Anemia can be found in horses of any age but is particularly common in seniors. Not surprisingly, the list of possible causes is longer for them too.
Anemia is a lower-than-normal number of circulating red blood cells. Red blood cells (RBCs) contain hemoglobin, the oxygen-carrying protein that contains iron.
Before going into causes, it's important to stress what is not the likely reason: iron deficiency.
Educated horse owners know that dietary iron deficiency is virtually nonexistent in horses, and that supplementing iron doesn't stimulate red-blood cell production. Still, it's amazing how many people pay for iron-containing supplements.
Iron supplementation is more than a waste of money, though, as it can harm your horse. it's common to find the livers of horses, especially older horses, so overloaded with iron that they are black.
Excess iron promotes oxidative stress and inflammation, which has been associated with arthritis and the development of Cushing?s disease.
Iron deficiency from any cause is very rare but possible if there is constant loss of blood into the intestinal tract over a long period of time (e.g. from a malignancy), but the fact is that other symptoms would likely become apparent and critical before the anemia developed.
Horses that lose a large volume of blood from an injury should be monitored for iron-deficiency anemia, but even then it's unlikely.
If tHere's question about iron status, don't just wait and see. The correct way to test for iron stores is by measuring serum ferritin and transferrin saturation. Serum iron doesn't tell you anything.
Causes of Abnormal RBCs.
- Age related. As the horse ages, metabolic rate slows down. Most older horses are also not exercising regularly. These two factors combine to result in red-cell test results that are often at the very lowest of the normal ranges, or even slightly below. As a general rule, if the hemoglobin is 10 or above and hematocrit/PCV 30 or above, you don't have to worry even if that falls below what the lab calls ?normal.? It does bear watching though, to make sure it doesn't fall further.
- B vitamin deficiencies.B vitamins are important to maintaining normal red blood cell counts and are included in all equine ?blood builder? supplements. However, research on B-vitamin status in horses is spotty at best, let alone in older horses. We do know that full-blown deficiency states involving B vitamins don't occur in horses.This is because the teeming populations of bacteria in the horse's intestine are a B-vitamin factory. Whether older horses with less hardy bacterial populations may be more susceptible to suboptimal levels is unknown. Because the toxicity of B vitamins is low, supplementing them ?just in case? is reasonable but we really don't know if it's effective or not.
- Other deficiencies.A host of other deficiencies can also contribute to anemia. Copper is one of the most important, since a critical protein (ceruloplasmin) that shuttles iron around in the body requires copper. Mineral deficiencies have a way of catching up with an older horse. A lifetime of marginal intake means low stores in the tissues. When digestive efficiency starts to decline, this can push the horse over the edge into inadequate mineral supplies for bodily functions. Other key plays here can be vitamin E, selenium, protein quality or quantity, even inadequate calories.
- Hormonal problems.Cushing?s disease (a benign pituitary gland tumor) and the secondary thyroid underfunctioning that goes along with it are very commonly associated with some degree of anemia.
- Anemia of chronic disease.This is a huge category that includes chronic lung disease, cancers, any organ disease, chronic infections and the hormonal problems mentioned above. Long story short is that when the horse's body is facing a challenge it scales back on things like red blood cell production to keep it at a level that will sustain life but also preserve precious nutrients to fight the major battle. Limiting available iron is often a key element in this process because tumors and infections have very high iron requirements. Anemia of chronic disease can be recognized by the fact that RBC, hemoglobin and PCV/hematocrit are decreased, but MCV, MCH and MCHC are normal (see table). Ferritin will be normal to high, transferrin saturation normal to low.
- GI blood loss. Ulcers often get blamed for mild anemia but very few horses have ulcers that are severe enough to cause a sizable blood loss. If they did, there would be unmistakable symptoms of pain and loss of appetite. Treating ulcers for even 1 month is a lot more costly than having the stomach scoped to find out for sure. If scoping isn?t an option, try a 3- to 7-day trial of GastroGard. If the horse perks up and appetite clearly improves, ulcer treatment is warranted, but it still might not be the cause of the anemia. Horses do get more susceptible to parasitism as they age. Again, if parasitism is severe enough to cause sizable blood loss and anemia you'll also see weight loss, poor coat and a pot-bellied appearance. In other species, intestinal cancer (rare in horses) and bleeding diverticulitis (not an equine problem) can cause anemia.
Bottom Line.If your senior?s hemoglobin is at least 10 and hematocrit/PCV 30, you don't have to do anything except monitor periodically to make sure a more significant drop isn?t developing. However, if those numbers are a significant drop from recent blood counts, your vet will need to look for an underlying cause.
If no disease is at the root of the counts, be sure the horse's diet is adequate. Never give iron unless ferritin and transferrin saturation testing has proven there is an iron deficiency.
We suggest you try feeding a good multi-ingredient supplement, such as a hoof product, like Integrity Hoof (http://www.ka-hi.com/, 717-274-3676), Focus?HF (http://www.4source.com/, 800-232-2365) or Farrier?s Formula original or double strength (http://www.lifedatalabs.com/, 256-370-7555).
If you're unsure of the protein level, get a supplement that's also high protein. These are typically fed at 1 to 2 lbs./day. We like Triple Crown 30 (http://www.triplecrownfeed.com/,?800-451-9916) or TDI-30 (http://www.tdihorsefeeds.com/,?800-457-7577).
You could also try supplementing with a human whey protein concentrate or isolate. Look for one that is 80 to 95% protein. Amount needed depends on what's in your horse's diet but 1 to 2 oz./day works as a general recommendation.
Adding a few pounds per day of alfalfa hay is also a good way to boost protein and improve amino acid variety for horses on diets of grass hay.
Article by our Veterinary Editor, Dr. Eleanor Kellon.