372 Genetic parameters for methane emissions and residual feed intake in Nellore cattle.

Abstract The objective of this study was to obtain (co)variance components, heritability, and genetic and phenotypic correlation estimates for enteric methane emission, residual feed intake, growth and carcass trait and reproductive indicators. Data from 146 feed efficiency trials with male and female Nellore cattle born between 2008 and 2023 from 146 herds in Central Brazil were analyzed. Trial data along with diet NDF content were used to estimate the methane emission intensity (g CH4/kg ADG) for each individual, using an equation developed by Medeiros et al., 2014: CH4 (g/d) = -0.1011 + 0.02062*DMI (kg/d) + 0.001648*NDF (% of DMI). Other data included pedigree information, body weight, carcass traits and reproductive indicator traits. Numbers of records varied from 3,869 (methane) to 42,840 (carcass data). Continuous traits were analyzed using a linear animal model. Two-trait analyses were performed using the restricted maximum likelihood to estimate the variance components, heritabilities and genetic and phenotypic correlations among traits. The estimated heritability of methane emissions was 0.117 ± 0.025. The genetic correlations of methane emissions with most performance and reproductive traits were low and not different from zero: BW at 240 d (0.019 ± 0.0003), BW at 450 d (0.022 ± 0.0003), ribeye area (-0.077 ± 0.098), rib fat (-0.020 ± 0.094), rump fat (0.091 ± 0.089), intramuscular fat % (-0.008 ±0.109), scrotal circumference (0.015 ± 0.0004), and age at first calving (0,072 ± 0,187), The same was true for early calving probability (-0,139; -0,384, 0,106) and stayability (-0,079; -0,324, 0,166) (means and highest posterior density intervals). Exceptions were the moderate genetic correlations of methane emissions with DM intake (0.486 ± 0.018) and the high correlation of methane with residual feed intake (RFI; 0.808 ±0.015). Thus, selection to improve weaning and yearling weights and carcass traits would not affect methane emissions. Genetic selection to reduce methane emissions is feasible and would also reduce DMI and RFI. Conversely, selection to improve RFI can be used to identify animals with lower methane emissions. Medeiros, S. R, L. G. Barioni, A. Berndt, M. C. Freua, T. Z. Albertini, C. Costa Jr., and G. B. Feltrin (2014) Modeling enteric methane emission from beef cattle in Brazil: A proposed equation performed by principal component analyses and mixed modeling multiple regression. Anais, Livestock, Climate Change and Food Security Conference, Madrid.