Methane and carbon dioxide emissions in Australian Angus – past and present

Methane production (MP) and carbon dioxide production (CP) records have been collected on Australian Angus cattle in both past and current projects. The historic records consisted of animals measured in respiration chamber (n=887 animals) and using Greenfeed Emission Monitor (GEM, n=318 animals), while recent records were collected using GEM units (n=892 animals). The aims of this study were to estimate variance components and genetic relationships between emission traits based on historic respiration chamber records, current GEM records, and combined current and historic GEM records. The heritabilities of MP were similar in the respiration chamber (0.39, SE 0.10), current GEM (0.38, SE 0.11), and combined current and historic GEM (0.36, SE 0.08) datasets. The heritability of CP was higher in the respiration chamber dataset (0.49-0.50, SE 0.26) than the current GEM (0.38, SE 0.10) or the combined current and historic GEM (0.33, SE 0.08) datasets. Low to moderate positive genetic correlations were observed between the respiration chamber records and either the current or combined current-historic GEM datasets. The large SEs were likely due to the relatively small data sizes, particularly for the respiration chamber CP records (263 records). The results indicated that including both historic and current records may be beneficial for the estimation of genetic parameters of emissions in Australian Angus cattle.