Effect of aluminized reflective hutch covers on calf health and performance.

The effect of polyethylene hutches wrapped in aluminized reflective covers (ARC) on health and performance of pre-weaned Holstein heifers during summer was evaluated. Ambient and hutch temperature and temperature-humidity index (THI) were also assessed. The study was conducted from June to October 2016 where temperature, humidity, and THI ranged from -1.3 to 38.4°C, 9.8 to 99.7%, and 33.6 to 81.1 units, respectively. Heifers enrolled at 1 d of life and housed in individual polyethylene hutches with (covered) or without (control) ARC were monitored until 60 d of life in 2 study groups (SG1, n = 94, monitored from June to September; and SG2, n = 101, monitored from August to October 2016). Calves were assessed twice per week for health status, behavior, rectal temperature, and respiratory rate. Similarly, hutch inner wall and sand bedding temperatures were determined for comparison between covered and control hutches housing calves. Four empty hutches per treatment group were continuously monitored for temperature and THI. The odds (95% confidence interval) of presenting diarrhea were 1.30 (1.01-1.60) times greater for calves housed in covered hutches than for those in the control group. Similarly, the odds of an abnormal ear score were 1.40 (1.03-2.00) times greater for calves in covered hutches compared with calves in control hutches. The odds of nasal discharge, eye discharge, and clinical dehydration did not differ between treatment groups. Rectal temperatures and respiratory rates were also similar in both groups. No differences were found in average daily gain between calves housed in covered and control hutches. Calf location determined at a fixed time during the day (starting at 1200 h) was associated with the use of ARC. The odds of remaining inside the hutch were 1.33 (1.03-1.70) times greater for calves housed in control compared with covered hutches. Overall, the average of hutch interior temperature was higher in covered compared with control hutches in both studies (SG1, 23.2 ± 0.06 vs. 22.8 ± 0.06°C; SG2, 17.1 ± 0.07 vs. 16.9 ± 0.07°C). Hutch THI was higher in covered empty hutches compared with control hutches in both study groups (SG1: 68.6 ± 0.06 vs. 67.6 ± 0.06°C; SG2: 60.2 ± 0.08 vs. 59.6 ± 0.08°C). Average temperature (measured at 1200 h) of the inner surface of the hutch wall was lower in covered compared with control hutches by 1°C (24.4 ± 0.13 vs. 25.4 ± 0.13°C), whereas the temperature of the sand bedding did not differ between groups. Our results suggest that the use of ARC did not generate a hutch microclimate that resulted in significant improvements on health and performance of pre-weaned dairy calves under these specific study settings.