The impact of pasteurization on the microbiota in bovine milk and calf feces

Pasteurization is a conventional method to reduce pathogen transmission from milk to calves. Previous studies primarily focused on the effects of pasteurized colostrum or short-term pasteurized milk feeding on neonatal dairy calves. This study examines the impact of continuous pasteurized milk feeding on early growth and the gut microbiome in dairy calves. Fecal samples were collected from 15 newborn dairy calves over one month, using high-throughput sequencing and microbial cultivation to analyze microbiome variations. Continuous feeding of pasteurized milk did not adversely affect growth performance but significantly reduced the abundance of L. reuteri in feces, likely due to the depletion of microbial resources from heat treatment. Extensive cultivation of Lactobacillus from milk and feces identified 40 distinct clusters out of 218 isolates using Rep-PCR. Whole-genome sequencing of 40 L. reuteri strains confirmed the presence of shared isolates in milk and the hindgut of calves. These L. reuteri isolates displayed a broad range of capabilities in metabolizing various oligosaccharides, including FOS, GOS, and inulin, contributing to early-life carbohydrate metabolism in dairy cattle. When optimizing calf growth strategies, it is essential to consider the impact of pasteurized milk on gut microbiota and the potential role of combined probiotics in maintaining intestinal health.