RESUMEN
The aim of the present study was to evaluate the effect of feeding green fodder, rice straw and concentrate-based total mixed rations (TMR) on dry matter (DM) intake (DMI), nutrient utilization, rumen fermentation patterns and body weight (BW) gain (BWG) in mithun (Bos frontalis) calves. In a randomized block design, male mithun calves (n = 18, 8-10 months of age, 121 +/- 2 kg BW) were randomly divided into three experimental equal groups (six animals in each group) and fed isonitrogenous TMRs ad libitum for 120 days. The TMR(1) contained 30% Napier grass and 30% rice straw, TMR(2) contained 60% rice straw and TMR(3) contained 30% tree leaves (Lagerstroemia speciosa) and 30% rice straw (DM basis). All the TMRs contained 40% concentrate mixture (DM basis). The results indicated that the BWG, DMI and feed conversion efficiency were significantly (p < 0.01) increased with the inclusion of green fodder in TMRs. The apparent digestibility of DM, crude protein, ether extract, crude fibre and nitrogen free extract were also improved significantly (p < 0.01) with the inclusion of green fodder in TMRs. The higher concentration of total nitrogen and total volatile fatty acid in rumen liquor, but low ruminal pH were evident in animals fed green fodder supplemented TMRs. An increased (p < 0.01) molar proportion of acetic acid was evident in animals fed rice straw-based TMR. In contrast, the molar proportion of propionic and butyric acids were significantly (p < 0.01) higher in animals fed green fodder supplemented TMRs. On the basis of higher DMI and higher daily BWG, it is concluded that Napier grass and L. speciosa tree leaves may be incorporated upto 30% (DM basis) in TMR of growing mithuns for feeding in complete confinement system.