DairyNZ Limited, Newstead, Private Bag 3221, Hamilton 3210, New Zealand.
School of Agriculture and Environment, Massey University, Palmerston North 4410, New Zealand.
J Dairy Sci. 2019 Mar;102(3):2708-2713. doi: 10.3168/jds.2018-15234. Epub 2019 Jan 11.
Reducing enteric methane (CH) production and improving feed conversion efficiency of dairy cows is of high importance. Residual feed intake (RFI) is one measure of feed efficiency, with low RFI animals being more efficient in feed conversion. Enteric CH is an important source of digestible energy loss in ruminants and, because research in beef cattle has reported a positive relationship between RFI and daily CH production, we hypothesized that low RFI dairy heifers, which are more feed efficient, would produce less CH/d. We measured the daily methane production (g of CH/d), methane yield [g of CH/kg of dry matter intake (DMI)], and CH per kilogram of body weight (BW) gain for 56 heifers (20-22 mo old) in a 2 × 2 factorial arrangement: factors included 2 breeds (Holstein-Friesian and Jersey; n = 28/breed), with equal numbers of animals previously determined as being either high [+2.0 kg of dry matter (DM)/d] or low RFI (-2.1 kg of DM/d; n = 28/RFI category). All heifers were commingled and offered unrestricted access to the same diet of dried alfalfa cubes. Between RFI categories, heifers did not differ in BW or BW gain but low RFI heifers had 9.3 and 10.6% lower DMI and DMI/kg of BW, respectively, than high RFI heifers. Similarly, RFI category did not affect CH/d or CH/kg of BWg, but CH/kg of DMI was higher in low RFI heifers because of their lower DMI. These results might reflect more complete digestion of ingested feed in the more efficient, low RFI heifers, consistent with previous reports of greater apparent digestibility of organic matter. Holstein-Friesian heifers were heavier and consumed more total DM than Jersey heifers, but breed did not affect DMI/kg of BW or BWg. Jersey heifers produced less CH/d, but not CH/kg of DMI or CH/kg of BWg. We detected no interaction between breed and RFI category in any of the variables measured. In conclusion, differences in RFI in dairy heifers did not affect daily CH production (g/d); however, low RFI heifers had a greater CH yield (g/kg of DMI) on a high forage diet.
降低反刍动物甲烷（CH）的产生并提高奶牛的饲料转化效率非常重要。剩余采食量（RFI）是饲料效率的一种衡量标准，低 RFI 动物在饲料转化方面效率更高。反刍动物的肠道 CH 是可消化能量损失的重要来源，并且由于对肉牛的研究报告称 RFI 与每日 CH 产量之间存在正相关关系，因此我们假设，低 RFI 奶牛干奶牛更能有效地利用饲料，因此每天产生的 CH 量更少。我们测量了 56 头（20-22 月龄）干奶牛的每日甲烷产量（g/d）、甲烷产量[g/kg 干物质采食量（DMI）]和 CH/kg 体重（BW）增重：因素包括 2 个品种（荷斯坦-弗里森和泽西；n=28/品种），每个品种的动物数量相等，之前被确定为高 RFI[+2.0 kg 干物质（DM）/d]或低 RFI（-2.1 kg DM/d；n=28/RFI 类别）。所有奶牛混合在一起，并自由采食相同的干苜蓿块日粮。在 RFI 类别之间，奶牛的 BW 或 BW 增重没有差异，但低 RFI 奶牛的 DMI 和 DMI/kg BW 分别比高 RFI 奶牛低 9.3%和 10.6%。同样，RFI 类别不会影响 CH/d 或 CH/kg BWg，但由于低 RFI 奶牛的 DMI 较低，因此 CH/kg DMI 较高。这些结果可能反映出更有效的低 RFI 奶牛对摄入饲料的消化更完全，这与先前报道的有机物表观消化率更高的结果一致。荷斯坦-弗里森奶牛比泽西奶牛重，消耗的总 DM 也更多，但品种对 DMI/kg BW 或 BWg 没有影响。泽西奶牛的 CH/d 产量较低，但 DMI/kg 或 BWg/kg 中的 CH 产量没有差异。我们没有检测到在测量的任何变量中品种和 RFI 类别之间存在交互作用。总之，奶牛干奶牛的 RFI 差异不会影响每日 CH 产量（g/d）；然而，在高草料饮食中，低 RFI 奶牛的 CH 产量（g/kg DMI）更高。
