by Dr. Joseph Thomas
Printed in: Natural Horse Magazine
Volume 16, Issue 1
Frustrated that you can’t figure out what is going on with your horse? Something’s not right, but what? Is your horse losing weight despite your best care? Or has he not ever recovered from being sore after that last laminitic episode, months ago? Maybe it’s time for blood work to get a good look at what is going on inside. When the correct blood chemistry tests are performed, then carefully analyzed and accurately interpreted, you can find out exactly what is going on with your horse. Blood chemistry is an intricate, elegant, and essential diagnostic “tool” that allows for the assessment of core health issues and can direct early treatment.
Blood Chemistry Test Result Patterns:
Equine metabolic syndrome (EMS) is a profile of physical symptoms stemming from an underlying metabolic dysfunction. Unchecked it will eventually lead to insulin resistance (IR) and an array of associated health problems. 1Briefly: IR is the essential metabolic dysfunction that is characterized by a decrease in insulin’s ability for “glucose utilization,” i.e. push glucose from the circulating blood into cells where it can be used for sustaining life. 2Blood work is the only definitive methodology to determine your horse’s placement along the IR continuum. Not only can it show how far your horse may have progressed from EMS to IR, but also what associated health risks your horse may be experiencing.
Typically, blood work reports for horses identified as having EMS, Cushing’s, IR and/ or laminitis include a very limited number of tests; e.g. ACTH, T4 (Thyroxine), and, as of late, glucose and insulin. It is common for each test to be considered in isolation and interpreted only when the results fall outside the reference range. There are two major drawbacks to this type of analysis. The first is that a single test can be too easily misinterpreted because single test results can have multiple interpretations. When test results are considered in patterns, i.e. more than one blood chemistry “related” test result, interpretations emerge that are reliable indicators of the underlying dysfunction. For example, if the CBC (complete blood count) test result WBC (“undifferentiated” white blood cells) is low, the list of possible interpretations includes: drug toxicity, bone marrow failure, dietary deficiency, autoimmune disease, or an overwhelming infection. But when that result is placed in the context of a test result pattern from the differential aspect of the CBC of elevated Percentage Segmented Neutrophils along with high Percentage Lymphocytes, the low WBC result can now reliably be interpreted as an overwhelming bacterial infection. The second limitation of this type of analysis is that even when a single test is definitive for a diagnosis, it cannot give the full scope of the health profile that the whole pattern reveals. IR is a primary example of this limitation. When a horse is diagnosed with IR by just the measurement of elevated insulin there is no other information included about the progression of IR and what other health issues may be present or developing.
Test Result Pattern Identifying IR:
Elevated insulin (hyperinsulinemia) is the essential blood chemistry variable for identifying IR. When the insulin value moves into the high-normal range it is likely that the beginning EMS signs such as fat deposits in the rump, shoulders, cresty neck; excessive urinating and drinking will be noticeable. Another leukocyte indicator of IR is low eosinophils. As IR continues untreated, glucose levels will rise to the point of being elevated above the range (hyperglycemia) and then your horse has type 2 diabetes with compensatory hyperinsulinemia, which is the end result of IR. 3Potassium will move above the range at this time bringing the possibility of one of the types of metabolic acidosis, most likely anion gap, one of the acid-base disorders.
Table 1 is a graphic representation of the above blood chemistry process.
|Glucose||135||60 - 123||mg/dl|
|Insulin||120||10 - 40||ulU/dl|
|Eosinophils||0.1%||0 - 11%|
|Potassium||4.9||2.4 - 4.7||mEg/L|
Table 1 is an example of the blood chemistry test result pattern of a horse with IR that has progressed to type 2 diabetes with compensatory hyperinsulinemia.
Immune Deficiency and Infection:
Once insulin has moved beyond the upper limit of the reference range, a deficiency of immune function is likely. This can be seen in the blood work analysis of the Differential Count of the CBC as low percentage Lymphocytes. By not having adequate lymphocyte protection, your horse will have an inadequate ability to fight infections. Most commonly with an EMS, Cushing’s, or IR horse, this will show up as an inability to readily heal hoof capsule abscesses, a frequent occurrence closely following a laminitic event. 4The blood test result that indicates this within the Differential aspect of the CBC is high Percentage Segmented Neutrophils; whenever this aspect of neutrophils is high, even high-normal, there is bacterial infection present. If this bacterial infection lingers and becomes chronic, the WBC count will move above the range. This is because there is an increase in disease fighting cells, mostly immature lymphocytes (leukocytes), in your horse’s circulating blood.
