A COMPARISON OF 5 PROTEIN-SOURCES AS SUPPLEMENTS FOR GROWING STEERS FED GRASS-SILAGE

An experiment conducted at three sites in eastern Canada, Kapuskasing, LeMoxville and Nappan, compared the efficacy of five protein sources as supplements for growing steers fed grass silage. For 20 wk, a total of 171 growing beef steers, average initial weight 247 kg, were offer ed grass silage ad libitum, either alone or supplemented with isonitro genous amounts of FM, SBM, Ch?, a mixture of corn gluten meal and bloo d and, at two sites, MM. There were no significant treatment-by-site i nteractions for any of the parameters measured. Combined across the th ree sites, liveweight gain was low on the all-silage diet, 0.51 kg d(- 1), and FM increased gain by 0.44 kg d(-1) or 86%. Soybean meal, CM an d the CGM/BM increased liveweight gain by an average of 0.35 kg d(-1) or 68%, while MM increased gain by 0.28 kg d(-1) or 58%. All supplemen ts increased liveweight gain (P < 0.001) with FM being superior to the other sources (P < 0.01). The supplements increased total DM intake ( kg 100 kg LW(-1), P < 0.01) but had no effect on silage intake (P > 0. 05). Gain/feed ratio was 0.091 on the all-silage diet and was increase d (P < 0.001) by all supplements, with FM (0.142) being superior (P < 0.01) to the other protein sources which averaged 0.129. The supplemen ts did not affect organic matter digestion (P = 0.06) in measurements made at Lennoxville. Rumen degradability did not explain the differenc es in the extent to which the protein sources improved the performance of growing steers.