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.
The purpose of this on-farm trial was to evaluate the impact of supplementing slow-release nitrogen (SRN; min. 40% N) and exogenous fibrolytic enzyme (EFE; cellulase, xylanase, glucanase, mannanase and xylanase-potentiating factor) products on milk yield and composition in dairy cows. Twelve early-tomidlactating crossbred cows were divided into 2 groups with comparable milk production. Animals were fed on a total mixed ration comprising of green maize, wheat straw and concentrate mixture. Group T 1 was supplemented with urea at 80 g/animal/d, whereas that of T 2 received a novel combination of cellulopolymer-coated SRN at 80 g and EFE at 4 g/animal/d for a period of 20 days. Results showed no difference in milk yield (13.8 vs. 15.1 kg/d; P=0.559) between the groups; however, milk fat (3.49 vs. 3.87%) and solid not fat (7.92 vs. 8.35%) levels were higher (P0.05) in group T 2 than T 1 . Furthermore, on applying 2-axis milk payment system, group T 2 demonstrated a return on investment of 8.3:1. It was, therefore, concluded that supplementing a combination of SRN and EFE carries practical worth to enhance milk composition, thereby boosting economic gain in dairy farming under Indian context.
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