How do you know when to worm your chickens? My girls are alittle over 2 yrs. old and never been wormed. I know my egg production is down, but I just thought that was due to the time of year. All seem to be happy and healthy birds. So what are the symptoms that go along with chickens needing wormed? Or do you do it every so often just to be on the safe side. I bought some Valbazen just in case I needed it, they say it's pretty good and kills most all kinds of worms.