It is not uncommon for them not to eat or drink at first.
When people pick up their animals from surgery, we tell them to offer a little bit of water early evening, and wait. If they hold that down (some can get sick with vomiting), then, they can offer a small amount of food. If they don't eat or drink, don't worry.
The day following surgery, they ususally don't eat or drink much either.
If you have any concerns, please contact your vet.
Sabrina Jay JeSaJay's Boxers
MidWest Boxer Rescue/Mo-Kan Boxer Rescue http://www.midwestboxerrescues.com