Milk production (47.3 kg/d) and its fat and trueprotein levels (35.4, 28.6 g/kg) did not differ, and changes in body condition and locomotionscores were also not impacted by treatment. However mammary health improved basedon lower SCC (somatic cell counts; P < 0.04) of CED versus Control cows (160,000 versus196,000 cells/L), and lower linear SCC scores (P < 0.01; 2.12 versus 2.30). Feeding this CEto lactating dairy cows during summer heat decreased SCC with no impact on other aspectsof performance.