The severity of subacute ruminal acidosis of primiparous transition cows affects the fecal metabolome, without affecting the fecal microbiome of the cows or their calves

Abstract Aims To evaluate the effects of the severity of subacute ruminal acidosis (SARA) on the fecal microbiome and metabolome of primiparous transition cows, and the fecal microbiome and blood composition of the offspring; to investigate the effect of transition from gestation to lactation on the fecal microbiome of cows. Methods and Results The study included 24 cows; three SARA severities were evaluated: low, moderate, and high. Analyses of the fecal microbiome and metabolome of cows were performed from week 3 before parturition until week 10 in lactation; fecal microbiome of calves was evaluated at 1 week of age. Blood composition of calves was evaluated at days 1 and 7. Compared to low, greater SARA severity did not affect the fecal microbial diversity or abundance in cows, but increased concentrations of fecal amino acids and their derivatives in high SARA, resulting in enrichment of metabolic pathways for amino acid metabolism. No negative effects of SARA severity were found on the offsprings’ fecal microbiome or blood composition. Fecal amylolytic bacteria increased in cows post-calving at the expense of fibrolytic and methanogenic taxa. Conclusion SARA severity influenced the fecal metabolome of transition cows, but no negative impacts were found on the fecal microbiome of cows or on the microbiome and blood composition of the offspring.