Université Clermont Auvergne, INRAE, VetAgro Sup, UMR 1213 Herbivores, 63122 Saint-Genès-Champanelle, France.
Université Paris-Saclay, INRAE, AgroParisTech, GABI, 78350 Jouy-en-Josas, France.
Animal. 2022 Aug;16(8):100583. doi: 10.1016/j.animal.2022.100583. Epub 2022 Jul 4.
In the current economic and environmental context, the selection of livestock phenotypes combining high feed efficiency (FE) and low greenhouse gas emissions is interesting. This study aimed to quantify methane (CH) emissions and other gas flows (carbon dioxide (CO) and dihydrogen (H) emissions, oxygen (O) consumption) in growing bulls fed with two contrasting diets in order to (i) evaluate the persistence of individual variability in gas flows through time, and (ii) assess the inter-individual relationship between gas flows and FE across diets. Charolais bulls were fattened for 6 months during two consecutive years in two independent batches (50-51 per year). In each batch, half of the animals received a total mixed ad libitum ration either based on maize silage (62% dietary DM) or high-starch concentrate (MS-S), and half based on grass silage (59% dietary DM) and high-fibre concentrate (GS-F). The absolute gas flows (g/d) were individually measured with 2 GreenFeed systems during 88 days (group 1) and 64 days (group 2). All gas flows were also expressed in g/kg DM intake (gas yield), in g/kg average daily gain (CH intensity) and residual of daily emissions for CH (R CH). Different FE metrics (residual feed intake (RFI), residual gain (RG) and feed conversion efficiency (FCE)) were investigated during the same period. The relationships between gas flows and FE metrics were tested by linear regression with the diet as fixed effect. For both diets, we observed a consistent individual variability over the measurement period for absolutes values (g/d) of CH CO, and O (repeatability >0.7 for GS-F and >0.6 for MS-S). Gas flows (g/d) were positively correlated with RFI with both diets: animals that ingested food in excess of their theoretical maintenance and growth requirements emitted more CH, CO and consumed more O. The positive relationship between absolute CH emissions and RFI highlighted the interest for low-CH emitters and efficient growing bulls when fed with high-energy diets rich in starch or fibre. For both diets, RCH, CH yield and CH intensity were not related to RFI whereas a significant negative relationship was reported between CH intensity and RG, and FCE. These data suggest that intake is the main driver of the phenotypic relationships between CH traits and RFI. Further studies including larger numbers of animals on highly contrasting energy diets are needed to investigate the underlying biological regulatory mechanisms of the methanogenic potential of an animal in relation to production traits.
在当前的经济和环境背景下，选择兼具高饲料效率（FE）和低温室气体排放的家畜表型是很有趣的。本研究旨在定量测定生长公牛在两种不同日粮下的甲烷（CH）排放和其他气体流量（二氧化碳（CO）和氢气（H）排放、氧气（O）消耗），以便（i）评估个体间气体流量随时间的变化的持续性，以及（ii）评估不同个体间气体流量与两种日粮 FE 的关系。夏洛莱公牛在两年的两个独立批次中进行了 6 个月的育肥（每年 50-51 头）。在每个批次中，一半的动物自由采食全混合日粮，一半日粮基于玉米青贮（日粮干物质的 62%）或高淀粉浓缩物（MS-S），另一半日粮基于草青贮（日粮干物质的 59%）和高纤维浓缩物（GS-F）。使用 2 个 GreenFeed 系统在 88 天（第 1 组）和 64 天（第 2 组）期间分别测定个体的绝对气体流量（g/d）。所有气体流量均以每千克干物质采食量表示（气体产率），以每千克平均日增重表示（CH 强度），并以 CH 日排放量的残差表示（R CH）。在同一时期还研究了不同的 FE 指标（剩余采食量（RFI）、剩余增重（RG）和饲料转化效率（FCE））。通过线性回归，以日粮为固定效应，测试了气体流量与 FE 指标之间的关系。对于两种日粮，我们观察到在整个测量期间，CH、CO 和 O 的绝对值（g/d）的个体变异性一致（GS-F 的重复性>0.7，MS-S 的重复性>0.6）。对于两种日粮，气体流量（g/d）与 RFI 呈正相关：摄入超过其理论维持和生长需要的食物的动物排放更多的 CH、CO 和消耗更多的 O。绝对 CH 排放量与 RFI 之间的正相关关系突出了高能日粮下低 CH 排放和高效生长公牛的重要性，这些日粮富含淀粉或纤维。对于两种日粮，RCH、CH 产率和 CH 强度与 RFI 无关，而 CH 强度与 RG 和 FCE 呈显著负相关。这些数据表明，摄入是 CH 特性与 RFI 之间表型关系的主要驱动因素。需要进行更多的研究，包括在具有高度差异的能量日粮上进行更多的动物研究，以研究动物甲烷生成潜力与生产特性之间的潜在生物学调节机制。
