Effect of a cooling jacket on calves in a hot environment

To minimize heat stress in calves, we created a cooling jacket and investigated its effects. In Experiment 1, seven 2-week-old Japanese Black cattle raised in a hot environment were used. The body temperature, heart rate and respiration rate were measured before and 30 minutes, 1, 2, 3 and 5 hours after placing the cooling jacket, and their changes were investigated. The body temperature decreased significantly 30 minutes after jacket application(39.2 ± 0.3℃) compared to the baseline value(39.5 ± 0.3℃)and remained at significantly lower levels until 5 hours after jacket application(39.2 ± 0.1℃). The heart rate and respiratory rate also remained at significantly lower levels until 5 hours after jacket application. In Experiment 2, ten 2-week-old Japanese Black cattle raised in a hot environment were divided into two groups of 5: a treatment group in which the cooling jacket was used and a control group without treatment. Blood sampling as well as body temperature, heart rate and respiratory rate measurements were performed before and 1 hour after jacket application. The body temperature, heart rate and respiratory rate at 1 hour after jacket application in the treatment group were significantly lower than their baseline values and those of the control group at both time points. Blood tests showed significantly lower cortisol concentrations at 1 hour after jacket application in the treatment group than those before jacket application and those of the control group at both time points. From these results, it was concluded that the cooling jacket was useful to decrease body temperature, and that this effect continued for at least 5 hours. In addition, the decreased cortisol concentration in the treatment group suggests that the jacket was effective in reducing stress in a hot environment.