Department of Animal Science, The Pennsylvania State University, University Park, PA 16802.
Paradox Nutrition LLC, West Chazy, NY 12992.
J Dairy Sci. 2024 Nov;107(11):9289-9308. doi: 10.3168/jds.2024-24783.
The objective of this meta-analysis was to quantify the potential of CH-mitigating strategies in dairy cattle when accounting for the effects of treatment dose, dietary nutrient composition, and supplementation period. Data from 218 studies with dairy cattle published between 1963 to 2022 were reviewed. Individual CH mitigation strategies selected for the analysis were algae (Asparagopsis spp.), 3-nitrooxypropanol, nitrate, lipids, plant secondary compounds, and direct-fed microbials (DFM). Response variables evaluated were daily CH emission (g/d), CH yield (g CH/kg DMI), and CH intensity (g CH/kg milk yield [MY] and ECM). Relative mean difference between treatment and control means reported in the studies were calculated and used in the statistical analysis. Robust variance estimation method was used to analyze the effects of CH mitigation strategies. Dose, forage-to-concentrate ratio (F:C), dietary concentrations of CP, ether extract (EE), NDF, ADF, and starch, and supplementation period were used as continuous explanatory variables. Data for algae supplementation were limited and responses to studied species were contrasting but, overall, Asparagopsis spp. effectively decreased daily CH emission, CH yield, and CH intensities by 29.8 ± 4.6%, 23.0 ± 5.3%, 34.0 ± 4.3%, and 22.6 ± 7.3%, respectively. Supplementation of 3-nitrooxypropanol decreased daily CH emission, yield, and intensity (per kg MY and ECM) by 28.2 ± 3.6%, 28.7 ± 2.8%, 29.2 ± 3.1%, and 31.8 ± 2.8%, respectively, compared with control. Decreasing dietary fiber (i.e., F:C, NDF, and ADF), whereas increasing dietary starch concentration increased the efficacy of 3-nitrooxypropanol at mitigating enteric CH emission. Nitrate supplementation decreased CH emission, yield, and intensity (per kg ECM) by 18.5% ± 1.9%, 17.6 ± 1.6%, and 13.0 ± 0.2%, respectively, compared with control. Efficacy of nitrate at mitigating enteric CH yield and CH intensity was positively associated with dose, and efficacy of nitrate at mitigating CH yield was positively associated with dietary starch concentration. Lipid supplementation decreased CH emission, yield, and intensities by up to 14.8 ± 2.3%, respectively, compared with control. Efficacy of lipids supplementation was positively associated with dietary EE, starch, and supplementation period, but negatively associated with dietary ADF concentration. Free oil supplementation tended to increase lipid efficacy by 31% at decreasing CH emission, compared with control. Condensed tannins and plant-derived bioactive compounds decreased CH yield by 11.3 ± 2.9% and 5.7 ± 2.5%, respectively, but oregano did not affect enteric CH emission metrics in the current meta-analysis. Direct-fed microbials were not effective in mitigating enteric CH emission variables. Data were limited to determine the effects of dietary nutrients and duration of supplementation on efficacy of Asparagopsis spp., plant secondary compounds and DFM. Overall, supplementation of the diet with Asparagopsis spp., 3-nitrooxypropanol, nitrate, and lipids were the most effective strategies for decreasing enteric CH emission in dairy cattle. Variability in the efficacy of most CH mitigation strategies can be partially explained by differences in treatment dose, dietary nutrient composition, and supplementation period.
本荟萃分析的目的是量化在考虑治疗剂量、日粮养分组成和补充期的情况下，奶牛中 CH 缓解策略的潜力。共综述了 1963 年至 2022 年间发表的 218 项奶牛研究的数据。分析中选择的个体 CH 缓解策略包括藻类（Asparagopsis spp.）、3-硝基氧基丙醇、硝酸盐、脂质、植物次生化合物和直接饲喂微生物（DFM）。评估的反应变量是每日 CH 排放（g/d）、CH 产量（g CH/kg DMI）和 CH 强度（g CH/kg 牛奶产量[MY]和 ECM）。计算了研究中报告的处理与对照平均值之间的相对平均差异，并用于统计分析。使用稳健方差估计方法分析 CH 缓解策略的效果。剂量、粗饲料与精饲料比（F:C）、日粮 CP、醚提取物（EE）、NDF、ADF 和淀粉浓度以及补充期被用作连续解释变量。藻类补充的数据有限，且研究物种的反应不一致，但总体而言，Asparagopsis spp. 可有效降低 29.8 ± 4.6%、23.0 ± 5.3%、34.0 ± 4.3%和 22.6 ± 7.3%的每日 CH 排放、产量和强度。3-硝基氧基丙醇的补充可降低 28.2 ± 3.6%、28.7 ± 2.8%、29.2 ± 3.1%和 31.8 ± 2.8%的每日 CH 排放、产量和强度（每公斤 MY 和 ECM），与对照组相比。降低日粮纤维（即 F:C、NDF 和 ADF），而增加日粮淀粉浓度可提高 3-硝基氧基丙醇缓解肠道 CH 排放的效果。硝酸盐补充可降低 18.5% ± 1.9%、17.6 ± 1.6%和 13.0 ± 0.2%的 CH 排放、产量和强度（每公斤 ECM），与对照组相比。硝酸盐缓解肠道 CH 产量和 CH 强度的效果与剂量呈正相关，硝酸盐缓解 CH 产量的效果与日粮淀粉浓度呈正相关。脂质补充可使 CH 排放、产量和强度分别降低高达 14.8 ± 2.3%，与对照组相比。脂质补充的效果与日粮 EE、淀粉和补充期呈正相关，但与日粮 ADF 浓度呈负相关。与对照组相比，游离油补充剂在降低 CH 排放方面可使脂质补充的效果提高 31%。单宁和植物源生物活性化合物可使 CH 产量分别降低 11.3 ± 2.9%和 5.7 ± 2.5%，但牛至在当前荟萃分析中对肠道 CH 排放指标没有影响。直接饲喂微生物对降低肠道 CH 排放变量没有效果。数据有限，无法确定日粮养分和补充期对 Asparagopsis spp.、植物次生化合物和 DFM 效果的影响。总的来说，在奶牛日粮中补充 Asparagopsis spp.、3-硝基氧基丙醇、硝酸盐和脂质是降低肠道 CH 排放最有效的策略。大多数 CH 缓解策略效果的差异部分可以用治疗剂量、日粮养分组成和补充期的差异来解释。
