Blood cells of a horse

I learnt from an article of one ex-trainer who told us that trainers are used to extract the blood of a horse to vertify if she is in a good condition (form) before they place bets on
her.  Sometimes, through tough training, as a normal horse fan, he can't tell if the
training has already raised the form of a horse  ready to win the race unless  a horse's red blood cells are increased and white blood cells are eliminated. HKJC has never published such information to all horse fans. Do any brothers have more information on this area?