National Organic Standards Board

Livestock Subcommittee

Proposal to Amend Use of Parasiticides in Organic Livestock Production

January 19, 2016

I. INTRODUCTION:

The use of parasiticides in organic production is strictly confined to emergencies. Parasiticides cannot be 

used routinely, but sick animals must be treated. Typically farmers bring clean animals into their herds 

or flocks, select breeds which have high resistance to parasites, and manage their land, especially 

pastures, in a manner which reduces the likelihood of parasite infection. If an increased parasite load is 

noted in fecal egg counts, farmers have a broad array of alternative treatments available. But when all 

else fails and animals are not doing well, the farmer, working with the veterinarian, may need to use one 

of the synthetic parasiticides on the National List.

At the present time there are three (3) substances on the National List which are approved for use as 

parasiticides for organic livestock: ivermectin, moxidectin and fenbenzadole. All three of these materials 

were reviewed in 2015 as part of the regular five-year Sunset process. At the October 2015 meeting in 

Stowe, Vermont, after considerable discussion and extensive public comment, it was recommended that 

all three parasiticides continue to be listed. Ivermectin was renewed with great reluctance owing to the 

recent research indicating serious negative impact of ivermectin on dung beetles in pastures. A 

Discussion Document was also presented at the October 2015 meeting seeking public comment on 

possible changes in use of the parasiticides. Extensive public comment indicates broad support to 

propose amendments on parasiticide use. 

All three materials have annotations and other language limiting usage. Such language was developed 

when ivermectin was first added to the National List. Recent data and information indicates that milk 

withholding and other restrictions could be modified in a manner which would be beneficial to the sick 

animal in emergency situations without jeopardizing the quality of the organic product. In conventional 

milk production, there is no withholding period for fenbenzadole or moxidectin. For organic production, 

there is a 90 day withholding period for organic milk. Synthetic parasiticides are prohibited in organic 

slaughter stock. Wool and fleece from organic fiber bearing animals, such as sheep, cannot be sold as 

organic even with a single use of a synthetic parasiticide. Organic regulations allowed moxidectin for 

internal use only. Fenbenzadole use requires a veterinarian order prior to use in organic production, but 

ivermectin and moxidectin do not have such a requirement. 

As discussed below, in 2007 it was agreed that the NOSB could use double FDA or Food Animal Residue 

Avoidance Databank (FARAD) withholding periods. 

This proposal recommends:

* That parasiticides continue to be prohibited in slaughter stock. 

* That the milk withholding period after treatment with fenbenzadole or moxidectin be changed from 

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

* That the listing for ivermectin remains as presently listed, with a 90 day withdrawal period. 

* That moxidectin be allowed for both internal and external use.

* 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 fenbenzadole be allowed without written order of a veterinarian. 

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Acronyms used herewith:

FDA – Food and Drug Administration

FARAD – Food Animal Residue Avoidance Databank

CVM – Center for Veterinary Medicine

NADA – New Animal Drugs Application – under the FDA

AMDUCA – Animal Medical Drug Use Clarification Act

NOEL – No Observable Effect Level is used by the FDA, CODEX etc. 

NRP – National Residue Program

ADI – Adult Daily Intake

MRL – Maximum Residue Limit

TR – Technical Report

Trade names—examples: 

Fenbenzadole: Panacur, Safeguard

Ivermectin: Ivomec, Primectin

Moxidectin: Cydectin

II BACKGROUND: 

In October 1999, the NOSB voted on three parasiticides for inclusion on the National List. Only 

ivermectin had sufficient votes be added to the List. The votes were: Ivermectin 8-3-0, Fenbendazole 5-

6-0, and Levamisole 0-11-0. 

In April 2004, the NOSB voted to add moxidectin to the National List by a vote of 11-1-1-1. The 

annotation, “for control of internal parasites only,” was included for moxidectin for the given reason 

that, “There is much less chance of any kind of contamination if it is used for internal parasites versus 

external“. Moxidectin was added to the National List in 2012 (77 FR 28472).

