Assessment of methane emission traits in Canadian Holstein cows
Enteric methane production from ruminants represents a loss of productive energy and contributes to greenhouse gas emissions. This thesis presents a phenotypic data description and genetic parameter estimates of three methane emission traits (methane production, yield, and intensity) in Canadian Holstein cows. The variation of methane production across different times of recording within a day was also assessed. Lastly, the potential re-ranking of estimated breeding values for the alternative methane traits was evaluated. Methane emission traits were found to be moderately heritable, and moderate to high genetic correlations between pairs of methane traits were found. Therefore, genetic selection for methane emission is possible. Direct selection for one trait will indirectly improve the other traits, however, substantial re-ranking of estimated breeding values was observed, especially among the sires. Thus, the methane emission trait of choice will depend on how it will possibly be included in the genetic evaluation program.