Garway Veterinary Services

In the previous article (Understanding Heat Stress in Dairy Cattle: The Impacts) we covered the importance of avoiding heat stress. This article explains how that can be done giving practical examples and advice.

Practical mitigation strategies can be combined to capitalise on multiple cooling mechanisms to enhance their overall effectiveness.

Water Provision:

Ensure constant adequate access to clean, cool drinking water to prevent dehydration and facilitate evaporative cooling.

Install water troughs strategically throughout grazing areas and barns to encourage regular hydration. Cows returning from milking often look to drink immediately. Ensuring enough water troughs are available in the transfer lanes and the entrance to the barns facilitates this.

Nutritional Management:

Adjust feed rations to optimize energy and nutrient intake during periods of elevated temperatures including feeding 70% of the ration during the low THI hours, usually at night.

Supplement diets with electrolytes and antioxidants to support immune function and alleviate physiological strain.

Provide high-quality forage and balanced mineral supplements to mitigate nutrient deficiencies exacerbated by heat stress and ensure minimal heat production during digestion.

Behavioral Monitoring and Intervention:

Regularly monitor temperature, humidity and THI levels to identify heat stress risk factors.

Implement behavioral observation protocols to detect signs of heat stress, including increased respiration rate, reduced feed intake, and altered resting behavior. Many cow wearable systems have alerts built in for increased breathing rates.

Intervene promptly with cooling measures and nutritional adjustments to alleviate heat stress and prevent adverse health outcomes.

Environmental Modifications

Shade Structures:

Providing shaded areas in pastures and barns allows cows to escape direct sunlight and reduce heat stress.

Shade structures can be natural, such as trees, or constructed, such as shade sails or roofed areas.

Evaporative Cooling:

Misting Systems: Misting systems spray fine water droplets over the cows, creating a cooling effect as the water evaporates from the cow’s skin. These systems are often installed in holding areas, milking parlors, and barns where cows spend significant amounts of time.

Soakers and Sprinklers: Soaker systems or sprinklers installed in feeding areas or grazing fields wet the cows’ skin, facilitating evaporative cooling. These systems are particularly useful in open-air environments where access to shade may be limited.

Conductive Cooling:

Contact with cooler surface: Heat wicking through lying on cooler surfaces such as cool sand or mattresses is common.

Active conductive cooling is a relatively new concept in dairy cattle. Mattresses with active cooling mechanisms including water transfer to increase conductive cooling are yet to be tested in the field.

Forced Convection:

Cooling Fans: High-pressure fans can be used in conjunction with misting systems to enhance evaporative cooling. The fans help circulate air and distribute the mist more effectively, promoting heat dissipation from the cow’s body.

Air Circulation: Fans or blowers are strategically positioned to generate airflow within the barn or housing facility where the cows are kept. These devices create a continuous stream of air that moves across the surface of the cows’ bodies aiding evaporative cooling.

Ventilation and Airflow: Proper ventilation in barns and housing facilities is essential for maintaining airflow and dissipating heat. Adequate ventilation helps prevent the buildup of humidity and stagnant air, creating a more comfortable environment for the cows. This can be as simple as appropriate inlet and outlet vent sizes or as complicated as active ventilation via tunnel- or cross-ventilated barns. It is all about air changes per hour. In order to just provide fresh air we aim for 4-8 changes/hour but in high THI environments this should be around 40-60/hour.

Examples of complex cooling mechanisms

Effective mitigation strategies encompass a multifaceted approach aimed at optimizing cow comfort.

Through-the roof coolers (also known as Korral Coolers) bring in hot air from outside and cools it by injecting high-pressure mist into it. These coolers ensure that chilled and misted air is injected into the middle of the barns allowing appropriate ventilation and cooling in all areas.

Tunnel ventilated barns involve inlet fans pulling air into the barns and outlet fans actively pulling it out. It is important that the barn is fully enclosed with no inlets along the side walls or roof space. These can be combined with misters or spray nozzles by the inlet fans to cool the entrance air.

This can be improved with fans down the barn continuing to push the cooler air, improving the air movement and forced ventilation. Misting nozzles can be installed with these fans to ensure air continues to be cooled alongside providing some evaporative cooling ability for the cows under tha fans.

Feed rail soakers are often used in conjunction with fans to provide evaporative cooling for the cows when standing to eat. The wetting of the cows combined with increased airflow ensures maximum evaporative cooling, leading to increased milk yields of 15%. The correct timings for wetting and drying cycles are not agreed on by experts but the principles remain the same. Technologies now exist to decrease water usage by altering wet/dry timings and amount of water used depending on environmental readings within the barns, to reduce water usage while still providing adequate cooling. They can also detect cow movement, ensuring only feed line soakers in range of a cow will expel water to ensure optimal coverage while reducing water usage.

It is important to remember that evaporative cooling relies heavily on the environmental humidity. High humidity levels reduce the ability of cows to cool through evaporation due to the reduced moisture gradient between skin and air. Consequently hot and humid conditions make cow cooling much more challenging and expensive.

Drylot barns and T-shades often have mounted fans in the eaves. These can be combined with misters if animals require it and removes the need for curtains. In high humidity areas drylot barns are generally not used for adult milking cattle as the bedding can become like a quagmire with a saturated environment.

Conclusion

Heat stress poses a significant challenge to dairy farmers, impacting the welfare and productivity of their herds. By understanding the dynamics of heat stress, recognizing its impacts on dairy cattle, and implementing proactive management strategies, farmers can mitigate its adverse effects and ensure the well-being of their herds. As temperatures continue to rise, proactive adaptation and innovation will be crucial in safeguarding the sustainability of the dairy industry.

Understanding Heat Stress in Dairy Cattle: The Mitigation Strategies

Water Provision:

Nutritional Management:

Behavioral Monitoring and Intervention:

Environmental Modifications

Shade Structures:

Evaporative Cooling:

Conductive Cooling:

Forced Convection:

Examples of complex cooling mechanisms

Conclusion

Further Reading

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Water Provision:

Nutritional Management:

Behavioral Monitoring and Intervention:

Environmental Modifications

Shade Structures:

Evaporative Cooling:

Conductive Cooling:

Forced Convection:

Examples of complex cooling mechanisms

Conclusion

Further Reading

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