By Kimberly S. Brown

We humans think nothing of having our blood drawn once a year to have a “screen” of tests run in order to give us an accurate account of where some of our important baseline “numbers” stand. In fact, we often look forward with anticipation (or maybe dread) to knowing what our cholesterol, triglycerides, blood sugar, or other levels are at that time, and seeing how they have changed for better or worse since our last tests.

Did you know the same type of testing is available for your horse?

With advances in equine laboratory testing, you now can have – and should have – a general health profile chemistry panel and a complete blood count (CBC) run on your horses annually. These are the equine versions of what you get with your annual checkup and blood test.

Best of all, the equine blood tests can be done with that one blood sample your equine veterinarian draws for your annual Coggins test.

All equine veterinarians have access to the blood analysis systems used for this general health profile. Some veterinarians own the equipment needed to analyze these blood parameters right in their clinic or hospital. Other veterinarians use local or national laboratories to have blood chemistry profiles run on their patients.

Whether your horse is a backyard buddy or a high-level competitive athlete, there is value in knowing what his baseline numbers are in order to catch any abnormalities early, to monitor levels that are outside normal boundaries, and to protect your horse and the horses he comes in contact with (which is why you have a Coggins test run each year to detect the presence of equine infectious anemia, or EIA).

There are an estimated 1.7 to 2 million Coggins tests run each year in the United States. Think of the additional information that could be provided to each of those horse owners and veterinarians if a complete blood panel was run on each horse! And think of what that array of samples could mean for advancing the general knowledge of equine health in the United States!

For example, with the concern today about outbreaks of equine herpesvirus type 1 (EHV-1) at major competitions – from Thoroughbred racetracks to Quarter Horse events – simple blood tests could detect the presence of the virus’s DNA in the horse’s bloodstream. (This test should be done in conjunction with nasal swab testing.) While positive findings are not a predictor of potential illness, detection of the EHV-1 virus in a seemingly healthy horse could provide the veterinarian and trainer opportunities to proactively manage that subclinical horse differently to perhaps prevent him from becoming sick or spreading the disease.

Blood samples also could detect if a horse’s immune system is below par, which might make him more susceptible to disease. If, for example, that immune-deficient horse comes in contact with a horse that has a latent herpesvirus infection, it could set the stage for virus transfer.

But for more normal, day-to-day uses, the complete chemistry profile from a blood test could give veterinarians, owners, and trainers valuable insights into the wellbeing of their horses.

Kim Sprayberry, DVM, Dipl. ACVIM, in an article titled “Why Perform the CBC, And How Can the Information Be Used to Manage Cases,” noted that, next to performing an expert physical examination, a blood sample submitted for a complete blood count is the most basic tool available to veterinary practitioners.

“The CBC is commonly performed by equine veterinarians as the foundation of diagnostic evaluation, for serial monitoring of a patient’s response to therapy, for pre-surgical screening, as an adjunct to insurance or pre-purchase examinations, and as part of a routine well-horse care program,” Sprayberry continued. “Many of us fall into a pattern of taking into account only the hematocrit, total protein, and total leukocyte count, thus depriving ourselves of much important and relevant information pertaining to our understanding of the state of health or disease present in the patient that stands before us.”

An example of the use of a blood chemistry profile in a healthy horse was given by Nicola Pusterla, DVM, Dipl. ACVIM, of the Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, who said: “Early detection of metabolic derangements (metabolic syndrome, i.e. hyperglycemia) could help minimize long-term effects such as laminitis.”

Pusterla said this type of blood chemistry panel testing also is routinely used on newborn foals.

“The 24 hour wellness foal check has become a routine evaluation for most neonates,” said Pusterla. “The 24 hour mark is often chosen since this is the time where 90 percent of antibody absorption has occurred.”

But it’s not just foals that can benefit from routine blood work, he said. “Routine blood work should be encouraged in order to improve the wellbeing of equids and recognize subclinical diseases. Such approach should apply to all age groups – foals, adults, and older horses.”

Pusterla gave some specific examples of using a complete blood count (CBC) and biochemical panel in adult horses. He said that in horses routinely receiving NSAIDs, “it would be beneficial to determine their renal parameters on a regular basis.”

For competition horses, Pusterla said, “Performance-limiting factors that could be recognized via routine blood work would include altered RBC (red blood cell) parameters (which would decrease oxygen-carrying capacity) as well as underlying subclinical myopathies (suboptimal performance).

He noted that older horses benefit from a regular CBC “to monitor inflammatory parameters (nucleated cell count, fibrinogen, globulin levels).”

Josie Traub-Dargatz, DVM, MS, Dipl. ACVIM, is a professor in the population health section of the Department of Clinical Sciences at Colorado State University’s College of Veterinary Medicine and Biomedical. When recently asked what she thought were the top five advances in equine veterinary medicine in the past 25 years, she included this: “Biochemistry panels versus having to request individual tests that cost as much as a panel does now.”

Sources quote the cost of these additional blood tests at between $100 and $200 depending on your geographic location and any additional tests you have run.

Before you think that blood test screenings are the answer to all medical questions, be aware that there are many other types of blood tests for specific problems and diseases that are extremely valuable, especially for sick or subclinical horses. Those include screenings for Strep equi (strangles) and other respiratory and gastrointestinal diseases.

Let’s look a little further into what a simple blood sample can tell us, and what is tested.

