Effects of magnesite on nitrogen conversion and bacterial community during pig manure composting

•The 10% MS (magnesite) addition was a promising candidate.•MS facilitated enzymatic activity, N conservation, and NH3 reduction in composting.•MS improved the abundance of Firmicutes, Actinobacteriota, and Halanaerobiaeota.•MS enhanced the metabolic activity of microbe and the metabolic pathway of nitrogen.•Complementarity enhancement in core bacillus primarily facilitated N conservation.