ABSTRACT Climate change has intensified the need to reduce greenhouse gas emissions, particularly methane (CH 4 ) from enteric fermentation. Genetic selection has emerged as a promising mitigation strategy; however, studies on Bos taurus indicus , especially Nellore cattle, remain limited. This study aimed to estimate heritabilities and genetic correlations for CH 4 emission traits and their relationships with feeding behaviour, feed efficiency, and performance, as well as to evaluate the direct and correlated responses to selection for lower CH 4 emissions. Data were from 2418 Nellore cattle evaluated in feed efficiency trials. Traits included dry matter intake (DMI), feeding time per day (FTd), feed events per day (FEd), and feeding rate (FR), residual feed intake (RFI), average daily gain (ADG), and mid‐test body weight (MBW). Methane emissions were measured in 1153 animals using the SF 6 tracer technique, providing daily CH 4 emission (g/day), CH 4 per unit of DMI (CH 4 DMI, g/day), and residual CH 4 (CH 4 res). Variance components were estimated using the single‐step genomic BLUP (ssGBLUP) method through Bayesian inference. Heritability estimates were moderate for CH 4 (0.25), CH 4 DMI (0.14), CH 4 res (0.14), and performance traits such as DMI (0.35), ADG (0.36), and MBW (0.40). Higher estimates were observed for feeding behaviour traits FTd (0.49) and FR (0.42). Genetic correlations between CH 4 and production traits were high, particularly with DMI (0.79), ADG (0.90), and MBW (0.91), indicating that selection for reduced CH 4 emissions may affect growth. Direct selection for CH 4 led to a modest annual reduction in emissions but also a correlated decline in MBW. These results demonstrate that while CH 4 emissions are heritable, their strong genetic association with productivity traits indicates that isolated selection for reduced emissions may lead to undesirable outcomes in feed intake and performance. Therefore, strategies aiming to reduce CH 4 emissions should consider the genetic relationships with growth and efficiency traits to avoid compromising animal productivity.
Silva et al. (Fri,) studied this question.