A healthy digestive tract in dairy cows is critical for their production, health and welfare. An unhealthy digestive tract reduces feed intake, milk production, and milk quality, and may predispose cattle to laminitis, inflammation, diarrhea, and increased pathogen shedding. Excessive grain feeding reduces gut health by increasing the acidity, osmolarity, and endotoxin content of digesta, as well as by reducing the absorptive and barrier functions of gut epithelia, the utilization of nutrients, and the functionality of gut microbiota. Moreover, it affects the composition of digesta, and the sites of nutrient digestion. A healthy digestive tract in cows, therefore, requires healthy digesta, microbiota, and epithelia. The effects of excessive grain intake on gut health vary among cows. Hence, cows vary in their susceptibility to gut health disorders. Understanding the reasons behind this variation enables better management of gut health of dairy cows. Reasons behind the inconsistent impacts of high grain feeding on gut health include variations in the functionality of epithelia, the functionality of gut microbiota, and feeding behavior. Variation in the absorption of volatile fatty acids (VFA) in the rumen has a genetic component. Variation in the composition of gut microbiota is caused by a multitude of factors, including host genetics and environmental exposures. Feeding behavior and feed intake are also influenced by cow genetics, and medium values of heritabilities of feeding behavior traits, have been calculated. A challenge in estimating breeding values for “gut health robustness” is assessing phenotypes for this trait. This assessment may need to involve a standardized grain challenge followed by the monitoring of several gut health parameters to be effective. This approach is complicated by the invasiveness and inaccuracies of monitoring rumen pH. Metagenomics and metatranscriptomics of microbiota are probably too complex and costly to be used for routine diagnosis, but abundances of key taxa may contribute to the diagnosis. A combination of parameters, such as feed intake, fat yield and fatty acid profile, and markers of inflammation, such as acute phase proteins and endotoxins may be required. The presentation wil focus on genetics of gut health robustness in dairy cows.