If he hasn't been eating, it's entirely possible that the fit he had was a seizure from hypoglycemia, which is low blood sugar, because that's fairly common after not eating.
It's good that you're taking him back on Monday, although I'll bet that if he eats the chicken and rice over the weekend, his blood sugar will be at an acceptable level by then. You do, however, need to get to the bottom of what made him go off his food to begin with.
Please let us know on Monday how you make out with him at the vet. Good luck to you.
He has had his back passage checked, but he does not like vets. We are having to bring him back on Mon, as he was so stressed. He will then be sedated. We have been told to feed him 4 times a day with chicken and rice
What else was done besides taking the dogs temperature?