Nutritive value and in vitro gas production of fungal treated maize cobs

Abstract

Studies were conducted to evaluate maize cob cultured with white-rot fungi: Pleurotus ostreatus and P. pulmonarius for 21 days as a means of improving their nutritive value for ruminant animals. The substrates obtained after biodegradation were analyzed for the chemical composition, mineral content and in vitro fermentation. The results of the chemical composition showed an increase in the crude protein from 3.89% (control) to 10.11% for Pleurotus ostreatus treated maize cob (POC) and 7.46% for P. pulmonarius (PPC) treated maize cob. On the contrary, the crude fiber (CF) decreased significantly (p<0.05) from 28.69 % in the control to 19.53% in POC and 21.48% in PPC. Decrease in the values of neutral detergent fiber (hemicellulose, cellulose and lignin) and acid detergent fiber (lignin and cellulose) were detected. The value obtained for cellulose ranged from 28.70 to 34.70%; hemicellulose ranged from 19.05 to 23.18% and acid detergent lignin ranged from 12.44 to 16.88%. There were significant (p<0.05) increase in the Calcium, Magnesium, Iron and Manganese contents of the treated substrates compared with the untreated. The fractional fermentation rate (c h -1 ) was highest for PPC followed by POC. The fermentation of the insoluble but degradable fraction (b) increased significantly (p<0.05) from 37.00% in the control to 52.33% in POC and 49.33% in PPC. Gas volume at different incubation period was highest in POC. Methane decreased from 15 ml to 11 ml in the control and PPC, respectively. There were significant (p<0.05) differences among the treated and untreated substrates in terms of estimated metabolisable energy (ME), short chain fatty acid (SCFA) and organic matter digestibility (OMD). The estimated metabolisable energy (ME) ranged from 6.63 to 8.59 MJ/Kg DM for the control and POC. The POC showed the highest values for SCFA 0.9517 (΅m) and OMD (60.75%). The result showed that fungi treated maize cobs had potential of being converted to value added ruminant feed.