These chicks are 2 days short of 3 weeks of age. Note the advanced feathering (please forgive the tragic pen floor, but it rained unexpectedly last night)! Actually you should have seen them a week ago as then the advancement was more obvious.
Their parentage has a little to do with the amount of feather, but not everything. The father was meat hybrid x white leghorn; the mothers were a mix of commercial layers (black, white and red). While both parent birds could be expected to mature quickly, the feathering on these birds is quite advanced for such a young age.
Now as it happens, these birds have been raised with more kefir in the mix than usual. This is because I bought a new kitchen chopper just for processing sprouts etc for chick food, and for the machine to work the mix must be fairly wet.
The benefit of doing things this way is that I can mix up the adult feed, keep a bit leftover, bring it inside and add kefir and sometimes extra soy meal to make it higher in protein (and easier to digest) for the little ones. I'll admit the extra liquid caused a couple of cases of pasting (unusual otherwise) but all were fixed, and the benefit of quick feathering has been enormous.
I'm pretty convinced that the extra (100% natural) methionine in soured milk has caused these chicks to grow faster and feather earlier than usual. What a nice byproduct of feeding only natural vitamins!
Now to shift the chick tractor so the poor things aren't standing on wet soil!