The ability to understand and model the role of fatty acids in early lactation has direct impact on dairy industry recommendations and the usefulness of supplementation strategies. We will briefly review the biological processes and quantitative changes during the metabolism of fatty acids in the rumen and the effect this has on fatty acid availability to the dairy cow. Our emphasis will be on recent research supplementing individual fatty acids and combinations of fatty acids on feed intake, nutrient digestibility, milk production, body weight, and energy balance in the early lactation dairy cow.