Estimates of repeatability and heritability of methane production in sheep using portable accumulation chambers

Abstract

This study was designed to screen a large number of sheep to identify individuals with high and low methane (CH4) production, and to estimate repeatability and heritability of CH4 emissions in sheep, utilising portable accumulation chambers (PAC) designed for in-field use. Mature ewes (n = 710) selected from a research flock with known sires had their CH4 production over 1 h measured in PAC [CH4 (g1h)]. Individuals with High (n = 103) or Low (n = 104) CH4 (g1h), adjusted for liveweight (LW), were selected and re-measured on three occasions 1–4 months later, at another site with more abundant and better quality pasture. Mean of the selected (207) ewes CH4 (g1h) emissions were ~50% higher than at the first measurement site (0.66 g vs 0.42 g). LW was a significant correlate of CH4 production (r = 0.47). Correlations between CH4 (g1h) for the three PAC measurements at Site 2, before adjusting for LW ranged from 0.44 to 0.55. After adjusting for the effect of LW, repeatability was 0.33 at the first and 0.43 at the second site. The correlation between estimates of an animal’s emissions at the first and second sites, adjusted for LW, was 0.24. Initial CH4 production of the selected High group was 32% greater than the Low group (P < 0.0001). On re-measurement there was still a significant difference (9–15%, P < 0.006) between Low and High groups. The initial estimate of heritability of CH4 (g1h), based on variation between the ewes’ sires (0.13), was not maintained across the two sites. This may be due to genotype × environment interactions. We postulate that aspects of rumen physiology, which modulate CH4 production, could be expressed differently in different nutritional environments. Our results indicate that field use of PAC to screen sheep populations for CH4 production is both robust and repeatable. However, further investigations are required into the relationship between CH4 output of individual animals in PAC compared with the more controlled conditions in respiration chambers.

More feed efficient sheep produce less methane and carbon dioxide when eating high-quality pellets

“…Therefore, our results need to be tested using different quality feeds before they can be applied to commercial conditions. Our estimate of heritability for CH 4 production (0.09) was similar to the estimate by Goopy et al (2016;0.13) measured in portable respiration chambers but lower than that by Pinares-Patiño et al (2013;0.29) measured in respiration chambers. Our estimate of CH 4 yield (CH 4 corrected for intake; 0.19) was higher than that of Pinares-Patiño et al (2013;0.13).…”

“…We analyzed CH 4 recorded at 40 min. Methane concentration was converted to milligrams per minute using the modified formula described by Goopy et al (2016): CH 4 concentration (mg/min) = (CH 4 concentration (L) at standard temperature (0°C) and pressure × 16.04/22.4 L) × 1,000/60/60, in which 16.04 is the molecular weight of CH 4 concentration and 22.4 is the molar volume of gas at standard temperature and pressure. Atmospheric pressure and temperature data were collected from an on-site electronic weather station at the start and end of every measurement group.…”

Methods for Measuring Greenhouse Gas Balances and Evaluating Mitigation Options in Smallholder Agriculture

“…This technique initially showed close agreement with respiratory chamber measurements (Goopy et al 2009(Goopy et al , 2011. Subsequent investigations demonstrated such measurements to be moderately repeatable in the fi eld and to have potential for genetic screening of animals (Goopy et al 2015 ). Longer-term comparisons of PAC measurements and respiratory chamber data, however, suggest that these two methods may be measuring quite different traits and further investigation is required before committing signifi cant resources to PAC measurements (Robinson et al 2015 ).…”

“…Subsequent investigations demonstrated such measurements to be moderately repeatable in the fi eld and to have potential for genetic screening of animals (Goopy et al 2015 ). Longer-term comparisons of PAC measurements and respiratory chamber data, however, suggest that these two methods may be measuring quite different traits and further investigation is required before committing signifi cant resources to PAC measurements (Robinson et al 2015 ). Madsen et al ( 2010 ) proposed using the ratio of CH 4 :CO 2 in exhaled breath to assess EMP in ruminants.…”

Review of current in vivo measurement techniques for quantifying enteric methane emission from ruminants

“…The time period of use should be limited to avoid negative effects of increased chamber CO 2 concentration, as discussed previously, and thus the PAC techniques provides a single spot sample of accumulated gases emitted by an animal. Moderate repeatability (correlation of 0.33-0.43) of measurements of CH 4 emission by individual sheep (n = 207) using PAC was reported in studies at different sites (Goopy et al, 2015). The time period of measurements relative to feeding and any postprandial changes in CH 4 emission is a potential source of variation in these measurements and thus should be accounted for when the technique is used.…”