Abstract:
In order to relieve the summer heat stress in South on production performance of beef cattle and investigate the effects of different environmental regulation forms, 24 Jinjiang beet cattle were randomly divided into 3 groups, and each group had 8 cattle. Environmental regulation forms of Group 1, Group 2 and Groups 3 were interior ventilation, interior spray ventilation and roof sprinkling ventilation, respectively. The average weight of 3 groups was(250.38±24.54), (247.93±24.54) and(250.00±24.02) kg(P>0.05), respectively. Experiment was conducted in July and August, 2014. Environment temperature, relative humidity, cattle rectal temperature, breathing rate and daily weight gain were measured. Economic benefits of interior spray ventilation and roof sprinkling ventilation were analyzed. The results showed that compared with Group 1, during running time(between10:00 and 18:00) for the roof sprinkling ventilation, the temperature at 0, 1, 2 and 3 m under the roof decreased by 4.79(P<0.01), 2.13(P<0.01), 1.37 and 1.42 ℃, respectively; the relative humidity increased by 9.66%(P<0.01), 6.76%(P<0.01), 2.66% and 1.80%; respectively; the temperature of 1.5 and 0.5 m from the ground decreased by 1.2(P<0.05) and 1.07 ℃, respectively at 14:00; the dry-bulb temperature and relative humidity from the ground were(33.61±1.55) ℃ and 61.23%±4.03%, respectively, while those of Group 1 were(35.28±1.62) ℃ and 56.43%±3.62%, respectively. Compared with Group 1, the temperature of Group 3 decreased by 1.67 ℃(P<0.01), but the relative humidity increased by 4.80%(P<0.05). The dry-bulb temperature and relative humidity of Group 2 before spray ventilation were(34.58±1.73) ℃ and 57.34%±4.25%. The temperature and relative humidity of Group 2 after spray ventilation were(32.03±1.85) ℃ and 67.65%±5.65%. Compared with Group 1, the temperature of Group 2 before and after spray decreased by 0.70 and 3.25 ℃(P<0.01), respectively, but the relative humidity increased by 0.91%(P>0.05) and 11.22%(P<0.01), respectively. At 14:00 and 18:00, the temperature-humidity-velocity index(THVI) of Group 2 before and after the spray decreased by 0.51 and 0.70 ℃(P<0.05), respectively; meanwhile the THVI of Group 3 before and after the spray decreased by 0.99(P<0.05) and 0.85℃(P<0.05), respectively. The breathing rate of Group 2 and 3 decreased by 13 and 12 times/min(P<0.05), respectively. The rectal temperature of beef cattle in all groups was within normal range. Compared with Group 1, the daily weight gain of Group 2 and 3 increased by 11.11% and 26.36%(P<0.05), and the input-output ratio improved by 14.01% and 14.65%, respectively. These results suggest that the heat stress of beef cattle in South can be relieved by interior spray ventilation and roof sprinkling ventilation in some way. Economic benefits of Group 2 and 3 are improved. Moreover, the effect of roof sprinkling ventilation is prior to that of interior spray ventilation.