The Horse

MAR 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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Page 42 of 75

A34 March 2019 The Horse | AAEP Wrap-Up comparing measurements from season to season, they also saw differences in both ID and normal horses. All horses had a lower BCS in April than in February, and higher scores in August than in April. But Macon said these changes were not always significant. As expected, she said, baseline insulin levels were significantly higher in the ID group than in the control group, regard- less of season; these values made ID diagnosis clear. Interestingly, she said, season did not affect these values in the controls, but affected horses had signifi- cant variability in their baseline insulin values from season to season. Their Octo- ber insulin values were significantly lower than their February and April values and below what veterinarians typically use to diagnose ID. The ID and control groups' T60 post- OST insulin values were significantly different, regardless of season, but con- trol horses' values were not significantly different across seasons, said Macon. The control horses all remained under the threshold for ID diagnosis. However, the ID horses had insulin values more than 2.5 times higher than the threshold for diagnosis in February and April, dropping to just over 1.5 times the threshold in October. Therefore, she said, season had a significant effect on the ID horses' levels in February, April, and October. The pasture's nonstructural carbohy- drate (NSC) content stayed relatively stable (below 10%) across seasons and was only significantly higher in October. Crude protein content was significantly higher in February and April (just under 30%) than in August and October (just under 20%). "NSC has been directly correlated to stimulating insulin responses," Macon said, and UK researchers recently showed that protein can also stimulate insulin re- sponses. "Since these horses are consum- ing forage only throughout the yearlong study, it is important to note what factors could stimulate insulin responses." Macon concluded that season affects baseline insulin and insulin response to the OST in ID horses but not in control horses. Another interesting finding from this study, she said, was that the ID horses' BCS and cresty neck scores did not reflect their baseline insulin scores. Therefore, they do not appear to be driv- ing factors behind ID development. For- age nutrients don't appear to be driving factors, either, she said. Macon is currently investigating other possible factors they could reliably test. The study did have limitations, she said, namely that they only measured meta- bolic responses once per season and col- lected and analyzed forage only once at the same time each day (forage's nutrient content fluctuates throughout the day). The study horses were obese ID horses; it's not clear whether the same findings would have occurred had they been leaner or had PPID, she said. This research does clearly show that horses need to be diagnosed and moni- tored for ID, and vets must remember that both baseline and post-OST insulin responses vary across seasons in these horses, Macon said. Researchers might need to develop seasonal reference ranges like those that have been created for diag- nosing PPID using ACTH, she said. Could A Supplement Help Reduce Insulin Concentrations? Any tool to reduce insulin levels could be valuable for reducing the risk of laminitis developing in certain horses. Re- searchers recently evaluated one option with encouraging results. Research in humans has shown that a compound called resveratrol can improve insulin sensitivity. When combined with the amino acid leucine, it takes even less resveratrol to improve insulin sensitiv- ity in rats. So Jane Manfredi, DVM, MS, PhD, Dipl. ACVS-LA, ACVSMR, assistant professor of pathobiology and diagnos- tic investigation at the MSU College of Veterinary Medicine, in East Lansing, and her team recently tested whether a supplement containing that combina- tion could improve metabolic function in horses with EMS and/or ID. The researchers supplemented 15 hors- es previously diagnosed with EMS and/or ID for six weeks with a high- or low-dose mix of synergistic polyphenol ( resveratrol) Handle Older Horses' Dental Care With Diligence Despite widely held beliefs that horses' teeth grow throughout their entire lives, the truth is they do "expire." With an estimated 88% of horses over 20 years of age diagnosed with dental disease, veterinarians must be sure to maintain these patients differently than younger horses. Apryle A. Horbal, VMD, MRCVS, from University Veterinary Equine, in Pittsburgh, Pennsylva- nia, said the main goal for managing any horse's teeth is to preserve oral health and remain- ing dentition—particularly by avoiding overfloating. This helps the horse chew adequately to support his energy demands and maintain condition. When diving into a sedated senior's mouth and running through the list of dental diseases that might affect him, Horbal stressed the importance of a complete and thorough physical and dental exam. She emphasized that even seemingly unrelated conditions—such as pitu- itary pars intermedia dysfunction and degenerative joint disease—could impact dentition. Horbal said one of the more recently recognized concerns in older horses' mouths is equine odontoclastic tooth resorption and hypercementosis (EOTRH), which occurs when incisor and canine roots begin to resorb, abscess, and loosen. After confirming this painful disorder using radiography, Horbal said she advises removing all affected teeth in a single surgical procedure in the standing heavily sedated horse. Patients reportedly do very well afterward, continuing to eat and work normally, often living long after extractions occur with improved health, she said. Other topics Horbal touched on included periodontal disease and diagnosing and manag- ing senile diastemata (gaps between adjacent cheek teeth that, if left untreated, can trap food material, leading to painful ulceration of the gums, periodontal disease, and eventual tooth loss). The veterinary dentist will need an oral endoscope or a mirror to identify these lesions, which often occur deep in the mouth. They typically must perform several treatments to thoroughly clean out senile distemata, and it can recur. "I recommend re-evaluating these horses every four to six months and providing additional treatment as needed," said Horbal. "As horses continue to live longer … awareness of the particular challenges in geriatric dentistry is of utmost importance," Horbal said. "If properly recognized and understood, den- tal disease in geriatric horses can be well-managed, and horses may even long outlive their teeth."—Stacey Oke, DVM, MSc

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