Genetic relationship between methane emissions and conformation traits in Danish Holstein cattle

Abstract Text: Conformation traits have been widely explored in dairy cattle evaluation, being a part of the total merit index for Holstein cows in different countries. They have been used as a way to access the cow’s condition in general, based on its body features. Lots of studies have analyzed the relationship between conformation traits and other traits of interest in dairy cattle, such as fertility, longevity and feed efficiency, but little is known about how methane emissions correlate with conformation traits. Therefore, our goal was to evaluate the genetic correlations between methane and six conformation traits in Holstein cows: height (H), body depth (BD), chest width (CW), dairy character (DC) and body condition score (BCS).  Data was collected on 1114 Holstein cows from 11 commercial herds in Denmark. Methane emission was measured during milking in milking robots, and then quantified using information on milk production, weight and days carried calf to predict carbon dioxide production and multiplied by the ratio between methane and carbon dioxide. Bivariate linear models were used in the analysis to estimate the correlations between methane and each one of the traits analyzed. Heritabilities estimates were moderate, ranking around 0.3 for methane and between 0.11 (for CW) and 0.5 (for H) for the other traits. The estimated genetic correlations were mainly positive, implying that the bigger the cow, the more methane it produces. Our results could be partially explained by the fact that, in general, broader, deeper cows eat more, and it is a known fact methane production is associated with higher feed intake in ruminants. Due to high standard errors of the estimates further analyses are being conducted in order to more deeply evaluate and understand how conformation traits relate to methane emissions.  

Keywords: methane, conformation traits, genetic correlations