National Organic Standards Board

Livestock Subcommittee

Petitioned Material Discussion Document

Fenbendazole

August 16, 2019

Summary of Petition:

A petition requesting a revision to the annotation for Fenbendazole to expand the use to poultry. This 

petition requests an annotation to 7 CFR §205.603(a)(23)(i) to include laying hens and replacement 

chickens intended to become laying hens.

Background of Current Listing:

In May 2012, fenbendazole was added to the National List of organic materials for use in organic 

livestock, as specified in 7 CFR §205.603(a): 

Parasiticides—Prohibited in slaughter stock, allowed in emergency treatment for dairy and 

breeder stock when organic system plan-approved preventive management does not prevent 

infestation. Milk or milk products from a treated animal cannot be labeled as provided for in 

subpart D of this part for 90 days following treatment. In breeder stock, treatment cannot occur 

during the last third of gestation if the progeny will be sold as organic and must not be used 

during the lactation period for breeding stock. 

(i) Fenbendazole (CAS #43210-67-9)—only for use by or on the lawful written order of a licensed 

veterinarian.

In 2016 the NOSB recommended that the annotation for Fenbendazole be amended to include the 

following:

• That parasiticides continue to be prohibited in slaughter stock.

• That the milk withholding period after treatment with fenbendazole be changed from 90 

days to 2 days for dairy cows, and 36 days for goats and sheep.

• That fleece and wool from fiber bearing animals be allowed to be certified organic even if 

use of parasiticides was necessary at some time in the animal’s life.

• That fenbendazole be allowed without written order of a veterinarian.

The NOP issued a final rule with an effective date of January 28, 2019, with the following language:

Paragraph (a)(23)(i) is revised to read as follows: Fenbendazole (CAS #43210-67-9)—milk or milk 

products from a treated animal cannot be labeled as provided for in subpart D of this part for: 2 

days following treatment of cattle; 36 days following treatment of goats, sheep and other dairy 

species. AMS has reviewed and agrees with the NOSB recommendation that the annotation for 

fenbendazole be amended to clarify its use in organic livestock production.

In addition, paragraph (b)(2) of § 205.238(b) is revised and paragraph (b)(3) is added to 

§ 205.238(b) as follows: (b)(2) Dairy animals, as allowed under § 205.603; and (b)(3) fiber 

bearing animals, as allowed under § 205.603. AMS has reviewed and agrees with the NOSB 

recommendation that § 205.238(b) be amended to clarify its use of parasiticides for dairy 

animals and for fiber bearing animals.

NOSB October 2019 proposals and discussion documents Page 227 of 230
In the Spring of 2018 the NOSB recommended clarifying “emergency” for use of synthetic parasiticides 

in organic livestock production. The following language was recommended for a rule change:

Add this definition to 205.2

Emergency treatment to allow synthetic parasiticide use in livestock: A livestock emergency is an 

urgent, non-routine situation in which the organic system plan’s preventive measures and 

veterinary biologics are proven, by laboratory analysis or visual inspection, to be inadequate to 

prevent life-threatening illness or to alleviate pain and suffering. In such cases, a producer must 

administer the emergency treatment (§205.238(c)(7)). Organic certification will be retained, 

provided that such treatments are allowed under § 205.603 and the organic system plan is 

changed to prevent a similar livestock emergency in individual animals or the whole herd/flock in 

future years as required under §205.238(a).

Add this to § 205.238 (b)

(4) Organic livestock as provided in §205.238 (b) (1), (2), and (3) and only in the event of an 

emergency where management strategies have been proven insufficient to prevent or control 

parasites within the accepted threshold for specific parasites, age and species of the animal. 

These management strategies include but are not limited to, grazing systems and living 

conditions that prevent infestation and re-infestation, forage height diversity, use of allowed 

non-synthetic botanicals, biologics and minerals to maintain parasite levels below treatment 

thresholds, and could include monitoring and documentation of parasites through use of 

methods such as fecal monitoring and FAMACHA.

This NOSB recommendation is still pending NOP review.

Summary of Review:

The Livestock Subcommittee reviewed the petition seeking to add an annotation to fenbendazole to 

expand its use in laying hens and replacement chickens intended to become laying hens. The 

Subcommittee did not feel the need to request an update technical report (TR) on Fenbendazole since a 

TR was conducted in June 2015.