In December 2007, after much public comment and consultation, the NOP agreed that the NOSB could 

require double FDA withdrawal times, or double Food Animal Residue Avoidance Databank (FARAD) 

times (when appropriate), on a number of livestock materials: 

As a proposed compromise to satisfy the intent of the NOSB, many commenters suggested that 

USDA should consider amending the annotations of Atropine, Butorphanol, Flunixin, 

Furosemide, Tolazoline, and Xylazine by establishing extended withdrawal periods, calculated 

using withdrawal times from the Food Animal Residue Avoidance Databank (FARAD).The FARAD 

is a National Food Safety Project administered through the USDA Cooperative State Research, 

Education, and Extension Service. It is a system designed to provide livestock producers, 

extension specialists, and veterinarians with practical information on how to avoid drug, 

pesticide and environmental contaminant residue problems. FARAD is a repository of 

comprehensive residue avoidance information. It is also sanctioned to provide ‘‘withholding 

period’’ (also known as withdrawal period) estimates to the U.S. Pharmacopeia-Drug 

Information (USP–DI) Veterinary Medicine Advisory Committee. Commenters suggested that 

USDA account for an extra margin of at least double the withdrawal times of FARAD to safely 

capture the intent of the NOSB. USDA agrees with the position stated in the comments... 

Based on public comment, USDA consulted further with the FDA, concerning the ability to 

extend the withdrawal period on these approved drugs. Based on our consultations, USDA 

agreed to clarify the rationale for extending the FDA established withdrawal period. Secondly, 

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USDA agreed to clarify the language used to authorize the use of the substances by indicating 

the extended withdrawal periods (at least two-times that required by the FDA) were only 

relevant for use of the substances under the NOP regulations. Therefore, to clarify our rationale 

for extending the withdrawal periods established by the FDA, we acknowledge that this 

determination was not based on scientific research or risk assessments. The decision to extend 

the FDA withdrawal periods (or any other withdrawal period) for the use of Flunixin and 

Furosemide (and other substances) was based on consumer preference and the 

recommendations of the NOSB. FDA exercises full responsibility for determining and enforcing 

the withdrawal intervals for animal drugs. No food safety arguments are used or implied to 

support the use of extended withdrawal periods authorized under the NOP regulations. Rather, 

we determined that extended withdrawal periods are more compatible with consumer 

expectations of organically raised animals. (72 FR 70479)

In May 2008, Fenbendazole was approved by the NOSB for addition to the National List by a vote of 14-0 

and added to the National List in 2012 (77 FR 28472). The Withholding period was the same as for 

Ivermectin.

Three Technical Reports are relevant for this proposal: A 1999 TAP (fenbendazole, ivermectin); a 2003 

TAP for moxidectin; and a June 2015 Technical Report on all three parasiticides (fenbenzadole, 

ivermectin and moxidectin) requested by the Livestock subcommittee as part of its Sunset Review of 

these parasiticides. 

In 2015, all three parasiticides were reviewed as part of the regular Five Year Sunset Review. At the 

October 2015 NOSB meeting in Stowe, Vermont: 

• Moxidectin was recommended for continued listing on a Motion to Remove: 0 Yes; 12 No ; 2 

abstentions. 

• Fenbenzadole was recommended for continued listing on a Motion to Remove: 0 Yes ; 12 No ; 

2 abstentions. 

• Ivermectin was recommended for continued listing on a Motion to Remove: 6 Yes ; 4 No; 4 

abstentions. 

In addition a Discussion Document on parasiticides was presented at the October 2015 NOSB meeting. 

This is discussed below in the Discussion section.

III RELEVANT AREAS OF THE RULE: 

The USDA organic regulations at 7 CFR part 205 describe required preventive health care practices and 

regulations for the use of synthetic parasiticides in organic livestock production: 

§205.238 Livestock health care practice standard.

(a) The producer must establish and maintain preventive livestock health care practices, including: 

(1) Selection of species and types of livestock with regard to suitability for site-specific 

conditions and resistance to prevalent diseases and parasites; 

(2) Provision of a feed ration sufficient to meet nutritional requirements, including vitamins, 

minerals, protein and/or amino acids, fatty acids, energy sources, and fiber (ruminants); 

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(3) Establishment of appropriate housing, pasture conditions, and sanitation practices to 

minimize the occurrence and spread of diseases and parasites; 

(b) When preventive practices and veterinary biologics are inadequate to prevent sickness, a 

producer may administer synthetic medications: Provided, that, such medications are allowed 

under §205.603. Parasiticides allowed under §205.603 may be used on: 

(1) Breeder stock, when used prior to the last third of gestation but not during lactation for 

progeny that are to be sold, labeled, or represented as organically produced; and 

(2) Dairy stock, when used a minimum of 90 days prior to the production of milk or milk 

products that are to be sold, labeled, or represented as organic. 

