Abstract:
Animal Production in Australia THE NITROGEN REQUIREMENT OF STEERS FED ALKALI-TREATED STRAW - LIBITUM AD JANE LEIBHOLZ* and R.C. KELLAWAY* Experiments from this laboratory (Kellaway et al. 1978) have shown that steers can be maintained on a diet of straw sprayed with NaOH (4 g/kg straw) if a nitrogen supplement is provided, but the amount of nitrogen required was not determined. Therefore, pen studies were carried out in order to determine the optimum level of urea to be fed with alkali-treated straw. Wheat straw was sprayed with urea per kg straw. The straw was a nitrogen : sulphur ratio of 10 : steers with a calcium, phosphorus design. The steers were prepared Sample collections were made over TABLE 1 NaOH (40 g/kg straw) and 10, 19, 28 or 37 g of also sprayed with sodium bisulphate to maintain 1. The diets were fed - libitum to four ad and trace mineral supplement in a Latin square with rumen, abomasal and ileal cannulae. the last five days of each 21-day feeding period. Dry matter intake, digestion of nitrogen and concentration of ammonia in the rumen The retention of nitrogen by straw sprayed with 37 g urea per ence between 28 and 37 g urea per and the digestion of nitrogen in the steers was greatest when they were kg straw, but there was no significant kg straw. The synthesis of microbial the small intestines followed the same fed the differprotein trend. The concentration of ammonia in the rumen was below the optimal level for microbial protein synthesis when the steers were fed the straw sprayed with 10 g urea per kg (Raffler et al. 1976), but the synthesis of microbial protein was increased further as the concentration of ammonia in the rumen increased from 16.16 to 19.68 mg/l. It may be concluded that 28 g urea per kg should be sprayed on alkalitreated wheat straw where it is fed as the sole diet to steers. KELLAWAY, RX., CROFTS, F.C., THIAGO, L.R.L., REDMAN, R.G., LEIBHOLZ, J.M.L. and GRAHAM, C.A. (1978). Anim. Feed Sci. Technol. 3: 201. ROFFLER, R-E., SCHWAB, C.C. and SATTER, L.D. 59: (1976). J. Dziry Sci. E 80. * Department of Animal Husbandry, University of Sydney, Camden, N.S.W. 2570. 481