I have had luck getting pullets by putting apple cider vinegar in the hens water. I had read this somewhere and it seems to work for me. It is also good for the hens and keeps the water cleaner. I am making no claims as I don't have many years of experience with it. I had 15 pullets and 5 cockerels on the batch I used it on this year. I don't remember the numbers from last year but it was similar. I stopped using it because I wanted more cockerels for the freezer.