Department of Molecular Biology and Genetics, Aarhus University Foulum, DK 8830 Tjele, Denmark; Department of Animal Science, Aarhus University Foulum, DK 8830 Tjele, Denmark.
Department of Breeding and Genetics, Nofima AS, PO Box 210, N-1431 Ås, Norway.
J Dairy Sci. 2020 Aug;103(8):6967-6981. doi: 10.3168/jds.2019-17489. Epub 2020 May 29.
Residual feed intake (RFI) is a measure of feed efficiency in dairy cattle. This study modeled phenotypic RFI of first- and second-parity Holstein and Jersey dairy cows within 9 lactation segments (consecutive segments of 4 wk each) covering the first 36 lactation weeks. We aimed to evaluate physical activity and daily methane production as additional energy sinks in the estimation of RFI, to examine the correlations of RFI among the first 36 wk of lactation (WOL), and to evaluate whether parities and breeds show similar results. Records for first-parity Holstein (n = 449), second-parity Holstein (n = 298), first-parity Jersey (n = 195), and second-parity Jersey cows (n = 146) were used. Model 1 included the following energy sinks: energy-corrected milk yield, metabolic body weight (BW), body condition score (BCS), daily changes in BW (ΔBW) and BCS (ΔBCS), and physical activity. Model 2 was based on a subset of the data and only for Holstein cows, and included the same energy sinks as Model 1, plus daily methane production. The trajectories of segment-specific partial regression coefficients (PRC) of DMI on activity were similar across parities but differed slightly between breeds. For daily methane production, the trajectory in PRC decreased over lactation segments for first- and second-parity Holstein cows. The trajectories in PRC of DMI on energy-corrected milk yield, metabolic BW, BCS, and ΔBW were generally similar across parities, except for ΔBCS. Activity accounted for on average 7.3, 6.8, 7.2, and 6.4% of DMI for first-parity Holsteins, second-parity Holsteins, first-parity Jerseys, and second-parity Jerseys, respectively. Methane losses accounted for 8.7% and 8.5% of DMI for first- and second-parity Holstein cows, respectively. Repeatability estimates for RFI over 36 WOL for Model 1 were 0.63 for first-parity Holsteins, 0.65 for second-parity Holsteins, 0.76 for first-parity Jerseys, and 0.80 for second-parity Jerseys. For Model 2, the estimates were 0.59 and 0.61 for first- and second-parity Holstein cows, respectively. Correlations of RFI between WOL varied in strength, with weak correlations for the first 2 to 3 WOL with other WOL. In conclusion, physical activity and daily methane production accounted for part of DMI, and RFI of dairy cattle is not the same trait throughout lactation.
残留采食量（RFI）是衡量奶牛饲料效率的一个指标。本研究在 9 个泌乳阶段（连续 4 周的阶段）内对荷斯坦和泽西奶牛的第一和第二胎次的表型 RFI 进行建模，涵盖了前 36 个泌乳周。我们旨在评估物理活动和每日甲烷产量作为 RFI 估计的额外能量消耗，检验 RFI 在泌乳前 36 周（WOL）的相关性，并评估品种和胎次是否显示出相似的结果。本研究使用了第一胎次荷斯坦（n=449）、第二胎次荷斯坦（n=298）、第一胎次泽西（n=195）和第二胎次泽西（n=146）奶牛的数据。模型 1 包括以下能量消耗：校正乳能、代谢体重（BW）、体况评分（BCS）、BW 和 BCS 的每日变化（ΔBW 和 ΔBCS）和物理活动。模型 2 基于荷斯坦奶牛的数据子集，且仅包含模型 1 中的相同能量消耗，加上每日甲烷产量。DMI 对活动的特定部分回归系数（PRC）的轨迹在胎次间相似，但在品种间略有不同。对于每日甲烷产量，PRC 的轨迹在第一和第二胎次荷斯坦奶牛的泌乳阶段中逐渐下降。DMI 对校正乳能、代谢 BW、BCS 和 ΔBW 的 PRC 轨迹在胎次间通常相似，除了 ΔBCS。活动分别平均占第一胎次荷斯坦牛、第二胎次荷斯坦牛、第一胎次泽西牛和第二胎次泽西牛的 DMI 的 7.3%、6.8%、7.2%和 6.4%。甲烷损失分别占第一和第二胎次荷斯坦奶牛 DMI 的 8.7%和 8.5%。模型 1 在 36 WOL 内对 RFI 的重复率估计值分别为第一胎次荷斯坦牛 0.63、第二胎次荷斯坦牛 0.65、第一胎次泽西牛 0.76 和第二胎次泽西牛 0.80。对于模型 2，第一和第二胎次荷斯坦奶牛的估计值分别为 0.59 和 0.61。RFI 在 WOL 之间的相关性强度不同，与其他 WOL 的前 2 到 3 个 WOL 的相关性较弱。总之，物理活动和每日甲烷产量占 DMI 的一部分，奶牛的 RFI 不是整个泌乳期的相同特征。
