Ammonia and sodium hydroxide treatment of wheat straw in diets for fattening steers

Abstract

The effects of treating Neepawa wheat straw with anhydrous ammonia (35 kg t −1), sodium hydroxide (50 kg t −1) and pelleting were evaluated in two experiments. The diets consisted of 51% rolled barley, 40% straw, 4% rapeseed meal, 2% tallow, plus minerals and a vitamin supplement. Straw was treated as follows: (1) shredded into 2.0-cm lengths; (2) shredded into 0.64-cm lengths and pelleted; (3) ammoniated and shredded; (4) ammoniated and pelleted; (5) sodium hydroxide and pelleted; (6) ammoniated, sodium hydroxide and pelleted. Apparent digestibility was measured with six steers per treatment. Pelleting had no effect on organic matter (OM) digestibility, but decreased neutral detergent fibre (NDF) and cellulose digestion. Respective increases for OM and NDF digestibility following chemical treatment of the straw were as follows: ammoniation — 15 and 17%; sodium hydroxide — 4 and 13%. The six diets were given to 144 Hereford steers (240 kg) for 92 days in the second experiment. Feed consumption ranged from 8.51 to 10.39 kg day −1 for diets 1 and 4, and body weight gains ranged from 0.83 to 1.26 kg day −1 for diets 1 and 6, respectively. Respective increases for intake, gain and feed efficiency compared to untreated shredded straw were as follows: pelleting — 11, 34 and 17%; ammoniation — 12, 36 and 17%. Sodium hydroxide treatment prior to pelleting improved intake, gain and feed efficiency by 5, 10 and 5%, respectively. There was no evidence of additive effects between ammoniation and either pelleting or alkali treatment, though treatment with sodium hydroxide prior to pelleting did result in the highest gains and feed efficiency.