Effects of probiotic supplementation on preweaning Holstein × Angus calf performance and health

The study objective was to determine the effect of a probiotic containing Lactobacillus acidophilus and Lactobacillus casei fed daily to preweaning Holstein × Angus calves on growth, incidence of morbidity, liver score, gut morphology, rumen development, gut microbi-ome, and fecal pathogen shedding from 0 to 60 d. Preweaning Holstein × An-gus cross calves age <48 h with serum total proteins ≥5.2 g/dL were randomly enrolled on 1 of 2 treatments: (1) Control (CON: n = 149), and (2) probiotic (PRO: n = 150). The PRO dose added to individual milk bottles and starter grain was to supply not less than 1 billion cfu/calf per day in milk and not less than 1 billion cfu/calf per day in starter grain. There were no differences in growth performance, meaures of scours, gut community structure, α-diversity or health indicators between treat-ments. But, there were tendencies for increased ileal crypt depth, increased blood glucose from 7 to 35 d and redued fecal shedding of Shiga toxin-producing Escherichia coli ( E. coli STEC), corona virus at 42 d and Cryptosporidium at 21 d in PRO calves. Reducing fecal shed-ding of pathogens will reduce contamination of the en-vironment and potentially reduce exposure of calves to pathogens.