CASE STUDY: Evaluation of Different Cooling Systems in Lactating Heat-Stressed Dairy Cows in a Semi-Arid Environment

Two independent trials were conducted from June 3 to September 30 of 2004 and 2005. In each trial, 400 multiparous and 100 primiparous Holstein cows were randomly assigned to 1 of 2 cooling treatments [Advanced Dairy System fan plus misters - Shade Tracker (ADS-ST) vs. Korral Kool (KK)]. In 2004, production did not differ for multiparous cows housed in ADS-ST or KK (41.8 kg/d) pens, but primiparous cows housed under KK conditions tended (P = 0.10) to produce more than cows housed under ADS-ST conditions (37.8 vs. 36.7 kg/d). Respiration rates (RR) of multiparous cows cooled with ADS-ST were greater [P < 0.05; 60.5 vs. 58.3 breaths/min (BPM)]; however, RR in primiparous cows did not differ between treatments (59.2 BPM). In 2005, milk yields for multiparous(42.2 vs. 38.3 kg/d) and primiparous (35.2 vs. 32.7 kg/d) cows housed in KK were greater (P < 0.01) compared with cows housed in ADS-ST pens, respectively. In 2005, multiparous (70.9 vs. 59.3 BPM) and primiparous (72.2 vs. 61.3 BPM) cows cooled with ADS-ST had greater (P < 0.05) RR. During both trials, ADS-ST cooling system used less (P < 0.05) electricity (526 vs. 723 and 517 vs. 840 kwh/d; 2004 and 2005, respectively) and water (291 vs. 305 and 290 vs. 460 L/d; 2004 and 2005, respectively) than KK coolers. During moderate to severe heat stress conditions of these studies, cows housed under KK coolers outperformed those housed under ADS-ST fans, but the KK system used more resources than ADS-ST fans.