Intake and physiological response of Jersey cows to cooling measures in a hot humid environment
In order to evaluate the response of Jersey cows to cooling measures in a hot environment, four cows were subjected to four cooling treatments using a Latin square design. Treatments consists of control (access to shade without extra cooling), cooling with fan, cooling with shower, cooling with fan and shower. Animals were grazed daily from 9.00 to 13.00 h (32-34°C) and later cooled under shade. Rectal temperature (RT) and respiratory rate (RR) of test animals were measured in the morning (8.00h), afternoon (13.00h) and 1h after application of treatments using a clinical thermometer and counting the flank movement for one minute of regular breathing using a stop watch respectively. Blood profile (packed cell volume, PCV; red blood cell, RBC; and white blood cell, WBC) of animals was monitored at switch-over periods while dry matter intake (DMI) of cows was determined as the difference between feed offered and feed refused. There were no significant differences (P > 0.05) in RT and RR of animals either in the morning or afternoon. However, 1hour after the application of the treatments, these parameters reduced significantly (P < 0.05). The RT was 39.5, 38.9, 38.5 and 38.1 ºC while RR was 40.2, 38.5, 36.3 and 33.8 breaths/min for control, fan, shower and fan + shower respectively. Blood profile of animals were similar prior to experimentation but varied significantly (P < 0.05) during experimentation. The PCV, RBC and WBC varied from 30.2 – 36.6%; 14.9 – 19.4 x 106/ìL; and 15.1 - 23.1 x 103/ìL respectively while DMI of animals varied from 1.94 – 3.38% of body weight (BW). Performance of animals improved in the following order, fan + shower > shower > fan >control. These results indicate that application of cooling treatments on Jersey cows reduced heat load, enhanced intake and health status of cows under hot and humid conditions.
Key words: evaporative cooling; heat stress; cows; tropical region; thermo-regulation