Effects of Weizmannia faecalis DSM 32016 on growth performance, gut microbiota, and health parameters in Holstein Friesian calves

Weizmannia-based probiotics (formerly allocated to Bacillus) have been studied for their benefits on intestinal health in monogastric animals, but their effects on calf rearing and diarrhoea-related intestinal challenges remain unclear. This is the first study evaluating the effect of Weizmannia faecalis DSM 32016 (WF-32016) on immunity and gut microbiota in female Italian Holstein Friesian calves. The trial was based on 20 female Italian Holstein Friesian calves, monitored from birth to ensure only healthy animals were included. Calves were randomly assigned to control (CTR) or probiotic (PRO) groups, with PRO receiving WF-32016 (109 CFU/kg feed), individually housed until nine weeks, and received a diet of colostrum, milk replacer, and starter feed. Colostrum samples, collected from dams at 6 h and 12 h post-birth to assess immunoglobulins G content, showed IgG levels above 50 g/l. At end of trial (day 56), probiotic-fed calves showed significantly greater body weight (PRO: 75.55 ± 4.55 kg; CTR: 67.90 ± 6.09 kg; p ≤ 0.05), and improved faecal scores in the first two weeks (PRO: 0.49 ± 0.84; CTR: 1.06 ± 1.14; p ≤ 0.01). Blood analysis indicated significantly higher IgG levels (p < 0.01) and antioxidant capacity (p < 0.01) in probiotic-fed calves at day 56. 16S rRNA analysis revealed significant beta-diversity differences (p < 0.05) and shifts in Lactobacillaceae, Streptococcaceae, Lachnospiraceae, and key genera (p < 0.05). Functional predictions indicated a significant increase in the pentose phosphate pathway in PRO samples (p < 0.05). WF-32016 supplementation enhanced growth, gut health, and immunity, supporting its potential as a natural alternative to reduce antibiotic dependence.