Table 2 is a graphic presentation of this blood chemistry process.
|Glucose||105||60 - 120||mg/dl|
|Insulin||85||10 - 40||ulU/dl|
|% Segmented Neutrophils||62%||30 - 60%|
|% Lymphocytes||31%||25 - 70%|
|WBC||13.2||5.5 - 12.5||103/uL|
Table 2 is an example of a blood chemistry test result pattern for a horse with IR who has had a laminitic episode and chronic bacterial infection (hoof capsule abscess) with immune function deficiency.
Another health problem commonly associated with IR horses is intestinal malabsorption. This is a digestive disorder that leaves a horse unable to assimilate nutrients from food no matter the quality or quantity. This can reach the point of “systemic” malnutrition when not treated effectively. Within the blood work pattern, the primary test result indicative of malabsorption is low Albumin and /or Total Protein. Albumin is formed in the liver and makes up approximately 60% of the body’s protein. When this test result is low your horse is likely to have difficulty maintaining weight, may appear bloated, have loose stools, and, when advanced, lose muscle tone, especially in the hind end. When this happens, Creatinine will also become low as the daily production of Creatinine depends on muscle mass. Other corroborating test results of malabsorption are: low Calcium, Alkaline Phosphatase, and Cholesterol.
Table 3 is a graphic presentation of this blood chemistry process.
|Glucose||101||60 - 120||mg/dl|
|Insulin||57||10 - 40||ulU/dl|
|Total Protein||5.6||5.4 - 7.8||g/dl|
|Albumin||1.8||2.3 - 3.8||g/dl|
|Globulin||3.8||2.2 - 4.4||g/dl|
|Calcium||10.9||10.8 - 13.5||mg/dl|
|Alkaline Phosphatase||58||50 - 250||U/L|
|Cholesterol||47||50 - 140||mg/dl|
|Creatinine||0.8||1.0 - 2.2||mg/dl|
Table 3 is an example of the test result pattern for a horse with early IR and intestinal malabsorption. If this horse’s malabsorption advances significantly, he will lose muscle tone and the test result for Creatinine will move below the reference range.
Other associated health concerns for horses with IR that are found in blood work include: e.g. from the CBC with Differential: simple and complex category anemia; vascular problems (the most common being increased viscosity of the circulating blood); acute and chronic inflammation, and from the rest of the panel: the array of acid-base disorders; biliary interference (a colic risk); kidney function deficiency and kidney failure, which comes with uncontrolled type 2 diabetes.
The possibilities within blood chemistry are seemingly limitless with appropriate tests accurately analyzed and interpreted. This elegant diagnostic system offers a window into what is “going on” with your ailing horse. When the full list of tests (the author uses fourteen tests other than the ones listed in this article) are “measured” you will not only know if your horse has IR, you will also know how far the IR has progressed and what other health problems are of concern.
About the author:
Joseph Thomas, PhD has been a practitioner, teacher and consultant in Chinese medicine for more than twenty years. Prior to that Dr. Thomas was a researcher at MIT’s Department of Psychology and Brain Science investigating the development of single cells during congenital eye diseases. He put both these skills together with his love and knowledge of horses and developed www.forloveofthehorse.com, along with his wife and their daughter. For Love of the Horse is a Chinese Herbal Solution company where precision and sophistication of proprietary formulations provide you with effective choices, results, and integrity of service.
- Equine Internal Medicine; 2004, Reed SM, Bayly WM, Sellon DC
- Equine Vet J; 27: 364-367, 1995 “Descriptive Epidemiological Study of Equine Laminitis”
Slater MR, Hood DM, Carter GK
- Equine Drugs and Vaccines: A Guide for Owners and Trainers, Breakthrough Publications, Eleanor M. Kellon, V.M.D.
- The Second International Equine Conference on Laminitis and Diseases of the Foot and the 2003 American Association of Equine Practitioner Annual Conference