The nutritive value of white clover and perennial ryegrass for young sheep

Abstract

Perennial ryegrass (PRG) and white clover (WC) grown during spring and early summer 1967 were harvested and preserved frozen. The frozen herbages were later fed as pure or mixed diets on an ^{ad libitum} or restricted basis to Romney wether hoggets in a 94-day feeding trial from April to July 1968. Nitrogen retention studies were conducted using both comparative slaughter and balance techniques. The balance technique appeared to have a positive bias in estimating N retention.

The WC had 20% higher N levels than the PRG feed. N digestibilities, N intakes, total N retention, wool N retention, empty bodyweight gain, and wool growth were all significantly greater for WCfed sheep than for PRG-fed sheep. The results from sheep on mixed diets were not significantly different from the average results of the two pure diets.

N retention was highly correlated with N intake, and the N from each diet appeared to be utilised with equal efficiency. The calculated average intakes of feed N and digestible N to support zero N retention were 9.7 and 7.2 g daily respectively for these sheep (average weight 23.1 kg).

Partitioning N retention showed that daily retentions in total body, carcass, offal and blood, and wool ranged 0.8-3.5 g, 0.3-1.3 g, 0.1-0.9 g. and 0.4-1.4 g respectively, depending on diet and plane of nutrition.

There were significant correlations between total N retention, carcass N retention, and N retention in wool and empty body-weight gain, carcass-weight gain, and wool growth respectively.