feeding chickens bread and bio yoghurt

how often can i feed them this without causing a problem. i feed them layers pellets and green stuff, they love the bread and yoghurt and i thought it would be a good way to tame them down even the shy one was really happy.

Firstly can I just say that all chickens need to "graze" at feed all day and not have meal times.  They are not like cats or dog, more like sheep or cattle in there feeding habits.

You probably know this but I just wanted to say  .

Anywho. 

Next

Do not feed bread to chickens, unless soaked in water as when it gets to the crop it can expand and cause compaction of the crop.

For a treat I would suggest split corn or meal worms.
A chicken will take your arm off for meal worms.
Not to many though as a fat hen does not lay and meal worms are high in energy and so is split corn.

............ i know that they can be used for crop impaction.

I have heard that as well but I have never tried it so I can not comment. It does seem a bit far fetched.

I do not know why you can not feed none coloured maggots to a chicken.  I am sure if the chickens came across them in the wild they would eat them.
Coloured maggots would be a definite no as you  do not know what is contained in the colouring and if it has been passed for human consumption.

I've read of people giving maggots[left over from fishing] and reckon its ok

I read on here to give chooks toast and marmite? Can't remember who said it?
They love it though.