Treatment of barley straw with urea or anhydrous ammonia for growing cattle

Abstract

ABSTRACTIn experiment 1, nine Hereford × Friesian steers weighing 325 kg were used in a changeover design and offered long barley straw that had been treated with 30 g anhydrous ammonia per kg for 8 weeks, a solution providing 25 g urea per kg straw dry matter or a solution providing 23 g urea and 3 g ammonium sulphate per kg straw dry matter. In addition they were offered 3 kg/day of mineralized rolled barley. In experiment 2, 30 Hereford × Friesian steers weighing 380 kg were used in a continuous growth trial of 10 weeks duration. They were allocated to one of the following barley straw treatments, straw that had been exposed to 30 g anhydrous ammonia per kg for 4 weeks, untreated straw with a urea supplement in the barley or untreated straw. The straw was fed ad libitum with either 2·8 or 4·4 kg rolled barley daily.The barley straw contained 43 and 27 g crude protein per kg dry matter in experiment 1 and 2 respectively. In both experiments, ammonia treatment increased the crude protein content of the straw and resulted in improved straw intakes and higher live-weight gains. The results of experiment 2 cast doubt on the practice of providing supplementary nitrogen with food based on long barley straw and barley when steers weighing about 400 kg are used.