Strategies To Support Cooling

During exercise, horses effectively produces ATP to fuel muscle contraction. However, 80% of this energy is released as metabolic heat, meaning a large amount of heat is produced each time the muscles contract. This heat is produced regardless of the external environmental temperature, but how the horse releases heat to cool depends on fitness, acclimatisation, external heat and humidity.

During maximal exercise the horse has little opportunity to dissipate heat as blood flow is directed to the muscles. As the horse slows, blood flow to the skin starts to increase, allowing heat to be transferred from the blood to the external environment. Fortunately, horses can effectively dissipate heat through a number of different mechanisms.

Horses rely on sweating as their main cooling mechanism, with roughly 70% of heat lost from exercise being through evaporation of sweat. Horses can produce up to 12L/hr sweat, representing about 4% total body water per hour. This is on average 33% more than the human. You may notice sweat dripping from a horse. Heat loss from sweat dripping is only 5-10% of that through evaporation from skin, making it far less effective. To reduce sweat dripping, horse sweat contains latherin, a surfactant which to bubbles up sweat and prevents it from dripping. Respiration also effective, with a high respiratory rate dissipating 25% of the metabolic heat produced during exercise (Mejdell et al).

Whilst horses can effectively dissipate heat, when exercising in a hot, or hot and humid environments, they may require additional support to cool effectively.

Numerous studies have been carried out comparing different cooling methods. Takahashi et al. compared walking alone, walking with a fan, intermittent cold water (10˚C) application every 3 minutes that was scrapedd off, intermittent cold water that was not scraped, and constant tap water (26˚C) for 30 minutes. This study demonstrated constant cooling with tap water to be the most effective cooling method. Intermittent water application was the next most effective, particularly when water was not scraped off. Kang et al., 2022 reported similar results, demonstrating that application of cold water without scraping was the most effective cooling method.

A recent study at Kentucky Equine Research compared the following cooling methods:

• Hosing for 5 minutes, followed by hand walking for 10 minutes
• Halking for 10 minutes followed by 5 minutes hosing
• 15 minutes hand walking only
• Control with no cooling strategies applied.

Hosing was shown to significantly improve gluteal muscle temperature recovery. Temperatures returned to baseline within 30 minutes when hosed, whereas temperatures still exceeded baseline at 90 minutes for horses that were only walked or controls. Another measure of recovery is respiratory rate, which significantly decreased following 5 minutes of hosing.

Suggestions to support cooling

• Continual hosing
• Misting fans
• High velocity fans if no water available

For advice on supporting your horses post exercise recovery, contact the Saracen Horse Feeds nutrition team at 01622718487.