RESPONSES OF LACTATING HOLSTEIN COWS TO CHILLED DRINKING-WATER IN HIGH AMBIENT-TEMPERATURES

In Experiment 1, 12 lactating Holstein cows were provided drinking water of either 10.6 or 27.0°C for 24 h/d in a changeover design to examine the effects of water temperature on feed intake, water intake, respiration rate, rectal temperature, plasma thyroid hormone concentration, and milk yield. The 1st wk of each 3-wk treatment period was for adjustment and the next 2 wk were comparison periods. Least squares means for DM intake as a percentage of body weight were 3.68 and 3.57 for 10.6 and 27.0°C treatment groups. Water intakes in liters per kilogram of dry feed consumed as a percentage of body weight were 21.3 and 20.3. Respiration rates were 70.5 and 81.0 breaths per minute; rectal temperatures were 39.7 and 39.9°C, Triiodothyronine averaged .88 and .75 ng/ml; thyroxine. 42.4 and 39.2 ng/ml; cortisol, 3.03 and 2.06 ng/ml; and progesterone in milk, 4.58 and 3.15 ng/ml for the 10.6 and 27.0°C treatment groups. Milk yield averaged 25.9 and 24.7 kg/d and FCM averaged 25.6 and 23.6 kg/d, respectively. In Experiment 2, 24 cows given a choice of chilled or warm water showed a clear preference (about 98%) for the warm water. If cows are given chilled water of 10°C continuously, no warm drinking water should be available. Chilled drinking water lowered respiration rates and body temperatures and increased feed intake and milk yield. © 1990, American Dairy Science Association. All rights reserved.