§205.603 Synthetic substances allowed for use in organic livestock production. 

(a) As disinfectants, sanitizer, and medical treatments as applicable.

(18) 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.

(ii) Ivermectin (CAS #70288-86-7).

(iii) Moxidectin (CAS #113507-06-5)—for control of internal parasites only. 

IV DISCUSSION:

Fenbenzadole, ivermectin and moxidectin are the only antihelmintics approved for use in organic 

livestock production. They represent two of five antihelmintic drug classes. Fenbenzadole is in the 

benzimidazole group and Ivermectin and Moxidectin are in the polyene group within the macroyclic 

lactone group. In organic livestock production they are never used on a routine basis, only in emergency 

situations. They are used in doses as indicated on the label, by body weight and species of animal, and, 

under veterinarian supervision can be used “extra label/off-label” (see detailed discussion below).

Parasiticide Uses: 

Fenbenzadole:

The US Food and Drug Administration Center for Veterinary Medicine and the US Department of 

Agriculture National Organic Program permit oral administration of fenbendazole in dairy cattle for the 

removal and control of lungworm (Dictyocaulus viviparus); brown stomach worm (Ostertagia ostertagi), 

barberpole worm (Haemonchus contortus and H. placei), small stomach worm (Trichostrongylus axei), 

hookworm (Bunostomum phlebotomum), threadnecked intestinal worm (Nematodirus helvetianus), 

small intestinal worm (Cooperia punctata and C. oncophora), bankrupt worm (Trichostrongylus 

colubriformis) and nodular worm (Oesophagostomum radiatum); in beef cattle (beef) for the removal 

and control of stomach worm (Ostertagia ostertagi ) and tapeworm (Moniezia benedeni); in goats for 

the removal and control of stomach worms (Haemonchus contortus and Teladorsagia circumcincta); in 

swine for the removal and control of lungworms (Metastrongylus apri and M. pudendotectus), 

roundworms (Ascaris suum), nodular worms (Oesophagostomum dentatum, O. quadrispinulatum), small 

stomach worms (Hyostrongylus rubidus), whipworms (Trichuris suis) and kidney worms (Stephanurus 

dentatus) and in turkeys for the removal and control of round worms (Ascaridia dissimilis) and cecal 

worms (Heterakis gallinarum). Fenbendazole is sold by Merck Animal Health as Panacur® and SafeGuard®. It is available in liquid suspension, as granules, as a paste and in blocks. Products are dispensed 

both by veterinarian’s prescription and over the counter, but must be used in organic production only 

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under veterinary supervision. For swine, turkeys, and wild sheep the NADA (141-144, 140-954, 136-116, 

131-675) for fenbendazole is for use in medicated feed only. Other uses for these animals are extralabel. 

Furthermore, the use of fenbendazole in medicated feed for domestic sheep in food production is not 

permitted by the FDA. (TR 2015, 284-302). 

Ivermectin: 

The US Food and Drug Administration Center for Veterinary Medicine and the US Department of 

Agriculture National Organic Program permit topical, subcutaneous and oral administration of 

ivermectin in cattle for the treatment and control of gastrointestinal nematodes: Haemonchus placei, 

Ostertagia ostertagi, O. lyrata, Trichostrongylus axei, T. colubriformis, Cooperia oncophora, C. punctata, 

C. pectinata, Oesophagostomum radiatum, Nematodirus helvetianus, N. spathiger, Bunostomum 

phlebotomum, lungworms: Dictyocaulus viviparous, grubs Hypoderma bovis, H. lineatum, sucking lice: 

Linognathus vituli, Haematopinus eurysternus, Solenopotes capillatus, mites: Psoroptes ovis (syn. P. 

communis var. bovis), Sarcoptes scabiei var. bovis, in reindeer for treatment and control of warbles 

