Abstract
The presented study aimed at investigating the residual feed intake (RFI) of Sahiwal calves, nutrient utilisation as affected by RFI and its relationship with methane (CH4) emissions and some blood metabolites. Eighteen male Sahiwal calves (10–18 months of age; mean body weight 133 kg) were fed ad libitum with a total mixed ration. After calculating RFI for individual calves (−0.40 to +0.34 kg DM/d), they were divided into three groups with low, medium and high RFI, respectively. Dry matter intake (DMI) was higher (p < 0.05) in Group High RFI, whereas digestibility of all nutrients except crude protein and ether extract was significantly higher in Group Low RFI. Nitrogen balance was also significantly higher in Group Low RFI (20.2 g/d) than in Group High RFI (17.0 g/d). Average daily gain and feed conversion ratio were similar among the groups. With exception of glucose, concentrations of all measured blood metabolites were higher in Group High RFI (p < 0.05). Compared with Group High RFI, the CH4 emission of Group Low RFI was significantly lower (on the basis g/d and g/kg DMI by 11% and 19%, respectively). Furthermore, the CH4 emission [g/d] was significantly correlated with RFI (r = 0.77). Because higher feed efficiency and less CH4 production were observed in Group Low RFI, it was concluded that RFI can be used as a measure of feed efficiency, which has a potential to select Sahiwal calves for lowered CH4 emissions.
Acknowledgements
We sincerely thank the Director of the National Dairy Research Institute, Karnal, India, for providing necessary research facilities during the course of this study. The authors are thankful to the anonymous reviewers and the chief editor, whose suggestions greatly improved the merit of this paper.