Effects of gamma irradiation on the composition and in vitro digestibility of crop by-products

Abstract

Samples of barley straw, pea straw, sugarcane bagasse, sunflower hulls and pine sawdust were irradiated to provide dosages of 10, 100, 200 or Mrad. Compared with untreated samples, irradiation with 10 Mrad caused only small changes in composition whilst 100 Mrad or more caused substantial losses of fibre components. In particular, the higher dosage levels resulted in lower values for neutral detergent fibre than for acid detergent fibre, thus yielding apparently negative values for hemicellulose. At the same time, sequential analysis with acid detergent solution and neutral detergent solution indicated that proportions of the cellulose and of the lignin were degraded to simpler molecules. Exposure to 10 Mrad had no significant effect on in vitro organic matter digestibility, 100 Mrad increased the digestibility of sunflower hulls and pine sawdust whilst 200 and 250 Mrad increased the digestibility of all materials. With 250 Mrad the digestibility of barley straw was increased from 40 to 61%, of pea straw from 42 to 61%, of bagasse from 33 to 57%, of sunflower hulls from 17 to 49% and of pine sawdust from 6 to 45%. It is suggested that, if gamma irradiation has any role in the treatment of by-products, it is more likely to be useful for highly refractory materials, such as sunflower hulls and sawdust, which do not respond appreciably to other physical and chemical treatments.