The effect of cell wall degrading enzymes on the preservation of grass and on the silage intake and digestibility in sheep

Abstract

Two experiments were carried out to study the effects of cell wall degrading enzymes as silage additive. A primary growth of timothy was cut with a mower and picked up with a precision-chop forage harvester in Exp. I (early cut), and harvested as direct-cut with a precision-chop harvester in Exp. II (late cut). The additive treatments were in Exp. I: 1) unwilted formic acid (FA) applied as AIV II (4.5 l/t), 2) wilted untreated, 3) wilted FA (4 l/t), 4) wilted enzyme A (glucose oxidase (GO) + hemicellulase (HC) 150 ml/t + cellulase (C) 200 ml/t), 5) wilted enzyme B (HC 150 ml/t + C 200 ml/t); and in Exp. II: 1) untreated, 2) FA (4 l/t), 3) E200 (C 200 ml/t + GO), 4) E400 (C 400 ml/t + GO), 5) E800 (C 800 ml/t + GO). The rate of application of GO was 50 000 IU/t. The silages were ensiled in pilot scale silos (3 m3) and the voluntary intake and digestibility in sheep were determined in two experiments designed as a 5 x 5 Latin square. The use of enzymes decreased the fibre content of silages, mainly the cellulose fraction, as compared with FA and untreated silages. Enzyme silages were well preserved with a low pH (3.93—4.15), moderate ammonia N (72—119 g/kg total N) and no butyric acid. As compared with untreated silages (mean pH 4.6, ammonia N 131) the preservation was improved. The FA silages were also well preserved (pH 4.0, ammonia N 57) with more restricted fermentation than enzyme silages. FA and especially higher levels of enzymes increased the amount of effluent. In Exp. I, the digestibilities of dry matter (DM), organic matter (OM) and crude fibre were not significantly (P>0.05) affected by the silage treatment. In Exp. II, the digestibility of DM and OM decreased linearly (P