Veterinarians working with many laminitic horses are well acquainted with winter foot pain in horses, but others may be unfamiliar with it. It's a laminitis-like syndrome triggered by cold weather.
Horses with cold-induced hoof pain show obvious lameness and often typical laminitis stance, but without bounding pulses or heat in their feet.
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Horses normally have a very high tolerance for cold. In all species, cold causes a reflex shunting of blood away from the extremities and toward the core to limit loss of body heat.
Healthy horses prevent the hoof from being damaged by low blood/oxygen supply with the use of local arteriovenous shunts - pathways which allow them to divert blood quickly back to the veins for return rather than sending it to the local tissues.
When low blood supply reaches a critical level, the arteriovenous shunts to that part of the hoof can close, and tissue damage can occur when blood supply returns to tissue.
The only adverse effect of cold weather and reduced blood flow to the hoof in healthy horses is slower hoof wall growth. In horses with metabolic issues that result in high insulin levels, it may be a different story.
We don't know all details of the mechanism, but it is clear from research that high insulin can cause laminitis. We also know that even if they have never had a full-blown laminitis episode, there are similar abnormalities in the structure of their laminae. One thing we do know about it is that levels of endothelin-1 are greatly elevated.
This is a chemical in the body which causes blood vessels to contract down. It has also been shown that the vessels in the hoof become more sensitive to other messengers that cause contraction. These changes may interact with cold-induced blood vessel constriction to cause a critical interruption of blood supply to the hooves of those horses.
Horses with cold-induced hoof pain show obvious lameness and often typical laminitis stance, but without bounding pulses or heat in their feet. In milder cases it may be mistaken for the sensitivity to moving over frozen uneven ground that all horses show. However, it doesn't go away on level surfaces. There is variability in individual sensitivity to cold, but signs may appear beginning at 40F [4.4C].
Even horses that usually have their insulin well controlled by a low carbohydrate balanced diet can be susceptible. This may be because cold weather has also often been observed to cause wide swings in insulin levels and/or because of previous damage to the circulation in the feet.
The first step in helping these horses is protecting their extremities from the cold. Leg wraps such as lined shipping boots work well and are safe to leave on because they won't slip out of place and cause uneven pressure on the tendons [aka "bandage bows"]. Boots with pads and socks or fleece lining are essential.
The horse, pony or donkey can be supported nutritionally by supplements that encourage the production of nitric oxide. Nitric oxide is a vessel dilating messenger that is the natural counterbalance to endothelin-1.
The herb Gynostemma pentaphyllum (Jiaogulan) is a powerful support for nitric oxide. This is helped by providing the precursors for nitric oxide in the form of L-arginine and L-citrulline. Antioxidants also combat oxidative stress that inhibits the activity of the enzyme that produces nitric oxide inside blood vessels [eNOS - endothelial nitric oxide synthesis].
Winter laminitis has historically been regarded as very difficult to manage, but understanding the vascular issues has led to significant strides in helping these horses balance the forces affecting the blood supply to their feet.
Uckele Health & Nutrition, maker of CocoSoya®, offers supplements to support healthy circulation to the foot.
LaminOx provides full spectrum support for hoof health and comfort, healthy circulation and metabolic balance. Supports healthy vascular function with Jiaogulan to promote circulation and structural hoof health. Contains the amino acid Arginine, a precursor to nitric oxide, which also plays an important role in healthy blood flow.
Jiaogulan supports circulation in the feet, which nourishes the tissue with potent antioxidant potential via increased levels of the enzyme Superoxide Dismutase (SOD). It also helps maintain clear airways and supports healthy immune responses, muscular function, circulation, and respiratory function.
About Dr. Kellon
Dr. Eleanor Kellon, staff veterinary specialist for Uckele Health & Nutrition, is an established authority in the field of equine nutrition for over 30 years, and a founding member and leader of the Equine Cushings and Insulin Resistance (ECIR) group, whose mission is to improve the welfare of horses with metabolic disorders via integration of research and real-life clinical experience. Prevention of laminitis is the ultimate goal. www.ecirhorse.org
Uckele Health & Nutrition, maker of CocoSoya, is an innovation-driven health company committed to making people and their animals healthier. On the leading edge of nutritional science and technology for over 50 years, Uckele formulates and manufactures a full spectrum of quality nutritional supplements incorporating the latest nutritional advances. www.uckele.com.
Note - Updated article was first posted on EquiMed in 2019
Press release provided by Susan Libby - Uckele Health & Nutrition