Beef production from lucerne and subterranean clover pastures. 2. Bloat occurrence and effect of anti-bloat capsules

Abstract

Over 3 years (1975-77), the occurrence of bloat was recorded in steers grazing two legumedominant pastures, one (LC) containing lucerne (Medicago sativa) and subterranean clover (Trifolium subterraneum) and the other (C) subterranean clover. The effect of intraruminal capsules on both the occurrence of sub-lethal bloat and liveweight gain was assessed in spring 1976 (anti-bloat capsules), and in spring 1977 (anti-bloat and monensin capsules, singly and together). In unprotected steers, bloat occurred only during winter or early spring on both pastures. Over the 3 years, seven steers died from bloat on LC, and three on C. Sub-lethal bloat (rumen distention) was more frequent and severe on LC than on C in 1975 and 1976. However, in 1977 it was more frequent on LC in June-July, but more frequent on C in August-September; there was no difference in severity between pastures. The anti-bloat capsules halved the rumen distention index and improved liveweight gain by an average of 0.2-0.3 kg/head day-1 for short periods in October 1976 and August 1977. The results with monensin capsules were inconclusive. Bloat occurrence is discussed in relation to pasture and environmental conditions, and to beef production on lucerne-clover and clover pastures.