Winter Laminitis

Veterinarians working with many laminitic horses are well acquainted with the problem but others may be unfamiliar with it.  It’s a laminitis-like syndrome triggered by cold weather.

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 tissue from being damaged from low blood/oxygen supply by using local arteriovenous shunts – pathways which allow them to divert blood quickly back to the veins for return or to send it to the local tissues. When low blood supply reaches a critical level, the arteriovenous shunts to that part of the hoof can close, perfusing the 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 the 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 have their insulin usually well controlled by a low carbohydrate balanced diet can be susceptible. This may be because cold weather has also been observed to often 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 equine can be supported nutritionally by supplements which 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 which 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 mechanism has led to significant strides in helping these horses balance the forces affecting the blood supply to their feet.

Eleanor Kellon, VMD

About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions, www.drkellon.com, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition.
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3 Responses to Winter Laminitis

  1. Cheryl Peters says:

    I have a 30 year old Arab mare who is Cushing and IRfor several years. She is not lame at this time but had a abscess for 2mos this fall sept oct. I was wondering if I should put her on a jaiogulun supplement for winter. Or a biotin supplement. She takes 1and 1/2tab of prascend and 1/4 previcox daily, has 5lb grain daily and 1lb of enrich plus grass hay. This fall i’ve had trouble keeping weight on her. She also has beet pulp at night 1lb. Vets wants me to keep uping her grain and i’m not sure about doing that.

    • Dr. Kellon says:

      Trouble maintaining weight in the fall usually means your pergolide/Prascend dose is not sufficient to control ACTH during the seasonal rise. In PPID horses that are also IR, this also damages the laminae even if you don’t see full blown laminitis and this is probably why you have abscessing then. Jiaogulan won’t help with Previcox and you shouldn’t need Previcox if you have her insulin and ACTH controlled plus a proper trim. Very few “grains” are safe for an IR horse. For more detailed information, see http://www.ecirhorse.org.

      • Cheryl Peters says:

        Dr. Kellon, thank you for answering my questions yesterday about my 30 year old Arab mare. I’m wondering if I should give her any supplement such as Bolton or Jaiugolan, if I take her off previcox. Vets wanted her on previcox for arthritis. Her ACTH in June was 43.4 and insulin was 28.27 testing done at Cornell. They didn’t want her prascend upped 1 1/2 tabs daily (vet). Her grain TC senior 5lb daily, enrich plus 1lb daily, 1lb beet pulp daily. 5 flakes hay daily, her weight is 900-950lb. She had abscesses this fall for almost 2 months. I can’t seem to get her to gain weight. She is on grass four hours a day with muzzle in summer but off now for the winter. She had been Cushing and IR for probably10 years. Her hair looks awful but I clip her in the summer but very thin as of now.

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