Potential Environmental Benefits of Residual Feed Intake as Strategy to Mitigate Methane Emissions in Sheep

Residual feed intake was evaluated as alternative strategy to decrease methane emissions from sheep. About 24 ewes (30 +/- 2 kg of BW) and 16 rams (32 +/- 2 kg of BW) were individually fed (42 days). Residual Feed Intake (RFI) was calculated for each individual by sex as the difference between actual and expected feed intake adjusted for metabolic body weight and gain weight rate. Animals were categorized (by sex and overall) as low (more efficient), medium and high RFI (less efficient). Methane emissions were estimated using gross energy intake (EF-CH(4)) and dry matter intake (EM-CH(4)). No effects (p>0.05) were observed on initial or final body weight neither on average daily gain' Methane production (kg day(-1)) from low RFI ewes were lower (p<0.01) being 0.021 and 0.025 than for high RFI averaging 0.027 and 0.032, respectively for EF-CH(4) and EM-CH(4). Positive relationships were found in rams between RFI and CH, predicted emissions (r = 0.46; p = 0.07) however, no effect (p>0.05) was observed on RFI over methane production. Overall low RFI produced 0.023 and 0.028 for EF-CH(4) and EM-CH(4), respectively in comparison with 0.028 and 0.033 observed in high RFI sheep. Results showed that low RFI sheep decreased methane emissions without affecting productive parameters.