| The effects of local ventilation and air cooler on heat dissipation of dairy cows was investigated, the evaluation of the using effects of cooling protection from heat for dairy cows, feeding in free stall barns located at Wandashan dairy farm in Heilongjiang Province, was conducted. Furthermore, the modification for cooling protection from heat was provided. The purpose was to reduce the impact of summer high temperature on performance of dairy cows, and protection for the productivity efficiency of dairy farm.Propeller fans were installed above the yoke which was on both sides of feeding channel in free stall barn. The space between propeller fans was12m, the distance from the ground to the bottom of the fan was2.1m, the installation angle was10°. The propeller fans were operated from08:00to18:00. A total of30healthy Holsteins were selected randomly, dairy cows shell temperature and respiratory rate was measured at different temperature, as well as under the condition of the fan on or off. Moreover, air temperature, relative humidity, concentration of harmful gases, wind speed, and wind speed distribution were measured also. The experimental results showed that the maximum air temperature was27.1℃, achieved at15:00, the minimum was22.6℃, at04:00; On the other hand, the relative humidity changed just the reverse, the maximum relative humidity was96%, achieved at04:00, the minimum was79%, at15:00; Wind speed in dairy cows barn was high during the day, and uneven distribution, average wind speed was0.98m/s, the night wind speed is low, uniform distribution, the average wind speed was0.34m/s; Concentration of carbon dioxide in dairy cows barn was uneven distribution, higher in the central area, lower near the window, and the average concentration of carbon dioxide was536mg/m3during the day,554mg/m3at night; Concentration of ammonia in dairy cows barn was uneven distribution, and the average concentration of ammonia was4.7mg/m3during the day,5.8mg/m3at night; In horizontal direction, uneven distribution of wind speed was observed, the highest wind speed appeared in the bed near the feeding channel side, lowest wind speed appeared in the bed near the window; In the vertical direction, the wind speed at1.5m was higher significantly than at0.5m and1.0m (P<0.05), and there was no significant difference between0.5m and1.0m; The uniformity and stability of wind speed was poor when the fans were opened in dairy cow barns; The effects of air temperature on shell temperature and respiratory rate of dairy cows were significant (P<0.05); Local ventilation decreased shell temperature of dairy cows significantly (P<0.05), but had no significant effect on dairy cows respiratory rate (P>0.05). Six propeller fans and three air coolers were installed in milking preparation area. The space between propeller fans was7m, the distance from the ground to the bottom of the fan was2.7m, the installation angle was10°. Air coolers were operated twice a day, four hours for the first time, three hours for the second time. Change of air temperature and relative humidity was measured for24h. A total of20healthy Holsteins were selected randomly, dairy cows shell temperature was measured before and after spray. The experimental results showed that the average wind speed was1.23m/s; Air coolers decreased the air temperature and THI, and increased the relative humidity in milking preparation area; The air temperature was decreased by2.2℃-3.4℃, and THI was decreased by5-7; Air cooler decreased the shell temperature of dairy cows significantly (P<0.05) when the air temperature was28℃(THI=78), but had no significant effect on it (P>0.05) when the air temperature was30℃(THI=80)... |
PDF Full Text Request