Strategies are being implemented in European countries to reduce the use of antimicrobials in farm animals. In this context, innovative husbandry practices that support animal health and productivity will likely play a key role in the near future. OmniGen-AF^® (Phibro Animal Health, Teaneck, NJ) is a feed product that has been shown to influence key markers of immune function in cattle. The objective of this study was to evaluate the effects of feeding OmniGen-AF on health and milk records in European dairy farms. Seventy-six dairy farms from Belgium, Italy, and the Netherlands were enrolled in this study in 2016. Farm records were collected for the 120 or 150 d before (Pre-OG), and during feeding 55 g/hd/d of OmniGen-AF to all dry and lactating cows (OG). Metrics recorded by number of farms included: cases of mastitis (n = 44), retained placenta (n = 49), metritis (n = 47), and culled cows (n = 17); milk yield (n = 70) and bulk tank SCC (n = 74). Incidence of mastitis and culled cows was expressed as % total cows, while incidence of retained placenta and metritis as % fresh cows. Farm was the statistical unit, OG vs. Pre-OG data were analyzed using a paired t-test, and statistical significance was declared when P < 0.05 and trends when P < 0.10. Average farm size was 154 cows/farm; 24% of farms were less than 100 cows, 59% had 100 to 200 cows, and 17% were greater than 200 cows. Overall, the incidence of mastitis, retained placentas and metritis all decreased (P = 0.001) during the OG vs. Pre-OG period: −27% mastitis (14.7% Pre-OG vs. 10.7% OG), −38% retained placentas (16.7% vs. 10.3%), and −32% metritis (24.5% vs. 16.7%); no significant difference was detected in number of culled cows. Bulk tank SCC decreased (P = 0.001) an average of −55,000 cells/mL during the OG period (309k vs. 254k cells/mL) while milk yield tended to increase (P = 0.057): 31.3 vs. 31.8 kg/hd/d. These data suggest that feeding OmniGen-AF to dry and lactating cows along with sound nutritional and management practices can have a positive influence on health parameters, milk yield and milk quality in European dairies.