as have been thus 

 far reported. Experiments are also on record in which the 

 addition of feeding stuffs rich in protein, such as oil cake or 

 legumes, has distinctly increased the digestibility of the crude 

 fiber of a basal ration and others in which such an addition 

 has stopped an excretion of undigested starch in the feces. 



728. Effect of non-protein. The addition to the basal ra- 

 tion of ruminants of digestible non-protein in the form of plant 

 extracts as a rule tends to diminish the apparent digestibility 

 of the protein of the basal ration, i.e., to increase the excretion 

 of nitrogen in the feces, while the simpler forms of non-protein, 

 such as asparagin or ammonium salts, have not usually pro- 

 duced this effect. 1 



1 Compare U. S. Dept. Agr., Bur. Anim. Indus., Bui. 139 (1911), pp. 14-28. 



