包被尿素对活体外瘤胃发酵特性和微生物蛋白合成的影响

Effect of polyurethane coated urea supplement on ruminal fermentation traits and microbial protein synthesis

选用普通尿素、包被尿素和大豆分离蛋白为氮源,以蒸汽压片玉米为主要碳源,配制等氮日粮,利用人工瘤胃双外流连续培养系统,研究包被尿素在基于蒸汽压片玉米日粮条件下对瘤胃发酵和微生物蛋白合成的影响。结果表明：大豆分离蛋白组的干物质（DM）和有机物（OM）消化率最高,普通尿素组最低（P=0.02）,包被尿素组居中。普通尿素组的氨态氮NH3-N质量浓度最高（1.99 mg/dL）,相比之下,包被尿素组的NH3-N质量浓度降低了30.2%（1.39 mg/dL）,但仍然高于大豆分离蛋白组（1.04 mg/dL,P〈0.000 1）。各处理间的总挥发性脂肪酸（TVFA）浓度无显著性差异（P=0.72）,但TVFA中,各挥发酸摩尔比在处理间存在显著性差异（P〈0.05）,相比大豆分离蛋白组日粮,普通尿素和包被尿素组具有较高的乙酸摩尔比例和乙酸/丙酸值（P〈0.001）,而大豆分离蛋白组的异丁酸摩尔比是其他2种日粮的3.9~6.8倍;日粮处理间的微生物蛋白合成效率（MOEFF）差异显著（P=0.05）,与普通尿素组（真可消化有机物的含氮量为11.27 g/kg）相比,包被尿素组提高了15.6%（真可消化有机物的含氮量为13.03 g/kg）,大豆分离蛋白组的微生物蛋白合成效率最高（真可消化有机物的含氮量为14.66 g/kg）。由此可见,与普通尿素相比,日粮中添加包被尿素并未明显改变瘤胃发酵模式,但显著提高了瘤胃微生物蛋白的合成效率。

This experiment was performed to evaluate the effect of polyurethane coated urea on rumen fermentation and microbial protein synthesis in vitro in dual-flow continuous culture system.Isonitrogenous diets were formulated with regular urea（negative control）,coated urea and ISP（positive control） based on steam-flaked corn.The results showed that the group of ISP had the highest digestibility in DM and OM,and the group treated with regular urea had the lowest digestibility（P=0.02）,where the group treated with coated urea was in the intermediate.The highest NH3-N concentration was in the group treated with regular urea（1.99 mg/dL）,which was 30.2%（1.39 mg/dL） greater than the group treated with coated urea,while it is lowest in the group of ISP（1.04 mg/dL,P0.000 1）.Significant differences were observed in individual VFA molar proportion（P0.05）.There was a difference（P=0.07） in microbial nitrogen flow（MN） among treatments,with the maximum in the group of ISP and the minimum in the group of regular urea.The efficiency of microbial protein synthesis in vitro was increased in the group of coated urea（13.0 g nitrogen per kg true digested organic matter）,compared with the group pf regular urea（11.3 g nitrogen per kg true digested organic matter）.It was concluded that compared with regular urea,the addition of coated urea in the diet could not change ruminal fermentation pattern in vitro,but significantly improve the efficiency of microbial protein synthesis.