I was thinking about this last evening...
If it is an electrolyte vitamin pack... I would skip the electrolytes
unless he has been off water or had diarrhea... those can actually be overdosed... And do the vitamins at least a few doses directly to the beak... A standard amount of supplement in water that would be used on a bird who may not need them will NOT be sufficient to correct the issue.
Putting your general location in your profile can help to make more appropriate suggestions without having to ask first.
While I truly don't believe my recent case was vitamin deficit either... My recent hatches have had a lot of early quitters, plus some splay leg and bent toes... when I work very hard to maintain quality of my genetics. Upon researching... all indicators say vitamin deficit (other possibilities seemingly ruled out). So frustrating not knowing the whole truth.
Yes this is nature, but that doesn't make it easy. It's OK to be emotional about it.
Have you ever had a fecal float ran... internal parasite load could cause nutrient deficit even in a bird who eats the most. I won't worm without confirmation it is needed though... as only large round worms and tape worms will ever be seen in droppings and all others will stay in the digestive track and only their microscopic oocysts (eggs) will pass. Of course an external parasite load could also cause an issue, though I might expect that to be a bit more obvious, definitely check him for mites and lice if you haven't already. Night time with a flash light is best as it makes things much easier to see.
@rebrascora @Eggcessive are you able to offer suggestions here?
Please, if you can and don't mind... will you share what tests were performed in addition to the x-rays, what anti inflammatory they gave you, and why or how an anti inflammatory was to help the twisted neck if it was't an injury? Also was the specialist just an Avian Vet or something else? What was the specific med he gave you to help her and what vitamins and dosage they had you give for what age and breed of chicken? Had there been an actual reason for deficit in your case such as excess treats, bullying, or incorrect feed being used? And what did it cost you at the end of the day?
The support and info you offered is great!
But this information might be extremely helpful!
For me... if I suspect Marek's... euthanasia is a first resort not a last one. I need to protect the rest of my flock. But also more than that... even if it was JUST a vitamin deficit... in a bird with NO reason to have it.. that is genetic weakness... and since I breed... I don't want that bred into my flock... therefor... I believe even in the case of simple vitamin deficit... I will still cull. That would most likely mean eliminating the bird. But it took me many year to arrive at this conclusion, and I know it won't be the right answer for MANY. Unfortunately... with Marek's you can see recovery and think that wasn't it... but it may rear it's ugly head again... plenty of birds live WITH Marek's KNOWN to be effecting them.
Regarding a closed flock... Marek's cannot be passed to hatching eggs/embryos... so I consider incubator chicks and eggs safe to go out, presuming there was some sort of quarantine followed after collection. I don't personally feel like letting birds go with no symptoms is any different than letting birds go that have been vaccinated... as they can still be unidentified carriers, typhoid Mary's essentially... and in fact NO vaccinated birds welcome here. If you decide or confirm it is Marek's... you will have to decide when you bring in new birds if they will be vaccinated and quarantined long enough for it to take effect. Or if they will be unvaccinated and have to use whatever natural resistance they have on board. There was one gene identified that does create resistance to Marek's. Vaccinated birds can still get Marek's they are just less likely to get the tumors that push on the nerves that cause the symptom of paralysis. If you can't accept any loss... vaccinated might be the right choice for you.
Also... can you post a short video using youtube or vimeo and upload or link here so we can see? Maybe someone else has seen this and can offer more insight! It sounds neurological... but SO many things are and so many thing can look like Marek's that aren't! Any chance there was an auto oil spill, recent herbicide or pesticides applied, poisonous plants, rotting carcass, or rotting compost? I really try to look at the whole picture and not jump to conclusions.
Whether you choose to let adult birds off your pasture or not... It wouldn't be ideal. In the US... Marek's is not even considered report able since it isn't a threat to our food supply chain AND "is considered to be in EVERY poultry environment". With disclosure, so people can make their own choice... maybe.
I recommend not bringing in any birds that have ever been to pasture or broody raised to your place again. For me Marek's isn't nearly as scary as respiratory disease or some other things that can pass to the egg... But I am on a nonstop learning journey... even after more than 9 years there are still things I am learning and have so far to go. And my take may change with new information.
It was a difficult choice to process our own cockerels. But having the skill to help in the need of illness or injury and knowing I am doing so efficiently without adding more harm or pain especially when looking in the eyes of a bird that has been with us and we are attached is quite a blessing. I'm thankful for every day and every life! It doesn't make you cold... it basically brings me full circle in understanding how it is ALL interconnected. More aware of my personal consumption and I am humbled by the sheer amazement of what a miracle LIFE is!