INTRODUCTION
A variety of dietary supplements on the market for horses boast efficacy in treating and preventing various conditions affecting horses. Many of these products have not been tested in horses, and little scientific evidence exists regarding their efficacy or safety. A recent article discussing the use of supplements in horses competing in high-level three-day events showed that horses were receiving an average of 4.2 supplements daily.1 That said, several supplements have undergone scientific testing for efficacy and safety in horses with gastric ulcers and lameness (Table 1). It should be emphasized that supplements should not be used in place of pharmaceutical agents to treat disease.
CHOOSING A SUPPLEMENT
There are several ways to counsel your clients on choosing supplements for their horse. My recommendations regarding choosing supplements are: research, ingredients, dose, efficacy (R.I.D.E). This acronym was put together by Purina Animal Health and makes sense when discussing supplements with your clients. First, when choosing a supplement, you should look for research on that product in horses. Many supplements extrapolate efficacy and safety from studies conducted in other species and humans. The research studies should be published in peer-reviewed journal or synopses of articles. Searches can be done on Google Scholar to find articles that discuss research on a particular supplement of ingredient within a supplement.
Second, ingredients—and the purity of those ingredients—are very important. Are the ingredients safe to use in competition or racehorses? Are the ingredients approved for feed? In the U.S., the Association of American Feed Control Officials (AAFCO) approves ingredients in feeds. Are the ingredients endorsed by a governing body? In the U.S., the National Animal Supplement Council (NASC) endorses pure and safe ingredients for supplements.
Dose is also important in selecting a supplement. Providing the right dose in the supplement is crucial, as is ensuring the ingredient is absorbed into the blood and reaches the actual site of action. Is there published efficacy data on the correct dose? What is the right dose? Is the supplement palatable? Will the horse eat the supplement? Is there a more cost-effective solution, such as a pharmaceutical agent, that is more efficacious? For example, for lameness, would Adequan be more cost-effective than a lameness supplement containing chondroitin sulfate or glucosamine?
Efficacy is a concern with supplements. Was there a difference in the horse after administering the supplement? Most supplements found on the internet have great marketing information but little data on efficacy. We will discuss some of the supplements that we have examined and some in the literature that show efficacy. To see efficacy with supplements, long-term administration is required—sometimes weeks or even months—before improvement in clinical signs are seen. Also, as mentioned before, supplements should not be used to treat or prevent disease. A pharmaceutical agent should be used first to treat disease, and then a supplement can be added to maintain long-term health.
PROBIOTICS
Oral administration of lactulose resulted in increased Lactobacillus growth and colonization of the ulcer bed, which may facilitate ulcer healing. In a recent study in horses with spontaneously occurring gastric ulcers, an antibiotic (trimethoprim- sulfhadimidine) or a probiotic preparation containing Lactobacillus agilis, L. salivarius, L. equi, Streptococcus equinus, and S. bovis administered orally decreased ulcer number and severity compared with untreated controls.2 In addition, adhering microorganisms were isolated from the stomach of horses and identified Lactobacillus salivarius, L. crispatus, L. reuteri, and L. agilis by DNA-DNA hybridization and 16S rRNA gene sequencing techniques. These lactobacilli associated with the horse, except for L. reuteri, were found to adhere to horse epithelial cells in vitro. A symbiotic relationship of these lactobacilli with the horse is suggested.
In addition, probiotic preparations may facilitate ulcer healing after two weeks of treatment, but a full effect did not occur until after four weeks of treatment. Probiotic preparations containing Lactobacillus spp. (and Streptococcus) may help prevent gastric ulcers or serve as an adjunct to pharmacologic treatment.
However, the effects of probiotics on diseases and flora in the small intestine and hindgut have been more problematic.4 Several studies have shown ambiguous results. On the other hand, studies using Saccharomyces boulardii have shown promise in horses with acute enterocolitis. In that study, Saccharomyces boulardii was assessed in a randomized, blinded placebo-controlled clinical trial.5 Horses receiving S. boulardii had a shorter duration of diarrhea and watery diarrhea but not loose feces. Unfortunately, there was no difference in the outcome, and the study only evaluated seven horses. The types of bacteria, dose and length of administration of probiotics need further study before they can be recommended for hindgut issues. However, typically, the administration of probiotics is considered safe and is used by many practitioners and owners.
