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 2 of the latest question and answer installment that you can share with your footcare clients.
Q: I have several horses on bute for pain control. Are there any side effects I need to be aware of in regard to other health issues?
By Juliet M. Getty, PhD
Bute (phenylbutazone) is the most commonly used NSAID (non-steroidal anti-inflammatory drug) for pain resulting from injury to the joints and feet. But while you’re relieving your horse’s pain, you may be putting it at risk of developing an ulcer.
Bute functions by blocking the cyclo-oxygenase (COX) enzymes responsible for converting arachidonic acid (a fatty acid) to prostaglandins, some of which contribute to pain and inflammation.
There are two types of COX enzymes, COX-1 and COX-2, which differ in their impact on your horse’s digestive system. COX-2 is the one we want to inhibit because it is involved in producing the problematic prostaglandins. COX-1, however, is a beneficial enzyme that maintains a healthy gastrointestinal lining and also promotes proper blood clotting.
Unfortunately, bute blocks both of these enzymes. This alleviates the horse’s discomfort (because it blocks COX-2), by making the mucosal lining of the stomach more vulnerable to stomach acid (by blocking beneficial COX-1), potentially leading to ulcerations anywhere along the digestive tract.
Bute disrupts the natural surface barrier within the stomach’s mucosal lining. Within this lining is a fatty bilayer made up of two rows of molecules called phospholipids. The outer portion is hydrophilic (attracted to water) while the inner portion is hydrophobic because of its fat content. Because bute inhibits COX-1, it causes the inner hydrophobic barrier to become hydrophilic, allowing acid to permeate the mucosal lining, resulting in ulcerations.
To protect against ulcers, many veterinarians prescribe omeprazole, which goes by the brand names of full-strength GastroGard used to treat ulcers or the lower-dosed UlcerGard to prevent ulcers while the horse is receiving bute.
Omeprazole is a proton-pump inhibitor, which blocks the final step of acid production within the stomach. Since the protective mucus lining of the stomach may be compromised by bute, it becomes vulnerable to acid. Omeprazole reduces the acid content of the stomach, thereby preventing the formation of ulcers.
However, sudden discontinuation of omeprazole can cause a rebound acid effect, at increased levels, making your horse more vulnerable to ulcer formation. Omeprazole can also lead to malnutrition because stomach acid is necessary to start protein digestion and absorption of key minerals. In addition, omeprazole doesn’t protect against ulcers that may show up in the colon.
Juliet M. Getty, PhD is an independent equine nutritionist with a wide U.S. and international following. Located in Lewisville, Texas, her research-based approach optimizes equine health by aligning physiology and instincts with correct feeding and nutrition practices. Dr. Getty’s goal is to empower the horse person with the confidence and knowledge to provide the best nutrition for his or her horse’s needs.
Click here to read Part 1 of the October 1, 2017 installment: Can the quality of a hoof tell me anything about the general health of my horses?