You might also want to read the article on handfeeding to make sure your pet is getting enough food. Some people swear by OxbowHayCo´s Critical Care. Try fresh grass too. Small poops may also indicate dehydration so make sure your pet is getting adequate liquids.
What antibiotic is it (what dose is being administered)? Some pigs will lose appetite on drugs like baytril and should be switched to another drug.
Lynx, I know pigs will stop eating from malocclusion -- will they also stop drinking?
I would have an animal dentist give you a second opinion. Vets misss malocclusion often, even when looking for it.
Cornwes´s pig Kallie´s malocclusion was missed by a vet who insisted her teeth were fine. By the time her malocclusion was diagnosed by a better vet, scurvy had set in because she couldn´t eat enough food to give her adequate C. This is not an isolated case.
Stacia´s Dixon was checked by 2 vets before a third was found who actually understood how to plane the teeth. I think that was how it panned out, can´t remember all the details. Another pig I know saw 3 vets who missed the malocclusion. By the time he saw an animal dentist, it was too late, he couldn´t be helped and was euthanized.
Things to watch for in the examination:
Did the vet use a buccal pad separator?
Did the vet take xrays to look for signs of abscesses?
Did the vet feel the outside of the jaw looking for spurs?
Things to watch for in the pig:
Does he seem to work at chewing like he has something caught in his mouth that he is trying to unstick?
Is there exaggerated ear movement when he chews?
Is there discharge from the eyes or nose(can indicate an abscess)
Does he seem to chew to one side?
Are the front teeth even and lined up?
Does he eat at the same rate/speed the other pigs eat at?
Can he rip and tear?
Can he eat the peel as well as the apple from an apple slice?
Does he chew(carrots in particular) and let little pieces drop out of his mouth?
Does he pick up a pellet in his mouth and let it drop out again?
Does he show great interest in food, yet not eat?
Is he steadily losing weight?
Is he drooling?
Any one of these signs is reason for concern.