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.” 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. with 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 quantities of soluble carbo- 
hydrates, as has been stated. It has been found, in general, in ex- 
7 Report 1909, part i, pp. 82-131. 
