N-氨甲酰谷氨酸对荷斯坦奶公牛生长性能、瘤胃发酵及微生物区系和甲烷排放量的影响

本试验旨在研究添加不同水平的N-氨甲酰谷氨酸（N-carbamylglutamate，NCG）对荷斯坦奶公牛生长性能、瘤胃发酵、瘤胃微生物区系和甲烷排放量的影响。试验选择45头健康、体重相近（（478±13.66）kg）的荷斯坦奶公牛，随机分成3组，每组15头，每头分别添加0 g·d^-1（Ⅰ组，对照）、15 g·d^-1（Ⅱ组）、25 g·d^-1（Ⅲ组）的NCG。预试期7 d，正试期90 d。结果表明：1）与对照组相比，饲喂15 g·d^-1和25 g·d^-1 NCG的公牛饲料转化效率分别改善6.91%（P<0.01）和7.91%（P<0.01）；2）与对照组相比，饲喂15 g·d^-1和25 g·d^-1 NCG的公牛瘤胃微生物蛋白的浓度显著升高了22.91%和15.17%（P<0.01）；随着NCG的增加，丙酸浓度显著线性升高（P<0.01），且15 g·d^-1 NCG组最高；3）从瘤胃产甲烷古菌属水平的相对丰度上分析，25 g·d^-1的公牛甲烷短杆菌属最低，其相对丰度为80.05%；随着NCG的增加，甲烷球菌属、甲烷丝状菌属的相对丰富度显著下降（P<0.01）；4）添加不同水平的NCG均显著降低了甲烷的排放量，饲喂15和25 g·d^-1 NCG公牛甲烷排放量分别比对照组降低了8.44%和10.51%（P<0.01）。综上，在本试验条件下，添加NCG能有效调控荷斯坦奶公牛瘤胃发酵，提高饲料转化效率，降低甲烷排放量。推荐添加量为15 g·d^-1。

Effects of Dietary Addition of N-carbamylglutamate on Growth Performance,Rumen Fermentation， Rumen Microflora and Methane Emission of Holstein Bulls

The present study was conducted to investigate the effects of dietary supplementation of N-carbamylglutamate (NCG) on growth performance, rumen fermentation, rumen microflora and methane emission of Holstein bulls. Forty-five healthy Holstein bulls (body weight (478±13.66) kg) were randomly assigned into 3 treatments with 15 replicates in each treatments, the bulls were supplemented with 0 (group Ⅰ, control), 15 (group Ⅱ) and 25 g·d^-1 (group Ⅲ) of NCG per head, respectively. A 7-day adaptation period and a 90-day experimental period were included in this study. The results showed that: 1) The feed-gain ratio (F/G) was reduced by 6.91% (P<0.01) and 7.91%(P<0.01) in bulls fed 15, 25 g·d^-1 NCG, respectively, compared with control; 2) The microbial protein concentration in rumen increased by 22.91% (P<0.01) and 15.17%(P<0.01) of bulls fed 15, 25 g·d^-1 NCG, respectively, compared with control; The concentrations of propionic acid in rumen increased linearly (P<0.01) while NCG supplementation increased, with the highest value for 15 g·d^-1 NCG group; 3) From the analysis of the relative abundance of rumen methanogenus at genus level, the relative abundances of Methanobrevibacter in rumen was the lowest when supplemented with 25 g·d^-1 NCG, which relative abundance was 80.05%;The relative abundance of Methanosphaera and Methanosaeta in rumen decreased linearly (P<0.01) while NCG supplementation increased; 4) Dietary supplemented with different levels of NCG all decreased the methane emission of Holstein bulls,the methane emission were decreased by 8.44% and 10.51% in bulls fed 15, 25 g·d^-1 NCG (P<0.01), respectively, compared with control. In conclusion, under the conditions of this experiment, supplemented wiht NCG can effectively regulate rumen fermentation of Holstein bulls, improve the efficiency of feed conversion ratio and reduce methane emissions. The recommended NCG supplementation level is 15 g·d^-1.