Factors affecting response to urea-molasses supplements by yearling cattle in tropical Queensland

Abstract

Two experiments were conducted over a five-year period in north Queensland to examine : 1. the effects of supplements of molasses, phosphoric acid, superphosphate, mono-ammonium phosphate, urea or biuret on liveweight performance of yearling cattle during wet and dry seasons, and 2. the effects of different urea levels (28, 56 and 84 g) in the urea-molasses supplement on dry season performance. Responses to urea-molasses or biuret-molasses occurred in all years after May when faecal nitrogen level fell below 1.3%. In three of the four dry seasons studied, maximum response occurred with the lowest level of urea, 289, in the urea-molasses supplement. Responses occurred up to 849 urea in the remaining year. Compensatory growth during the following wet season reduced liveweight advantages in all years. A faecal nitrogen level of 1.3% should be a useful critical value for feeding urea-molasses supplements in the northern spear grass region.