CONDITIONS INFLUENCING DIGESTION 131 



192. Influence of season and storage.^It is well 

 known that the composition of fodder crops grown on the 

 same soil may vary somewhat from year to year accord- 

 ing as the season is wet or dry, cold or warm. Such varia- 

 tions may influence digestibility, though no actual 

 demonstration of this fact appears to be on record. Th^ 

 question is often asked whether the storage of hay for 

 a long period affects its nutritive value. The data from 

 four series of experiments touching on this point indicate 

 that there is a perceptible, though not marked, decrease 

 in digestibility of hay during long-continued storage. 



193. Influence of the combination of food nutrients. — 

 Among the apparently important and freely exploited 

 conclusions drawn from investigations in animal nutri- 

 tion is the statement that the digestibility of food is 

 influenced to a marked degree by the relative propor- 

 tions of the several classes of nutrients. It is taught that 

 if more than a certain percentage of starch and sugar, or 

 of feeding-stuffs rich in carbohydrates, like potatoes 

 or roots, is added to a basal ration, the digestibility of 

 the latter is decreased, the protein and fiber being especi- 

 ally affected. The condusions, as stated by Dietrich and 

 Konig, on the basis of a critical study of the data involved 

 are that if pure carbohydrates are used to the extent of 

 more than 10 per cent of the dry substance of a basal 

 ration, or if potatoes and roots are fed equivalent in dry 

 matter to more than 15 per cent, a depression of digesti- 

 bility occurs, which increases with the amount of carbo- 

 hydrate material added. Kellner taught that if the crude 

 protein in a ration falls below one part to eight of digesti- 

 ble non-nitrogenous nutrients (carbohydrates -|- fat X 2.25) 

 a depression digestibility occurs. It is suggested that 

 when much easily digested carbohydrate material is 



