Two types of agroforestry wastes as bedding materials: Microenvironmental dynamics, microbial community structure, and impacts on growth performance of heifers

The economic and ecological benefits of recycled manure solids (RMS) make them a popular choice for bovine bedding. The stable operation of the fermentation-based RMS beds hinges on understanding their internal dynamics. This study utilized sawdust (SD) and fermented cow manure (FCM) as bedding materials to investigate the microenvironmental changes during in situ fermentation and their impacts on heifers. Results demonstrated FCM exhibited lower fermentation temperature, higher nitrate-nitrogen, smaller pH variation rate, and reduced ammonia concentrations, but higher electrical conductivity (EC) and methane emissions compared to SD. Bedding type significantly influenced the composition of both bacterial and fungal communities, whereas bedding duration affected only bacterial community structure. Key physicochemical factors shaping microbial communities included EC, C/N ratio, total nitrogen, water content, temperature, pH, organic matter and nitrate-nitrogen; ammonium nitrogen exclusively impacted fungal communities. Predictive functional analysis of bacteria revealed higher relative abundances of metabolic pathways related to nucleotide metabolism, carbohydrate metabolism and genetic information processing in FCM bedding. Notably, bedding type had no significant effects on heifers’ growth performance and serum parameters. This research provides a theoretical foundation for the resource utilization of cattle manure and scientific management of bedding materials in livestock systems. • The FCM possessed a lower fermentation temperature and higher NO 3 - -N • Concentrations of the CO 2 , N 2 O, NH 3 , and CH 4 were positively correlated with the pH • The fungal but not bacterial community composition was related to the NH 4 + -N • FCM had higher relative abundance of carbohydrate and amino acid metabolic pathways • FCM had no significant effect on the growth and serum parameters of heifers