(Oedemagena tarandi), in swine for treatment and control of gastrointestinal roundworms: Ascaris 

suum; red stomach worm, Hyostrongylus rubidus; nodular worm, Oesophagostomum species; 

threadworm, Strongyloides ransomi, somatic roundworm larvae-threadworm, Strongyloides ransomi, 

lungworms: Metastrongylus species, lice: Haematopinus suis, mites: Sarcoptes scabiei var. suis and ear 

mites: Otodectes cynotis, in american bison for the treatment and control of grubs: Hypoderma bovis 

and in sheep for treatment and control gastrointestinal roundworms: Haemonchus contortus, H. placei, 

Ostertagia circumcincta, Trichostrongylus axei, T. colubriformis, Cooperia oncophora, C. curticei, 

Oesophagostomum columbianum, O. venulosum, Nematodirus battus, N. spathiger, S. papillosus 

Chabertia, Trichuris ovis, lungworms: Dictyocaulus filaria and all larval stages of the nasal bot Oestrus 

ovis. Ivermectin is marketed by Merial, Inc. and other companies under a number of pharmaceutical 

labels. It is available as a drench, in liquid solution, for medicated feed, as a sustained release bolus and 

as a paste. Products are dispensed both by veterinarian’s prescription and over the counter. (TR 2015, 

303-321). 

Moxidectin:

The US Food and Drug Administration Center for Veterinary Medicine and the US Department of 

Agriculture National Organic Program permit topical, subcutaneous and oral administration of 

moxidectin in cattle for treatment and control of internal and external parasites, gastrointestinal 

roundworms: Ostertagia ostertagi, Haemonchus placei, Trichostrongylus axei, T. colubriformis, Cooperia 

oncophora, C. pectinata, C. punctata, C. spatulata, C. surnabada, Bunostomum phlebotomum, 

Oesophagostomum radiatum, Nematodirus helvetianus, lungworms: Dictyocaulus viviparus, cattle 

grubs: Hypoderma bovis, H. lineatum, mites: Chorioptes bovis, Psoroptes ovis, P. communis var. bovis, 

lice: Linognathus vituli, Haematopinus eurysternus, Solenopotes capillatus, Bovicola(Damalinia) bovis 

and horn flies: Haematobia irritans and in sheep for the treatment and control of Haemonchus 

contortus, Teladorsagia circumcincta, T. trifurcata, Trichostrongylus axei, T. colubriformis, T. vitrinus, 

Cooperia curticei, C. oncophora, Oesophagostomum columbianum, O. venulosum, Nematodirus battus, 

N. filicollis, and N. spathiger. Moxidectin is sold by Boehringer Ingelheim Vetmedica, Inc. as Cydectin. It 

is available in liquid solution. Products are dispensed over the counter (TR 2015, 322-332).

Regulated approvals:

The use of fenbendazole for food animals is approved under six FDA New Animal Drug Applications 

(NADA) (TR 2015, Table 3). It is dispensed over the counter. The use of ivermectin for food animals is 

approved under nineteen FDA new animal drug applications. It is dispensed both by veterinary 

prescription and over the counter (Table 3). The use of moxidectin is approved under three NADAs. It is 

available over the counter. Moxidectin is in the polyene group and of macrolides and is not antibiotitic in 

its function. (TR 105-113). The approved FDA NADA numbers for the eight additional anthelmintics 

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approved by the FDA are provided in Table 3 of the TR. (TR 2015, 243-248).

“Off label/ Extra label use”. Once a NADA is approved, the FDA, under the Animal Medicinal Drug Use 

Clarification Act of 1994 (AMDUCA), can permit the use of the approved drug under specific conditions 

outside the designated or intended label use, e.g. use in species not listed in the labeling, use for 

indications (disease or other conditions) not listed in the labeling, use at dosage levels, frequencies, or 

routes of administration other than those stated in the labeling, and deviation from the labeled 

withdrawal time based on these different uses (FDA, 1994). 

This “off-label use” is only permitted in the context of a valid veterinarian-client-patient relationship 

and is limited to treatments when the health of an animal is threatened or suffering or death may 

result from failure to treat. 

