From birth until weaning, calves undergo rapid hindgut microbial development as they transition from a predominately milk diet to grazing.  The fermentation that occurs in the hindgut of calves is essential for diet nutrient utilization and growth performance as well as defense against pathogenic gastro-intestinal disease (ex. scours).  Little is currently known about beef microbial development and no studies have been previously conducted looking at different management systems on farm or looking at the capacity for nutrient utilization.  Therefore, the overall goal of this research is to better characterize this development and to identify management factors that could impact microbial development and consequently health and performance both while nursing and later in life.  The data collected from this study will allow for identification of factors that impact beef calf health and performance both pre and post-weaning.  These data could also help develop strategies for maximizing overall animal performance and consequently improving profitability of this production system for Kentucky cow/calf producers.

Three cow/calf operators were identified in Anderson County for participation  in this study for the 2019 spring calving season.  Fecal Samples were collected serially for the first 30 days post-partium for monitoring of microbial community development (d 0, 4,8,15, 30) including microbes that utilize milk components, fiber, protein and sugars.  All calves monitored appeared to have few bacteria (in relation to their dams) and minimal microbial fermentation capacity in the first 24 hours of life.  These bacteria and their fermentative  capabilities increased with age, with the rate and composition of development being vairable.  Generally, the microbial community that ferment milk components (sugars, proteins) rapidly increase with age in healthy calves.  In contrast, fiber fermentation (important for future pasture utilization and a marker of microbial community health in adult animals) development was extremely variable with some calves having detectable bacteria and activity at 4 days of age and others not having any detected in the first 30 days.  Based on the data collected so far, it appears that there are impacts of farm (management system)., antimicrobial treatment, and milk availability early in life on hindgut microbial development and consequently early health and performance.  Additionally, cow hindgut microbial communities varied greatly between management systems.  Selected animals from Spring 2019 are still being monitored and will continue through weaning.  Additionally, 4 farms in Andeson County have been identified for participation in this study for the Fall 2019 calving season.