Sustainability & efficiency

Genetic analysis of methane and its relationship with milk yield and heat tolerance in smallholder dairy systems

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Abstract

Alarming trends in climate change are already evident with global surface temperature reported to be 1.5°C higher compared to pre-industrial levels. This has significant impact on livestock-based food systems in terms of feed resources and emergence of new diseases. The Sub-Saharan Africa's contribution to global livestock emissions expectation is to be tripled by 2050 due to anticipated human population growth. Therefore, research for sustainable improvement in dairy performance, reduction in methane emission and heat tolerance in the smallholder dairy system, is paramount. This study estimated heritabilities for methane (CH4), daily milk yield (MY), and heat tolerance trait and their genetic relationships. Data consisted of 5241 MY records on 479 crossbred cows from 27 farms in Ethiopia and 16658 CH4 measurements from 899 cows captured by the handheld laser methane detectors. Heat tolerance was determined based on temperature-humidity index (THI) computed from online weather information on the day of CH4 measurements and 3 days preceding it. Also, pedigree information and a 90k SNP genomic data for 459 individuals were available. Initially, a random regression model with polynomial of order two was fitted to estimate changes in MY and CH4 in response to varying THI at the population level. Two models were then fitted to estimate genetic parameters. A repeatability univariate model to heritabilities for CH4 and MY using ssGBLUP with fixed effects of region, year-season, breed, parity, and age nested within parity and random effects for animal and permanent environment. Secondly, the same repeatability model was fitted for CH4 and MY but with an additional random effect for animal effects was fitted as a of THI function (RR) fitted to estimate the effects of heat tolerance. Thus, the intercept from this model indicates the animal's ability to produce MY or CH4 in thermoneutral conditions and the slope describes the animal's sensitivity to heat stress. The breaking point with marked changes in CH4 and MY was about at THI of 70 with CH4 increasing by 19.9g/day and MY decreasing by 0.8kg/day after the breaking point. The heritability for CH4 and MY from the ssGBLUP were 0.1±0.04 and 0.19± 0.11 respectively. The heritability estimates from the RR for CH4 and MY under thermoneutral conditions (intercept) were 0.09± 0.02 and 0.13±0.01 respectively. The corresponding estimates for sensitivity to heat stress (slope) were 0.01 ±0.004 (CH4) and 0.02±0.002 (MY). The genetic correlations between the intercept and the slope from the RR model 0.43±0.11 for CH4 and 0.12±0.15 for MY. The study has shown that at high heat load, MY decreased with increasing THI while CH4 emitted increased. Therefore, selection for improvement in productivity and CH4 reduction in dairy cattle should also incorporate resilience to heat stress as an additional trait for optimum efficiency.

Keywords: 2026

How to Cite:

Ehsani, A., Ekine-Dzivenu, C., Meseret, S. & Mrode, R., (2026) “Genetic analysis of methane and its relationship with milk yield and heat tolerance in smallholder dairy systems”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286667. doi: https://doi.org/10.31274/wcgalp.24088

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