sorry for not responding to you sooner--i only get to get on the internet pretty late at night most days, so the board tends to move faster than my ability to keep up with it. i apologize if any of the below is too basic:
synthetic epo and transfusing are both forms of blood packing/blood doping--they have the same goal, to increase the percentage of red blood cells circulating in the blood (the hematocrit level)--the more red blood cells you have, the more oxygen available and the better the aerobic capacity.
there is a test for synthetic (recombinant) epo (testing for natural epo is pointless since we all produce it, humans and horses). testing for blood packing via transfusion is harder--esp. if you pack with your own blood. there\'s an antigin test to determine if someone else\'s blood is present in your blood, a plasticizer test (that picks up the residual plastic in your blood from from the IV bag), and a reticulocyte test (which measures the ratio of new blood cells to old blood cells present in your blood). but there is no direct test for autologous (your own blood) transfusions.
in human sports, all forms of blood packing are illegal, i\'m not sure in horse racing, but it wouldn\'t make sense to prohibit epo for performance enhancement, if you don\'t prohibit all forms of blood packing, since the end result is the same.
a low red blood cell count would definitely have a negative impact on performance, and absent illness, the most likely cause is cessation of epo, after prolonged epo use (basically after a while on epo, your body stops making it on its own).
i used to be skeptical of epo having any effect on horses to be honest, because they are natural bloodpackers, like dogs)--the more horses exert themselves, the more epo their bodies make. with us, we only make epo when we are at rest; physical exertion uses up our epo. but as long as the hematocrit level is less than 60%, you get the benefit, without the viscosity problems (i.e.sludge blood). i have a feeling the most significant benefits are felt by the least talented horses, just like it is with humans. a naturally superior horse will only see marginal gains, but an inferior horse will see substantial gains.
one of the hallmarks of transfusing is sudden fevers for no reason--blood has to be handled just right, even if its your own, or it causes problems. there would be whole cycling teams exiting races en masse due to a sudden illness that affected the whole team at the same time, usually blamed on food poisoning (to which all of the other teams were immune) (teammates usually transfuse together on the same day--their blood bags are all handled the same way, so if one bag got a little too warm in transit, they all did...)
the crazy thing is that lasix negates the benefits of bloodpacking, because it cause dehydration, and dehydration increases blood viscosity, and oxygen delivery decreases as blood viscosity increases. so it must be a pretty sophisticated combination of lasix, bloodpacking, and and blood thinner administration.
