Quick Steps to Help Manage Heat Stress in your Dairy Cows


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Cows do best when the air temperature is between 5.0 C and 21.0 C. When it gets hotter than that, cows’ efforts to maintain normal body temperature become costly. Learn how to kelp keep your dairy cows cool and productive.

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Quick Steps to Help Manage Heat Stress in your Dairy Cows

  1. 1. Heat Stress in Dairy Cows
  2. 2. Heat Stress in Dairy CowsCows do best when the air temperature is between5.0 C and 21.0 C.When it gets hotter than that, cows’ efforts tomaintain normal body temperature become costly.
  3. 3. Table 1. Relative changes in expected dry matter (DMI) and milkyield and water intake with increasing environmentaltemperature.Expected intakes and milk yieldsTemperature DMI Milk yield Water intake(°C) (kg) (kg) (litres)20 18.2 27 68.125 17.7 25 73.830 16.9 23 79.135 16.7 18 12040 10.2 12 106Sources: National Research Council. 1981. Effect of Environmenton Nutrient Requirements of Domestic Animals. NationalAcademy Press, Washington, D.C. Dr. Joe West, Extension DairySpecialist, University of Georgia.
  4. 4. Figure 1. To each temperature/humidity index corresponds a level ofthermal stress (Modified from F. Wierama. University of Arizona. 1990).How to evaluate heat stress?Body temperature (rectal) > 39.4ºCRespiratory frequency >100/mnDM intake decreases: -10% = highstress - 25% = severe stress
  5. 5. Figure 2: Heat stress, with its physiological and behavioralconsequences, increases the risks of rumenacidosis.(LallemandAnimal Nutrition)
  6. 6. Heat Stress in Dairy Cows Reduced feed intake 10% to 25% lower milk production Decreased milk fat percentage Decreased fertility Depressed immune system and potential death Higher maintenance requirements Over all less efficient milk production.
  7. 7. Heat Stress in Dairy CowsNot only do cows tend to eat less during heatstress, but their bodies partition the nutrientsdifferently.Much of it has to do with the way the cow utilizesglucose, a precursor for milk production.
  8. 8. Heat Stress in Dairy CowsGlucosethat would normally be used for milkproduction often gets diverted for other usesduring times of heat stress.Burning glucose generates less metabolic heatthan burning fat, so a heat-stressed cow prefers toutilize more glucose in her muscle and organs.
  9. 9. Heat Stress in Dairy CowsThe heat-stressed cow goes into survival mode; byswitching over to glucose, it produces less heatand, the animal can survive the bout of heatstress.But this comes with a price.With less glucose reaching the mammary gland,the body is deprived of an important building blockfor milk production.What can we do?
  10. 10. Heat Stress in Dairy Cows Provide shade and water for pastured animals. Improve ventilation. Use tunnel ventilation in stall barns. Use mixing fans and misters over feeding areas.Use sprinkling systems holding pens andexit lanes Don’t overcrowd the milking herd.
  11. 11. Heat Stress in Dairy Cows
  12. 12. Heat Stress in Dairy Cows
  13. 13. Heat Stress in Dairy Cows
  14. 14. Nutritional Strategies1. Water– the most important nutrient.Once the environment is as comfortable aspossible, nutritional changes can be made to helpimprove hot-weather productivity.During periods of heat stress cows’ waterrequirements increase 1.2 to 2.0 times.Provide cows with an unlimited quantity of fresh,clean water (21 C to 27 C)in an area close to thefeeding area to encourage eating and drinking.
  15. 15. Nutritional Strategies2. Protein – quantity and formLook at both quantity and form of protein whenfeeding heat-stressed cows.Too much or not enough crude protein increasesbody heat production.Ensure that bypass and degradable protein areboth balanced.
  16. 16. Nutritional Strategies3. Forages - high qualityFeed highly palatable, highly digestible forages.Dry matter intake (DMI) can be maintained andcows will gain more energy from the forage portionof the diet.In the summer, people are tempted to feed moregrain to keep energy levels up. But the heat-stressed cow is already prone to acidosis, sofeeding more grain can be a problem.
  17. 17. Nutritional Strategies3. Forages - high qualityIf a larger portion of the energy can be supplied bythe forage, relative to concentrates, you can avoidsome of the conditions that lead to acidosis.The more digestible the forage is, the less time itwill stay in the rumen. Digestion of fiber createsmore heat in relation to concentrates, however, ifthe fiber passes through the system quickly, itproduces less heat of fermentation.
  18. 18. Nutritional Strategies4. Fat – a dense form of energyAlthough a dense ration, high in energy isrecommended during times of heat stress, it isimportant not to feed more than 6% fat in the totaldry matter and avoid high fat levels (greater than4%) in fresh cows.Always introduce fat slowly into a TMR!!
  19. 19. Nutritional Strategies5. Minerals – think potassium (K)Cows sweat, and they lose potassium rather thansodium through sweating.Both sodium and potassium are important in heat-stressed cows, make sure they are wellsupplemented in the ration and provide free choicesalt in free stalls or managers.I balance K @ +1.6% in the DMI with potassiumcarbonate.
  20. 20. Nutritional Strategies6.Sodium bicarbonateI feed 200-220 gm/h/day of sodium bicarbonate toall of my herds to avoid acidosis and aid with heatstress.My producers also offer free choice bicarb in thefree stall.
  21. 21. Nutritional Strategies7. Other feed additivesUse an ionophore such as monensin increasesproduction of propionate. Propionate is laterre-converted to glucose and makes its way tothe mammary gland for milk production.All of my herd use CRC boluses 3 weeksprepartum followed by 200 mg/h/day ofmonensin in the milking premix.
  22. 22. Nutritional Strategies7. Other feed additivesYeast cultures may have some benefit in times ofextreme heat.Their action is related to rumen buffering andreduced acidosis as well as improved fibredigestion.
  23. 23. Feeding Management Strategies Increase the number of feedings. Feed will befresher and consumption will be encouraged. Ifyou are feeding once a day, increase it to 2 ormore. Push up feed 5 to 6 times per day. Time feeding right.During the hot weather, cowseat mostly at night and after milking. Have freshfeed in the managers after milking and makesure that fresh feed is fed out at night.
  24. 24. Feeding Management StrategiesAdd water. Water softens fibre feeds and reducesdustiness and dryness of the ration, increasingpalatability and DMI. Total ration DM should be~50%.Keep bunks clean. Remove refused feed everyday. Check and clean any moldy &/or heated feedfrom corners and edges of feeding areas at leastthree times/week, more often if feeding animalproteins or fats. A decaying feed smell may reduceDMI even if fresh feed is put on top.
  25. 25. Feeding Management StrategiesAvoid drastic ration changes.Avoid small particle size in TMR’s or TMR’s thatallow sorting.Add liquid molasses or brewers grains toencourage consumption.
  26. 26. Heat Stressless!