Abstract:

【Objective】The objective of this study was to evaluate the effects of glycerol supplementation on rumen fermentation, urinary excretion of purine derivatives, nutrients digestibility, energy metabolism and nitrogen balance of steers.【Method】 Eight ruminal cannulated Simmental steers were used in a replicated 4 × 4 Latin square experiment and fed with basic diet and added with glycerol at 0, 100, 200 and 300 g per steer per day, respectively. 【Result】 The results showed that ruminal pH, ratio of acetate to propionate and ammonia nitrogen of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were lower than steers supplemented with glycerol at 100 g?d-1 and the control significantly (P＜0.05). Total VFA concentration, the molar proportions of propionate and butyrate of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were higher than steers supplemented with glycerol at 100 g?d-1 and control significantly (P＜0.05). Ruminal DM, OM, NDF and ADF degradation of corn straw, and ruminal DM and OM degradation of concentrate of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were higher than the control significantly (P＜0.05). Ruminal CP degradation of concentrate of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were lower than steers supplemented with glycerol at 100 g?d-1 and the control significantly (P＜0.05). Allantoin concentration and urinary excretion of purine derivatives of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were higher than steers supplemented with glycerol at 100 g?d-1 and control significantly (P＜0.05). Dietary OM, EE, CP, NFE, NDF and ADF digestibilities of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were higher than the control significantly (P＜0.05). Digestible energy and metabolizable energy of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were higher than the control significantly (P＜0.05). Retenion energy of steers supplemented with glycerol at 200 g/d and 300 g/d were higher than the control and supplemented with glycerol at 100 g?d-1 significantly (P＜0.05). Retenion nitrogen of steers supplemented with glycerol at 200 g?d-1 and 300 g?d-1 were higher than steers supplemented with glycerol at 100 g?d-1 and the control significantly (P＜0.05). 【Conclusion】 These results indicated that the optimum dose of glycerol supplementation was 200 g?d-1.

Key words: Simmental steer, glycerol, rumen fermentation, purine derivative, digestibility, energy metabolism, nitrogen balance