I am giving some info that was told to me many years ago by my Veterinarian. New and more up to date info could be more correct today. I was told a dog could clear the water or fluids from and via it's kidneys in six hours after drinking.

So we took the water away from a dog at the 24 hour mark before weigh in, and let the dog drink water or broth at the 12 hour mark and the six hour mark before weigh in time. Dog was allowed to drink till it lifted it's head. No fluids past the 6 hour mark. J. Crenshaw said he gave fluids up to the three hour mark before weigh in.

On the feeding twice a day, never gave any solid food in the AM work out. The AM workout for me was a 2 1/2 mile walk out and back in. Was mostly to break boredom, bonding time with the dog, to keep the dog limber and work soreness out of the muscles. Gives the dog time to empty out his kidneys numerous times.

I gave a fluid drink similar to what Jack mentions, the fluid was not all water but strong Chicken or Beef broth in cold weather and a weaker broth in the hot weather season. Depending on the dog's weight, size, how wet it appeared to be and time of year could be 8 oz. to 16 oz. of fluid. Always at least 12 hours before the hard work out and the main solid feed.

Feeding a dog two solid meals a day in the type climate I live in may not work out so well. May be to hard to keep dog on weight or get a true weight. In much colder weather and higher altitudes two solid feedings a day may be necessary.

The feeding in Desert type weather is probably different even the best time to feed the dog and work the dog. JMHO am no expert. Cheers