IntroductionAs a core nutrient regulating ruminant metabolic networks, immune homeostasis, and rumen microbial community structure, the source and supply of protein influence the adaptive capacity of breeding cows to metabolic stress during physiological transitions in the peripartum period.MethodsSixty healthy, periparturient cows with similar body weights (573.14 ± 76.67 kg) and gestation lengths (228.77 ± 37.86 d) were selected and randomly divided into four groups (n = 15), each group receiv