Comparison of sugar-beet pulp and barley with and without soya bean meal as supplements to silage for growing steers

The optimum live-weight gain for growing steers in winter depends on the cost of feed and subsequent compensatory growth. The objectives of this experiment were: (1) to determine the response in growing steers to increasing levels of molassed sugar-beet pulp (MSBP) as a supplement to grass silage, (2) to compare MSBP and barley, and (3) to ascertain if there was a response to the inclusion of soya bean meal as a protein source with both MSBP and barley. Weanling steers (n = 154) were assigned to the following treatments: (1) silage only, (2) silage plus a low level of MSBP, (3) silage plus a low level of MSBP plus soya bean meal, (4) silage plus a high level of MSBP, (5) silage plus a high level of MSBP plus soya bean meal, (6) silage plus a high level of barley, and (7) silage plus a high level of barley plus soya bean meal. Low MSBP, high MSBP and barley levels were 1.5 kg, 3.0 kg and 3.0 kg per head daily, respectively. Where soya bean meal was included it replaced 0.2 kg/day (low) or 0.4 kg/day (high) of MSBP or barley. The duration of the treatments was 125 days (winter) after which the animals grazed together for 148 days. Silage intake decreased linearly (P < 0.001) with increasing MSBP level. Addition of soya bean meal had no effect on silage intake with low MSBP or barley but increased (P < 0.05) intake with high MSBP Live-weight gain increased both linearly (P < 0.001) and quadratically (P < 0.01) with increasing MSBP There was a significant live-weight response to the addition of soya bean meal which was greater at the high than at the low MSBP level and was greater for MSBP than barley. Across all treatments, growth rate at pasture was inversely related to growth rate in winter. Final live weights for the treatments as listed were 376, 395, 411, 400,430,427 and 428 (s.e. 14.2) kg. It is concluded that there was a curvilinear live-weight gain response to increasing MSBP level. There was no end-of-grazing-season live-weight response to the inclusion of soya bean meal with barley but there was with MSBP, particularly at the high level. MSBP with soya bean meal was equivalent to a similar quantity of barley.