Relationship between residual feed intake and enteric methane emission in Nellore cattle

Abstract

Feed intake and average daily gain (ADG) in Nellore cattle were determined to calculate residual feed intake in two performance tests: first during the growth phase (RFI growth) and then during a measurement of the methane emission phase (RFI met). During the RFI growth test, 62 males and 56 females were classified as low-, medium-, and high-RFI. Enteric methane emission was measured in 46 animals; 23 males used for RFI met measurement plus 23 females (22 low-RFI growth and 24 high-RFI growth). Diet consisted of Brachiaria brizantha cv. Marandu hay (445 g/kg DM) and concentrate (555 g/kg DM). During the RFI growth and RFI met phases, DMI was lower in the animals with low RFI, with no difference in ADG. Residual feed intake was -0.359 and 0.367 kg DM/d for low- and high-RFI animals. Enteric methane emission (g/d, g/kg BW 0.75 and g/kg ADG) did not differ between RFI growth classes. Enteric methane emission (g/d) was higher in high RFI met and lower in low RFI met males. Spearman correlations among traits obtained during both tests, which were high between metabolic BW (r = 0.959) and between DMI (r = 0.718), and zero between ADG (r = -0.062), resulted in moderate correlation between RFI growth and RFI met (r = 0.412). However, it is not possible to confirm that high-efficiency animals release less enteric methane, since different results were obtained when enteric methane was compared between the RFI growth and RFI met classes.