If you haven't brought any new chickens in recently, and you haven't moved them to a new coop recently- you probably do not have coccidia. It is from exposure to the organism in contaminated soil or feces. Maybe a wild bird could bring it (or a new strain in), but if your birds are older- they likely have run across coccidia before and are already immune. It causes diarrhea and depression, but not head shaking and gagging.
If they were all fine, and did not have access to oyster shell- then you added it and they ate a huge amount- they could impact on it I suppose. Their crop or further on down could be impacted. Can you feel their crops?
Your comment on guessing about antibiotic dose and vitamin dose is odd- what are you doing? If you have something from a pet or feed store, it should have directions. If you have a human drug left over from something else- you should quit it, as if you are giving them a sub theraputic amount you are contributing to resistant bacteria in the world, or possibly overdosing them.
My recommendation when someone has multiple sick birds with sudden and severe respiratory signs would be to take one (the sickest) to a knowledgeable vet and let them sort it out. Or if you are really serious about getting the facts (and cheaply!)- call your state vet or local poultry extension person (if you are in the US), most states offer a cheap or free necropsy- they are doing disease survey for influenza and newcastles- but they will also tell you everything wrong with your bird (bacteria, viruses, parasites). Be prepared to cull one and send it to the state lab, or allow someone to come collect a bird if they offer that service.
If they were all fine, and did not have access to oyster shell- then you added it and they ate a huge amount- they could impact on it I suppose. Their crop or further on down could be impacted. Can you feel their crops?
Your comment on guessing about antibiotic dose and vitamin dose is odd- what are you doing? If you have something from a pet or feed store, it should have directions. If you have a human drug left over from something else- you should quit it, as if you are giving them a sub theraputic amount you are contributing to resistant bacteria in the world, or possibly overdosing them.
My recommendation when someone has multiple sick birds with sudden and severe respiratory signs would be to take one (the sickest) to a knowledgeable vet and let them sort it out. Or if you are really serious about getting the facts (and cheaply!)- call your state vet or local poultry extension person (if you are in the US), most states offer a cheap or free necropsy- they are doing disease survey for influenza and newcastles- but they will also tell you everything wrong with your bird (bacteria, viruses, parasites). Be prepared to cull one and send it to the state lab, or allow someone to come collect a bird if they offer that service.
