National Organic Standards Board

Crops or Livestock Subcommittee

Petitioned Material Proposal

Zinc Sulfate

February 24, 2015

Summary of Proposed Action:

A petition has been received to allow zinc sulfate to be used as a footbath for control of foot rot 

in livestock, particularly dairy cattle, sheep and goats. Zinc, a trace element, is necessary for all 

living organisms. It plays in a role in many cell regulatory processes, including the innate 

immune response. Commercially, zinc sulfate is manufactured from zinc ore mined from 

underground or open pit mines. Zinc ore deposits are spread widely throughout the world. Zinc 

ores are extracted in more than 50 countries. China, Australia, Peru, Europe and Canada are 

the biggest zinc mining countries. Zinc sulfate is most commonly produced by the interaction of 

zinc salts and sulfuric acid. 

Foot rot is a contagious disease. Temperature and moisture play an important role in the 

transmission and invasion of the bacteria that causes the disease. Most outbreaks occur in 

seasons with high rainfall, warm temperatures and lush pasture growth. Infectious material may 

be transferred directly from the soil to animals. 

Foot rot is a significant cause of lameness in sheep, goats and cattle caused by the interaction 

of three bacterial species. Since the first identification of foot rot in sheep, cattle and goats 

several substances have been used for treatment with varying degrees of efficacy including 

ethanol, copper sulfate, formalin, and other materials. They vary in side effects and cost. 

However, most of the substances that are used are not included in the National List. Copper 

sulfate and zinc sulfate are two of the most accepted treatments and are comparable in efficacy. 

Zinc sulfate has proven particularly effective at controlling the bacteria associated with foot rot, 

and is sometimes used in combination with other materials, including copper sulfate. The 

combination of zinc sulfate with sodium lauryl sulfate (as an excipient) has proven to be more 

effective than zinc sulfate with copper sulfate. Aspirin (Salicylic Acid) is allowed for use in 

organic livestock production for health care use to reduce inflammation. Salicylic acid has also 

been shown to be effective in treatment of foot rot in dairy cattle. A combination of Australian 

Tea Tree Oil, Jojoba oil, Benzathonium Chloride, water, propylene glycol and emulsifiers 

(HoofmateTM) as a topical application has been used with some success in treating foot rot 

(Schivera, 2014). Literature mentions that peracetic acid and hydrogen peroxide foams are also 

used in the treatment and control of foot rot, although the efficacy of these treatments is 

controversial. 

Spent footbath liquids are typically discarded in the on-farm lagoon system and/or washed out 

with manure. Water from lagoons is then applied to agricultural lands, leading to concerns 

regarding the accumulation of the footbath active ingredients in soils. The potential for the 

accumulation of copper in the environment has led to serious concerns about continued use of 

copper sulfate as an ingredient in footbaths. Zinc sulfate has the potential to accumulate in the 

soil, but the bioavailability levels of zinc are dependent upon a number of factors including soil 

pH, soil aggregates and moisture levels, and therefore it is difficult to determine what level of 

zinc in soils would be considered toxic. Unlike copper contamination, excess zinc can be 

successfully removed from soil by planting sunflower and canola. 

Page 213 of 249
Request for public comment:

The Livestock subcommittee seeks input from the public regarding the effectiveness of 

alternative methods for controlling foot rot, including management practices, and the use of 

hydrogen peroxide, peracetic acid or other materials. Further, the subcommittee seeks 

feedback on whether the availability of zinc sulfate for use in organic livestock production would 

likely reduce the use of copper sulfate for treatment of foot rot.

Evaluation Criteria (see attached checklist for criteria in each category)

 Criteria Satisfied? 

1. Impact on Humans and Environment ☐ Yes ☐ No ☐ N/A 

2. Essential & Availability Criteria ☐ Yes ☐ No ☐ N/A

3. Compatibility & Consistency ☐ Yes ☐ No ☐ N/A 

Substance Fails Criteria Category: [ ] Comments: 

Subcommittee Action & Vote

Classification Motion: Move to classify zinc sulfate as synthetic 

Motion by: Tracy Favre 

Seconded by: Jean Richardson

Yes: 7 No: 0 Absent: 1 Abstain: # Recuse: # 

Listing Motion: Move to list zinc sulfate for use as a footbath only, at §205.603(b) of the 

National List, 

Motion by: Tracy Favre 

Seconded by: Calvin Walker 

Yes: 4 No: 3 Absent: 1 Abstain: 0 Recuse: 0 

 

Proposed Annotation (if any): For use as a footbath only

Basis for annotation: X To meet criteria above 

Approved by Tracy Favre, Subcommittee Chair, to transmit to NOSB February 24, 2015

Page 214 of 249
NOSB Evaluation Criteria for Substances Added To the National List - Livestock

Category 1. Adverse impacts on humans or the environment? Substance: Zinc Sulfate 

Question Yes No N/A Comments/Documentation (TAP; 

petition; regulatory agency; other)

1. Is there a probability of environmental 

contamination during use or misuse? 

[§6518(m)(3)]

X X Zinc sulfate has a particular mode of 

action in soils which makes it very difficult 

to assess regarding contamination levels. 

Soil pH, soil composition, moisture and 

other factors all affect the amount of 

bioavailability of zinc. 

2. Is there a probability of environmental 

contamination during, manufacture or 

disposal? [§6518(m)(3)]

X X Using good manufacturing practice, the 

likelihood of contamination from 

manufacture is unlikely. However, some 

less developed countries are less likely to 

have environmental controls on the 

manufacturing process.

