Effects of ensiling on Irpex lacteus fermentation in wheat straw: Chemical composition, in vitro rumen digestibility, and fungal community

Abstract

Ensiling before incubation with Irpex lacteus is effective in controlling spoilage microbes and improving the delignification of wheat straw, however, the interactions between I. lacteus and surviving fungi in silages and their further effects on chemical composition and in vitro rumen digestibility are still unclear. In the present study, 4 % I. lacteus spawn (w/w) was inoculated in untreated (WSI) and ensiled wheat straw (EWSI), and the same substrates without inoculation were set as control and named WS and EWS, respectively. Results show that EWS and EWSI had lower pH than WS and WSI at day 3, but the changing trends of EWS and WSI were opposite in the subsequent fermentation. Although the pH of WSI and EWSI was at an equal level and remained constant from day 7, there were more aerobic bacteria and molds in the former. After 56 days of fermentation, the lignin (sa) content of EWSI decreased by 36 %, and NDS content increased from 292.6 g/kg to 378.1 g/kg. The in vitro rumen dry matter digestibility of EWSI significantly increased by 22 % compared with that of intact wheat straw. The α-diversity of fungal community in all the samples decreased over time, and EWSI had the lowest Shannon index, reflecting only a few fungi dominated the substrates. Several fungi with hemicellulolytic and cellulolytic ability dominated the samples of EWS and WS before day 7, and then microbes with ligninolytic ability, such as Chaetomium, Aspergillus, and Sordaria, replaced them. However, I. lacteus had been the dominant fungal species in WSI and EWSI, though Sordaria and Chaetomium partly replaced it in WSI. The abundance of most fungi in WSI and EWSI decreased in the middle and late stages of fermentation. Negative correlations were observed between I. lacteus and pH, hemicellulose, and lignin (sa), and the relationship with lignin (sa) was further improved by ensiling. Above all, ensiling is an effective method to control unwanted fungi and to improve the delignification and digestibility of wheat straw with I. lacteus.