Influence of environmental conditions across day on respiratory rate and panting score of beef cattle in a hot and humidity weather

Abstract Text: Twenty growing bulls 278 ± 11.8 kg (75% Black Angus blood with remainder of Brahman and Brown Swiss in undetermined proportion, n = 10; and Brahman white coated bulls, n = 10) were used in an experiment to determine the influence of environmental conditions across day on respiratory rate and panting score of beef cattle in a hot and humidity weather. The experiment was performed during August of 2013. In groups of five, bulls with same breed were placed in provided or no shade ground pens (6 x 12 m). During 12 days from 0800 to 1600 h, inside of pens with 1 h intervals, air temperature (At), air relative humidity (RH), air velocity (Av), and soil temperature (St) were measured; one bull in each pen by time and day was randomly selected to respiratory rate (RR) in breaths per min (bpm) and panting score (PS) measurement by direct observation. Data of 12 d were pooled and analyzed by ANOVA. Across experiment, weather conditions were: At 36.30 °C (range 25.2 to 53.0), RH 50.30% (range 21.5 to 82.6), Av 3.20 km/h (range 0 to 12), THI 85.93 (range 75 to 98), and St 35.47 °C (range 15.7 to 73.9). Mean values of RR and PS were 65.95 ± 1.034 bpm and 1.18 ± 0.037, respectively. At 0800 h RR and PS were 44 bpm and 0.61 with 29.66 °C At, 67.86% RH, and 80.35 THI. Mean maximum air temperature (40.65°C), soil temperature (41.10 °C), and THI (89.08) were observed at 1300 h, while maximum respiratory rate (72.81 breaths/min) and panting score (1.57) delayed 1 h peaked at 1400 h. Means value of At and THI diminished (P < 0.05) at 1500 h; whereas RR, PS were coupled with Soil temperature and delayed two hours more (1700 h) to descend below of climax values (P< 0.05). It is concluded that respiratory rate and panting score delays proximately one hour to reach the highest values after air temperature and THI arrive at its day peak values, and spend around two hours to declines after air temperature and THI decreases; data suggest that descend of respiratory rate and panting score could be associated with soil temperature.

Keywords: Air temperature, Cattle, Respiratory rate