3. Are there any adverse impacts on 

biodiversity? (§205.200)

X X Perhaps. See comments #1 above. High 

levels of zinc in the soil could have 

negative impact on soil organisms. 

4. Does the substance contain inerts 

classified by EPA as ‘inerts of 

toxicological concern’? [§6517 

(c)(1)(B)(ii)] 

X Zinc Sulfate is considered an inert, not 

listed as one of toxicological concern. It 

is also considered as GRAS by FDA and 

is used as a nutritional supplement.

5. Is there potential for detrimental chemical 

interaction with other materials used in 

organic farming systems?

[§6518(m)(1)]

X Can bind with other metals (particularly 

copper compounds) to form compounds 

less likely to degrade in soils.

6. Is there a toxic or other adverse action of 

the material or its breakdown products?

[§6518(m)(2)]

X X In some cases, and depending upon soil 

pH and other characteristics, zinc can 

change forms into those that are more 

persistent in the environment.

7. Is there persistence or concentration of 

the material or breakdown products in 

the environment? [§6518(m)(2)]

X X Yes, but again, depends upon soil 

conditions.

8. Would the use of the substance be 

harmful to human health or the 

environment? [§6517 (c)(1)(A)(i); §6517 

(c)(2)(A)(i); §6518(m)(4)]

X Zinc is actually an essential nutrient. It is 

unlikely that there would be the possibility 

of high levels of zinc affecting human 

health, given its petitioned use.

9. Are there adverse biological and 

chemical interactions in the agroecosystem? [§6518(m)(5)]

X X Unclear what the levels of zinc are that 

would be detrimental to the environment. 

Some soil microorganisms have the 

ability to adapt to higher zinc levels.

Page 215 of 249
10. Are there detrimental physiological 

effects on soil organisms, crops, or 

livestock? [§6518(m)(5)]

Perhaps. Difficult to determine because 

of the way zinc interacts with the soil. 

Zinc sulfate foot bath water is typically 

discarded in the farm lagoon system with 

the water later applied to the agricultural 

land. A buildup of zinc in the soils could 

be the result.

Category 2. Is the Substance Essential for Organic Production? Substance: Zinc Sulfate 

Question Yes No N/A Comments/Documentation (TAP; 

petition; regulatory agency; other)

1. Is the substance agricultural? [§6502(1)] X Mineral mined and then refined and 

purified.

2. Is the substance formulated or 

manufactured by a chemical process? 

[§6502(21)]

X Produced using either high heat of an

acid agent to create Zinc sulfide 

compound.

3. Is the substance formulated or 

manufactured by a process that 

chemically changes a substance 

extracted from naturally occurring plant, 

animal, or mineral sources? 

[§6502(21)]

X Mined or reclaimed from zinc ore. 

4. Is the substance created by naturally 

occurring biological processes? 

[§6502(21)]

X

5. Is there a natural source of the 

substance? [§ 205.600(b)(1)]

X Zinc salts do exist but produced using 

sulfuric acid.

6. Is there an organic substitute? 

[§205.600(b)(1)]

X Mineral source

7. Is there a wholly natural substitute 

product?

[§6517(c)(1)(A)(ii)]

X

8. Are there any alternative substances? 

[§6518(m)(6)] 

X Copper sulfate, hydrogen peroxide and 

other materials can be used as foot baths 

to eradicate foot rot, but in some cases 

are not as effective, and in the case of 

sheep, can be toxic.

9. Are there other practices that would 

make the substance unnecessary? 

[§6518(m)(6)] 

X X Hoof trimming, dry flooring and isolation 

of infected animals can help control foot 

rot. However, the infection can become 

increasing debilitating to the animal as it 

progresses, and can be difficult to control 

without proper treatment.

Category 3. Is the substance compatible with organic production practices? 

Substance: Zinc Sulfate

Page 216 of 249
Question Yes No N/A Comments/Documentation (TAP; 

petition; regulatory agency; other)

1. Is the substance consistent with organic 

farming and handling? 

[§6517(c)(1)(A)(iii); 6517(c)(2)(A)(ii)]

X X If used after other management practices 

are put in place, it can be effective means 

of controlling an infectious disease in 

cattle, sheep and goats. But there are 

some drawbacks to using this material, 

including the potential for buildup of zinc 

in agricultural soils when lagoon water is 

applied to the land.

2. Is the substance compatible with a 

system of sustainable agriculture? 

[§6518(m)(7)]

3. If used in livestock feed or pet food, is

the nutritional quality of the food 

maintained with the substance? 

[§205.600(b)(3)]

X

4. If used in livestock feed or pet food, is

the primary use as a preservative? 

[§205.600(b)(4)]

X Zinc sulfate is allowed as a feed 

supplement, but in this case is being 

petitioned for foot bath.

5. If used in livestock feed or pet food, is

the primary use to recreate or improve 

flavors, colors, textures, or nutritive value 

lost in processing (except when required 

by law)? [§205.600(b)(4)]

X

6. Is the substance used in production, and 

does it contain an active synthetic 

ingredient in the following categories:

[§6517(c)(1)(B)(i);

copper and sulfur compounds

X Zinc interacting with sulfuric acid to 

create zinc sulfate.

toxins derived from bacteria X

pheromones, soaps, horticultural oils, 

fish emulsions, treated seed, vitamins 

and minerals

X

livestock parasiticides and medicines X

production aids including netting, tree 

wraps and seals, insect traps, sticky 

barriers, row covers, and equipment 

cleansers

X

Page 217 of 249