EFFICIENCY OF PROTEIN UTILIZATION OF FORMALDEHYDE TREATED RAPESEED MEAL BY SHEEP AND ITS INFLUENCE ON CATTLE'S PERFORMANCE

This study was purposed to investigate the efficiency of protein utilization of rapeseed meal (RSM) and formaldehyde-treated RSM (TRSM) by sheep, and their influence on performance of growing heifers. Experiment 1 was conducted according to a double $3{\times}3$ Latin square design involving sex yearling Hu Sheep and three experimental diets. All diets contained 600 g ammoniated rice straw and 200 g concentrate mixture. Three dietary treatments were: (1) 100 g RSM + 40 g soybean meal (URUS), (2) 100 g TRSM + 40 g soybean meal (TRUS) and (3) 100 g TRSM + 40 g treated soybean meal (TRTS). Apparent nitrogen digestibility was significantly higher for diet TRUS than that for URUS or TRTS (p<0.05), but with no significant difference between URUS and TRTS (p>0.05). Proportion of nitrogen retention (NR) to the digestible nitrogen intake for diet TRUS and TRTS was 25.57 (p<0.05) and 23.44% (p<0.05) higher than that for URUS respectively. As a result, proportion of NR to nitrogen intake for diet TRUS and TRTS was 34.74 (p<0.05) and 23.78% (p<0.05) higher than that for URUS respectively. Experiment 2 was conducted with 59 Holstein heifers. They were 12-20 months of age at the start of the trial. The experiment was a $2{\times}2$ factorial trial in which the heifers were given the ammoniated rice straw ad libitum and 1.5 kg hay, and supplemented with either RSM or TRSM at a daily allowance of 1.2 or 1.8 kg per day. The live weight gains for heifers receiving 1.2 and 1.8 kg/d of RSM or TRSM were 0.491 and 0.556 or 0.564 and 0.665 kg/d, respectively. The results suggest that formaldehyde treatment can effectively improve the efficiency of protein utilization of rapessed meal and cattle's performance.