SEA BUCKTHORN BERRY EXTRACT
Interest is increasing in the use of herbs and berries that may have therapeutic applications in humans and animals. Berries and pulp from the sea buckthorn plant (Hippophae rhamnoides) are high in vitamins, trace minerals, amino acids, antioxidants, and other bioactive substances and have been used successfully to treat mucosal injury, including decubital ulcers, burns, and glandular and duodenal ulcers in humans. In addition, sea buckthorn berries have been shown to successfully treat and prevent acetic acid-induced gastric ulcers in rats. Two previous studies failed to show efficacy in the treatment or prevention of squamous ulcers in horses fed supplements containing sea buckthorn berry pulp and extract (SeaBuck Complete, Seabuck, LLC, Midvale, Utah), however; glandular ulcer scores remained zero when compared with untreated controls in the later study.6 Sea buckthorn berries are high in antioxidant, flavonols, vitamin C, and vitamin E, which have been shown in many in vitro and in vivo studies to facilitate the healing of glandular ulcers in other species.
CALCIUM CARBONATE AND GASTROPROTECTANTS
Many supplements on the market contain calcium carbonate, sodium bicarbonate, and other antacids. These products contain varying concentrations of calcium carbonate and various other herbs and coating agents. The author (FMA) performed a small study with an antacid preparation containing calcium carbonate (Neigh-Lox, Kentucky Performance Products, Versailles, Kentucky, 124.5 g, top-dressed on feed, every 12 hours, for three weeks) and found no effect on squamous ulcer scores in a small study (published data, 2001); however, gastric juice pH, as measured by an indwelling pH meter, was increased (≥4) two hours after feeding this supplement. In addition, calcium carbonate resulted in recovery of volatile fatty acid-induced sodium transport in squamous tissue in an in vitro Ussing chamber system.7 This data suggest that calcium carbonate preparations may have some efficacy in maintaining mucosal integrity, but because of the short-duration effect on gastric juice pH, more frequent feedings may be necessary to prevent squamous ulcers.
Two other commercially available supplements (Egusin 250; [E-250] and Egusin SLH; E-SLH, Centaur Inc., Olathe, Kansas) containing sodium bicarbonate, calcium carbonate, pectin, and lecithin were evaluated and both supplements showed improvement in squamous ulcer scores, compared with untreated controls, after 35 days of treatment in stall-confined horses.8 There was no effect on gastric juice pH in this study, and blood gases did not show a significant increase in total carbon dioxide.
The other ingredients that might have been effective were pectin and lecithin. In horses, the surface of the nonglandular stomach is coated by dense osmophilic surface-active phospholipids (SAPL), like the structure of pulmonary surfactants. Because the nonglandular mucosa has only a very thin to nonexistent mucus layer, and no bicarbonate secretion compared with the glandular mucosa, these hydrophobic SAPLs may provide the primary defense mechanism against hydrochloric and other organic acids in gastric fluid. Feed additives containing pectin and lecithin have been previously evaluated in horses with gastric ulcers and the results have been mixed. Pectin is a soluble complex polysaccharide derived from the cell walls of fruits and vegetables. Lecithin is a phospholipid derived from soybeans. It is an emulsifier, lubricant, and surfactant. Pectin acts with lecithin to form a hydrophobic (water repellent) barrier on the gastric mucosal membranes, protecting it against the corrosive effects of gastric acids.
HYDROLYZED COLLAGEN
Porcine hydrolyzed collagen (HC; Hydro-P Premium, Sonac, a Darling Ingredients Company, Son, the Netherlands) was recently evaluated in stall-confined horses treated with omeprazole and undergoing intermittent feeding.9 The HC (45 grams) was mixed with sweet feed twice daily for 56 days in a two-period crossover study. Mean gastric juice pH was higher in the HC-treated horses while the horses were on omeprazole treatment. In addition, HC-treated horses had fewer ulcers at each gastroscopic examination, and a significant effect on ulcer scores was seen on day 56 of treatment.
