Optimization of Fungal (Pleurotus ostreatus) Treatment of Babul (Acacia nilotica) Pods and its Effect on Chemical Composition, in vitro Nutrient Digestibility and Biodegradation of Tannins

Acacia nilotica pods (pulp plus seeds) were treated with Pleurotus ostreatus fungus under solid state fermentation process using different levels of moisture contents (50, 55, 60, 65%) and incubation periods (3, 6, 9, 12, 15 days) to optimize the changes in its chemical composition, in vitro nutrient digestibility and biodegradation of tannins. The results revealed that crude protein contents increased from 14.75 in control (native pods) to 15.82% in 60% moisture content. The ADF content also increased linearly as the level of moisture increased. However, NDF and hemi cellulose contents decreased significantly. Organic matter content remained higher in treated pods than control. The dry matter loss was higher (7.64%) in treated material than control. Both IVDMD and IVOMD were higher in treated samples than control and the highest values noticed at 55% moisture where as IVCPD was highest at 60% moisture. Both hydrolysable and condensed tannins decreased considerably due to treatment as a result total tannins degradation to the extent of 57.94% was noticed at 60% moisture level. In another experiment, whenAcacia pods were treated with different incubation periods with optimum moisture content caused similar trend in chemical composition and tannins degradation with high degree of degradation on extended incubation period. The highest tannins degradation was noticed to the extent of 83.03% at 15 days incubation period. The dry matter loss increased substantially beyond 6 days incubation period as a result both IVDMD, IVOMD decreased significantly due to prolonged incubation periods. The values of IVCPD were found variable. In conclusion, the treatment optimization was achieved with best response at 55% moisture with 6 days incubation period during solid state fermentation in terms of tannin degradation and nutrient utilization from Acacia nilotica pods.