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Two experiments were conducted on a commercial dairy farm in eastern Saudi Arabia to investigate the effects of Korral Kool (KK; Korral Kool Inc., Mesa, AZ) cattle cooling systems complemented with feedline soakers on core body temperature (CBT) of dairy cows. In both experiments, cows had access to KK 24 h/d. In the first experiment, 7 primiparous and 6 multiparous lactating Holstein dairy cows were assigned to 1 of 2 pens, which were assigned randomly to treatment sequence over 4 d in a switchback design. Soakers were on (ON24) or off (OFF24) for 24 h/d. For the second experiment, 20 multiparous lactating Holstein cows were assigned randomly to 1 of 2 pens, which were assigned randomly to treatment sequence in a switchback design. This experiment lasted 4 d and feedline soakers alternately remained off or were on (ON12) for 12 h/d. In experiment 1, average ambient temperature was 30 +/- 0.9 degrees C and average relative humidity was 44 +/- 14% (mean +/- SD). Feedline soakers complementing KK systems for 24 h/d decreased the mean CBT of lactating dairy cows compared with KK systems alone (38.80 vs. 38.98 +/- 0.061 degrees C, respectively). A significant treatment by time interaction was found. The greatest treatment effects occurred at 2100 h; treatment means at this time were 39.26 and 38.85 +/- 0.085 degrees C for OFF24 and ON24 treatments, respectively. In experiment 2, average ambient temperature was 35 +/- 1.5 degrees C and average relative humidity was 33 +/- 16%. Feedline soakers running for 12 h/d significantly decreased the mean 24-h CBT from 39.16 to 38.99 +/- 0.084 degrees C. Treatment by time interaction was also significant; the greatest treatment effects occurred at 1500 h, when ON12 reduced CBT from 39.38 to 38.81 +/- 0.088 degrees C. These results demonstrate that complementing the KK system with feedline soakers decreased the CBT of dairy cows housed in desert environments. However, the combined systems were not sufficient to lower CBT to normal temperatures in this extreme environment.