MULTIPLE COMPONENT FEED SUPPLEMENT
In a recent study, a commercially available supplement (SmartGut Ultra, SmartPak LLC, Plymouth, Massachusetts; 40 grams, mixed with grain feed every 12 hours) containing a proprietary blend of sea buckthorn, pectin, lecithin, and other ingredients showed a significant decrease in the number of squamous ulcers 14 days after omeprazole treatment was discontinued, and fewer squamous ulcers after a week of alternating feed deprivation, in the treated group compared with untreated controls.10 Feeding a supplement with sea buckthorn berries, pectin, lecithin and antacids, such as SmartGut Ultra, might be an affordable alternative to aid in the protection of the squamous mucosa from acid injury in stall-confined horses undergoing intermittent feeding.
CHELATED MINERALS
A recent study, using a chelated mineral supplement (Zinpro Performance Minerals—zinc methionine, copper lysine, manganese methionine and cobalt glucoheptonate); Zinpro, Inc., Eden Prairie, Minnesota, showed that ZPM treatment resulted in lower gastric ulcer scores in horses participating in the latter period of this study, when the nutritional plane was higher. ZPM, at the levels fed in this study may be beneficial in preventing gastric ulcers after omeprazole treatment in horses housed in stalls and fed intermittently, especially when horses are fed a well-balanced diet.
OILS (CORN OIL, RICE BRAN OIL)
Dietary fats delay gastric emptying time in humans and other species. In contrast to most species, gastric emptying rates are slower in horses fed a high-carbohydrate diet compared with horses fed a high-fat diet, although these rates were not statistically significant. Gastric relaxation was significantly greater in horses fed the high-carbohydrate diet, however, compared with horses fed the high-fat diet. Supplementation of dietary fat may not have a profound effect on gastric emptying in horses. In another study, ponies fitted with gastric cannulas and fed dietary corn oil (45 milliliters, orally once daily) by dose syringe had a significantly lower gastric acid output and increased prostaglandin concentration in gastric juice.11 The authors concluded that corn oil supplementation could be an economical approach to the therapeutic and prophylactic management of glandular ulcers in horses, especially those associated with the use of nonsteroidal anti-inflammatory drugs. In contrast to the previous study, results from an evaluation of the antiulcerogenic properties of corn oil, refined rice bran oil and crude rice bran oil (240 milliliters, once daily, mixed in grain) showed no statistical differences in nonglandular ulcer scores between the treatment groups. However, glandular ulcers were rare in these horses. In this model, dietary oils did not prevent nonglandular gastric ulcers in these horses, suggesting that dietary oils may not be useful in the treatment or prevention of nonglandular ulcers, but may be helpful in the treatment or prevention of glandular ulcers, since alteration in the protective barrier is the primary cause of glandular ulcers.
CONCENTRATED ELECTROLYTE PASTES OR SOLUTIONS
Repeated oral administration of hypertonic replacement electrolyte solutions, commonly given to endurance horses, has been shown to increase the number and severity of gastric ulcers. These products should be used with caution in horses and may be best given after exercise with feed to minimize their effects on the gastric mucosa.
SUMMARY
Supplements are commonly fed to horses, and some information exists on their efficacy and safety. However, supplements should not be used as a treatment for disease states. Care should be taken when recommending supplements for horses, and scientific evidence should be used whenever possible when recommending supplements. Supplements are not pharmaceutical agents and might take months of feeding to see improvement in health. In addition, when recommending supplements you should use reputable companies.
References upon request
About the Author
Frank M. Andrews, DVM, MS, DACVIM (LAIM)
Dr. Frank M. Andrews, DVM, MS, DACVIM (LAIM) is a 1983 graduate of Washington State University College of Veterinary Medicine and is LVMA Equine
Committee Professor and Director of Equine Health and Sports Performance Center of Excellence at Louisiana State University School of Veterinary Medicine (LSU Vet Med), Baton Rouge, Louisiana. He is a Diplomate in the American College of Veterinary Internal Medicine and an equine internal medicine specialist. He has an international reputation in the study of gastric ulcer disease and other gastrointestinal diseases in horses. He has a special interest in evaluating supplements fed to horses. Frank is a member of the American Association of Equine Practitioners and received the Faculty Distinguished Scholar Award at LSU. He was also recognized as one of the top 15 Large Animal Veterinary professors, educating the next generation of large animal veterinarians.