Effect of incubation periods with white-rot fungi on the nutritive value of corn stalks

The present work was carried out to investigate the effect of different incubation periods using different species of white rot fungi on the chemical composition and nutritive value of corn stalks as animal feed for small ruminants. The experiments were carried out during April and Nov. 2000 using Pleurotus sp.112 (obtained from Institute of Forest Botany, University of Gottingen, 37077 Gottingen, Germany. ) and Pleurotus columbinus (obtained from local market). Two kg from chopped wet and pasteurized corn stalks (65 % moisture content) were inoculated in each plastic container (40 x 25 x 30 cm) with a 5% (wt/wet wt) spawn. 70 containers with each strain were covered tightly with plastic sheets and incubated up to 8 weeks. Samples were taken every week to determine the chemical changes of corn stalks. Crude protein, ash content, lignin, cellulose and hemicellulose were determined. In vitro dry matter and cell wall constituents disappearance of corn stalks after different incubation periods using Pleurotus species 112 were determined. The percentage of crude protein and ash in the raw corn stalks were 5.3 and 7.6 respectively. Many changes in corn stalks composition took place due to the fungal growth during the incubation periods of corn stalks. Pleurotus sp. 112 increased the protein and ash content, by 80 % and 21 %, respectively after two weeks of incubation. The highest increase in protein and ash contents was 90.8 % and 49 % for Pleurotus columbinus after eight weeks of incubation period. Cellulose and hemicellulose contents decreased by 21 % and 14 %, respectively after two weeks incubation period when Pleurotus sp. 112 was used. The highest decrease in cellulose and hemicellulose content for Pleurotus columbinus were recorded after 8 weeks of incubation .The decrease in cellulose and hemicellulose were 22.6 % and 54 % respectively. Changes in lignin contents were negligible . It was clear that the highest improvement in the nutritive value , i.e. increase in crude protein content and decrease in both cellulose and hemicellulose contents, took place after 2 and 8 weeks of incubation due to the use of Pleurotus sp.112 and Pleurotus columbinus, respectively. Pleurotus sp. 112 was chosen for performing in vitro dry matter digestibility and In-vivo digestibility with sheep. The results showed that, the digestibility of dry matter increased to 48.5 % after two weeks incubation compared with 40.9 % for the raw corn stalks. The improvement of in vitro digestibility reached 18.6 % as a result of white- rot fungi treatment. The results demonstrated clearly the potential of white rot fungi improving the nutritive value of corn stalks within two weeks instead of 10 to 12 weeks in the traditional methods.