A valid veterinarian-client-patient relationship is one in which: (1) A veterinarian has assumed the 

responsibility for making medical judgments regarding the health of (an) animal(s) and the need for 

medical treatment, and the client (the owner of the animal or animals or other caretaker) has agreed to 

follow the instructions of the veterinarian; (2) There is sufficient knowledge of the animal(s) by the 

veterinarian to initiate at least a general or preliminary diagnosis of the medical condition of the 

animal(s); and (3) The practicing veterinarian is readily available for follow up in case of adverse

reactions or failure of the regimen of therapy. Such a relationship can exist only when the veterinarian 

has recently seen and is personally acquainted with the keeping and care of the animal(s) by virtue of 

examination of the animal(s), and/or by medically appropriate and timely visits to the premises where 

the animal(s) are kept (FDA, 2015b). (TR 2015, 249-266)

For example, there is not an FDA approved use for fenbendazole in domestic sheep; however, it is used 

under veterinary supervision for this purpose. (TR 2015, 266-267)

There are some limitations for the AMDUCA including extra label use of an approved new animal or 

human drug by a lay person (except when supervised by a veterinarian). (TR 2015, 269-270).

The no observable effect level (NOEL) for parasiticides is determined by drug manufacturer and 

approved by the US Food and Drug Administration, Codex Alimentarius or other national or 

international standard setting organization. Protocols are provided by these federal agencies that detail 

testing and evaluation of the drugs. The NOEL is usually determined in an animal model. The NOEL 

values for fenbendazole, ivermectin and moxidectin are respectively, 0.7 milligram/kilogram body 

weight per day (mg/kg bd/day), 1.5 mg/kg bd/day and 10 mg/kg bd/day. The NOEL is used to determine 

the Adult Daily Intake (ADI) or the maximum residue limit (MRL). Withdrawal time is the time that it 

takes for the concentration in milk, eggs and meat that will be consumed by people to drop from the 

residue level at administration to the ADI, MRL, or safe level. (TR 2015 807-814)

Withdrawal periods for Milk: 

Fenbenzadole: FDA—zero withdrawal; FARAD does not include recommendations.

Moxidectin: FDA—zero withdrawal, although some products state not established; FARAD—Cows: zero 

withdrawal when administered topically, and not established when administered subcutaneously; 

FARAD—Goats one day for topical administration and up to 18 days if administered orally (drench) 

(based on weight of animal and dosage)

International Use and Restrictions (TR 2015, 432-507): 

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CANADA:

The organic standards of Canada prohibit the use of parasiticides with exceptions: If no alternative 

treatment exists a parasiticide may be administered under veterinary supervision as directed by the 

standard and mandated by law. Treated livestock with a withdrawal period equivalent to double the 

label requirement or 14 days, whichever is longer is still considered organic. Organic status for 

chronically infected animals is discontinued, but use in slaughter stock is allowed within limitations. 

The Canadian Organic Standard requires organic livestock operations to have a comprehensive plan to 

minimize parasite problems in livestock, including monitoring and emergency measures. Normally, 

parasiticides cannot be administered to meat, dairy or laying animals, but in emergencies, production 

operations can use them: (1) if parasites are detected, (2) under veterinary instructions, (3) with double 

the label withdrawal time or 14 days whichever is longer, (4) with one treatment for slaughter animals 

under one year and two treatments for older animals (requiring more treatments will lose organic 

status), (5) but dairy animals requiring more than two treatments lose organic status and require a 12 

month transition, (6) but dairy animals cannot be organic for slaughter, (7) and a dam may be treated 

during gestation, (8) and poultry flocks can be treated, but laying hens with more than one treatment 

per 12 months lose organic status and (9) the operator must provide a written action plan with 

amendments to the parasite control plan. 

CODEX:

The organic standards of CODEX Alimentarius, do not allow routine use of parasiticides, but they allow 

some provisions for emergency uses of parasiticides if preventive animal husbandry practices and 

natural remedies have been used and not found to be effective. Withdrawal periods should be double 

that required by legislation, with a minimum of 2 days.

IFOAM:

Like the Canadian standards, IFOAM organic standards require that use of antihelmintics will cause 

animal to lose its organic status – But an exception is allowed when livestock are treated with synthetic 

parasiticides the required withdrawal time is not less than double the withdrawal period required by 

legislation, or a minimum of 14 days, whichever is longer. And use in slaughter stock is allowed within 

limitations. 

