Responses of Crossbred Lactating Cows to Heat Stress and its Alleviation under a Tropical Environment
Joaquín Castro-Montoya1, Elmer Edgardo Corea2
1University of Hohenheim, Animal Nutrition and Rangeland Management in the Tropics and Subtropics, Germany
Rising temperatures in the world are an increasing concern for the welfare and production of livestock. Dairy cows are particularly sensitive to heat stress (HS) due to their metabolic heat production from milk synthesis. Heat stress decreases milk yield (MY) beyond decreases in dry matter intake (DMI), by impairing the carbohydrate and protein metabolism. In high yielding cows, multiparous are more susceptible to HS than primiparous, due to their greater MY (~10 kg) and body weight (BW) (~100 kg) compared with primiparous. However, in the tropics, smaller size, lower production, and long-term exposure to HS may influence the cows' response to HS and its alleviation. To prove this hypothesis, 12 cows, six primiparous and six multiparous (3/4 Holstein, ¼ Brahman, 520±35 kg BW, 16.6±1.2 kg d-1 MY) were exposed to four 15-days-long periods, two controls (no cooling), alternated with two cooling periods (fans and sprinklers in 1-hour cycles at 10:00, 12:00, 14:00 and 16:00 h). Cows were monitored for rectal temperature (RT) and respiration rate (RR) at 09:00, 11:00, 13:00, 15:00 and 17:00 h, and for MY.
Keywords: Dairy cattle, heat stress, multiparous, primiparous
Contact Address: Joaquín Castro-Montoya, University of Hohenheim, Animal Nutrition and Rangeland Management in the Tropics and Subtropics, Fruwirthstrasse 31, 70599 Stuttgart, Germany, e-mail: jcmuni-hohenheim.de