Genetic Correlations Between Daily Dry Matter Intake, Body Weight, and Enteric Methane in Norwegian Red

Abstract

Selecting for reduced enteric methane emissions and improved feed efficiency in cattle is of interest. These are important traits both considering climate and utilization of feed resources on farm. Before genetic selection on new traits can be implemented, a base population with phenotypes on the desired trait(s) must be established. This study collected and analyzed data on feed intake, methane emissions, and body weight on Norwegian Red dairy cows in commercial dairy farms in Norway. Our goal was to estimate genetic parameters and breeding values for the three traits, and to estimate genetic correlations amongst them. We also calculated correlations to current breeding indices in Norwegian Red dairy cows. The relevant traits were daily dry matter intake (dDMI), average daily body weight (dBW), and average daily methane emissions (dCH4). There were 452 055 daily records on 2 074 cows in the dataset. Bivariate linear animal repeatability models were used. The model included fixed effects of parity week, age at calving, and herd in addition to permanent environmental effects of herd testday, additive genetic effects and residual as random effects. The pedigree was traced 8 generations back and contained 18 697 animals. The estimated heritabilities were 0.29, 0.39, and 0.57 for dDMI, dCH4, and dBW, respectively. Standard errors were low (0.04 to 0.05). Genetic correlations among all three traits were significant and strong, and ranged from 0.50 to 0.65. The strongest correlation (standard error) was found between dDMI and dCH4 of 0.65 (0.10). Positive and relatively strong genetic correlations imply that selection for lower level of one trait also will reduce the level of the other two traits. The correlation between the breeding values of the three novel traits to current indices from routine genetic evaluations of Norwegian Red ranged from (-0.26 to 0.16), and the fertility index had strongest favorable correlation to the three traits with -0.19, -0.22, and -0.26 for dBW, dCH4, and dDMI, respectively. This indicate that higher feed intake, larger cows and more methane emissions are associated with lower genetic merit for fertility. Further research is needed to investigate the consequences of selecting for reduced methane emissions or reduced body weight and how this will affect cows’ ability to utilize gras. For Norwegian Red it remains to define the feed efficiency trait, but we started to analyze traits that are key ingredients of a future feed efficiency trait.