The Milk Producer - August 2011 - (Page 38)

RUMINATIONS By Mario S. Mongeon Bovine bathing Cows exhibit individual preferences when making choices about how to cool off during summer heat D airy cows like it cool, and farmers have responded by installing sprinkler and misting systems to dampen hot weather’s effects on their herds. Given the opportunity, however, cows apparently prefer to choose for themselves when and how they get wet. A Holstein cow’s comfort zone can vary between five and 20 degrees Celsius. As the temperature gets above 25 degrees, especially if the relative humidity is high, signs of heat stress may start to show up—lower dry matter intake and reduced milk production. Prolonged heat stress can affect breeding efficiency, as well. Keep this in mind if you keep more cows in the barn during warmer months. Overcrowding raises the barn’s heat load and may prove a drag on production. You have several ways to reduce the effects of warmer temperatures. Providing plenty of drinking water and making it easily available for cows is an excellent first step. Access to shade, good ventilation and air movement are other simple means to reduce heat’s impact. You can also use water to cool your herd. Sprinkler or misting systems are fairly common in large New Zealand and U.S. herds. Most sprinkler systems are hooked up with fans. Evaporation induced by the fans enhances the water’s cooling effect. Dairy farmers usually install these systems where the herd congregates, such as waiting areas before milking or above the cows at the feed bunk. Studies indicate wetting a cow’s back effectively reduces its respiration rate, or panting, and body tem- peratures—both indicators of heat stress. Other studies have shown cooling cows with water results in increased feed intake and milk production when compared to control groups. Aversion to sprinklers Despite the effectiveness of cooling with sprinkler systems, some cows show behaviour indicating an aversion to it. For example, animals will position their heads outside the sprinkler to avoid getting their faces wet. Others will lower their heads in response to overhead water or avoid Mean time spent in the shower stall according to time of day and variation observed between animals. 30 27 Time in the shower (minutes per hour) 24 21 18 15 12 9 6 3 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Time of day Ruminations is prepared by Ontario Ministry of Agriculture, Food and Rural Affairs livestock technology specialists to provide information you can use on your farm. The vertical black bar represents the variation observed between animals for a specific time of day. (Adapted from A. Legrand , K. E. Schütz , and C. B. Tucker) 38 | August 2011 | MilkPRODUCER

Table of Contents for the Digital Edition of The Milk Producer - August 2011

The Milk Producer - August 2011
Contents
Editor's Notes
DFO Chair's Message
Dairy Update
Industry Roundup
DFC Promotion
Applied Science
Ruminations
Rearing Replacements
Calf Health
Markets
New 'N' Noted
Back Forty

The Milk Producer - August 2011