Modifications in freestall housing were tested over three summers in three-treatment switchback trials with 10 lactating dairy cows per treatment group. Modifications were 1) overhead insulation, 2) overhead insulation plus roof sprinkling, 3) roof sprinkling, 4) inspired-air-cooling, and 5) no cross ventilation. Freestall areas were cross ventilated except 5). Compared with unmodified control, roof sprinkling plus insulation and inspired-air-cooling reduced body temperature and respiration rate while roof sprinkling lowered body temperature. No cross ventilation elevated body temperature and respiration rate. Roof sprinkling resulted in higher milk production. The inconsistent response of milk production to modification apparently was related to nutritional management. In blood samples drawn at 1500 h, urea nitrogen was higher in the controls during the second summer. In plasma of samples taken at 0800 h during the third summer, cows under roof sprinkling had higher concentrations of calcium, cholesterol, and protein than controls. No cross ventilation lowered protein in plasma. As indicated by reductions in body temperature and respiration rate, roof sprinkling, roof sprinkling plus insulation, and inspired-air-cooling improved the comfort of lactating cows during the summer and provided potential for higher milk production while no cross ventilation reduced animal comfort. © 1979, American Dairy Science Association. All rights reserved.