Many organic laying hens have meaningful direct access to the soil, and this is one area where birds that 

are truly out grazing the land are at a disadvantage compared to birds on concrete porches. With the 

shifting demand for eggs from hens with humane certifications such as Free Range or Pasture Raised 

production models requiring 2.0-108.9 square feet per bird of outdoor access, many laying hen flocks 

are seeing large internal parasite infestations. When birds are out grazing, they are scratching and 

digging in the dirt for worms and in return picking up intestinal parasites. When a chicken has intestinal 

parasites some of the issues include having lower feed absorption, increased mortality, parasite 

transmission into the egg, and disease transmission to the hens. 

Currently poultry producers sometimes use a diatomaceous earth product to help control intestinal 

worms. There are several concerns with this product including the amount needed to be ingested in 

relation to daily feed intake (non-balanced diets), worker and animal health hazards when using 

diatomaceous earth (respiratory concerns), and lack of efficacy to control severe parasite infestations.

If fenbendazole is added to the national list for laying hens and replacement chickens, it would be 

allowed only for emergency treatment when organic system plan-approved preventive management 

does not prevent infestation. Producers and certifiers would need to work together to define what an 

NOSB October 2019 proposals and discussion documents Page 228 of 230
emergency is for each producer. Examples include the discovery of internal parasites during routine 

posting or autopsy sessions of flocks, and/or observation of parasites in manure droppings. The 

Subcommittee feels strongly that fenbendazole should be used only in emergency situations and not on 

a routine basis.

Even though the current listing for fenbendazole for cattle, sheep, goats, and other dairy species

specifies withdrawal times, the Subcommittee does not intend to restrict the use of fenbendazole on 

poultry by specifying a withdrawal time. The FDA reviewed fenbendazole’s use as an approved animal 

drug and determined that it did not require a withdrawal time for poultry. “The data in study #S12173-

00-DWF-MET-PO show that total residues of fenbendazole in eggs of treated chickens at zero-day 

withdrawal are well below the safe concentration of 2.4 ppm for residues in eggs.”1

 

Use of the Substance:

• 200 mg of fenbendazole/ml for oral administration via drinking water

• Safe-Guard® AquaSol must be administered orally to chickens via the drinking water at a daily 

dose of 1.0 mg/kg BW (0.454 mg/lb.) for 5 consecutive days.

Conventional poultry producers typically administer fenbendazole to pullets (replacement layers age 0-

17 weeks of age) or before outdoor access is given to birds to ensure birds have no internal parasites

before starting egg production. When birds receive access to the outdoors they come into contact with 

soil and in turn come into contact with internal parasites. Many producers find the need to re-treat

their flocks after a period of time when birds have access to the soil and come into contact with many 

internal parasites. Organic producers will need to utilize preventative management practices defined in 

their Organic System Plan as a first line of defense for internal parasites and if those preventative 

practices fail, an emergency treatment of fenbendazole could be used to control internal parasites. 

Mode of Action: 

Fenbendazole binds to β-tubulin, inhibiting assembly of microtubules, resulting in cell and parasite 

death. According to the Merck Veterinary Manual, “The wide safety margin of benzimidazoles is due to 

their greater selective affinity for parasitic β-tubulin than for mammalian tissues.” (Merck, 2006)

Questions:

1. Is this material needed by organic poultry producers? If so, why?

2. Do currently allowed alternatives work to control internal parasites? And at what level of 

effectiveness? 

3. What are some of the “emergency” events that would trigger use of this product? And how would 

producers determine those events? 

4. Is there a concern with the 2.4 ppm residue of fenbendazole in eggs? Please submit information that 

supports this concern, or lack of concern.

1 https://animaldrugsatfda.fda.gov/adafda/app/search/public/document/downloadFoi/3083

NOSB October 2019 proposals and discussion documents Page 229 of 230
Subcommittee Vote:

Motion to accept the fenbendazole petitioned-material discussion document

Motion by: Ashley Swaffar

Seconded by: Sue Baird

Yes: 6 No: 0 Abstain: 0 Absent: 0 Recuse: 0

NOSB October 2019 proposals and discussion documents Page 230 of 230