Piperazine is no longer available for chickens, and only kills some roundworms anyway. You will want to use fenbendazole, and dosage and days to be treated varies, depending on what you are treating. And to know what's actually there, have a fecal run at your veterinarian's.
I think @Wyorp Rock has dosage information for fenbendazole.
Mary
I think @Wyorp Rock has dosage information for fenbendazole.
Mary