In the feeding experiments which have been carried on at Rothamsted it has been shown that the amount consumed both for a given live weight of animal within a given time, and for the production of a given amount of increase, is, as current food-stuffs go, measurable more by the amounts they contain of digestible and available non-nitrogenous constituents than by the amounts of the digestible and available nitrogenous constituents they supply.
The non-nitrogenous substance (the fat) in the increase in live weight of an animal is, at any rate in great part, if not entirely, derived from the non-nitrogenous constituents of the food.
Hence it is that the amount of food consumed to produce a given amount of increase in live weight, as well as that required for the sustentation of a given live weight for a given time, should - provided the food be not abnormally deficient in nitrogenous substance - be characteristically dependent on its supplies of digestible and available non-nitrogenous constituents.
The average daily gain in live weight is thus arrived at, and as the animal increases in age this average gradually diminishes, until the daily gain reaches a stage at which it does not afford any profitable return upon the food consumed.
Amongst prize steers of two and a half to three years old, on the same occasion, the three highest daily average gains in live weight were 2.07 lb for an Aberdeen-Angus, 1.99 lb for a Shorthorn-Aberdeen cross-bred and 1.97 lb for a Sussex.
