A familiar practical method of estimating carcase weight from live weight is to reckon one Smithfield stone (8 lb) of carcase for each imperial stone (14 lb) of live weight.
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.
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.
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.