Blood Chemistries

TP or Total Serum Protein is a common blood test for horses. Your veterinarian might do a “total serum protein” test, which measures the total protein in the blood as well as the amount of two major proteins found blood: albumin and globulin. TP aids in diagnosing many different problems, including liver, kidney, and GI tract disease.

Albumin is mainly produced in the liver, and it is often used to determine how well the liver and kidneys are working, and to determine if the body is absorbing enough protein. The body uses albumin to move small molecules through the bloodstream, and albumin plays a key role in keeping blood from leaking out of blood vessels. You often will hear albumin mentioned when the veterinarian discusses “total serum protein” being tested.

Globulin is actually made up of several different types of proteins, which are categorized as alpha, beta, and gamma. Some globulins are produced in the liver, and others are manufactured by the immune system. Globulins are not soluble in pure water, but are soluble in dilute salt solutions. Globulins levels can help your veterinarian know if your horse is more susceptible to infection.

Alkaline phosphatase (ALKP) is an enzyme mostly produced by the liver and bones. This level is rarely low, but it can be high when specific problems occur in the horse’s body. Rapid growth in young animals can cause ALKP levels to be increased. In older horses, these increases can indicate excessive bone turnover associated with arthritis. ALKP also can indicate liver disease or vitamin D deficiency.

Aspartate Transaminase (AST) is an enzyme found in several places of the horse’s body, and it usually is found in low levels in the blood. When levels are elevated, it can indicate liver or muscle problems. It should be kept in mind that when AST is used for monitoring muscle problems, AST builds up slowly and remains in the blood for some time after something like a tying-up episode.

One use of AST by some veterinarians is as an indicator of how a horse is handling training. Alan McGregor, BVCSc, of McGregor Veterinary Clinic in Bunbury, Western Australia, said he uses blood-based analysis on many of his racing clients’ horses. "AST levels rise in early preparation work," noted McGregor in an article on AERC.org, "especially when young horses start programs. The AST values generally level out at 12 to 14 weeks of training. This gives the owner a measure of which horses have successfully handled the increased work, which horses can advance to the next step and which horses may need additional conditioning time."

Blood urea nitrogen (BUN) tests are used to judge kidney and liver health by measuring in the amount of urea nitrogen in the blood. When the liver breaks down protein, the waste product urea nitrogen is produced and circulates in the bloodstream. Healthy kidneys remove urea nitrogen from the bloodstream and excrete it in the urine.

Calcium (Ca) is tightly regulated by the body, so low or high levels of calcium in the blood sample can indicate a variety of diseases.

Creatinine kinase (CK) is used to measure muscle damage. Horse owners often hear of CK and AST being studied after a horse has a tying-up episode. When muscle cells are damaged, proteins are released into the bloodstream in a matter of a few hours. AST, as stated before, takes a while to accumulate in the bloodstream. CK accumulates quickly and can take a long time to go back to normal levels after a severe tying-up episode

Creatanine (CREA) or creatine phosphokinase (CPK) is also used to measure muscle damage and kidney function. CREA rises quickly after muscle damage (six to eight hours) and dissipates quickly (usually by two days). CREA testing also can help distinguish between kidney and non-kidney causes of elevated BUN levels.

GGT (gamma glutamyl transferase) is an enzyme that indicates liver disease or corticosteroid excess.

Glucose (sugar) is an important indicator of metabolic syndrome. The normal way that glucose and insulin interact, according to a succinct summary by Martin Furr, DVM, PhD, Dipl. ACVIM, of the Marion DuPont Scott Equine Medical Center, is that insulin regulates blood glucose. As glucose goes up, insulin goes up in response. Insulin stimulates cellular uptake of the glucose. Blood glucose goes down as a result.

Insulin resistance is an important health problem today, especially among aging and overweight horses. Here is a synopsis of insulin resistance from the University of Minnesota, where a tremendous amount of research has been undertaken on this complicated problem:

“In response to feeding, insulin is secreted by the pancreas into the blood stream. Insulin in the blood stream directs the glucose (sugar) absorbed from the food into the body’s tissues including liver, fat and muscle. Insulin resistance occurs when insulin no longer has a normal effect on the tissues. In the insulin resistant horse, the pancreas releases insulin into the blood stream, and the insulin arrives at the tissues and binds the cells, however the glucose enters the tissue cells at a much lower rate than normal. This lower rate of glucose uptake into tissues results in higher levels of blood glucose.

“Horses and ponies compensate for insulin resistance by secreting even more insulin into the bloodstream in order to keep the blood glucose concentration within the normal range. Therefore, horses and ponies with equine metabolic syndrome (EMS) have a higher concentration of insulin within the blood, which can be measured to determine if insulin resistance is present.”

LDH is short for lactate dehydrogenase (or sometimes called lactic dehydrogenase). High levels give indication of tissue damage.

TBIL (total bilirubin) Bilirubin is a component of bile, which is secreted by the liver. This might be elevated if the horse has liver disease or if the horse has not been eating.

Take-Home Message

Just like humans need to know their “numbers” from a simple blood test, it is valuable information for your horse, too. Ask your veterinarian about expanding the knowledge of your horse’s baseline health with the use of equine blood tests.

About the Author: Kimberly S. Brown has more than 30 years of experience writing and editing in the equine medical industry. She is president of The Homestead Information Network, Inc., a company focusing on marketing, business development, and editorial services.

Main Photo: Courtesy of Kimberly S. Brown