UTILIZATION OF GRASS SILAGE BY CATTLE: FURTHER OBSERVATIONS ON THE EFFECT OF FISHMEAL
Following weaning at 6–7 mo of age, 48 beef calves were used to determine growth response when two grass silages of contrasting nutritive value were supplemented with small amounts of barley or fishmeal. The silages were fed ad libitum for 112 d either alone or supplemented with 500 g barley or 500 g fishmeal per day. Both silages had similar cell wall and organic acid contents but silage 1 had higher nitrogen, 3.1 vs. 2.4% of dry matter (DM), and lower soluble sugar levels, 3.7 vs. 7.7% of DM, compared with silage 2. Animals fed silage 2 alone grew faster (P < 0.01) than calves fed silage 1 alone, 1.25 vs. 0.88 kg d−1. Supplementation with barley had no effect (P > 0.05) on liveweight gain; however, fishmeal substantially increased growth rate on both silages (P < 0.01), 0.49 and 0.3 kg d−1 for silages 1 and 2 respectively. Fishmeal tended to increase total DM intake of the silage 1 diet by an amount equivalent to the quantity of supplement offered but had no effect on DM intake of either silage (P > 0.05). Fishmeal supplementation also resulted in improved (P < 0.05) feed efficiency with both silages. Key words: Cattle, grass silage, fishmeal, growth