Direct evidence of preventive effect of severe diarrhea in calf by milk replacer-based probiotic feeding

Background Diarrhea is one of the major causes of death in calves directly linked to economic loss in cattle industry. Fermented milk has been widely used for calf feeding to reduce the diarrhea in clinical settings. However, the fermentation of raw milk has many difficulties, such as unstable fermentation due to large variances of nutrient composition in raw milk and contamination with coliform. Practical use of fermented milk replacer (FMR) has a strong potential to overcome these difficulties. However, the clinical efficacy of FMR on calf diarrhea is still unclear. Result In this study, we developed a stable condition of fermentation for FMR and verified the preventive effects of FMR feeding on calf diarrhea by an experimental infection model of bovine rotavirus (BRV) in newborn calf and a field study in dairy farms with calf diarrhea. Additionally, the clinical efficacy of lactic acid bacteria (LAB)-supplemented milk replacer (LAB-MR) was also evaluated in the experimental infection model. In the experimental infection model, control calves fed a milk replacer showed severe watery diarrhea after BRV challenge. Two out of three control calves were died after rapid decline of milk intake. In contrast, calves fed FMR or high-concentrated LAB-MR showed diarrhea, but the water content of feces was low and stable. In addition, the amount of milk intake decreased temporarily, but recovered immediately in the FMR- or LAB-MR-fed calves. Histopathological analysis of intestinal tracts revealed mucosal lesions were slighter in the FMR- or LAB-MR-fed calves than in the control calves. In a field study of FMR feeding in dairy farms with mixed infection with BRV and Cryptosporidium parvum, the incidence of enteritis and mortality of calf by enteritis were significantly reduced by the allocation of FMR. Additionally, the FMR-fed calves exhibited shorter duration of treatment, fewer consultations, and lower cost of medical care for enteritis compared with control calves. Conclusion These results suggest that feeding of milk replacer-based probiotics to calves reduces severity of diarrhea and tissue damage to intestinal tracts caused by BRV infection and provides significant clinical benefits for the prevention and treatment of calf diarrhea.