Your horse gets sore feet. He is diagnosed with laminitis and founder. You have a good TEAM: Veterinarian, Farrier, and Caretaker, who help you address your horse's underlying metabolic condition and provide rehabilitative care. The horse becomes sound, and returns to his normal personality and, if you're lucky, his pre-laminitic level of performance. You can finally relax and breathe.
Or can you?
I began my hoof care journey in 2004 because of my own horse who foundered. I had a wonderful farrier at that time who put the rasp in my hand and empowered me to help my horse. With the veterinarian, we identified his insulin resistance and eventual Cushing's syndrome. He became sound and went back to a fabulous dressage career, retiring many years later due to EPM. You can read his story here: https://www.daisyhavenfarm.com/case-studies/windy
Windy, post-laminitis, back to work and winning in the show ring.
Fast forward to today. Windy is now 29 years old. He has been in excellent health and quite sound; metabolically stable, until last fall. I try to assess body condition on my own horses once a week, and Windy had become quite thin, even though he was eating well. He was a 3.5 body condition score (BCS) on the Henneke Body Condition Scale, ribs and hips sticking out. Looking back, I only have this image of him at that time, taken out of a video of the pony you see in the foreground:
I increased his feed for six weeks and when that didn't improve his weight I worked with our farm veterinarian to eliminate other causes of his condition:
-Teeth were assessed and re-addressed by our excellent dentist, but weren't the issue.
-No symptoms of ulcers, or other pain and discomfort leading to weight loss.
-Cushing's and insulin resistance were controlled based on blood work.
-Basic blood work all normal except for indicators of intestinal inflammation. We wormed Windy aggressively as he is a worm shedder. We also wondered if he possibly had internal tumors.
By January, Windy was finally looking better. Until one day, upon assessing Windy's body condition, I realized he was now a 6 BCS, slightly overweight and decided to back off the feed. His soles were no longer retracted and he looked much healthier!
But was he? The weight difference between 3.5 to 6 BCS was significant in a fairly short period of time, when he hadn't been underfed to begin with. Maybe the intestinal inflammation resolved somehow? I was unsatisfied with such a mystery. I hypothesized my horse was actually a skinny old horse whose metabolic condition was no longer controlled. Even though he had gained weight and looked "good" to me, perhaps it was really an indicator he was in trouble.
Our veterinarian agreed and we tested Windy metabolically:
ACTH: 39 pg/mL ( > 35 considered elevated)
Insulin: 58 uU/mL ( > 42 considered elevated)
Glucose: 102 mg/dL (Lab reference range 70-120)
The blood results don't look alarming: Insulin only mildly elevated, ACTH a seemingly minor difference, and glucose normal. However, Windy had very similar blood work when he originally foundered in 2004. So I was very concerned. In these situations, the Glucose:Insulin (G:I) ratio can be quite helpful:
From ECIRHorse.com, one of the leading resources for managing Cushing's and insulin resistant horses:
"What is the G:I Ratio? The Glucose to Insulin Ratio (G:I ratio) is a very simple concept. This ratio/number indicates how many “units” of insulin are being secreted per “unit” of glucose. The smaller the number, the less sensitive the cells are to the insulin. For example, a normal horse may have a blood sugar of 100 and an insulin of 10, for a G:I ration of 100/10 = 10:1, where an insulin resistant horse may have an insulin of 25 for that same blood sugar of 100, yielding a G:I ratio of 100:25 = 4:1. Both insulins may be within the laboratory’s “normal range”, but these normals represent a variety of diets and various times after eating. Obviously the horse that has a circulating insulin level 250% higher than other horses with the same blood sugar level is less sensitive to insulin. A ratio < 4.5:1 is diagnostic for Insulin Resistance, while a ratio between 4.5:1 and 10:1 represents compensated IR."
Windy's G:I ratio was 1.76 = Severe IR, high laminitis risk.
The G:I ration confirmed my concerns, that his mildly elevated blood results were not the whole picture. In order to gather more information, we decided to test Windy even further with a glucose tolerance test.
The glucose tolerance test assesses the horse's insulin response to a dose of Karo syrup at 60 minutes and 90 minutes. Additionally we gathered a pre-Karo syrup insulin sample as a baseline. A horse whose insulin levels test within the laboratory reference range would indicate normal response and normal metabolic function.
Windy's insulin values came back highly elevated, above the testable range:
Pre: > 200 uIU/mL (Reference range 0-20)
Post @ 60 minutes: > 200 uIU/mL (Reference range 0-45)
Post @ 90 minutes: > 200 uIU/mL (Reference range 0-45)
This test was definitive. It is important to remember that the baseline metabolic blood work panel is only showing you a moment in time. So the insulin taken in the initial panel result of 58 uIU/dL, being mildly elevated, was catching a low moment. Where the pre-glucose tolerance test insulin showed us a different moment, and one that was of much greater concern, which validated the G:I ratio.
I wish there had been some way to know that the pre-Karo syrup insulin was so high. We probably would not have done the glucose tolerance test if the initial insulin had been that high. However, it did give me a clearer picture of my horse's laminitis risk status.
By being proactive and asking questions, I was able to identify that my horse's underlying metabolic condition was not truly controlled and a contributing factor to his weight change. It is imperative to be vigilant when managing the Cushing's/insulin resistant horse by working with your veterinarian and utilizing these diagnostic tools to be objective when needed.