As measures are enacted to reduce antimicrobial use in agriculture, finding management, feeding practices, and feedstuffs that could decrease diarrhea on dairy farms would be of benefit to animal and human health. A longitudinal observational study was conducted to assess the incident rate of undifferentiated diarrhea events by month on the farm and study the impact of exposure to different direct fed microbial dietary additives, to assess the effect of different common farm management practices, and farm design to affect the incidence rate of diarrheal disease. The study design was stratified by region, to target 150 farms in 10 different regions that corresponded to somewhat distinct management and environmental examples. A cross sectional survey instrument was administered to collect data relating to disease incident risk factors. Only 76 farms completed both the surveys and supplied electronic backups that provided information on incidents of diarrhea recorded in the herd records system. Sixty-nine farms either did not provide electronic dairy records with the survey, or there was no evidence they electronically recorded diarrhea events. The remaining 76 herds were analyzed for risk factors for incident of diarrhea using Proc Glimmix in SAS (version 9.4, SAS Institute., Cary, NC), both as a Poisson distribution and as a negative binomial distribution. The final multivariable negative binomial included a yeast culture fermentation product of Saccharomyces cerevisiae, (YC) whether the farm vaccinated for BVD, and whether the herd was located in the Eastern or Western US. Feeding YC had an Incident Risk Ratio (IR) of 0.707 (P = 0.043, CI = 0.505, 0.989). Having a herd in the eastern US was associated with an increased IR 2.036 (P = 0.066, CI = 0.953, 4.39). Vaccinating the herd with a BVD vaccine was associated with a decreased IR of 0.213 (P = 0.186, CI = 0.022, 2.111). The study shows there is a small association with feeding a yeast culture based additive and lower incidence of diarrhea on farms. This association although small, (a decrease of 2 cases per 1000 cows per month), indicates that further research should be conducted in this area.