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. The 

 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 conclusions, 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 



