Genetic parameters of methane emissions determined using portable accumulation chambers in lambs and ewes grazing pasture and genetic correlations with emissions determined in respiration chambers1

Abstract

Methane (CH4) emission traits were previously found to be heritable and repeatable in sheep fed alfalfa pellets in respiration chambers (RC). More rapid screening methods are, however, required to increase genetic progress and to provide a cost-effective method to the farming industry for maintaining the generation of breeding values in the future. The objective of the current study was to determine CH4 and carbon dioxide (CO2) emissions using several 1-h portable accumulation chamber (PAC) measurements from lambs and again as ewes while grazing ryegrass-based pasture. Many animals with PAC measurements were also measured in RC while fed alfalfa pellets at 2.0 × maintenance metabolizable energy requirements (MEm). Heritability estimates from mixed models for CH4 and CO2 production (g/d) were 0.19 and 0.16, respectively, when measured using PAC with lambs; 0.20 and 0.27, respectively, when measured using PAC with ewes; and 0.23 and 0.34, respectively, when measured using RC with lambs. For measured gas traits, repeatabilities of measurements collected 14 d apart ranged from 0.33 to 0.55 for PAC (combined lambs and ewes) and were greater at 0.65 to 0.76 for the same traits measured using RC. Genetic correlations (rg) between PAC in lambs and ewes were 0.99 for CH4, 0.93 for CH4 + CO2, and 0.85 for CH4/(CH4 + CO2), suggesting that CH4 emissions in lambs and ewes are the same trait. Genetic correlations between PAC and RC measurements were lower, at 0.62 to 0.67 for CH4 and 0.41 to 0.42 for CH4 + CO2, likely reflecting different environmental conditions associated with the protocols used with the 2 measurement methods. The CH4/(CH4 + CO2) ratio was the most similar genetic trait measured using PAC (both lambs and ewes, 63% and 66% selection efficiency, respectively) compared with CH4 yield (g/kg DMI) measured using RC. These results suggest that PAC measurements have considerable value as a rapid low-cost method to estimate breeding values for CH4 emissions in sheep.

Methane and Carbon Dioxide Emission of Beef Heifers in Relation with Growth and Feed Efficiency

“…On the other hand, the residual of CO 2 from MBW and ADG (r wg CO 2 ) was not related to RFI (R p = 0.04 and 0.10), whereas Arthur et al [31] found a low and significant correlation: R p = 0.27. The correlations of the CH 4 /CO 2 ratio with CH 4 were R p = 0.58 and 0.61, the same values obtained by Herd et al [18] with yearling beef animals measured with GreenFeed (R 2 = 0.40) and Jonker et al [29] with lambs measured in respiratory chambers, R p = 0.65. The correlations of CH 4 /CO 2 with CH 4 /DMI were low, R p = 0.24 and 0.33, much lower than the estimates obtained by Herd et al [18] (R 2 = 0.49) and Jonker et al [29], R p = 0.84.…”

“…The two emission rates were also highly correlated with the heifer body weight, slightly more for CO 2 (R p = 0.77 and 0.85) than for CH 4 (R p = 0.68 and 0.70). Similar results were obtained with dairy cows [30] and yearling beef cattle [14,31,32] measured with GreenFeed systems or with yearling beef cattle [5] and lambs [29] measured in respiratory chambers: R p = 0.57 to 0.74 for the correlation between CH 4 and BW and R p = 0.71 to 0.87 for the correlation between CO 2 and BW. In ruminants, DMI and gross energy intake (GEI) are considered to be the predominant drivers of enteric methane production [33].…”

“…The correlation was noticeably high between CH 4 and CO 2 (R p = 0.83 and 0.86). Similar high relationships, R p = 0.78 on average (R p = 0.57 to 0.91), were estimated with yearling beef cattle [16,18,26], dairy cows [28] or with lambs [29], measured either in respiratory chambers or with GreenFeed systems. The two emission rates were also highly correlated with the heifer body weight, slightly more for CO 2 (R p = 0.77 and 0.85) than for CH 4 (R p = 0.68 and 0.70).…”

Assessment of methane emission traits in ewes using a laser methane detector: genetic parameters and impact on lamb weaning performance

“…In addition, respiration chambers reflect an artificial environment, which is not representative of sheep kept in pasture-based production systems. Animals might show abnormal behavior (e.g., reduced dry matter intake, DMI) in the chamber, possibly influencing a CH 4 emission pattern (Kabreab et al, 2006;Bickell et al, 2014). Thus, Knapp et al (2014) and Huhtanen et al (2015) requested alternative reliable and cost-efficient methods for CH 4 recording, especially under field conditions.…”

“…In such a context, approaches based on feed supplements were unsuitable under grazing conditions (Baker, 1999). Predictions of CH 4 via deterministic modeling usually require a large amount of input data, e.g., DMI, dietary or milk components, which are difficult to record (Kabreab et al, 2006;Yin et al, 2015). Further indirect methods for CH 4 emission predictions based on the ruminal microbiome composition but associations between CH 4 production and microbiome characteristics were inconsistent (Shi et al, 2014;Ellison et al, 2017).…”