The effect of heat treatment of colostrum on the microbial composition of colostrum and calves feces

Colostrum plays a crucial role in transmitting infectious agents to calves, including Mycoplasma spp., Escherichia coli, Salmonella spp., and Mycobacterium avium subsp. paratuberculosis. To reduce bacterial contamination, on-farm heat treatment of colostrum is commonly employed. However, this heat treatment process may have an impact on the presence of beneficial probiotic strains in colostrum, potentially affecting the development of a healthy gut microbiota in dairy calves. To investigate this, the microbial composition of colostrum was analyzed before and after pasteurization, along with the feces of calves that consumed either pasteurized or unpasteurized colostrum.Colostrum samples were collected from 12 Holstein Friesian heifers (n=6) and cows (n=6) immediately after calving, with each dam providing 4 L of colostrum. Half of the collected colostrum was stored at -20 degrees celcius (CON, n=6), while the other half underwent heat treatment in an on-farm pasteurizer at 60 degrees celcius for 60 minutes before being stored at -20 degrees celcius (HT, n=6). Twelve bull calves received two feedings of 2L pooled colostrum (from two dams) within 2 and 6 hours after birth, with half receiving CON colostrum (n=6) and the other half receiving HT colostrum (n=6). Blood samples were taken from the calves 3 days after birth to measure serum IgG levels using electrophoresis. Meconium and feces were collected at birth before colostrum ingestion, as well as at 3 and 10 days of age. Bacterial DNA was extracted from colostrum, meconium, and feces, and amplicon sequencing of the V3-V4 region of the bacterial 16S rRNA gene was performed for microbial analysis.