Evaluation of in vitro digestibility of Aspergillus oryzae fungal biomass grown on organic residue derived‑VFAs as a promising ruminant feed supplement

Background As demand for high quality animal feed continues to raise,it becomes increasingly important to mini-mize the environmental impact of feed production.An appealing sustainable approach to provide feed fractions is to use organic residues from agro-food industry.In this regard,volatile fatty acids(VFAs)such as acetic,propionic and butyric acids,derived from bioconversion of organic residues can be used as precursors for production of micro-bial protein with ruminant feed inclusion potential.This study aims to investigate the in vitro digestibility of the Asper-gillus oryzae edible fungal biomass cultivated on VFAs-derived from anaerobic digestion of residues.The produced fungal protein biomass,along with hay clover silage and rapeseed meal were subjected to various in vitro assays using two-stage Tilley and Terry(TT),gas,and bag methods to evaluate and compare its digestibility for application in ruminant feed.Results The produced fungal biomass contained a higher crude protein(CP)(41%–49%)and rather similar neutral detergent fiber(NDF)(41%–56%)compared to rapeseed meal.The rumen in vitro dry matter digestibility(IVDMD)of the fungal biomass in the TT method ranged from 82%to 88%(statistically similar to that of the gas method(72%to 85%)).The IVDMD of fungal biomass were up to 26%and 40%greater than that of hay clover silage and rapeseed meal,respectively.The type of substrate and bag method had pronounced effect on the fermentation products(ammonium-N(NH4+-N),total gas and VFAs).Fungal biomass digestion resulted in the highest release of NH4+-N(340–540 mg/L)and the ratio of acetate to propionate ratio(3.5)among subjected substrates.Conclusion The results indicate that gas method can be used as a reliable predictor for IVDMD as well as fermenta-tion products.Furthermore,the high IVDMD and fermentation product observed for Aspergillus oryzae fungal biomass digestion,suggest that the supplementation of fungal biomass will contribute to improving the rumen digestion by providing necessary nitrogen and energy to the ruminant and microbiota.

<i>In Vitro</i>Digestibility and Gas Production from <i>E. crus-pavonis</i>Used in Wetlands from Domestic Wastewater Treatment

In order to evaluate the possibilities of valorization as the feed of the plant biomass produced during wastewater treatment in constructed wetlands, a study of the in vitro digestibility and gas production of Echinochloa crus-pavonis was carried out in the Laboratory of Animal Production and Nutrition of the University of Dschang. The in vitro digestibility of Echinochloa crus-pavonis was evaluated at different harvesting periods. The digestibility parameters of E. crus-pavonis samples were determined by the in vitro method at different phenological stages. The gas production (GP) during 24 h of incubation was assessed using the in vitro incubation technique with bovine rumen fluid. In vitro dry matter digestibility (IVDM) values ranged from 52.09% to 64.76% with a decrease observed with the phenological stages of E. crus-pavonis (from 64.76% at the leafy stage to 52.09% at the flowering stage). The microbial biomass (MB) values varied significantly between 67.99 and 88.45 mg, with no significant difference observed between the leafy (88.45 mg), bolting (82.93 mg), and early heading (80.26 mg) stages (P > 0.05). On the other hand, changes in the gas produced during 24 h from the studied samples of E. crus-pavonis (34.9 and 48 ml/500mg) and volatile fatty acids (VFA) values (1.08 and 0.80 mmol/ml) decreased significantly (P < 0.05) with the change in the phenological stage. The values of the partitioning factors (CF) of E. crus-pavonis in rumen fluid significantly decreased with advanced plant maturity (P < 0.05). The numerical values ranged from 0.52 to 1.19 ml/mg. A decrease in NDF-N was observed with the phenological stages of E. crus-pavonis. By combining the requirements of an optimal quantitative and qualitative production of E. crus-pavonis, harvesting at the bolting or early heading stage is an option of choice for exploitation as forage, under the conditions of this study. Based on the in vitro digestibility parameters studied, E. crus-pavonis is suitable as a ruminant feed.