包被尿素与蒸汽压片玉米组合对活体外瘤胃氨氮释放和发酵参数的影响

Effect of combination of coated urea and steam-flaked corn grains on ruminal ammonia release and fermentation traits in vitro

选用包被尿素、普通尿素（负对照）和大豆分离蛋白（正对照）作为氮源，普通玉米（对照）和蒸汽压片玉米作为碳源，采用2×3因子试验设计，利用活体外人工瘤胃产气法，研究包被尿素与蒸汽压片玉米组合对活体外瘤胃氮氮释放速度和发酵参数的影响。结果表明：在瘤胃发酵1～8h期间，无论基于哪种碳源，包被尿素处理的NH3-N值比普通尿素处理降低11．1％～17．1％（P〈0．001），也低于大豆分离蛋白处理；蒸汽压片玉米处理的氮氮释放速度比对照组降低3．3％～13．7％（P〈0．001）；并在发酵前4h中，有显著互作效应（P〈0．05）。蒸汽压片玉米处理的产气速度显著高于对照（0．1104h^-1，0．1226h^-1，P〈0．001），大豆分离蛋白的24h干物质消化率为73．13％，显著高于其他处理（P〈0．05）。普通玉米（对照）组的总挥发酸产量（101．33mmol／L，96．69mmol／L）和丁酸摩尔分数（13．58％，12．69％）显著高于蒸汽压片玉米处理组（P〈0．05），而处理组的丙酸摩尔分数（22．11％．21．68％）显著高于对照组（P〈0．05）。不同氮源与碳源的总挥发酸产量存在显著的互作效应（P〈0．05）。试验结果表明：包被尿素与蒸汽压片玉米组合可以显著减缓瘤胃氮氮释放速度，而对72h产气量及其他发酵参数没有明显影响。

An in vitro study was conducted to investigate the effect of combination of coated urea and steam-flaked corn grains on ruminal ammonia release and fermentation traits in a 2 × 3 factorial experiment. Regular urea （negative control）, isolated soybean protein （ISP; positive control） and coated urea were used as nitrogen sources, and typical corn （control） and steam-flaked com grains were used as carbon sources. The results showed that NH3-N concentrations of coated urea during t - 8 h of fermentation were much lower （by 11.1% - 17. 1 % ） than those of regular urea （ P 〈 0.001）, irrespective of carbon source. Steam-flaked corn grains also had lower （3.3 % - 13. 7 % ） concentrations of NH3-N than typical corn grains （P 〈 0.001 ） and there was a significant （P 〈 0.05） interaction between nitrogen and carbon sources during the first 4 h of fermentation. The rate of gas production of steam-flaked corn grains was faster （ 0.110 4 h^- 1, 0. 122 6 h^- 1 ; p 〈 0.001 ） than typical corn grains and I SP nitrogen source had the greatest DM digestibility（73.13%, P〈0.05）. Typical corn grains had higher total VFA production （101.33mmol/L, 96.69 mmol/L） and butvrate molar proportion （ 13.58 %. 12.69 % ） and lower pronionate molar proportion （ 22.11%. 21.68 % ： P 〈 0.05 than steam-flaked corn grains after 24 h ruminal fermentation. total ruminal VFA production was significant （P 〈 0.05）. It steam-flaked corn grains could slow ruminal ammonia release The interaction effect of nitrogen and carbon sources on was concluded that the combination of coated urea and but would not affect 72 h gas production and other ruminal fermentation traits.