Implementation of Methane Efficiency Evaluations for Canadian Holsteins

Abstract

Methane (CH₄) is a potent greenhouse gas (GHG) that warms the atmosphere at a rate 25 to 27 times more than that of carbon dioxide. The average first parity Holstein cow produces nearly 500 g of CH₄ per day or 180 kg per year, mainly due to enteric fermentation. A 30% difference above or below average can also be seen between cows, meaning two cows in the same herd can differ in their CH₄ emissions by up to 110 kg per year. As such, using genetics to select for cows with reduced CH₄ emissions is a strategy that can combat global warming and improve the efficiency of the dairy industry. In April 2023, Lactanet launched genomic evaluations for Methane Efficiency using milk mid-infrared (MIR) spectroscopy data. Previous research using artificial neural network methods determined that a cow’s milk MIR spectral data can be used as a good predictor of its CH₄ emissions. Lactanet developed CH₄ predictions using CH₄ data collected from research herds in Canada through two research projects, the Efficient Dairy Genome Project and the Resilient Dairy Genome Project, and milk spectral data collected via Canadian milk recording services. Predicted CH₄ (g/d) has a genetic correlation with collected CH₄ of 0.92 and a heritability of 0.23 (0.01). Lactanet’s genomic evaluation for Methane Efficiency was developed for the Holstein breed using a 4-trait Single-Step linear animal model including predicted CH₄ and milk, fat and protein yields as correlated traits. Methane Efficiency is defined as genetic Residual Methane Production in 120-185 DIM of first lactation and is genetically independent of production yields via a linear regression approach. The first genomic evaluation for Methane Efficiency included first lactation records on over 500 000 cows in Canadian milk recorded herds, of which more than 60 000 were genotyped. The average reliability of Methane Efficiency for genotyped young bulls and heifers exceeds 70%. Methane Efficiency is expressed as a Relative Breeding Value (RBV) averaging 100 and ranging from 85 to 115. For every 5-point increase in a sire’s RBV for Methane Efficiency, daughters are expected to produce approximately 3 kilograms less CH₄ per year. This equates to a 1.5% reduction in CH₄ emissions per cow per year and a herd can achieve a 20% to 30% reduction by 2050 through genetic selection. Methane Efficiency does not have a significant undesirable correlation with any other trait, including LPI, Pro$, production yields and Feed Efficiency.