The International Federation of Organic Agricultural Movements (IFOAM) Exception states that an 

animal can retain its organic status if the operator can demonstrate treatment is in compliance with 

IFOAM preventive animal husbandry practices, and natural and alternative medicines and treatments 

are unlikely to be effective to cure sickness or are not available to the operator, and the chemically 

synthesized allopathic veterinary medical products or antimicrobials are used under the supervision of a 

veterinarian, withdrawal periods are not less than double the withdrawal period required by legislation, 

or a minimum of 14 days, whichever is longer. The exception is granted for a maximum of three courses 

of remedial treatments within 12 months, or one course of treatment if the productive lifecycle of the 

animal is less than one year. (TR 2015 486-494)

EEC: 

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The European Economic Community states that preventive, routine use of parasiticides is not allowed 

but in the case of a sick animal needing immediate treatment the withholding period is double the 

withdrawal. And use is allowed in slaughter stock.

JAS:

The organic standards of Japan do not specify which parasiticides may be used. The withdrawal period is 

2 days prior to slaughter for foods, milk or egg collection or twice the period of drug withdrawal. Use in 

slaughter stock is allowed.

NOP: Does not allow for use in slaughter stock, and this proposal does not recommend any changes 

to this prohibition.

Alternatives:

There are many natural alternative parasiticides being used in organic livestock production today. 

Natural parasiticides include homeopathic remedies, diatomaceous earth and many herbs with 

antihelminthic properties. Table 10 of the 2015 TR lists over 50 botanical and alternative de-wormers. 

The efficacy of most of these natural alternatives is not well documented, and more research is needed. 

However, there does seem to be a lot of potential for the development of effective natural parasite 

control systems in the future.

Livestock develop an immune response to nematodes and becomes resistant or tolerates them without 

signs of disease. Because young livestock do not have a mature immune system, they may not be able to 

mount an immune response upon infection. The same is also true for older and immuno-compromised 

animals. Worming with homeopathic and botanical remedies should begin strategically during the first 

autumn of life to accommodate the low body reserves expected with calves (Karreman, 2004). 

Homeopathic wormers are available commercially that satisfy the organic rule. These are available as 

veterinary preparations with valid labeling systems so that their use may easily be audited (Brunetti and

Karreman, 2006). Users of these remedies should be sure that the material has an appropriate potency 

and the source from which it was extracted is verified and correct. A list of natural wormers is provided 

in Table 11 of the TR. Herbal remedies with anthelminthic properties were commonly adopted and used 

as a part of traditional animal husbandry. Some have not been evaluated with modern techniques, but 

may cause toxic side effects, however in most cases they represent a good alternative to the use of 

synthetic drugs (Duval, 1997) (TR 2015, 828-840).

Brunetti and Karreman found that with proper pasture management, a good diet with plenty of forage 

for livestock and knowledgeable coaches to provide appropriate strategies for husbandry and treatment 

healthy animals can be sustainably raised without synthetic parasiticides (TR 2015 943-946). 

Public comment included many producers, all species of livestock, who consistently use alternative 

natural materials and plants, pasture and browse, who never use any synthetic parasiticides. 

Emergency use of synthetic antihelmintics is not common in organic livestock production. This proposal 

only relates to milk production, not to slaughter stock, and only in emergency situations.

Confusion in present annotation language: 

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There are some inherent contradictions and problems in the way the three parasiticides are listed and 

annotated on the National List:

1. Fenbendazole, which is considered the most environmentally benign, is annotated to require 

the “written order of a licensed veterinarian”. Ivermectin and moxidectin have no such 

requirement. That may lead producers to choose a potentially more environmentally 

detrimental parasiticide for convenience.

2. Moxidectin is annotated “for control of internal parasites only.” However, moxidectin is widely 

used as a pour-on in conventional livestock production, and when used in that form for control 

of external parasites it is also a de facto control for internal parasites. Moreover, as mentioned 

above, the annotation “for control of internal parasites only”: was apparently written based on 

incorrect information on the half-life of moxidectin in the soil.

3. §205.603(a)(18) requires a 90-day withholding period for organic milk or milk products from a 

treated animal. There seems to be wide consensus that 90 days is much too long of a

withholding period, because 1) it may motivate a producer to withhold needed treatment of an 

animal because of the severe consequences of a 90-day withdrawal, and 2) fenbendazole and 

moxidectin have no milk withdrawal time for use in conventional production. There is no 

scientific rationale for the 90 day withholding for milk. The 90 days reflects a desire to assure 

consumers that organic standards exceed conventional use of restricted materials.

