Milk oligosaccharides have the potential to promote calf health and thereby contribute to more sustainable dairy production. In a field study conducted by Osnabrück University of Applied Sciences, calves received milk replacer with or without supplementation of the fermentatively produced milk oligosaccharide 2′-fucosyllactose (2′-FL). Initial results indicate positive effects on animal performance. Calves supplemented with 2′-FL achieved significantly greater live body weights and showed higher feed intake. Analysis of the gut microbiome revealed changes around the weaning period. The abundance of several bacterial genera, including Peptoclostridium, was significantly lower.