Invited Review: Strategic use of microbial-based probiotics and prebiotics in dairy calf rearing

The objective of this narrative review was to describe the effect of microbial-based products, specifically pro- and prebiotics, on gut health, function, and disease prevention during early life and at weaning in dairy calves. The main source of data and information compiled for this review was peer-reviewed literature. Diarrhea is responsible for the majority of mortality and morbidity early in life. Pro- and prebiotics have recently been explored as mechanisms to promote gut health and decrease diarrhea in young calves. In addition, the change in calf diet, where there is a transition from a predominantly milk diet to a solid diet in a relatively short period of time, may also provide an opportunity to use microbial-based products. Based on the current studies that have supplemented calves with pro- and prebiotics, the majority of responses in growth, feed efficiency, and health have either been nonsignificant (39/68, 32/70, and 15/68, respectively) or positive (22/68, 9/70, and 31/68, respectively). The results presented in this review highlight that health and growth were the most positively affected responses to supplementation and that most of the beneficial effects were observed when these products were supplemented during a bout of illness. It appears that pro- and prebiotic supplementation to calves is low risk with potentially positive benefits that are worthy of further investigation. Supplementation of pro- and prebiotics to young ruminants requires further investigation to better understand the underlying mechanisms responsible for the phenotypical responses observed to implement better supplementation strategies.