As mentioned before, some microorganisms can use Co to synthesize vitamin B12 and other rumen microbial growth factors, and vitamin B12 deficiency can impair methylmalonyl CoA mutase activity, thus affecting propionate production and causing dysregulation of glucose homeostasis in ruminants [26], Co can promote nonstructural carbohydrate digestion and increase propionate ratios by reducing rumenomonas [35]. Here, MMUT is linked to vitamin B12 deficiency.