Thermal conditioned of freestall facilities resting area and its consequences on productive and physiological responses in dairy cows
Keywords:
evaporative cooling, heat stress, milk production, physiological parametersAbstract
This work aimed to evaluate the efficiency of thermal conditioned in free-stall facilities and its consequences on productive and physiological responses in dairy cows. Experimental period was 28 consecutive days of November/2003. Fifteen dairy multiple cows with average milk production of 20kg/day were used. Treatments were: non-fan (NF); fan (F) and fan + misting (FM) directioned to animal bedding. Dry bulb temperature (DBT) and air relative humidity (RH) were measured every 15 minutes through a period of 24 hours inside and outside of facilities. Milking was realized at 1:00am; 9:00am and 5:00pm and date were collected. Animals were fed twice a day (10:00am and 3:00pm) and amounts of offered and rejected feed were daily registered. Physiological data such, as respiratory frequency (RF); rectal temperature (RT) and skin temperature (ST), were taken at 9:00am, 11:00am, 1:00pm, 3:00pm and 5:00pm. The RH was higher in V0 (61.8%) and VN (61.8%) treatments than in V (60.3%). The THI was higher in V (75.0) than in V0 (74.5) and VN (74.3) treatments. Related to physiological parameters, lactating cows of V0 treatment had lower rectal temperature at 11:00am (37.9ºC); 01:00pm (38.2ºC) and 05:00pm (38.2ºC). Respiratory frequencies (58; 55 e 58 mov/min, respectively, to V0; V e VN), white surface temperature (35.4ºC; 33.4ºC and 35.2ºC respectively, to V0; V and VN) and black surface temperature (31.9ºC; 31.5ºC and 31.8ºC, respectively, to V0, V and VN) were within normal variation in all treatments. Higher feed intakes were observed in animals of V0 (20.5kg DM/day) and V (21.3kg DM/day) treatments, but it did not increase milk production.
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