2022 AAEP Convention Bonus Coverage: Diagnosing Equine Metabolic Syndrome

A single bay Welsh cob stands in a paddock.

Huh, Who’d Have Thought?

Part Four: Who’d Have Thought Classic TV Can Help Vets Diagnose Metabolic Syndrome?

All the best-laid plans rely on having the correct facts. Without knowing the basics, we can’t develop or grow. We can’t adapt what we know to improve ourselves. Mr. Carlson, station manager of WKRP in Cincinnati, learned this lesson the hard way. If you’ve never seen the infamous episode of this classic ‘70s show, Turkeys Away should be on your must-see list. Facebook subscribers can watch the full episode here, and others can watch it here (with ads—it’s worth it). 

The gist of the story is that Mr. Carlson plans his own Thanksgiving event to promote the radio station. He refuses the help of his knowledgeable staff. He obtains live turkeys and hires a helicopter towing a sign that says, “Happy Thanksgiving from WKRP.” Over a busy shopping spot, Mr. Carlson pushes the turkeys out of the helicopter as a gift to the shoppers for listening to WKRP. As you can imagine, the advertising strategy failed. Mr. Carlson admitted his failure to his staff saying, “As God as my witness, I thought turkeys could fly.”

Perhaps (and hopefully) our errors won’t be as momentous as in Turkeys Away. But this episode does highlight the importance of using other people’s knowledge to improve your own ideas. This was highlighted during Sunday’s Convention offerings by Amanda Adams, PhD, from the Gluck Equine Research Center, University of Kentucky. 

Using the OST to Diagnose ID in Horses With Equine Metabolic Syndrome

Adams reviewed the basics of the oral sugar test (OST). This test helps diagnose insulin dysregulation (ID) in horses with equine metabolic syndrome (EMS). The classic means of performing this seemingly simple test involves measuring basal serum insulin levels, administering karo light corn syrup at 0.15 mL/kg, and measuring serum insulin levels again 60-90 minutes later. 

But wait! Should you perform the test on a fasted or fed horse? How much and what kind of syrup should you give? Can you perform this test any time of the year? Or, is it season-dependent like measuring adrenocorticotropic hormone (ACTH) levels in PPID (equine Cushing’s) horses? What other nuances should practitioners be aware of?

The Equine Endocrine Group’s (EGG) 2022 recommendations for the diagnosis and management of equine metabolic syndrome suggests a 3- to 6-hour fast before performing the OST. 

According to Adams, “fasted” means no grain or forage. “Fed” means grain fasted but not forage fasted. Thus, an equid can be tested while still on pasture and/or having access to hay. 

“We no longer recommend fasting for basal resting insulin. Further, because fasting is not always an option prior to the OST, we did a study to compare insulin responses of ID horses to the OST in a ‘fasted versus fed’ state and found no difference. You must take into consideration the level of nonstructural carbohydrates or NSC in the forage when considering a ‘fed’ state. If the forage is not low NSC then the OST results could be high. If you’re not sure of the NSC level then just stick with the short 3- to 6-hour fast,” Adams advised.

Syrup Dosage for the OST

You should consider dose of syrup. While some protocols call for only 0.15 mL Karo light syrup, others recommend 0.45 mL/kg. Available data show that the lower dose is appropriate for most cases. However, the higher dose may be considered in equivocal cases, relayed Adams. 

“We just published a study comparing low- versus high-dose and found no difference between insulin responses of ID horses. But if you looked at the diagnosis category of these responses, about 25% of these horses would have been misdiagnosed as not being ID with the low-dose OST. This supports the EEG findings if you have a suspect case, one early in disease stage, or your results are negative with the low-dose OST then go ahead and perform the high-dose OST,” Adams said.   

But for more cases, the low dose OST is appropriate.

Adams added, “The light syrup should be used. If unavailable, Karo light syrup can be substituted with Crown Lilly white corn syrup, which they use in Canada.”

Consistent Across Seasons

In terms of season, you can use the OST across seasons without needing to be corrected like basal ACTH levels in PPID horses. 

“What you will see is that basal insulin levels will vary across season and some horses can change their ID status if you looked at insulin levels alone. But if the OST test is performed then the results will be consistent across seasons,” Adams relayed. 

In sum, Adams recommends picking a single OST protocol and sticking to it. 

“If you’ve used a low dose of Karo light corn syrup in a fasted state in the spring, it would be best to consistently use this technique when monitoring the horse moving forward,” she advised.  

I, like Adams, extol the benefits of consistency. Like having yoga consistently offered as part of the AAEP wellness program at the Annual Convention. It’s the perfect activity to start the day, centering mind and body. The AAEP eliminated the activity this year due to lack of interest. Support the Bring Yoga Back movement by contacting the AAEP. And in the name of consistency, reach out to them more than once!

Mental Health Awareness

The holiday season can be exceptionally difficult for some. If you see someone struggling, consider sharing the wellness resources available from the AAEP.

Brought to you by ADM Cellarator Advantage

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