Genetic aspects of methane emissions and feed intake in growing Holstein bulls

Livestock contributes significantly to greenhouse gas emissions, particularly methane (CH4). Genetic selection offers a promising approach to reducing CH4 emissions in dairy cattle, as breeding for specific traits in bulls can have a lasting effect on their progeny. However, little has been done to validate environmental traits measured in Holstein bulls. The aim of this study was to estimate genetic parameters for CH4 (g/day), feed intake (FI) (g/day), and live weight (LW) (kg) in Holstein bulls, from March 2018 to November 2024, at the National Association of Breeders of the Holstein, Brown and Jersey Italian Breed (ANAFIBJ) genetic centre. A GreenFeed system col- lected a total of 3,664 records for CH4 and CO2 from 200 growing bulls. Feed intake was recorded using five Roughage Intake Control (RIC) systems, capturing 8,307 feed intake records from 258 bulls. 2,748 live weight records were collected from 586 bulls. Bulls were divided into contemporary and pen groups based on their time of arrival at the centre. A single trait GBLUP model was developed and tested in BLUPf90 to estimate heritability for CH4, FI, and LW as 0.461±0.142, 0.357±0.175, and 0.295±0.155, respectively. In future research, FI and LW data could support the development of a ‘feed saved while growing’ trait, by calculating residual dif- ferences between genomic estimated breeding values for feed intake and live weight. These find- ings support breeding as a tool for reducing dairy cattle’s environmental impact.