Disease & heat resistance

Genetic correlations between mid-infrared predicted methane production and heat tolerance in dairy cattle

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Abstract

Understanding how dairy cattle both affect and respond to environmental change is essential for sustainable production. Enteric methane emissions from dairy cows contribute to greenhouse gas emissions and resulting high temperatures have been shown to reduce productivity. Despite the importance of these challenges, the genetic relationship between methane emissions and heat tolerance in dairy cattle remains poorly understood. The objective of this study was to estimate the genetic correlation between mid-infrared-predicted methane production (MPMIR) and heat tolerance defined based on milk, fat, and protein yields. Data comprised test day records for the Canadian Holstein population collected between 60 and 185 days in milk. A random subset of 1,000 herds were selected from the full population resulting in a total of 142,054 MPMIR records and 461,992 milk, 429,174 fat, and 431,653 protein yield records collected between January 2018 and May 2025. Satellite data which included hourly ambient temperature and relative humidity were extracted from the NASA power database and temperature and humidity index (THI) values were calculated and averaged across each test-day and the two previous days. Heat stress effects were evaluated using a repeatability reaction norm model with thresholds of heat stress fit at THI 65, 55, and 60 for milk, fat, and protein yield, respectively. Two-trait models were fit between MPMIR and each production trait to estimate genetic correlations. Genetic correlations between MPMIR and heat tolerance (the reaction norm slope) were estimated to be -0.14 ± 0.08, -0.06 ± 0.06, and -0.01 ± 0.05 for milk, fat, and protein yields, respectively. Results indicate minimal genetic relationship between MPMIR and heat tolerance for production traits during mid-lactation. Future work will extend this analysis to additional stages of lactation and other environmental impact traits.

Keywords: 2026

How to Cite:

Dodd, G., Schenkel, F., Baes, C., Malchiodi, F., Richardson, C. & Miglior, F., (2026) “Genetic correlations between mid-infrared predicted methane production and heat tolerance in dairy cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2284173. doi: https://doi.org/10.31274/wcgalp.23552

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