Enteric Methane Emissions in Dairy Cows with Different Genetic Groups in the Humid Tropics of Costa Rica.

Enteric methane (CH 4 ) is one of the main greenhouse gases emitted in livestock production systems with ruminants. Among the options to reduce such emissions, animal genetics is one of the factors that is taking relevance in recent years. The aim of the present study was to assess the emission of enteric CH 4 in dairy cows with different genetic backgrounds. Sixteen cows belonging to the following three genetic groups were selected for this study: seven F1 (50% Jersey × 50% Gyr), five Triple cross (50% Jersey × 31% Holstein × 19% Sahiwal) and four Jersey. Enteric CH 4 emissions were measured in all cows for 15 months, at the middle of each month, using the SF 6 technique. Enteric CH 4 emissions did not differ ( p > 0.05) among genetic groups, although it varied with the stage of lactation, due to differences in milk yield and dry matter intake (DMI). Pasture DMI and the intensity of CH 4 emissions (g kg -1 DMI) differed ( p < 0.05) between dry and lactating cows, with higher DMI in the lactation period, while CH 4 emission intensity was higher for dry cows. Cows with the highest proportion of Bos taurus genes presented a higher annual mean methane conversion factor (Y m ), with 7.22, 7.05 and 5.90% for the Triple cross, purebred Jersey and F1, respectively. In conclusion, non-significant differences in enteric CH 4 emissions and Y m were detected among dairy cows with different genetic backgrounds. However, F1 cows tended to show lower enteric CH 4 emission and Y m , compared to those with more Bos taurus genes.