CHAPTER VII. 



FOODS. 



The Composition of foods. Detailed composition Proportion of nitre- 

 gen existing as true albuminoids Comparison of foods. Circum- 

 stances producing Variation. Influence of age and manuring 

 Changes during haymaking and ensilage. Digestibility of Foods. 

 Method of determination Experiments with ruminants Experi- 

 ments with horses Experiments with pigs Experiments with 

 geese and fowls. Circumstances affecting Digestibility. Influ- 

 ence of age of animal, daily ration, and labour Influence of 

 cooking on digestibility Influence of the maturity of fodder 

 crops on their digestibility Influence of one food on the diges- 

 tibility of another Common salt. Comparative Nutritive Value 

 of Foods. Comparative power of producing heat and work 

 Proportion of albuminoids to non-albuminoids Influence of pro- 

 portion of water General conclusions. 



IN the preceding chapter we have enumerated the 

 chief constituents of food, and described their functions 

 in the animal body; we may now proceed a step further, 

 and consider the detailed composition and feeding value 

 of the foods actually employed on the farm. 



The nourishing value of a food is plainly fixed by two 

 factors : 1. Its composition. 2, Its digestibility. The 

 first of these determines the richness of the food in albu- 

 minoids, fat, carbo-hydrates, and ash constituents. The 

 second determines the extent to which these various con- 

 stituents are made use of in the animal body. 



Composition of Poods. The average percentage com- 

 position of the foods commonly given to farm animals is 



