Ahmed et al., 2002. Asian-Aust. J. Anim. Sci., 15 (4): 522-527

The experiment was conducted for a period of 56 days using 12 Bangladeshi bull calves, with average body weight of 127.2011.34 kg. The calves were divided into 3 groups having 4 animals in each. The animals were fed urea-treated rice straw designated as (A) 4% urea-treated rice straw, (B) 4% urea+4% soyabean-treated rice straw and (C) 4% urea+6% soyabeantreated rice straw. In addition, all the animals were supplied 2 kg green grass, 350 g Til-oil-cake and 100 g common salt per 100 kg body weight of animals. Straw was treated with 4% urea solution; soyabean meal, at 4 and 6%, were added to treated straw and kept for 48 h in double layer polythene bags under anaerobic condition. Urea treatment improved crude protein (CP) content of the rice straw (2.68-8.70%), and it was further increased by 10.74 and 12.12% with the addition of 4 and 6% soyabean meal. Dry matter (DM) intake (kg) was higher (p<0.05) in C (4.2) followed by B (4.1) and A (4.0). Crude protein intake was significantly higher (p<0.05) in group B and C than group A. Total liveweight gains were 20.2, 24.8 and 25.6 kg for calves of group A, B and C, respectively (p<0.01). The addition of soyabean meal to treated rice straw did not affect the coefficients of digestibility of DM, OM, EE and NFE. However, CP and CF digestibilities were significantly higher in group B and C (p<0.05). The values for digestible crude protein (DCP), digestible ether extract (DEE), digestible nitrogen free extract (DNFE) and total digestible nutrients (TDN) were significantly (p<0.05) higher in diet C and B in comparison to diet A, but there were no significant differences in digestible organic matter (DOM) and digestible crude fibre (DCF) values among the groups. It may be significant differences in digestible organic matter (DOM) and digestible crude fibre (DCF) values among the groups. It may be concluded that 4% urea-treated rice straw can be fed to growing bull calves with 2 kg green grass and a small quantity of concentrate without any adverse effect on feed intake and growth. Moreover, soyabean meal, at 4 and 6%, can be added to urea-treated rice straw at the time of treatment for the rapid hydrolysis of urea, in order to improve the nutrient digestibility and utilization of rice straw for the growth of growing bull calves.