DIGESTIBILITY OF FEEDING STUFFS 69 



Influence of Different Nutrients — Carbohydrates. — It was 

 found, during the early studies of nutrition problems with farm ani- 

 mals, that the digestibility of a ration was appreciably decreased by 

 the addition of large quantities of carbohydrates; the effect was 

 noticed when more than 10 per cent of the dry substance of a ration 

 was composed of soluble or other carbohydrates, and was especially 

 marked as regards the digestion coefficients for protein, fiber, and 

 nitrogen-free extract. Potatoes, roots, or corn will cause such a 

 depression in the digestibility when added to rations of wider nutri- 

 tive ratios than 1:8; the wider the nutritive ratio is, the greater will 

 the depression be. If the protein content of a ration be increased 

 with the allowance of carbohydrates, the depression in the digesti- 

 bility of protein is decreased. High-protein feeds may, therefore, 

 be fed with starchy coarse feeds, like hay or straw, without affecting 

 their digestibility, but starchy feeds, like roots and tubers, cannot be 

 fed in larger proportions than 15 per cent of the ration, calculated 

 on the total dry matter content, without decreasing its digestibility. 



The Massachusetts station lately corroborated these results of 

 early investigators and showed that molasses and molasses feeds 

 have a similar effect on the digestibility of the hay, as given above 

 in the case of potatoes and roots. 7 When molasses constituted more 

 than 20 per cent of the dry matter of a ration of hay and gluten feed, 

 a marked depression in the digestibility of the ration was observed. 



Fat (oil). — A moderate amount of oil added to a ration for 

 cows, say one-half to one pound daily per 1000 pounds live weight, 

 exerts a favorable influence on its digestibility, but if larger quanti- 

 ties are fed, the nutritive ratio of the ration becomes very wide, with 

 a resulting depression in the digestibility; more can. be fed in the 

 form of the oil-bearing seeds, e.g., flaxseed, than clear oil, without 

 seriously affecting the digestibility of the ration or the appetite of 

 the animals. A heavy feeding of oil, even if it were economical, is 

 not advantageous, because it is likely to cause a loss of appetite. 



Protein. — An addition of easily digestible protein substances to a 

 ration does not influence its digestibility in any way. In experiments 

 with pigs in which potatoes and varying quantities of meat flour 

 were fed the crude protein of the meat was completely digested, while 

 the proportion of potatoes digested remained unchanged. Protein 

 added to a ration not only does not affect the digestibility of the 

 basal ration, but will counteract any depression in digestibility that 

 might be caused by the addition of large qauntities of soluble carbo- 

 hydrates, as has been, stated. It has been found, in general, in ex- 



7 Report 1919, part i, pp. 82-131; see also Georgia Bulletin 115, and 

 Rept. 28, p. 12^ 111. Bui. 20, and Science, 42 (1915), p. 58. 



