牛至油和过瘤胃蛋氨酸不同组合对奶牛产奶性能和氮排泄的影响

本试验旨在研究牛至油(Oo)和过瘤胃蛋氨酸(RPMet)的不同添加量组合对奶牛产奶性能与氮排泄的影响。选取年龄、体重、胎次、产奶量、乳成分及泌乳期(90±15) d相近的荷斯坦奶牛40头随机分为10个组,每组4头。对照(C)组饲喂基础日粮,试验组饲喂不同添加水平的Oo和RPMet,Oo添加水平分别为11.5(L)、13.0(M)、14.5(H) g·(d·头)^-1;RPMet添加水平分别为22.5(L)、25.0(M)、27.5(H) g·(d·头)^-1,共组成9个不同的添加量组合,分别为LL、ML、HL、LM、MM、HM、LH、MH、HH(第1个字母为Oo添加水平,第2个字母为RPMet添加水平)。预试期15 d,正试期60 d。结果表明:产奶量方面,LL、HL、HM、MH、HH组产奶量极显著高于对照组(P<0.01),以MH组最高。乳成分方面,MH、HM组乳脂率极显著提高(P<0.01);HM、HH组乳蛋白率极显著提高(P<0.01),各试验组在乳体细胞数均极显著低于对照组(P<0.01)。在氮排泄方面,LL、ML、LM、MM、HM、LH、MH、HH组氮排泄极显著低于对照组(P<0.01),以MH组最低。综合考虑上述指标,在本试验条件下,以MH组[Oo 13.0 g·(d·头)^-1、RPMet 27.5 g·(d·头)^-1]组合效果最好。

Effects of oregano oil and rumen-protected methionine on lactation performance and nitrogen excretion of dairy cows

This experiment was conducted to determine the effects of different combinations of oregano oil (Oo) and rumen-protected methionine (RPMet) on lactation performance and nitrogen excretion of dairy cows. Forty lactating holstein dairy cows of similar age, body weight, parity, milk yield, milk composition and lactation status [(90±15) days post-calving] were divided into 10 groups with 4 cows per group. A Control group was fed a basal diet, and experimental groups were supplemented with different levels of Oo [11.5 (L), 13 (M) or 14.5 (H) g·(d·head)^-1] and RPMet [22.5 (L), 25 (M) or 27.5 (H) g·(d·head)^-1] to make nine treatment combinations, which were designated LL, ML, HL, LM, MM, HM, LH, MH and HH (i.e. the first letter indicates Oo supplementation rate, and the second letter indicates RPMet supplementation rate). Following a pre-experiment adjustment period of 15 days, the experiment lasted for 60 days. It was found that: The milk yield of LL, HL, HM, MH and HH groups was significantly higher than in the Control group (P<0.01), with MH being the highest. In terms of milk components, the milk fat percentages of MH and HM groups were significantly higher than the Control group (P<0.01), and the milk protein percentages of HM and HH groups were significantly higher than the Control group (P<0.01). Milk somatic cell of the experimental groups were significantly lower than the Control group (P<0.01). Nitrogen excretion rate of LL, ML, LM, MM, HM, LH, MH and HH groups was significantly lower than the Control group (P<0.01), with the MH group being the lowest. Under the conditions of the experiment, the MH group [Oo 13 g·(d·head)^-1, RPMet 27.5 g·(d·head)^-1] was the best treatment combination.