Response of growing bulls to diets containing untreated or urea-treated rice straw with rice bran supplementation

Abstract

Untreated or urea-treated (4% w/w) rice straw supplemented with five levels of rice bran (0–1·6 kg/day) was given to 74 growing cross-bred bulls. Urea treatment significantly ( P < 0·001) improved feed dry matter intake at all levels of rice bran supplementation. Feeding treated straw alone increased dry matter intakes up to 30%. This could be partly due to the significantly higher ( P < 0·01) organic matter digestibility of the treated straw (59 vs 53%). At all levels of supplementation, treated straw gave significantly higher ( P < 0·001) liveweight gains than untreated straw. Animal fed on treated straw alone gained 93 g/day, whereas those fed on untreated straw lost 123 g/day. Treating straw with urea economises on rice bran supplementation or results in higher liveweight gain for the same level of supplementation.