You're right, sulfatrim is an antibiotic, actually it is a combination of two antibiotics sulfamethoxazole and trimethoprim. Sulfa drugs are sometimes used to treat coccidiosis.@Mrs Light Sussex She was treated with sulfatrim which is for the treatment of the cocci protozoa (which I presumed was an antibiotic, perhaps rightly or wrongly). She was one of 11 in the same pen who were all dead or dying when she was brought to me to take care of. Her poop was runny, foamy and full of blood but tbh the vet held out such a poor prognosis for her that they just gave me the medicine and didn’t bother with any tests (presuming she would be dead before they came back and with the poop photo I took in and the fate of all the other chickens, coccidiosis seemed the likeliest ailment). The sulfatrim is for pigeons and bearded dragons but they said they couldn’t give her anything else as her weight was too low for the usual medicine they prescribe (she weighed 800g) and it was a weekend emergency appointment, so I was grateful to try anything. I took her on as a sympathy case really as I have no experience in hen keeping at all and they couldn’t find any one else daft enough to take her. Just to be clear, she doesn’t have it any longer, but she has failed to thrive since. She eats but not like my next door neighbors chickens, she drinks very little too and is incredibly fussy and won’t eat the usual treats chickens seem to love except for mealworms in water which I give her twice a day.
You may want to give her lots of nutri-drench, the nutrients it contains are absorbed before they reach the gut so that should help her regain her strength and then appetite.