Supplementing a yeast probiotic to pre-weaning Holstein calves: Feed intake, growth and fecal biomarkers of gut health.

Diarrhea, resulting from gastrointestinal infection by pathogens, is a common cause of the high mortality and morbidity of neonatal calves. The objective of this study was to evaluate the effects of supplementing a yeast product in milk replacer (MR) on growth and health of calves, and on fecal populations of some targeted microorganisms related to calf health and growth (, total bacteria, , cluster XIVa, and spp.). We hypothesized that feeding a var (SCB) product would improve gastrointestinal health and growth performance of calves. Forty-two Holstein bull calves (42.6 ± 0.77 kg at birth) were randomly assigned on day 2 of age to either a control or SCB treatment. The SCB was supplemented in MR and fed at 5 g/d per head to supply 10 billion colony-forming units per day. All calves received high quality colostrum (>50 mg/mL of immunoglobulin G) during the first 24 h of life, and were fed with 8 L MR (150 g/L mixed with 40 °C water) daily from day 2-35, and 4 L daily from day 35-42. Calves were also fed calf starter from day 7-56. Daily MR and starter offered and refused, daily fecal scores, nasal scores, ear scores, and weekly body weight of calves were recorded. Fecal samples were collected on day 7, 35 and 56 after the first feeding of that day for microbial targets analysis. Overall, there is no serious disease challenge for all the calves during the entire experimental period. No differences were observed in MR intake, starter intake, metabolizable energy (ME) intake, average daily gain, ME intake to gain ratio, fecal score, nasal score, eye score or any targeted microorganisms between treatments throughout the experiment. These results suggest that supplementing SCB in MR has no additive effects on animal growth or fecal biomarkers of gut health when calves do not show deteriorated health status.