Hi
@bugawk
I'm sorry to hear about your hen.
I agree with
@theuglychick 9years old is impressive....even more impressive you still have one alive from a 2002 hatch - we should be getting advice from
you!
I don't see any harm in the medicated chick starter if you are going to give it for a short period of time. The Manna Pro usually comes in a small bag, so once you're done with that switch to regular chick starter or a flock raiser.
I agree - with her age, it could just be "old age" that is causing most of her symptoms. Her eyesight may be failing or she may be developing some cataracts (yep, chickens get cataracts like we do). The head movement sounds possibly neurological, but if she is having trouble seeing it could be some sort of compensation - moving the head to see better(?). You can try adding extra poultry vitamins that contain Vitamin E and A to see if those make a difference. Check her over for lice/mites as suggested - a Permethrin based poultry dust or spray is good. You may want to look at her ears to make sure there's no mites, infection or discharge - this can make a chicken off balance and have funny head movement too.
Since you separated her and she is now eating (She can easily get to food/water)- I suspect she may have had a bit of trouble getting to or finding the food/water - this would be another reason to suspect vision problems.
I hope she starts to improve now that she is getting the food/water. Age, heat and not eating/drinking well enough may have just overwhelmed her.
Keep us posted.