Microbial community shifts in response to colostrum feeding and pathogen exposure in beef-on-dairy calves
In this study, we examined the effect of colostrum feeding on the microbial community shifts in neonatal beef-on-dairy calves and the impact of colostrum regime on the microbiota during Salmonella Typhimurium exposure. Calves were randomly assigned into one of two groups (n = 12/group): colostrum-fed or colostrum-deprived. Calves in the colostrum group were fed via esophageal tube (approximate total volume of 10% of individual body weight) a pooled, unpasteurized bovine colostrum within four hours after birth. Colostrum quality was measured on-farm using a Brix refractometer with a Brix score of 26%. Calves in the colostrum-deprived group did not receive any colostrum or colostrum replacement at their first feeding after birth. Instead, calves were fed 700 g of a commercial antibiotic-free milk replacer at ~4 hours after birth (24% protein, 20% fat; All Milk Calf Milk Replacer - MB Nutritional Sciences, LLC Lubbock, TX). All calves continued to receive this milk replacer twice daily throughout the study (until 21 days of age +/-2 days). At 8 days of age, a subset of calves in each group (n=10) were orally inoculated with Salmonella Typhimurium (1.0x10^4 CFU) via milk replacer bottles to induce intestinal inflammation. The remaining calves were considered control calves in each group (without Salmonella inoculation). Calves inoculated with Salmonella were euthanized on day 11 (72 hours post-inoculation) for tissue sampling and inflammation scoring. Calves not subjected to Salmonella inoculation were kept in the study until 21 days of age to assess the lasting effect of colostrum feeding on the intestinal microbial dynamics of beef-on-dairy calves.