ENERGY DIGESTIBILITY AND NITROGEN RETENTION BY PIGS AND RATS FED DIETS CONTAINING NON-NUTRITIVE DILUENTS AND VARYING IN PROTEIN LEVEL

Abstract

Diets containing gross energy levels of 3.9 and 3.2 Cal./gm. and crude protein levels of 14 and 18 per cent on an air-dry basis (4.4 and 3.5 Cal./gm and 15 and 20 per cent respectively on an oven-dry basis) were fed in a 2 × 2 factorial design to weanling rats and pigs. The lower energy level was achieved by adding 20 per cent of a fine aggregate of vermiculite. In the rat experiment the vermiculite was compared with a similar level or non-nutritive cellulose. Dry matter, apparent energy and apparent nitrogen digestibility and nitrogen retention were determined with 4- to 5-week-old rats weighing approximately 80 grams and with pigs averaging approximately 8, 20 and 50 kilograms liveweight.The apparent digestibility of energy and nitrogen by rats and pigs was similar. The percentage apparent nitrogen digestibility was reduced in both species fed lower energy diets. Dry matter and energy digestibilities were lowered in rats fed lower energy diets containing vermiculite but a similar effect was evident only in 8-kilogram pigs.Nitrogen retention varied between the two species. Percentage gross or digestible nitrogen retention in rats was increased with higher energy and with lower protein diets. Retention of digested nitrogen in Pigs was reduced with higher energy compared to lower energy diets. Higher protein improved nitrogen retention in 8-kilogram pigs but lowered retention in heavier pigs.