The onset of summer’s heat means more attention should be given to cow comfort. Dairy cattle are generally predisposed to heat stress due to their metabolism, size, and skin thickness. At temperatures above 77° F, cows use energy to cool themselves through heat loss via surface skin and the respiratory tract.
As ambient temperature increases, it becomes more difficult for a cow to cool herself. Signs of heat stress in lactating cows are obvious — lethargic behavior, rapid shallow breathing, reduced dry matter intake (DMI), and milk production. When temperatures exceed 90° F, feed intake drops 8-12% and milk production drops 20-30%. This translates to 10-25 lbs. per cow per day. Dry cows whose last three months of gestation occur during hot weather have lighter birthweight calves, experience more metabolic problems after calving, and produce 12% less milk during their subsequent lactation. Conception rate decreases due to less activity during estrus, reduced follicular activity, and early embryonic death.
While there are numerous strategies to provide more cow comfort and optimize production, one factor must be present for dairy cattle to succeed: a clean, high-quality source of water.
Research conducted some 30 years ago suggests that the water requirement of a high-producing dairy cow is greater than that of any other land-based mammal because milk contains around 87% water. Cows should increase water intake by as much as 50% during heat stress periods to dissipate heat through the lungs (respiration) as well as by sweating. If the water supply is not adequate or heat stress becomes severe, the cow will divert water normally used for milk production to dissipate heat. Research shows that cows can consume 7 lbs. pounds of water per 1 lb. of DMI during hot weather, with high-producing cows capable of consuming 50 gallons of water per day.
To aid cows during the summer, consider the following:
• Put waterers under shade.
• Ensure enough water space by 1) providing at least two locations per group, and at least one watering station per 20 cows; 2) having a water supply of at least 3-5 gallons per minute; 3) maintaining a minimum of 3 inches of water depth; and 4) providing a minimum of 0.65 square feet of surface area per cow at single- or double-position waterers.
• Keep waterers clean. Consider emptying tanks each week and disinfecting the surface with a chlorine solution to minimize algae growth.
• Monitor water temperature. Cows prefer between 70 to 86° F.
• Make sure water is consumed several times per day. Cows can consume 30-50% of their daily water intake within one hour after milking.
• If water intake is low, have the water tested. Many commercial labs are available to test water quality. Unwanted compounds include sulfur, iron, nitrate, high total dissolved solids, or toxic compounds such as heavy metals or pesticides. Your local Co-op or ProTrition representative can help interpret water analysis results to help find the best remedy.
Remember, water is indispensable for life and is the most important essential dietary nutrient for dairy cattle.