In vitro and in vivo digestibility of soya-bean straw treated with various alkalis

Abstract

ABSTRACTThree trials were conducted to evaluate the effects of treating soya-bean straw with various alkalis plus ensiling on digestibility of various nutrients and on nitrogen retention in ruminants. Soya-bean straw was treated with sodium hydroxide, calcium hydroxide or ammonium hydroxide and ensiled at 650 g/kg moisture. In trial 1, the effects of level and type of alkali on in vitro digestibility of ensiled soya-bean straw were evaluated. Concentrations of alkalis used were 0 (control), 20, 30, 40 and 50 g/kg dry matter. Both in vitro digestibilities of dry matter and organic matter of soya-bean straw were significantly (P < 0·05) increased with alkali treatment at all levels plus ensiling compared with untreated or treated unensiled straw. The 40 g/kg alkali concentration level in combination with ensiling appeared to be the most effective overall. In trial 2, the effects of type of alkali on nutrient digestibility and nitrogen retention in wether lambs were evaluated. Sixteen wether Suffolk lambs were given untreated or alkali-treated (40 g/kg) ensiled soya-bean straw. Treatments were: (1) water-treated straw; (2) NaOH-treated straw: (3) Ca(OH)1-treated straw; and (4) NH4OH-treated straw. Lambs given NH4OH-treated ensiled straw digested the dry matter, organic matter, and crude protein better than those given water-treated ensiled straw (P < 0·05). NH4OH improved nitrogen intake by proportionately 0·181 but not nitrogen retention. For trial 3, eight Angus steers were used. Chopped soya-bean straw was treated with NH4OH and ensiled in Silopress bags. Treatments were: (1) untreated dry straw; (2) water-treated straw; (3) 30 g/kg NH4OH-treated straw; and (4) 40 g/kg NH4OH-treated straw. The trial consisted of a 7-day collection period which was replicated once. Apparent digestibilities of dry matter, crude protein and various fibre constituents were increased by ensiling or ensiling and NH4 OH treatment combinations (P < 0·05). Alkali treatments in combination with ensiling appeared to improve digestibility of soya-bean straw, but ammoniation did not improve nitrogen utilization. Ensiling appeared to have a more significant effect than alkali treatments per se on the degradability of soya-bean straw.