Hi Sue,
It can be most alarming seeing your birds practically oven ready! But it's a natural proccess, so try not to worry too much.
There are a few things you can do to help them through their first moult and make it a little easier on them.
Firstly, it's only like a dog moulting, only with more hair than feathers you don't notice it as much, a feather will take longer to appear than a hair.
Moulting effects all birds differently, some sail through it, others can get really miserable and seem lethargic, again, all normal. No one is the same!
Time of year is mostly effected by when the bird was hatched, the later they were hatched, the later they will moult, breed also has a part to play, hybrids sometimes don't moult for two years, they have been 'engineered' this way to produce more eggs. Some may moult from their first year.Again, normal.
Almost all birds will stop laying, and cockerels will be infertile, they can really only do one thing at a time, and should be allowed to moult, stop laying and filling eggs naturally, and not forced to do both. It takes so much out of their bodies to do either lay and moult, that they can really do just one.
Growing a new coat of feathers takes alot of protien with a feather being mostly protien (Kerotin) that it sometimes helps giving a slightly higher preotien feed such as growers pellets rather than layers. It certainly won't hurt your birds, and helps them get through it quicker, don't worry too much about them getting fat, whilst growing new feathers, all their energy will go into this rather than be stored as fat. And a small amount of extra fat going into winter won't cause any problems, it's naturally hard-wired into the bird to put on condition to see it through the harsher weather. They may prefere to eat grain rather than pellet, this too is normal, so a few handsful of mixed corn in the afternoon will fill them up and keep them warm through cold nights, also helping to provide extra protein for feather growth. Try not to feed it at the same time as their pellets, as they are a balanced feed compound and the birds will naturally pick out the corn leaving the pellets, and so make them lack other essential vitamins. But most folks feed a bit of mixed corn late PM.
Codliver oil mixed with the pellet also provides an essential oil of omega3 to make new feathers glossy, and it's a good source of vit D too helping to utilise the absorbtion of calcium, another compound of feathers.
A dry warm place is welcomed too for protection from cold wind and rain, although straw isn't ideal unless you change it regularly and don't allow it to become damp and mouldy as spores develop and cause respiritory problems.
ACV with crushed garlic or garlic powder added to the water is a great natural way of preventing snots and sneezes, it also helps birds to feather up quicker being a good source of protein and potassium.
A bit of TLC, and a few high protein treats fed sparingly won't hurt your birds at all, the key word here is 'sparingly'.
I have also had birds hatched early this year who have begun to moult, normally they don't have a full moult until their second year, most strange, but hey, chickens are very strange little creatures, and only do what they want to do!
Neck moults can happen at any time, and the normal contributer to this can be stress, moving to new homes can trigger one, or a bath getting ready for a show! (most annoying!)
Most birds moult in sections until they have replaced all their old feathers with new ones, it can take anywhere from a few weeks, to three months to complete!
Hope this has helped.
JubesXX