A feeding trial on growing cattle to evaluate effects of rice straw treatment with urea and/or lime

A 3 three month feeding trial was undertaken with 20 steers of a small breed (Bos indicus) allocated into 4 groups to be fed on straw treated according to a 2 x2 factorial arrangement of inputs to determine biological and economical effects of treatment with urea (4 percent vs. 0 percent) in combination with quick lime (3 percent vs 0 percent) on feed intake, digestibility, growth rate, feed conversion ratio and economic efficacy. Straw was given ad libitum together with 200g ground corn, 50g fish meal and 50g of a mixture of minerals and vitamin (A,D,E)/head/day. For those groups not fed on straw treated with urea, 2 percent urea was directly sprayed on straw at feeding. It was found that in comparison with untreated straw, straw treated with 3 percent lime, 4 percent urea or 4 percent urea plus 3 percent lime all brought about increased feed intake and organic matter digestibility (OMD), thus improving digestible organic matter (OMI) and metabolizable energy intake (MEI). Straw organic matter intake (OMI) increased from 1.88-2.06, 2.12 and 2.09 kg/100 live weigh for untreated, 3 percent lime treated, 4 percent urea treated, and 4 percent urea plus 3 percent lime treated straw, respectively. Diet OMD was 52.47, 56.58, 58.28, and 60.67 percent; total DOMI 1.30, 1.60, 1.73 and 1.78 kg/head/day; and total MEI 19.60, 24.25, 26.13 and 26.89 MJ/head/day, respectively for the four group. The treatment, especially with 3 percent lime, considerably reduced the eating time from 531.40 down to 354.60, 477.40 and 480.40 minutes/day, respectively. However, only treatment with 3 percent lime significantly shortened the ruminating time, which was 444.20, 352.20, 485.80 and 464.40, respectively. More importantly, the three treatments dramatically increased average daily gain (ADG), reduced feed conversion ratio (FCR)and thus improved economic efficacy in comparison with feeding untreated straw. The ADG was 73.78, 210.89, 279.89 and 302.78g/head/day; the FCR 33.59, 13.50, 10.64 and 9.74, respectively for four groups. A partial budget analysis showed that in comparison with the increase costs related to the straw treatments, the increased returns owing to increased gains was 2.42, 3.49 and 3.51 times higher, resulting in net change in come (benefit) being 142, 249 and 251 percent of respective additional investments. For these, 4 percent urea plus 3 percent lime treatment proved to be the best, followed by 4 percent urea, and then 3 percent lime treatment. It was therefore suggested that rice straw should be treated with either 4 percent urea or better 4 percent plus 3 percent quick lime to feed ruminants