Hematinics Administration (also known as "blood builders") for horses, either in the form of a dietary supplement or as an injectable compound, is generally carried out by the owners, trainers, and veterinarians.
The general objective in using these compounds is to increase the supply of nutrients essential for the synthesis of horse hemoglobin and red blood cells (RBCs) and, in doing so, "builds the blood" by increasing the number of red blood cells. The basis for this practice seems obvious – the higher the number of red blood cells, the performance will better workout. You can get more information on blood builder supplements at https://www.taylormadeequine.com/product/bio-blood-builder/.
Yes, hematinics do supply nutrients that are essential for the production of RBC. However, their reign does not always result in "blood increase," and the need to hematinics depends on a number of factors, especially the make-up of horse diets overall.
I am sure that many of you are aware of the current excitement in human athletics relating to the use of doping agent erythropoietin (EPO). EPO, the hormone pro-introduced by the kidneys, stimulates RBC production.
With the advent of genetic engineering, human EPO became commercially available and, inevitably, the human athlete regarded these drugs as a means to improve performance. We also know that the EPO has been used on horses, and this time there was concern among racing authorities about the illegal use of these drugs (ie, doping) in racehorses.