Cooling with fans and spray in closed cowshed and chromium supplementation improving growth performance of beef cattle

Abstract: Heat stress in summer can cause beef cattle to decrease feed intake and perform poorly, but such declines can be lessened if the beef cattle are cooled. Both the barn installed cooling fan and the chromium supplementation in diet are effective measures to relieve the degree of heat stress. The objective of this study was to investigate the effects of fanning and sprinkling and chromium added to diet on physiological indexes and growth performance of beef cattle in summer in the Southern China. Twenty-eight Simmental Crossbred beef cattle (average body weight 379.3 kg) were chosen and randomly divided into four groups, and were raised in enclosed feedlot barn for 30 days. In treatment I (T1), fans and spraying system were installed and chromium nicotinate was supplemented in the diet. Only fans and spraying system was assembled in treatment II (T2). In treatment III (T3), only chromium nicotinate was supplemented. Neither the fan and spraying system nor chromium nicotinate was used in the control (T4). The dosage of chromium was 800 μg/kg. The indexes such as environmental factors, temperature-humidity index (THI), rectal temperature (Tr), respiration rate (RR), average daily gain (ADG) and economic benefits were collected. The results showed that compared with the barn without fans and spraying system, the average room temperature was lowered by 1.84℃ (P<0.01) and wind speed increased by 8.27 times (P<0.01) in 14:00 in barns installed with fans and spraying system. The RR was reduced by 4.93 times (P<0.01) by fans and spraying system, and Tr was reduced by 0.23℃ (P<0.01) by chromium supplementation compared to T4. No interaction effect on RR and Tr was obtained between chromium supplementation and fans and spraying system. The ADG in T1 was increased by 12.37% (P<0.05), 19.59% (P<0.05) and 34.02% (P<0.05) respectively to T2, T3, and T4. Compared with the control group, the ADG of T2 were increased by 24.71% (P<0.05), and gross profit of T1 was increased by 4.44 yuan per head per day. In conclusion, both the fans and spraying system and chromium supplementation relieved the heat stress of beef cattle, and the average daily weight gain was improved, and finally the economic benefits was increased. However, the combination use of the two measures could lead to better results.