In vitro gas fermentation kinetics of compounded ration containing graded levels of biodegraded corncob

Abstract

Cob regarded as a waste product, constituting source of environmental pollution could be utilized as an energy source in feed formulation if properly processed and harnessed through fungal degradation. Hence, this study was designed to evaluate the nutritive value of biodegraded corncob meal based diet using in vitro gas production technique. Aspergillus niger was isolated and sub-cultured to obtain a pure culture. Degraded corn cob meals(DCCM) of four dietary treatments were prepared to include: T (0% DCCM which served as 1 the control), T (15% DCCM), T (30% DCCM) and T (45% DCCM). Each diet sample 2 3 4 (200mg) was incubated in buffered rumen liquor for 48 hours and gas volume was estimated using established in vitro gas production models. Amount of gas volume produced was determined every 3 hours for 48 hours of incubation in buffered rumen fluid. After 48 hours ofincubation, methane gas produced was estimated and determined in triplicates. The proximate composition of Aspergillus niger biodegraded corn cob indicated that Aspergillus niger improved the nutritive value of the corn cob. Untreated corn cob meal was lower in nutritive values when compared with treated corncob meal with crude protein, crude fibre and ash values ranging from 6.88 to 9.78%, 32.68 to 26.37% and 2.87 to 2.88% respectively.The proximate composition of the dietary treatments showed that the crude protein varied from (11.67-12.67%), crude fibre (10.94-21.56%), ether extract (2.12-4.88%), ash (6.48- 9.44%) and nitrogen free extract (58.17-62.99%). Results obtained for volume of gas (35.960-72.770mL/200mgDM) produced in time “t” denoted by (b) were significantly different (P<0.05) across the dietary treatments. However, rate of gas production (0.0297- 0.0425mL/hr) and time between incubation and gas production (2.083-2.683hr) were not significantly different (P>0.05) across the dietary treatments. Cumulative gas volumeproduction at 24 hours were significantly (P<0.05) influenced by different inclusion levels of DCCM with values obtained ranging from T (15.33 ml/gDM) to T (35.33 ml/gDM). There 4 3 were significant differences (P<0.05) across the dietary treatments. The post estimated parameters ranging from metabolisable energy (4.96-7.74MJ/Kg DM), organic matter digestibility (37.98-58.03%), short chain fatty acids (0.31-0.78μmol), Methane estimate (3-8 ml/200mgDM) and Carbon dioxide estimate (10-30 ml/200mgDM). It can be concluded that 30% DCCM based diet had the potential of meeting the nutritional needs as smallruminant livestock feeds, if properly biodegraded and incorporated into feeds.