Feeding a blood tonic and expecting an immediate result is unrealisticLook up and down any shedrow at feeding time and you will see grain rations top-dressed with scoops of this and dollops of that to ensure that each horse has the nutrition it needs to perform at its peak. Prominent among the tubs of powders, crystals, and crumbles, you will probably see a large brown jug with a pump top that delivers the horse's daily dose of one or another liquid iron products.
Blood tonics-or hematinics, as nutritionists and veterinarians call them-have long been a staple in the diet of hard-working Thoroughbreds. Most trainers consider them a cheap insurance policy, if not a downright necessity. Since iron is essential to the formation of hemoglobin in the horse's red blood cells, and hemoglobin is what carries oxygen from the lungs to the horse's muscles, trainers theorize that an iron tonic will insure a maximum oxygen-carrying capacity in the horse's blood. Feeding a blood tonic, they reason, protects the horse against performance-inhibiting anemia.

How the body uses iron
As blood pumps through the lungs, hemoglobin picks up oxygen and carries it to the body's cells. The essential oxygen is burned in the cellular energy cycle. After giving up its oxygen, the hemoglobin sops up carbon dioxide for the return trip to the lungs. Trainers feed hematinics to maximize hemoglobin formation, hoping to give the horse an oxygen edge that keeps him running his hardest an extra second or two longer before fatigue slows his pace.
Iron, copper, and various B vitamins are the ingredients to all blood tonics. Vitamin B12 is used by the bone marrow to help produce red blood cells. Iron is essential for the formation of the oxygen-carrying hemoglobin within these cells. Copper acts as a coenzyme in hemoglobin production.
Many hematinics also contain small amounts of cobalt, a mineral used by the bacteria in the horse's intestinal tract to synthesize B12.
Various brands also contain other minerals such as potassium, manganese, zinc, iodine, magnesium, phosphorous, selenium, or sulfur. Besides B vitamins, vitamins A, D, E, or K may be added. You may also find some amino acids and flavorings like sorbitol, liver fraction, or yucca. More on these extras later.
The horse's body contains from 32-to-53 quarts of blood, containing red cells and white cells suspended in yellowish liquid plasma. In a healthy horse, red cells outnumber white cells 1,000-to-1. Red blood cells are unique because they have no nucleus. Reddish hemoglobin makes up about a third of the watery contents of each of these plump, round disks with concave tops and bottoms. Each red cell lives about a month. It starts its life in the bone marrow, matures over a cycle of 21-to-28 days, then is destroyed in the spleen and the liver.

What the horse needs
The National Research Council, which collects and publishes data on equine nutrition, recommends that racehorses get about 18 milligrams (mg) of iron per pound of feed daily. That means a mature, 1,200-pound racehorse receiving a total ration of 24-to-36 pounds of hay and concentrates daily needs about 436-to-655 mg of iron in his daily diet.
While most grains are not particularly high in iron, sun-cured hay is. For example, early or mid-bloom alfalfa provides a little more than 93 mg of iron per pound, while a pound of 17% protein alfalfa meal provides just over 200 mg of iron. That means a 1,200-pound horse getting 18 pounds of mid-bloom alfalfa daily is getting over 1,600 mg of iron from his hay alone. If a horse is on alfalfa pellets, he is getting even more.
Many horses also get additional iron from the supplements in their diets, including hematinics, because many supplements include it. Iron is an inexpensive ingredient to add, and it looks good on the label.
Not everything that the horse eats actually finds its way into the bloodstream.
The NRC estimates that horses may absorb only 15% or less of the iron they take in. Chelation, a process which hooks minerals to an amino acid or peptide that helps them cross the gut wall more easily, can increase that percentage substantially. So horses will absorb more iron from a hematinic with chelated iron than from one with ordinary sources of iron. However, that increased absorption also means that horsemen must pay closer attention to the overall mineral balance in the horse's diet.

So who needs it?
If horses are getting sufficient iron from their hay, do they really need supplemental iron? Jim Hamilton, DVM, a former racetrack veterinarian now in private practice at the Tarheel Veterinary Clinic in Vass, North Carolina, feels that hematinics are probably wasted on the average pleasure or show horse because their normal diets provide sufficient iron, copper, and B vitamins.
The picture changes, however, when a hard-working horse is conditioned for peak racing performance. Appearances can be deceiving. The horse may appear fit and the picture of health. But analysis of his blood values may tell another story.
Veterinarians use three of the values obtained in a complete blood count (CBC) to assess the status of a horse's red blood cells and determine if it is anemic. For a fit equine athlete being kept in hard condition, Hamilton likes to see:
¥ a red blood cell count of between 7-million and 9-million red blood cells per cubic milliliter of blood;
¥ hemoglobin in the range of 13.5-to-15.5 grams per deciliter of blood;
¥ and a packed cell volume or hemacrit (measured by allowing the red and white cells to settle in a blood sample, then measuring the proportion of solid cells to liquid plasma) in the range of 40%-to-50%. These blood values can vary depending on the horse and the lab processing the sample. Sampling on a regular basis can establish a base line and a pattern for an individual horse.
Because it takes so long for a red blood cell to mature, feeding a blood tonic and expecting an immediate effect is unrealistic, Hamilton said. Over time, however, a CBC can tell a horse's owner and trainer if the horse is anemic and whether feeding a hematinic is having any effect on the horse's blood chemistry.

Everything in balance
While extra iron may have a place in the diet of hard-working mature horses, nutritionist Ginger Rich, PhD, of Rich Equine Nutritional Consulting, points out that excess iron can be lethal for younger animals. Because of the many complex mineral interactions within the body, excess iron can cause joint and bone problems, even liver failure, in young horses. Iron interacts with many other minerals in the horse's diet, affecting their absorption either positively or negatively. A dietary problem can cause a medical predicament.
These same nutritional complexities make iron toxicity much harder to detect in mature horses, said Rich, who is sometimes called in as a "nutritional detective" by farm managers and vets. The clinical signs can include anorexia, diarrhea, hypothermia, and/or metabolic problems with the liver, kidney, heart, brain, or spleen. Excess iron is also implicated in the formation of destructive free radicals thought to accelerate aging and general wear and tear on body tissues.
For example, Rich points out that the balance between iron and copper levels is critical for proper hemoglobin formation. If the horse is anemic because the level of copper in his diet is too low, feeding more iron will not correct the problem. That is why copper, as well as iron, is one of the ingredients common to all blood tonics.
Rich also feels that horsemen should look at the label of any hematinic they are feeding and see what it contains in addition to iron, copper, and B vitamins. Because they are water soluble, excess B vitamins are simply excreted by the horse. Not so with fat soluble vitamins A, D, E, and K, which are included in many supplements, including hematinics. Excess vitamin A and D can build up to toxic levels in the horse's tissues. Several readily available hematinics also include various levels of up to seven other minerals besides iron, copper, and cobalt.
Horsemen need to add up all the minerals and vitamins in the horse's total ration of hay, grain, all those scoops of crystals, powders, and crumbles, and that squirt of blood tonic. Even if a CBC shows a need for added iron, they need to make sure that feeding several supplements simultaneously for "insurance" does not wind up harming the horse by causing subtle nutritional imbalances.