Cell wall content and rumen dry matter disappearance of γ-irradiated wood by-products

Abstract Spruce sawdust and barks of spruce, pine and larch were irradiated with various doses of γ-rays (0; 0·1; 0·25; 0·5; 1·0 and 2·0 MGy). Cell wall constituents and rumen dry-matter disappearance (incubation time: 48 h) were determined. γ-Irradiation significantly reduced neutral detergent fibre (on average 78·2 to 54·3%) and acid detergent fibre content (average 69·2 to 49·5%) of all by-products; but in the case of spruce sawdust from 94·7 to 50·3 and 81·0 to 44·5%, respectively. The crude lignin of the wood by-products was not significantly influenced by γ-irradiation (contents between 30·8–32·6% of dry-matter). Rumen dry-matter loss of untreated sawdust was 5·6%, that of barks between 18·2 (pine) and 64·6% (spruce). γ-Irradiation significantly increased rumen dry-matter loss (up to 59·5, 49·0, 48·5 and 86·5% for sawdust and barks of pine, larch and spruce, respectively). Increased washout due to solubilization and particle breakdown was mainly responsible for the higher dry-matter losses in the rumen after irradiation. The results do not justify practical use because of the high dose of irradiation required.