Fungi as a Source of Exogenous Enzymes in Ruminant Feeding

The complex link between plant cell walls has rendered rumen microbes incapable of completely degrading feed consumed by ruminants, resulting in their inability to maximally utilize the nutrients available in the feed. In such cases, rumen microbes are unable to complete the fermentation process within the retention time of the feed in the rumen. Pleurotus ostreatus and Armillariella tabescens were found capable of degrading mycotoxin (aflatoxin) present in feed. Incubation of fodder with P. ostreatus and Trametes versicolor can improve its nutrient quality by increasing the protein content while rapidly degrading the acid detergent fiber in the plant biomass. Cellulase and xylanase enzymes from Trichoderma spp., Aspergillus awomori, and Piromyces fungi from the wild are capable of efficiently degrading starch, rice bran, banana peel, plant secondary metabolites, agroindustry by-products, and other crop residues and milling by-products. Fungal enzymes can be used in dairy and feedlot production systems, as tbey increased acetate and butyrate production in high fiber-containing diets and propionate in low forage rations. However, it should be noted that increased fiber digestion is sometimes associated with increased methane production. Feed treated with an appropriate enzyme or a combination of enzymes at different inclusion levels can improve ruminant nutrition especially in developing countries where feeds are scare and of poor quality and farmers face seasonal supply of forages due to an extended dry season.