The Chemical composition and digestibility of wheat straw treated

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					The Chemical composition and digestibility of wheat straw treated with urea and white rot fungi
Y Rouzbehan 1 , H. Fazaeli2 and A. Kiani 1 Animal Science Group, Agriculture College, Tarbiat Modarres University, Tehran, P.O. Box 14155-4838, Iran. 2 Institute of Animal Science Research, Karaj, P.O. Box 31585-1483, Iran.
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Introduction In Iran, wheat straw is produced in huge amount and has been used in animal feed. However, the use of straw as an animal feed is limited due to its low available energy as well as its low nitrogen content. Various chemical delignification methods to improve the digestibility of straw have extensively investigated (Sundstol and Owen, 1984). Biological methods of treating straw using fungi such as white-rot-fungi have also been reported (Zadrazil, 1984). The solid-state fermentation (SSF) of wheat straw with white-rot fungi is a complex process, which is influenced by factors such as the species of fungus, substrate, temperature and moisture (Zadrazil, 1984). Rouzbehan et al., (2000) noted that pre-treating the straw with urea and incubation with either pleurotus ostreatus or pleurotus Persian fungi has improved the digestibility of wheat straw. In this study, the effect of urea and another two species of white rot fungi on the nutritive value of wheat straw was tested. Materials and methods Wheat straw was cut into 3-5 cm lengths and treated with 2% of urea solution (3 kg of dried urea mixed with 100 litres of water). Fifty litres of this solution was added to 100 kg of the straw and kept for three weeks. The treated straw (TS) was then steamed and inoculated with, spawn of either cross between Pleurotus ostreatus and Pleurotus sajor caju (TS1) or Pleurotus of Iranian tissue (TS2) at a rate of 3 percent (w/w). Five plastic bags, 2 kg each, have TS1 or TS2 were incubated at 25-30o C for four weeks period. All fermented samples were chemically analysed (AOAC, 1984), and the digestibility of DM and OM were measured using in vitro technique (Tilley and Terry, 1963). A completely randomised design was used to find out the effect of the tested species on the nutritive value of straw. Results Table below shows the results. On average, treating wheat straw with urea and either of the two species has significantly (P<0.05) decreased the concentration of OM, NDF, and hemicellulose. The increase in the CP content of the treated straw was probably due to the addition of urea. Fermenting the straw with TS2 has led to improve significantly (P<0.01) the DM digestibily. Whereas both types of fungi have increased significantly (P<0.01) the OM digestibility of the treated straw. Table 1: Chemical composition and digestibility of wheat straw treated with 3% urea after 4 weeks of solid-state fermentation with two species of fungi (Pleurotus ostratus xPleurotus sajor caju) (TS1) and Pleurotus of Iranian tissue (TS2). Treatment WS UWS TS1 TS2 SEM P- value OM 94.4c 91.9 c 89.3b 87.3a 2.1 * CP 1.6a 2.7 b 2.5b 3.2c 0.4 ** NDF 75.8b 75.6b 68.4a 67.2a 2.7 * ADF 56.5a 56.9a 50.7b 55.9a 2.3 * HC 19.3c 18.7 c 14.7b 11.4a 1.3 * Cellulose 43.5 45.4 42.4 44.9 1.5 Ns Lignin 13.0 11.5 11.3 11.0 0.5 Ns IVDMD 25.2a 24.2a 28.5a 34.2b 2.3 ** IVOMD 26.0a 27.1a 34.2b 37.1b 2.6 **

WS = untreated wheat straw. UWS=(wheat straw +urea). HC = Hemicellulose. IVDMD=in vitro dry matter digestibility. IVOMD=in vitro organic matter digestibility. Ns: indicate a non-significant difference. *(P<0.05, **(p<0.01) a, b, c different letters in columns indicate significant differences (p<0.05).

Conclusion Incubating the straw with pleurotus ostreatus x Pleurotus sajor caju fungi has improved the IVDMD, however, both species have increased the OM digestibility. More research is needed to evaluate the performance of animal which fed such fungal treated wheat straw. References AOAC, 1984. Official methods of analyses of Association of Official Analytical chemists. In: William, S. (Ed.), 14th edn. Arlington, VA, U.S.A. Rouzbehan, Y., H. Fazaeli and A. Kiani. 2000. The influence of urea and white rot fungi on the nutritional value of wheat straw. Proceedings of the British Society of Animal Science (p.59). Sandston, F. and Owen, E. 1984. Straw and other fibrous by-product as feed. Elsevier, Amsterdam. Tilley, J.M.A. and Terry, R.A. 1963. A two-stage technique for in vitro digestion of forage crops. British Grassland Soc., 18:104-111. Zadrazil, F., 1984. Microbial conversion of lignocellulose into feed. Chap. 9. In: F. Sundstol and E. Owen (Editors), Straw and Other fibrous By-products as feed. Elsevier, Amsterdam. Pp. 276-292.

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