Neonatal Calf Diarrhea and Gastrointestinal Microbiota: Etiologic Agents and Microbiota Manipulation for Treatment and Prevention of Diarrhea

Simple Summary Diarrhea in newborn calves is a major global health concern, leading to significant illness and death. However, understanding the changes in the gut bacteria of calves with diarrhea and its causes still needs to be expanded. Various studies have shown that the gut bacteria in calves with diarrhea differs significantly from that of healthy calves of the same age. One crucial question is whether these bacterial changes contribute to, or result from, the gut inflammation caused by the pathogens associated with calf diarrhea. This review summarizes the current information on the alterations in the gut bacteria of calves with diarrhea and how the pathogens linked to diarrhea affect these bacterial communities. In human and dog medicine, strategies like pre-and probiotics, colostrum feeding, and fecal microbiota transplantation (FMT) have successfully treated and prevented gut diseases. While there is some information on using probiotics to prevent diarrhea in cattle, there is limited knowledge on employing these methods for treating calf diarrhea, including prebiotics or FMT. The second goal of this review is to provide an overview of the current knowledge about the use and efficacy of prebiotics, probiotics, synbiotics, colostrum feeding, and FMT can be used to treat and prevent diarrhea in calves.Abstract Neonatal calf diarrhea is the leading cause of neonatal morbidity and mortality globally. The changes associated with the gastrointestinal microbiota in neonatal calves experiencing diarrhea and its etiology are not fully understood or completely defined in the literature. Several studies have demonstrated that the fecal microbiota of calves that experience diarrhea substantially deviates from that of healthy age-matched calves. However, one key question remains: whether the changes observed in the bacterial communities (also known as dysbiosis) are a predisposing factor for, or the consequence of, gastrointestinal inflammation caused by the pathogens associated with calf diarrhea. The first objective of this literature review is to present the current information regarding the changes in the fecal microbiota of diarrheic calves and the impact of the pathogens associated with diarrhea on fecal microbiota. Modulation of the gastrointestinal microbiota using pre- and probiotics, colostrum feeding, and fecal microbiota transplantation (FMT) has been used to treat and prevent gastrointestinal diseases in humans and dogs. Although information regarding the use of probiotics for the prevention of diarrhea is available in cattle, little information is available regarding the use of these strategies for treating calf diarrhea and the use of prebiotics or FMT to prevent diarrhea. The second objective of this literature review is to summarize the current knowledge regarding the impact of prebiotics, probiotics, synbiotics, colostrum feeding, and FMT for the treatment and prevention of calf diarrhea.