The purpose of this study was to evaluate the effect of protected niacin and yeast rich in chromium on the productive and metabolic performance of dairy cows under thermal stress. 46 lactating Holstein cows were divided into four treatments: protected niacin (GN), yeast rich in chromium (GCr), niacin+chromium (GNCr) and control (GC). Were measured: milk production, SCC, MUN, NEFA, BHB, glucose, cholesterol, insulin, cortisol, T4 and T3. There was an 8% increase in milk production in the GNCr. The use of these elements is an alternative for producers who need to maintain production during periods of thermal stress.