404 Awardee Talk - Healthy gut, healthy calf, productive life

Abstract

Abstract The calf undergoes major transformations in early life that make it more susceptible to gastrointestinal tract (GIT) disease and disorders compared to all herd-mates. One of the most critical management factors in calf survival and health is feeding a sufficient amount of high-quality colostrum in order to improve passive transfer. However, further benefits to GIT function and health are now also being recognized. It has recently been shown that a delay in colostrum feeding of only six or twelve hours after birth can impact not only passive transfer but also the colonization of healthy bacteria (Bifidobacterium) in the small intestine of newborn calves. In addition, the heat treatment of colostrum has been shown to increase the colonization of Bifidobacterium and decrease the colonization of Escherichia coli in the small intestine of calves during the first 12 hours of life. New research is showcasing how the transition from colostrum to milk in the first days of life is critical to GIT development. For example, calves that transition directly to milk after the first meal of colostrum have less overall GIT mass and small intestinal villi development compared to calves fed transition milk or colostrum at three days of life. Based on these preliminary findings, there is a need to consider other bioactive components in colostrum and transition milk that impact GIT development in order to provide the calf with the best chance to combat GIT ailments later in life. With respect to the pre-weaning period of calf production, the amount of milk to be fed to calves has been a hot topic in the past decade, as it directly impacts pre-weaning average daily gain, which may be associated with lifetime production. Most dairy calves are only fed two meals per day and it is thought that increasing meal sizes may cause milk overflow into the rumen, resulting in digestive upsets and hyperglycemia. What recent research has shown however is that the GIT of the calf has a certain degree of plasticity and can adapt to large meal sizes (10% of birth bodyweight) in the first weeks of life by altering abomasal emptying as a means of controlling nutrient delivery to the intestine, thereby stabilizing blood metabolites such as glucose. In addition, new research investigating milk replacer composition, which is higher in lactose and lower in fat compared to whole milk, shows differences in abomasal function that may lead to a negative impact on insulin sensitivity. This research suggests that we have been underestimating how much milk calves can consume and how new milk replacer formulations may be impacting GIT health. An improved understanding of how diet, microbiota, and biomolecules interact to impact growth and barrier function of the calf’s GIT would greatly benefit the industry. A mechanistic understanding of such adaptations would also aid in the formulation of specific management regimens and the provision of diets that support or enhance gut function in young calves.