USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933.
J Anim Sci. 2013 Oct;91(10):4826-31. doi: 10.2527/jas.2011-4781. Epub 2013 Aug 21.
We hypothesized that CH4 production will decrease with increased feed efficiency. Two experiments were conducted to determine CH4 production of cattle that differed in feed efficiency. Cattle in both studies were selected from larger contemporary groups. Animals furthest from the confidence ellipse that resulted from regressing BW gain on DMI were selected. In the first experiment, 113 crossbred steers were evaluated for feed efficiency for 64 d. Steers were 355 ± 1 d of age and weighed 456 ± 10 kg when they began the study. Steers were fed a ration that consisted of (DM basis) 82.8% corn, 12.8% corn silage, and 4.5% supplement [contains 0.065% monensin, 32% CP (28% NPN), 7.5% Ca, 0.8% P, 4.8% NaCl, 1.8% K, and 55,116 IU/kg vitamin A]. Thirty-seven steers were selected to measure CH4 production. In the second experiment, 197 heifers were evaluated for feed efficiency for 64 d. Heifers were 286 ± 1 d of age and weighed 327 ± 2 kg when they began the study. Heifers were fed a ration that consisted of (DM basis) 60% corn silage, 30% alfalfa hay, and 10% wet distillers grains with solubles. Forty-seven heifers were selected to measure CH4 production. Methane production was measured with respiration calorimeters. In both experiments, cattle had ad libitum access to feed, and DMI consumed during the 24 h before CH4 production was measured. Methane production was collected for a 6-h period on untrained cattle. Consequently, methane production is not a quantitative measure of daily methane production; rather, it is an index value to rank cattle. Multiple regression analysis was used to determine the relationship between either BW gain:DMI ratio or residual feed intake (RFI) on CH4 production after adjusting for the previous 24-h DMI. In the steers, BW gain:DMI ratio and previous 24-h feed intake accounted for little of the variance in CH4 production (R(2) = 0.009), and neither did RFI and previous 24-h feed intake (R(2) = 0.001). In the heifers, the BW gain:DMI ratio contributed 28% toward the variance estimate and previous 24-h DMI contributed 72% toward the variance estimate (R(2) = 0.31). As the BW gain:DMI ratio increased, daily CH4 production increased. The regression coefficient for RFI (P = 0.45) did not differ from 0 for CH4 production. Our study does not support our original hypothesis that CH4 production decreases with increased feed efficiency and suggests that CH4 production may increase with increased feed efficiency.
我们假设甲烷产量会随着饲料效率的提高而降低。进行了两项实验来确定饲料效率不同的牛的甲烷产量。两项研究中的牛均从较大的当代群体中选择。选择那些从回归体重增加与饲料采食量的置信椭圆中距离最远的动物。在第一项实验中，评估了 113 头杂交阉牛的饲料效率，为期 64 天。阉牛的年龄为 355 ± 1 天，体重为 456 ± 10 公斤。研究开始时，阉牛的饮食由（DM 基础）82.8%玉米、12.8%玉米青贮和 4.5%补充料组成[含有 0.065%莫能菌素、32%CP（28%非蛋白氮）、7.5%Ca、0.8%P、4.8%NaCl、1.8%K 和 55116IU/kg 维生素 A]。选择 37 头阉牛测量甲烷产量。在第二项实验中，评估了 197 头小母牛的饲料效率，为期 64 天。小母牛的年龄为 286 ± 1 天，体重为 327 ± 2 公斤。小母牛的饮食由（DM 基础）60%玉米青贮、30%苜蓿干草和 10%湿酒精糟和可溶物组成。选择 47 头小母牛测量甲烷产量。甲烷产量通过呼吸量热计测量。在这两项实验中，牛可以自由采食饲料，在测量甲烷产量前的 24 小时内消耗的饲料量。在未经训练的牛身上收集了 6 小时的甲烷产量。因此，甲烷产量不是每日甲烷产量的定量测量值；相反，它是一个用于对牛进行排名的指数值。使用多元回归分析来确定在调整前 24 小时的饲料摄入量后，BW 增益与饲料采食量的比率或残余饲料摄入量（RFI）与甲烷产量之间的关系。在阉牛中，BW 增益与饲料采食量的比率和前 24 小时的饲料摄入量仅占甲烷产量变化的一小部分（R²=0.009），RFI 和前 24 小时的饲料摄入量也没有（R²=0.001）。在小母牛中，BW 增益与饲料采食量的比率对变异估计的贡献为 28%，前 24 小时的 DMI 贡献了 72%（R²=0.31）。随着 BW 增益与饲料采食量的比率增加，每日甲烷产量增加。RFI 的回归系数（P=0.45）与甲烷产量没有差异。我们的研究不支持我们最初的假设，即甲烷产量随着饲料效率的提高而降低，并表明甲烷产量可能随着饲料效率的提高而增加。
