Greetings, I am Dr. Pat. I have worked with birds for many years. I will do my best to help you.
Either the antibiotics were ineffective (OTC medications do not work, can cause calcium deficiency, and are immune suppressive) or you are dealing with something that is not a bacterial infection. With several deaths you have to be worried about viral infections, parasites, toxins (ingestion of things such as lead shot, slug bait, insecticide, poisonous plants). This time of year you have to consider emergence of toxic weeds as they avidly graze any new growth. Inadequate feed can complicate matters; if you are feed ing chicken feed, it is inadequate for gees and they should be on goose-specific crumbles as well as free grazing.
The problem you have here is to find out what exactly is the cause. There is nothing specific in what you describe, quite literally 100 different diseases can have the same presentation. Luckily there are labs that work with small producers and an start diagnostics for a very reasonable fee.
She is in very serious trouble, and needs local veterinary attention. These signs are of a very sick bird, and not specific to any one disease. And that means it is not fair to you or her to guess, there are so many possibilities.You are going to need local help on this, and a scientific and solid diagnosis to find safe and effective treatment.
You can examine the bird thoroughly again, including opening the mouth and having a good look in there for mucus, redness, masses or anything else unusual. You can take the temperature gently with a rectal thermometer. Anything above 105F/40C is significant. Palpate the tummy for an egg, fluid, lumps or anything else. Check all the joints for swelling, pain, and mobility.
Move the bird indoors to a pen, box or carrier with soft towels or hay in the bottom, no perch, and food and water in low bowls that can be reached easily. Keep her partially covered, warm and quiet.
Do not try to force food or water. You can offer warm cooked rice, pancakes, cornbread, grapes, melon, greens in addition to normal food.
I know it is expensive, but you may not have many home options, because the first thing you need a vet for is to find out what is going on. Treatment is only as good as the diagnosis. If you call around, you may find a vet to work within your means. We certainly try to do our best in my clinic.
She needs to see an avian/poultry-experienced veterinarian
ASAP for complete examination, diagnosis and appropriate treatment. Checkhttp://chickenvet.co.uk/http://poultrykeeper.com/poultry-vets-uk/poultry-veterinary-practices-services-uk/
The expense for this is going to be a lot less than inefficient, ineffective, dangerous treatments, guesswork, and loss of the flock. Many states/governments have poultry diagnostic labs that charge very reasonable fees to test for common diseases. In the UK, check: http://chickenvet.co.uk/lab/index.aspx
If this were my patient, I would start with complete fecal analysis and direct smear, for multiple parasites; bacterial culture and sensitivity of the feces and choana. Depending on the case I might do a fungal culture. Routine blood work is necessary to rule out other issues. I would very likely order a number of DNA tests for poultry viruses as well. If they have been exposed to metallic objects a radiograph may be helpful to confirm ingestion of things such as lead shot. Generally I start them out on calcium injections, tube feeding, sc fluids, basic antitoxicants, antibiotics as indicated by the tests (I use antibiotics that are injectable).
Pet/feed store medications and home remedies are harmful, ineffective, immuno-suppressive, and make them much worse and may interfere with the veterinarian's diagnosis and treatment. Do not use them.
The flock should be on a high quality pelleted diet with extra greens/pasturage. Of late, I have been recommending TOP pet bird pellets (TOP http://totallyorganics.com/t-pellets.php
) as they are more appropriate for the pet goose. Overcrowding, cleanliness, proper water, environmental temperature, humidity, ventilation, photoperiod, and toxic exposures should be addressed.
You need to check for fly and mosquito access, as they can carry certain diseases (eg several newly emerged diseases in the UK), and check for external parasites. Mites, lice and fleas (in some areas, ticks) can contribute to over-all health issues, anemia, and disease transmission.
She may need injectable antibiotics, calcium and many other medications. Act quickly and good luck.