Hoof Nutrition Intelligence is a twice-a-month web segment that is designed to add to the education of footcare professionals when it comes to effectively feeding the hoof. The goal of this web-exclusive feature is to zero in on specific areas of hoof nutrition and avoid broad-based articles that simply look at the overall equine feeding situation.
This edition is sponsored by the W.F. Young Co. (Absorbine) of East Longmeadow, Mass.
Below you will find Part 1 of the latest question and answer installment that you can share with your footcare clients.
Q: Can you explain how cold-induced laminitis might have an impact on my horses?
By Eleanor Kellon, VMD
It happens every winter when a horse that may not have a prior history of laminitis is found to be very lame and reluctant to move. It's more than the typical hesitation that horses often show on hard, frozen ground. It looks like laminitis but the feet aren't hot. So what's going on?
Cold-induced hoof pain strikes horses with insulin resistance (IR). It is a well-described risk factor for laminitis, but even when a horse is not glaringly lame it is still causing damage to the laminae. We haven't uncovered all the mechanisms behind laminar damage from high insulin levels, but one known factor is the elevated levels of endothelin-1.
Endothelin-1 is a peptide (small protein) produced by the cells lining the interior of blood vessels. It is the most potent vasoconstrictor known and is normally balanced by production of the vasodilating chemical nitric oxide. Cold-induced reduction in the blood supply flowing to the hoof when superimposed on the pre-existing high endotheli-1 activity may explain why some IR horses develop hoof pain in cold weather while normal horses do not.
Cold stress may also cause insulin levels to rise, as IR is part of the metabolic adaptation to cold weather for several species of animals. Researchers have also noted insulin levels often become erratic in horses with cooler weather.
Laminitis caused by high insulin is different from laminitis due to other causes. Activation of enzymes and inflammatory reactions are not part of the picture. This probably explains why the usual treatment with NSAIDs [nonsteroidal anti-inflammatory drugs] like phenylbutazone has little effect. There is help though.
Blanketing the horse when temperatures dip below the equine thermoneutral temperature of 45 F helps avoid cold stress. Keeping the lower legs wrapped and feet protected inside lined boots helps maintain normal circulation to the extremities.
Adaptogens are herbs that support a healthy response to stressors like cold weather. Jiaogulan [Gynostemma pentaphyllum] is a particularly good choice because this herb is also known to support production of the vasodilator, nitric oxide. Jiaogulan should be given twice daily, preferably before a meal. Most horses love the taste and will lick it up as a powder or paste.
L-arginine is the amino acid precursor for nitric oxide and can be supplemented along with the Jiaogulan. L-citrulline is another amino acid that the body can convert to L-arginine for nitric oxide production. Cold stress also results in considerable oxidative stress and antioxidants can help neutralize these free radicals.
Finally, acetyl-l-carnitine supplementation can be indicated for support of normal nerve function and glucose handling.
When you understand the trigger of winter laminitis you can support these horses with simple measures to minimize cold stress and maintain normal blood flow to the feet.
Dr. Eleanor Kellon, a staff veterinary specialist for Uckele Health & Nutrition, is an established authority in the field of equine nutrition for over 30 years. The owner of Equine Nutritional Solutions in Robesonia, Pa., she is 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.
Click here to read Part 1 of the January 1, 2017 installment: How important is the quality of feed with horses compared to other species of livestock?