Fendabazole Withdrawl Period


5 Years
Sep 18, 2014
Hi all, I have reviewed the past posts on deworming laying hens with various anthelmintics that are not labeled for laying hens. I have had free range laying hens for quite a while and have not had too many internal parasite issues until this year....the dreaded round worm. I have had several conversations with two veterinarians about using non-labeled for laying hen deworming products and both have advised against it since studies have not been done to show that dewormers do not systemically enter the ovum and potentially be in every egg that is laid after using chemical dewormers.

I do sell my eggs so I am concerned about the undocumented withdrawl time for fendabazole. I tried Rooster Booster daily in their feed mixture for 3 weeks. I am on my second round of this product after a 10 day rest period and while I have seen some improvement in egg production, I still have some pasty rear-ends. While I think this product may work for smaller flocks, I have 35 hens and they free range over the entire farm. They are eating the Rooster Booster pellets but I don't think the product is effective in ensuring each hen gets the proper amount needed and it really is just an antibiotic. So I am questioning its effectiveness.

I use ACV in drinking water for all farm animals. I do not believe in using DE as this kills beneficial insects as well as the bad ones, so that product is out and not shown to be an effective internal parasite control method anyway.

So what is consensus for withdrawl period for Fendabazole? I am ready to try this route and see if I can knock out the round worms. I was going to use 2.5 TBLS of Liquid Safeguard per gallon of drinking water.


Cows, Chooks & Impys - OH MY!
13 Years
Nov 9, 2007
SW Arkansas
Two weeks. Albendazole (Valbazen) is what I have always used and what my vet recommended. Fenbendazole and Albendazole would be "cousins".
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Spreadsheet Queen
BYC Staff
Project Manager
Premium Feather Member
8 Years
Jun 24, 2012
The Golden State
Wormng orally is the best way to worm, but if you can't do that, you might be better off mixing the wormer in their food because laying hens drink way more water than non laying hens and roosters. For treating roundworms and cecal worms with Safeguard I use 50mg/kg, which is 0.5ml per 2.2 pounds. To figure out the dose for a flock you can you this formula:

Estimated weight of flock in pounds, divided by 2.2, times 50, divided by 100 = the amount of Safeguard to put in their food.

Example using 40 six pound hens (240 pound flock)
240/2.2 x 50/100 = 54.54ml

Valbazen would be a better choice as it requires less and will treat more worms with just one dose. Same formula as above can be used, just use 20 instead of 50 and 113.6 instead of 100.
240/2.2 x 20/113.6 = 19.02ml



Premium Feather Member
12 Years
Nov 27, 2008
Glen St Mary, Florida
There's usually a 14 day withdrawal period after using fenbendazole. I havnt seen anything to the contrary.
Putting liquid fenbendazole in water is ineffective. It doesnt mix well and settles to the bottom.
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