Heat Stress in Cattle
August 2, 2024
Managing Heat Stress in Dairy Cows
As summer temperatures rise, so does the risk of heat stress in your herd. High-producing dairy cattle are particularly vulnerable, and even short periods of heat stress can negatively impact milk yield, fertility, and overall health.
Why It Happens
The critical temperature for cows is around 29°C, but the risk increases significantly when humidity is high.
Cows generate constant internal heat from their rumen, compounding the problem.
Recognising the Signs of Heat Stress
– Panting and increased respiratory rate
– Lethargy or reduced movement
– Reduced feed intake
– Reduced rumination
– Increased time standing
– Drop in milk yield
– Drop in conception rates
– Increased somatic cell count (SCC)
– Elevated rectal temperature
Reducing the Risks
Shade and Ventilation
– Provide plenty of shade, either from buildings, trees, or shelters.
– Use fans to increase airflow indoors.
– Where possible, open building sides for natural ventilation.
– Turn out to windier fields (if possible).
– Water Access. Water intake can double during extreme heat, so ensure:
~ Clean, plentiful water is always available.
~ Check trough flow rates to meet demand.
~ Check ponds and water sources regularly—beware of blue-green algae in stagnant water.
– Handling and Movement: Avoid handling tasks like TB testing, foot trimming, and moving cattle during the hottest parts of the day.
– Where possible, shift milking times earlier or later to cooler periods.
– Minimise walking distance between parlour and fields.
– Reduce time spent in holding pens.
– Cooling Systems: Use sprinkler systems combined with fans, especially in collecting yards. Water on the skin combined with airflow enhances evaporation and cooling.
– Clipping hair off backs can also help reduce heat load.
Nutrition Adjustments
Work with your nutritionist to:
– Increase the energy density of the ration to compensate for lower feed intakes.
– Ensure a well-mixed ration to minimise sorting.
– Push up feed regularly to promote intake.
– Make sure feed is always available.
Fly Control
Ensure good fly prevention, as fly irritation causes cows to bunch together, further increasing heat stress.
Other Important Considerations
– Mastitis risk increases during heat stress—monitor SCC closely.
– Parasitic Gastroenteritis (PGE) risk increases when dry weather traps worm larvae in faeces, which are then released after rainfall—plan for worm control.
– Blue Green Algae: Pay attention to fields with ponds or fields where the water troughs haven’t been used for a while. Make sure all troughs are regularly checked and that you can see to the bottom
Please give us a call on 01373 451115 if you have any concerns, or have any additional questions regarding heat stress.