CHAPTER VIII. 



FOODS. 



Tlie Composition of Foods. — Detailed composition — Proportion of 

 nitrogen existing as true albuminoids — Comparison of foods. 

 Circumstances producing Variation. — Influence of age and manur- 

 ing — Changes during hay-making and ensilage. Digestibility of 

 Foods. — Method of determination — Experiments with ruminants 

 — Experiments with horses — Experiments with pigs — Experiments 

 with geese and fowls. Circumstances affecting Digestibility. — 

 Influence 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 ensilage — Influence of one 

 food on the digestibility of another — Common salt. Comparative 

 Nutritive Value of Foods. — Quantities of digestible matter in 1,000 

 parts of food. — Comparative power of producing heat, work, and 

 increase — Proportion of albuminoids to non-albuminoids — In- 

 fluence of proportion of water — General conclusions. 



In Chapter VI. we have enumerated the chief con- 

 stituents of food, and described their functions in the 

 animal body. We may now proceed a step further, 

 and consider the detailed composition and the feed- 

 ing values of the foods actually employed on the farm. 



The nourishing value of a food is largely deter- 

 mined by two factors : (1) Its composition ; (2) its 

 digestibility. The first of these determines the rich- 

 ness of the food in albunlinoids, fat, carbohydrates, 

 and ash constituents. The second determines the 

 extent to which these various constituents become 

 available in the animal body. We will consider, first, 

 the composition of ordinary foods. 

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