Digestion and utilization of straw. 1. Effect of different chemical treatments on degradability and digestibility of barley straw by sheep

Abstract

ABSTRACTBarley straw was treated with anhydrous ammonia, sodium hydroxide, ammonia plus sodium hydroxide, sulphuric acid or ammonia plus sulphuric acid to study the effect on the digestibility of straw and the degradability of the straw in the rumen of sheep.In experiment 1 four wethers fitted with rumen cannulae were given ammonia-treated straw to appetite and were used for measuring the dry- and organic-matter degradability of straw in the rumen after different in sacco incubation times. The organic-matter degradability (g/kg) after 48 h in sacco incubation was 459, 603, 576 and 660 for control, ammonia, sodium hydroxide and ammonia plus sodium hydroxide-treated straw respectively. Each treatment improved the degradability significantly (P < 0·01). The effect of ammonia plus sodium hydroxide treatment on rumen degradability of straw was additive (P < 0·05).In experiment 2 the treated straws studied in experiment 1 were given to four wethers in a 4 × 4 Latin-square design, to measure the voluntary intake, digestibility, water consumption and urine excretion. The digestibility (g/kg) and daily intake of digestible organic matter (g/kg M0·75 per day) were 554, 12·5; 628, 24·7; 653, 19·7; and 668, 24·3 for the control, ammonia, sodium hydroxide and ammonia plus sodium hydroxide-treated straws, respectively. Intake of ammonia-treated straw was significantly greater than for sodium hydroxide-treated straw (P < 0·01). The water consumption and urine excretion by sheep were increased significantly by sodium hydroxide and ammonia plus sodium hydroxide treatments (P < 0·01).In experiment 3, either straw or ammonia-treated straw were treated with 20, 40 and 60 g sulphuric acid (200 ml/1 solution per kg). The degradability of the acid-treated straws was measured using three wethers fitted with cannulae and given ammonia-treated straw to appetite. The dry-matter degradabilities (g/kg) after 48 h in sacco incubation were 52·0, 53·9, 58·7 and 67·4 for the control, and 20, 40 and 60 g acid per kg treatments, whereas the values were 61·3, 60·4, 68·4 and 69·4 for the ammonia-treated straw, and 20, 40 and 60 g acid per kg treatments respectively. There was a significant effect of acid treatment and ammonia treatment on dry-matter degradability.