Help Alleviate Heat Stress in Dairy Cattle

Jun 19, 2023


Written by: Todd Steen, ProTrition Nutritionist
 
With the onset of summer and increasing temperatures, much attention should be given to cows to aid in their comfort. Dairy cattle are generally predisposed to heat stress due to their basal metabolism, size, and skin thickness. At temperatures above 77° F, cows must 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 reduced milk production.   High-producing cows are most sensitive to heat stress due to their need for high DMI. Feed intake drops (approximately 8-12%) and milk production losses of 20-30%, which may exceed 10-25 lbs. per day, occur when temperatures exceed 90° F. Additionally, dry cows who’s last 3 months of gestation occur during hot weather have lighter birth weight calves and experience more metabolic problems after calving. Also, they produce 12% less milk during their subsequent lactation. The conception rate decreases due to less activity during estrus, reduced follicular activity, and early embryonic death. While there are numerous successful strategies to provide more comfort for cows, this article will focus on one, single factor – water.
 
Water is probably the most important nutrient for dairy cattle. Dairy cattle need free access to a clean, quality source of water for optimal production. Research in 1985 suggested that the water requirement per unit of body mass 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 during heat stress periods to dissipate heat through the lungs (respiration) as well as by sweating. Water consumption will increase by as much as 50%. 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. Water intake increases by 5-6 gallons on summer days due to temperature alone. Research has shown that cows consume approximately 3 lbs. of water per lb. DMI with temperatures between 0-41° F. At higher ambient temperatures, cows can consume 7 lbs. of water per lb. DMI with high-producing cows capable of consuming 50 gallons of water per day.
 
To aid cows during periods of high temperature, consider the following:
  • Put waterers under the shade
  • Ensure enough water space by:
    1. Provide at least 2 water locations per group (at least 1 watering station per 20 cows)
    2. Have a water supply of at least 3-5 gal/minute (cows can consume 6 gallons per hour)
    3. Maintain a minimum of 3 in. water depth
    4. Provide 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 disinfect the surface with a chlorine solution to minimize algae growth
  • Monitor the temperature of water - cows prefer water at 70-86° F
  • Water is consumed several times per day:
    1. Water consumption is generally associated with feeding or milking
    2. Cows can consume 30-50% of daily water intake within 1 hour after milking
  • If water intake is low:
    1. Have water tested
    2. Unwanted compounds include sulfur, sulfate, iron, nitrate, high total dissolved solids, or toxic compounds (e.g. heavy metals, pesticides)
If water intake appears to be low, many commercial labs are available to test water quality. Generally, water-constituents or unwanted compounds that may affect water intake and animal performance include total dissolved solids, sulfur, sulfate, iron, manganese, nitrate, toxic compounds (e.g., heavy metals, pesticides), and microorganisms.
 
Remember, water is indispensable for life and is the most important dietary essential nutrient for dairy cattle. Your local Co-op is ready to help interpret your water analysis results to help find the best remedy. Find the Co-op nearest you, here.
 
For more content like this, check out the latest issue of The Cooperator.

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