Based on public comment during the first posting of these materials, in fall 2015 the NOSB posted a 

Discussion Document for public comment. The Discussion Document included the following questions:

1. Should the milk withholding period be modified for any or all of the parasiticides? If so, how 

many days for moxidectin, fenbenzadole and ivermectin? 

2. Should minimal use of parasiticides be allowed in organic slaughter stock such as is permitted 

under Canadian Organic standards with one treatment for slaughter animals under one year and 

two treatments for older animals (requiring more treatments will lose organic status)?

3. Should Sheep fleece and wool be allowed to be certified organic even if use of parasiticides was 

necessary at some time in the animal’s life?

4. Should use of Moxidectin be changed to allow both internal and external use?

5. Should use of parasiticides be allowed only under Veterinarian advice?

Public Comment:

Considerable public comment was received from a broad range of stakeholder groups and producers. 

To summarize public comment: 

* There was strong support to reduce the withholding period for milk following use of either 

fenbenzadole or moxidectin. Recommendations, based on science and research, suggested adoption of 

a withdrawal period of between zero days and 14 days as opposed to the present 90 days.

One large dairy stated the following: “We support the NOP’s consistent position of an organic milk 

withdrawal period of twice what is required by the...FDA and/or...FARAD for substances on the National 

List. However... Fenbenzadole and Moxidectin have no FDA required milk withdrawal interval and 

therefore organic dairy livestock treated with either of these substances should have milk requirement 

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withdrawal of zero days. Three other commenters also suggested zero withholding and one researcher 

commented that science indicates that small ruminants metabolize fenbenzadole even more rapidly 

than large ruminants. Research presented as part of public comment indicates Fenbenzadole in blood 

samples peaks at 7 hours and is gone from the blood in 72 hours. 

Veterinarians, consumer organizations, a trade organization, individual producers , certifiers, an 

inspector association, and dairy groups all supported reduction of the withholding period based on 

science and the FDA and FARAD.

* There was no support for reducing withholding from 90 days after treatment with ivermectin based on 

science and FARAD. Some commenters suggested the need to prohibit ivermectin treatment for 

lactating cows. 

* One certifier (Western US) noted that synthetic parasiticides are rarely used in dairy production. 

Several producers stated that they never use parasiticides.

* There was widespread public comment to remove ivermectin completely from the National list 

especially in light of recent science indicating the negative impact of ivermectin on dung beetles in 

pastures. However, some producers, notably small ruminant producers, urged that ivermectin be kept 

on the list at present for the following reasons: the fact that ivermectin is well known; has been allowed 

for the longest time; is commonly available without prior veterinarian advice or prescription; lack of 

experience of use of fenbenzadole. Veterinarians and a large dairy producer group recommended that 

ivermectin be prohibited for use on lactating cows. Since parasiticides, if used, are typically given to 

young stock, several public commenters requested that NOSB consider an annotation to state – 

Ivermectin- not for use in dairy animals of breeding age or older. Other commenters noted that because 

ivermectin is ONLY used in an emergency and not on a regular basis, dung beetle impact on organic 

pastures will be minimal.

* There was strong support to allow both external and internal use of moxidectin from individual dairy 

producers, larger dairy organizations, certifiers, an inspector organization, a trade group, and 

veterinarians. One certifier commented that the present annotation for internal and not external use 

makes verification difficult. A large dairy commented that moxidectin for both internal and external use 

is particularly critical in the Southern US states.

* There was little support for possible adoption of allowing parasiticide use in slaughter stock as per the 

Canadian Organic Standards. Consumer groups and dairy producer organizations expressed concern that 

this would reduce consumer confidence in organic food. Certifiers and veterinarians also did not support 

this suggestion. There were two individuals who felt that use of limited parasiticides could be allowed 

for slaughter stock.

* There was strong support for certification of sheep fleece and wool even after use of parasiticides. This 

support came from farmer producers, certifiers, veterinarians, farm producers in the West, consumer 

groups, an inspector organization, and trade groups. We were reminded that this is not a new idea, but 

one that was proposed to the NOSB in 1990 and never taken up by the NOSB.

