Coops,

What weight is your race dog and is he stocky in the shoulders or lean?

Some dogs can be like that though, i had a bitch who looked at food and you could see the weight gaining.
lol

Exercise routine is generally 1 x 440m free gallop up a straight track which they generally fly up. 1 x 5 minute swim (or a gallop, depends on weather) then a race or trial around the circle.

If the boy is having a bit of weight trouble, after the race do you feed the normal dinner feed? If so try boiling up 400gm beef (try and scoop out some of the excess fat that will rise to the top) as well as half a cup of pasta and 1/4 cup of rice. Add that to the vegies and itll make a nice hit stewy dinner for em.
Great for their system after a race ad the less fat is good as theyre stomachs settle well for the night.

Also for losing a bit of weight, cabbage in their dinner can help. Not too much of course but if u finely chop/slice some some and just put a little bit in the boys dinner every second night, it may help.

Mine also get a 1hr walk daily if thats any help either.