For many parts of the country cooler weather is just around the corner, which means many horse owners will be throwing extra hay, picking ice out of hooves, and pondering the age-old question: to clip or not to clip? But a team of Scandinavian researchers might help some owners with the final task, as they recently confirmed that clipped horses appear to achieve swifter post-exercise recovery than unclipped horses when working in cold temperatures.
Kristina Dahlborn, a study author and professor of integrative physiology in the Swedish University of Agriculture Science's Department of Anatomy and Physiology, explained that when horses exercise, only 20% of the energy metabolized in muscle cells goes toward physical activity, while the remaining 80% becomes heat.
Long hair coats, such as those grown in winter, are thought to act the same way blankets do, trapping heat close to the body to keep the core temperature high. Many owners of equine athletes clip these winter coats to allow for easier heat dissipation when the animals work in cold temperatures.
Dahlborn and colleagues recently completed a study evaluating how clipping and blanket use affect horses' thermoregulation (the ability to maintain body temperature) during exercise and recovery in cold climates.
The researchers monitored the heart rate, temperature, skin wetness, and respiratory rates of a 24-year-old Gotland pony gelding, a 14-year-old New Forest pony mare, and an 11-year-old Warmblood gelding as they exercised for 50 minutes. The researchers evaluated the horses on five different days when they were each unclipped; unclipped with a blanket during recovery; half clipped; clipped and exercised with a riding blanket; and clipped with a blanket during recovery.
The team found that unclipped horses tended to overheat, as judged by rectal temperature, while clipped horses' temperatures did not change as much with exercise as their unclipped counterparts. Maximum respiratory rate was also higher in unclipped horses.
Dahlborn also noted that the clipped horses were the only test subjects not sweating after exercise. She said it wasn't clear if this was due to a reduced need for sweat in the clipped horses due to the lack of hair coat insulation or if the sweat had evaporated more quickly. And finally, the team noted that the use of "blankets augmented heat dissipation in unclipped horses and dampened the responses in clipped horses."
Though the number of tested horses was relatively small in this study, the authors believe the results--that both blankets and long hair coats hinder the dissipation of excess heat--are likely true for most working horses.
"Clipped horses performing intensive exercise will have a better heat dissipation and will not be wet after," Dahlborn concluded. "The use of blanket limits heat dissipation both during and after exercise."
Conversely, she cautioned that a clipped horse has a more difficult time staying warm in cold climates, so blankets might be needed when the horse is not working, both in the stable and outdoors.
The study, "Temperature regulation in horses during exercise and recovery in a cool environment," appeared in July in Acta Veterinaria Scandinavica. The complete study can be accessed online.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.