EFFECT OF YEAST CULTURE ON GROWTH OF BEEF-CATTLE FED ON GRASS-SILAGE PLUS BARLEY-BASED CONCENTRATES

The effects of dietary inclusion of yeast culture (Yea-Sacc; Saccharom yces cerevisiae plus growth medium; 5 X 10(6) organisms/g) on growth, feed conversion efficiency and carcass traits of beef cattle were exam ined in three experiments. The animals were continental-breed crosses and in each experiment were offered grass silage ad libitum. In Experi ment 1, young bulls (14 per treatment, initial liveweight (LW) 315 kg) were offered either no additive or 10 g yeast culture per animal dail y for 203 days plus an average of 3.8 kg per animal daily of supplemen tary concentrate dry matter (DM). In Experiment 2, young bulls (20 per treatment, initial LW 310 kg) were offered either no additive or 15 g yeast culture per animal daily for 220 days plus an average of 3.5 kg per animal daily of supplementary concentrate DM. In Experiment 3, gr owing heifers (20 per treatment, initial LW 271 kg) were offered eithe r no additive or 15 g yeast culture per animal daily for 127 days plus an average of 0.86 kg concentrate DM per animal daily. In Experiment 1, yeast culture had no effect on feed intake or slaughter traits but did increase (P<0.05) average daily gain (1.18 v. 1.11 kg/day) and ten ded (P<0.1) to improve the conversion of dietary DM to liveweight gain (6.92 v. 6.57 kg DM intake/kg liveweight gain). In Experiment 2, neit her feed intake, liveweight gain, feed conversion ratio nor any measur ed slaughter trait was influenced by yeast culture. In Experiment 3, n either DM intake, liveweight gain nor feed conversion ratio was influe nced by yeast culture. It is concluded that dietary inclusion of yeast culture resulted in only a marginal improvement in growth and efficie ncy of cattle fed a basal diet of grass silage and barley-based concen trates.