Treatment using white rot fungi changed the chemical composition of wheat straw and enhanced digestion by rumen microbiota in vitro

Treatment with white rot fungi can effectively remove lignin and decompose the structure of biomass to enhance its nutritional value. The aim of this study is to identify high-performance fungi to improve the rumen degradability of wheat straw. In this study three species of white rot fungi (Phanerochaete chrysosporium, Pleurotus ostreatus, Irpex lacteus) were inoculated and incubated under solid state conditions at 28 °C for 0–28 days to determine changes in chemical composition. Samples obtained after 28 days of incubation were assessed for in vitro gas production and rumen fermentation products. Results showed that P. chrysosporium and I. lacteus had similar ability to degrade lignin, while P. ostreatus and I. lacteus had similar selectivity in lignin degradation. After 28 days of incubation, I. lacteus resulted in moderate losses of dry matter, hemicellulose, and cellulose, which were 22%, 46% and 20%, respectively. But the straw treated with I. lacteus had the lowest (P < 0.001) content of lignin (sa) and a 5% increase in the absolute amount of neutral detergent solute. After 96 h of in vitro fermentation, the total volume of gas production from the straw treated with P. chrysosporium dropped by 24%, but that from the straw treated with P. ostreatus and I. lacteus respectively had a 5% and 33% increase. What’s more, the straw treated with I. lacteus not only improved the production of volatile fatty acids (P = 0.047) but also lowered the acetate:propionate ratio (P < 0.001) in the fermentation fluid. However, all the treatments resulted in significantly lower (P < 0.001) concentration of ammonia nitrogen. It is concluded that I. lacteus has a great potential to improve the rumen fermentability and energy utilization of wheat straw, but the effect of fungal treatment on the utilization efficiency of nitrogen needs further research attention.