Department of Veterinary Science, Texas Tech University, Lubbock, TX 79409, USA.
Department of Animal and Food Science, Texas Tech University, Lubbock, TX 79409, USA.
J Anim Sci. 2022 Sep 1;100(9). doi: 10.1093/jas/skac243.
Previous research demonstrated that a fixed value of 0.2433 (SE = 0.0134) Mcal of CH4/kg of dry matter intake (DMI) could be used to predict CH4 production with accuracy and precision on par with similar equations in the literature. Slope bias was substantially less for the fixed-coefficient equation than noted for the other DMI- or gross energy intake (GEI)-based equations, but mean bias was substantially greater, presumably reflecting the failure of the fixed-coefficient approach to account for dietary factors that affect CH4 production. In this article, we report on the use of the dietary ratio of concentrations of starch to neutral detergent fiber (NDF) and dietary ether extract (EE) concentration to improve the accuracy and precision of the fixed-coefficient equation. The same development data set used to create the fixed-coefficient equation was used in the present study, which included 134 treatment means from 34 respiration calorimetry studies. Based on stepwise regression with dietary NDF, starch, crude protein, EE, and the starch:NDF ratio as possible dependent variables, the starch:NDF ratio and EE were the only dietary variables selected (P ≤ 0.15). The study-adjusted relationship with the starch:NDF ratio (r2 = 0.673; root mean square error [RMSE] = 0.0327) was: Mcal of CH4/kg of DMI = 0.2883 - 0.03474 × starch:NDF; whereas the relationship with a model that included both starch:NDF ratio and dietary EE (r2 = 0.738; RMSE = 0.0315) was: Mcal of CH4/kg of DMI = 0.3227 - 0.0334 × starch:NDF - 0.00868 × % EE. A previously published independent data set with 129 treatment means from 30 respiration calorimetry studies was used to evaluate these two equations, along with two additional equations in which g/d of CH4 was predicted directly from DMI, starch:NDF ratio, and/or dietary EE. The two Mcal of CH4/kg of DMI equations had superior fit statistics to the previously published 0.2433 Mcal of CH4/kg of DMI equation, with a substantial decrease in mean bias and improved concordance correlation coefficients. Moreover, the Mcal of CH4/kg of DMI equations resulted in improved fit relative to direct prediction of g/d of CH4 from DMI, the starch:NDF ratio, and % EE. Based on these results, further evaluation of the dietary ratio of starch-to-NDF concentrations and EE concentration to predict methane production per unit DMI in beef cattle is warranted.
先前的研究表明，使用 0.2433（SE=0.0134）兆卡 CH4/千克干物质采食量（DMI）的固定值可以准确和精确地预测 CH4 产量，与文献中的类似方程相当。与其他基于 DMI 或总能摄入（GEI）的方程相比，固定系数方程的斜率偏差要小得多，但平均偏差要大得多，这可能反映了固定系数方法未能考虑到影响 CH4 产生的饮食因素。在本文中，我们报告了使用淀粉与中性洗涤纤维（NDF）浓度的饮食比例和饮食乙醚提取物（EE）浓度来提高固定系数方程的准确性和精密度。本研究使用了与创建固定系数方程相同的开发数据集，其中包括 34 项呼吸量热法研究中的 134 个处理均值。基于逐步回归，以饮食 NDF、淀粉、粗蛋白、EE 和淀粉：NDF 比作为可能的因变量，淀粉：NDF 比和 EE 是唯一被选中的饮食变量（P≤0.15）。与淀粉：NDF 比的研究调整关系（r2=0.673；均方根误差[RMSE]=0.0327）为：CH4/kg DMI 的 Mcal=0.2883-0.03474×淀粉：NDF；而包含淀粉：NDF 比和饮食 EE 的模型的关系（r2=0.738；RMSE=0.0315）为：CH4/kg DMI 的 Mcal=0.3227-0.0334×淀粉：NDF-0.00868×% EE。使用了先前发表的包含 30 项呼吸量热法研究的 129 个处理均值的独立数据集，用于评估这两个方程以及另外两个直接从 DMI、淀粉：NDF 比和/或饮食 EE 预测 CH4/g/d 的方程。这两个 Mcal 的 CH4/kg 的 DMI 方程与之前发表的 0.2433 Mcal 的 CH4/kg 的 DMI 方程相比，具有更好的拟合统计数据，平均偏差有了实质性的降低，同时也提高了一致性相关系数。此外，与直接从 DMI、淀粉：NDF 比和% EE 预测 CH4/g/d 相比，Mcal 的 CH4/kg 的 DMI 方程的拟合效果更好。基于这些结果，有必要进一步评估淀粉与 NDF 浓度的饮食比和 EE 浓度来预测肉牛每单位 DMI 的甲烷产量。
