Genetic parameters for residual feed intake, methane emissions, and body composition in New Zealand maternal sheep

Abstract

There is simultaneous interest in improving the feed efficiency of ruminant livestock and reducing methane (CH4) emissions. The relationship (genetic and phenotypic) between feed efficiency (characterized as residual feed intake: RFI) and greenhouse gases [methane (CH4) and carbon dioxide (CO2)] traits in New Zealand (NZ) maternal sheep has not previously been investigated, nor has their relationship with detailed estimates of body composition. To investigate these relationships in NZ maternal sheep, a feed intake facility was established at AgResearch Invermay, Mosgiel, NZ in 2015, comprising automated feeders that record individual feeding events. Individual measures of feed intake, feeding behavior (length and duration of eating events), and gas emissions (estimated using portable accumulation chambers) were generated on 986 growing maternal ewe lambs sourced from three pedigree recorded flocks registered in the Sheep Improvement Limited database (www.sil.co.nz). Additional data were generated from a subset of 591 animals for body composition (estimated using ultrasound and computed tomography scanning). The heritability estimates for RFI, CH4, and CH4/(CH4+CO2) were 0.42 ± 0.09, 0.32 ± 0.08, and 0.29 ± 0.06, respectively. The heritability estimates for the body composition traits were high for carcass lean and fat traits; for example, the heritability for visceral fat (adjusted for body weight) was 0.93 ± 0.19. The relationship between RFI and CH4 emissions was complex, and although less feed eaten will lead to a lowered absolute amount of CH4 emitted, there was a negative phenotypic and genetic correlation between RFI and CH4/(CH4+CO2) of −0.13 ± 0.03 and −0.41 ± 0.15, respectively. There were also genetic correlations, that were different from zero, between both RFI and CH4 traits with body composition including a negative correlation between the proportion of visceral fat in the body and RFI (−0.52 ± 0.16) and a positive correlation between the proportion of lean in the body and CH4 (0.54 ± 0.12). Together the results provide the first accurate estimates of the genetic correlations between RFI, CH4 emissions, and the body composition (lean and fat) in sheep. These correlations will need to be accounted for in genetic improvement programs.

Combining host and rumen metagenome profiling for selection in sheep: prediction of methane, feed efficiency, production, and health traits

“…Apart from the difference in size in the datasets, other explanations for the slightly higher heritability estimates in our study are: 1) the Jonker et al [17] heritability estimates were obtained using pedigree-based relationships, rather than genomic relationships from high density SNPs; and 2) Jonker et al [17] had methane-related traits measured at multiple time points so were able to t a permanent environmental effect in their model, while in our study some of the permanent environmental effect of methane-related traits may have been captured by the animal genetic effect, in ating the heritability estimate. Johnson et al [5] recently published the pedigree-based heritability estimate on the full set of sheep that have gone through the Feed Intake facility at AgResearch's Invermay campus, and their estimate of 0.42 ± 0.09 is consistent with our genomic-based estimates of 0.39 -0.43 (Table 6). Pickering et al [29] estimated heritabilities for a number of traits of interest to New Zealand sheep breeders, including LW8 (>1M records), FEC1 (>130k records) and FW12 (>750k records).…”

“…The dual-purpose composite ewes used in this study were involved in a variety of feed intake [5] and methane [17] trials at the Invermay (Mosgiel) campus, and Woodlands farm, of AgResearch in New Zealand. Animals were born between 2014 and 2016 from three New Zealand ocks: one AgResearch ock (Flock 2638), one selection line ock containing sheep selected for high or low methane yield [18] (Flock 3633), and one Central Progeny Test ock (Flock 4640).…”

“…Residual feed intake was measured at AgResearch's Invermay campus, as described by Johnson et al [5]. In brief, over three years, ve cohorts of approximately 200 lambs had individual feed intakes measured through a feed intake facility.…”

“…Given that methane emissions are a result of digestion of feed, the two are inextricably linked. Therefore, the genetic relationship between feed e ciency and greenhouse gas emissions is an important consideration when developing tools to select for animals that have a lower impact on the environment and have fewer associated costs to the producer [5].…”

Insights into the influence of diet and genetics on feed efficiency and meat production in sheep

“…Table 5 provides a comprehensive overview of the numerous studies that have assessed heritability estimates for FE, carcass quality, and meat quality traits in sheep. The heritability estimates for RFI were observed to ranging from 0.11 to 0.45 (average heritability = 0.28) (Cammack et al., 2005 ; Johnson et al., 2022 ; Paganoni et al., 2017 ; Snowder & Van Vleck, 2003 ; Tortereau et al., 2020 ) and for feed conversion ratio (FCR) ranging from 0.1 to 0.3 (average heritability = 0.20) (Snowder & Van Vleck, 2003 ; Tortereau et al., 2020 ) suggesting that these traits are moderately heritable (average heritability estimate between 0.20 and 0.30). In addition, the estimates for carcass quality traits were quite varied, with the heritability estimates of HCW ranging from 0.17 to 0.35 (average heritability = 0.28) (Massender et al., 2019 ; Mortimer et al., 2010 , 2014 , 2018 ) and carcass dressing percentage ranging from 0.21 to 0.24 (average heritability = 0.22) (Mortimer et al., 2010 , 2018 ) indicating moderate heritability of these traits.…”