Is it usual for a retired race horse to gain a lot of weight the first month?

It is usual, race horses are on strict diets. When they start eating regular oats and hay, they gain weight. I use to ride an ex racehorse, and she gained a lot of pounds very quickly.

Please Stephanie if you are going to base your answers on an ill informed prejudice then don't answer until you grow up. RACE HORSES ARE NOT MALNOURISHED !!! In fact they are some of the best feed horses in the world. Would you consider Lance Armstrong malnourished because he was taut and fit while racing?? Of course not. And like Lance, when a horse stops racing the pounds start to add on. I am sick of people knocking racing because they mainlined Black Beauty as a child.

it is usual. most race horses are malnourished (to they can run faster) so he is just gaining weight to be his normal size of a regular horse. and especially if theyre feeding him good.