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* There was mixed response to requiring veterinarian advice before use of parasiticides. Certifiers like 

the idea that veterinarians would be involved as this would make the audit trail far easier to verify. One 

certifier stated: 

Overall we support an annotation update that requires veterinarian advice because it would 

clarify how producers should document the emergency necessity for treatment and provide for 

a clear audit. Currently parasiticides are “allowed for emergency treatment,” which requires 

that organic producers describe and provide documentation about how they determined that it 

was an emergency (fecal tests, animal condition, etc.)...A vet recommendation requirement 

would be more straightforward to document and audit than the existing 

annotation...but...situations also exist when a veterinarian may not be available to assess the 

situation quickly, such as when animals are in a remote location.

Most, but not all, veterinarians support requiring veterinarian advice prior to use of parasiticides. This 

would ensure that the right dosage of the most effective parasiticide is given to the various animal 

species. One large cow dairy organization stated that there was plenty of most of the parasiticides 

available without veterinarian advice. 

To quote one of the public comments: 

In preparing this proposal to recommend amendments to use of parasiticides, the NOSB must 

be very mindful that we need to remember that livestock producers are raising multiple species 

in diverse geographic regions facing diverse climatic conditions. 

V RECOMMENDATION: 

§205.238 Livestock health care practice standard.

(a) The producer must establish and maintain preventive livestock health care practices, including: 

(1) Selection of species and types of livestock with regard to suitability for site-specific conditions 

and resistance to prevalent diseases and parasites; 

(2) Provision of a feed ration sufficient to meet nutritional requirements, including vitamins, 

minerals, protein and/or amino acids, fatty acids, energy sources, and fiber (ruminants); 

(3) Establishment of appropriate housing, pasture conditions, and sanitation practices to minimize 

the occurrence and spread of diseases and parasites; 

(b) When preventive practices and veterinary biologics are inadequate to prevent sickness, a 

producer may administer synthetic medications: Provided, that, such medications are allowed under 

§205.603. Parasiticides allowed under §205.603 may be used on: 

(1) Breeder stock, when used prior to the last third of gestation but not during lactation for progeny 

that are to be sold, labeled, or represented as organically produced; and 

(2) Dairy animals stock, when used a minimum of 90 days prior to the production of milk or milk 

products that are to be sold, labeled, or represented as organic, as allowed under §205.603. 

(3) Fiber bearing animals, as allowed under §205.603.

§205.603 Synthetic substances allowed for use in organic livestock production. 

(a) As disinfectants, sanitizer, and medical treatments as applicable.

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(18) 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. Allowed in fiber bearing animals, when used a minimum of 90 days prior to production 

of fleece or wool that is to be sold, labeled, or represented as organic. 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. 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. 

(ii) Ivermectin (CAS #70288-86-7)—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. 

(iii) Moxidectin (CAS #113507-06-5)—for control of internal parasites only 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. 

Sub Committee Vote:

1. That the strikethrough language be removed, and the underlined language be added at:

Section 205.238(b)(2) Dairy animals, stock when used a minimum of 90 days prior to the production of 

milk or milk products that are to be sold, labeled, or represented as organic. as allowed under 205.603. 

AND

205.603(a)(18) ....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 . 

Motion by: Jean Richardson

Seconded by: Francis Thicke

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

2. That the underlined language be added at:

 §205.238(b)(3) Fiber bearing animals, as allowed under §205.603. 

AND

§205.603(a)(18) ... Allowed for fiber bearing animals when used a minimum of 90 days prior to 

production of fleece or wool that is to be sold, labeled or represented as organic.

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Motion by: Jean Richardson

Seconded by: Francis Thicke

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

3. That the strike through language be removed and the underlined language added at:

205.603(a)(18)(i) Fenbendazole (CAS #43210-67-9)—only for use by or on the lawful written order of a 

licensed veterinarian. 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. 

Motion by: Jean Richardson

Seconded by: Francis Thicke

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

4. That the underlined language added at:

205.603(a)(18) (ii) Ivermectin (CAS #70288-86-7)—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. 

Motion by: Jean Richardson

Seconded by: Francis Thicke

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

5. That the strike through language be removed and the underlined language added at:

205.603(a)(18) (iii) Moxidectin (CAS #113507-06-5)—for control of internal parasites only 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 animals. 

Motion by: Jean Richardson

Seconded by: Francis Thicke

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

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