Ensiled alkali-treated straw. II. The nutritive value for young beef cattle of mixtures of ensiled or frozen alkali-treated straw and ryegrass silage

Ensiled or frozen barley straw, treated with 7.5 g NaOH and 120 ml solution per 100 g DM prior to storage, was given in mixtures with ryegrass silage to young calves, initially 100 kg live weight. Urea was added to the straw at feeding at 2.5% of the dry matter (DM) and soya bean meal was given at 0.3% live weight per day in all treatments. Voluntary intake, digestibility and live-weight gain were similar for the two types of treated straw. Intake of metabolisable energy and weight gain decreased with increasing level of straw in the diet, averaging 889 g per head per day for a control diet of grass silage (91.7% of total diet DM), and 749, 550 and 150 g per head per day when the proportion of straw DM to grass silage DM was 33: 66, 66 : 33 and 100 : 0, respectively. Whilst alkali-treated straw cannot replace high quality grass silage with the same nutritional efficiency, weight gains in excess of 500 g/day can be reached if the proportion of straw is less than half the total DM.