What does it do to a laying or molting hen. I know you can't eat the eggs for a safe period? can someone explaine What is does to chickens during this period?
Worming with valbazen or safe guard
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I'm not sure exactly what your question is. Withdrawal period depends on which dewormer you are using, you would need to confirm that period by reading your label or contacting the maker of the product. As to "what does it do to a laying or molting hen", it should eliminate most worms present. Are you asking if it is harmful or why a withdrawal period? Generally it takes a certain amount of days for until drug residues to become an "acceptable level" in eggs or meat to be consumed by humans. If you are unable to determine the withdrawal period, then the suggested withdrawal period would be 30days.
Suggested withdrawal period is listed for the most common dewormers in the first link: