Recent events have heightened the concern of U.S. animal health officials and industry 

stakeholders regarding the potential role that imported non-animal origin feed ingredients

(NOFI) may have in the introduction (entry) of high consequence viral pathogens such as 

African swine fever (ASF) into the United States. Concerns over the potential role of feed 

ingredients in the introduction and spread of viral pathogens are informed by the following:

• An APHIS Veterinary Services (VS) pathways assessment estimating the risk of entry of 

exotic viral pathogens of swine to the United States, determined the entry likelihood of 

exotic swine viruses via animal feed ingredients derived from plants or plant products was 

low, with a medium amount of uncertainty if the material is unprocessed; 

• Epidemiologic investigations in Latvia and Lithuania that suggested feeding pigs fresh 

grasses and seeds harvested from areas with wild boar populations known to be infected 

with ASF may have been a possible source of ASF introduction to backyard farms (Guinat 

et al., 2016; Olsevskis et al., 2016; Olesen et al., 2018);

• A Canadian study (Pasick et al., 2014) found feed containing spray-dried porcine plasma to 

be epidemiologically linked to the introduction of PEDv to Canada, and samples of feed and 

spray-dried porcine plasma were positive for porcine epidemic diarrhea virus (PEDv) on 

RRT-PCR and RT-PCR;

• The VS Swine Enteric Coronavirus Introduction to the United States: Root Cause 

Investigation Report implicated totes as well as NOFI such as soybeans and rice hulls as

potential fomites of virus introduction;

• Recent experimental studies have shown that PEDv and foreign animal disease viruses 

such as ASF may be able to survive on feed ingredients during intercontinental shipping

(Dee et al., 2018a; Dee et al., 2018b). 

• Industry stakeholders who recently visited ASF affected countries observed production 

practices that raised concerns over possible contamination of NOFI from the environment.

There are regulations to prevent entry of hazards on unprocessed NOFI, such as straw, hay, or 

grass and rice straw and rice hulls. Consequently, the majority of our most frequently imported 

plant-origin feed ingredients are from Canada. However, other ingredients, such as corn, silage, 

soybeans, soybean meal, and flax are not regulated to mitigate the exclusion of foreign animal 

disease agents, and a portion of these ingredients are exported by countries affected by swine 

diseases of concern, such as ASF (). Among these products, there may be varying levels of risk 

among ingredient subcategories. For example, organic soybeans may represent a relatively 

higher risk pathway for ASF virus entry, because organic products are not treated by chemical 

agents used to reduce the level of bacterial and fungal pathogens as used in the storage and 

processing of conventional soybeans (Dee et al., 2016; Dee et al., 2018a). 

BACKGROUND

IMPORTATION OF NON-ANIMAL ORIGIN FEED INGREDIENTS
Because of the range of potentially contaminated ingredients and source countries, the 

variety of feed processing and associated kill steps, and multiple pathways of introduction 

and exposure of swine, a single comprehensive import risk analysis is not feasible. 

Therefore, our initial focus will be to identify and rank risk factors considered predictive of

whether any given NOFI shipment poses substantive risk of introducing ASF to the United 

States.

The product of this process, a ranked list of factors, will help focus research and 

management on pathways and mitigations most likely to impact NOFI risk status. The 

complexity of the NOFI topic demands input from experts from multiple fields, each with a 

specific niche focus, and means that group statistics are likely of limited value. Further, the 

fact that there is no data on the presence of ASF viruses in NOFI shipments, or any other 

transboundary viral pathogen, means that experts lack field experience with which to hone 

their predictions. Finally, ungrounded (without field experience) hypothetical models may 

exaggerate risk (McBride et al., 2012). Consequently, the process described here will 

identify risk factors, highlight key risk management concerns and potential mitigations, but 

will not directly estimate disease introduction risk.

EXPERT ELICITATION SCOPE 

AND OBJECTIVE
BACKGROUND

The elicitation will follow initial steps of an Integrative Group Process (IGP), often described 

as “estimate-talk-revise”. In an IGP, panelists are individually queried about their 

experience, results are summarized for panel review and discussion, and an opportunity for 

revision of individual responses is then provided. The process typically involves derivation of 

likelihood ratios from experience-based counts of the prevalence of traits (risk factors) 

among a hypothetical set of cases (here, contaminated shipments) and controls (here, noncontaminated shipments), and has been previously applied to animal health contexts (e.g., 

Gustafson et al., 2018). When the process elicits likelihood ratios, a predictive model can 

result. However, our elicitation process will conclude with a ranked list of factors, rather than 

a predictive model. The complexity of the NOFI topic demands input of experts from a wide 

range of fields, which means that group statistics on any particular topic may vary in their 

underlying level of expertise. Further, the impracticality of testing NOFI shipments for 

pathogen presence means that most experts will lack field experience with which to hone 

their predictions. Consequently, because ungrounded (without field experience) predictive 

models can exaggerate risk (McBride et al., 2012), our process will instead conclude with a 

ranked list of risk factors highlighting key concerns, and helping to direct future risk 

evaluations, mitigations, and research design.

STEP 1: INFORMAL PANEL SELECTION

Experts representing academic researchers, feed companies, and the American Feed 

Industry Association were identified through a convenience sample. This first step is simply 

a brainstorming process to construct a comprehensive (ideally both necessary and 

sufficient) set of factors facilitating contaminated NOFI introductions. Consequently, we aim 

to engage sufficient expertise, from a broad range of knowledge and experience, to cover 

each of the steps leading to (or preventing) introduction of ASF through contaminated NOFI.

STEP 2: IDENTIFICATION OF PLAUSIBLE RISK FACTORS

Informal telephone interviews with experts will generate a list of plausible factors predicting 

risk of disease (ASF) introduction via NOFI importation. The questioning process is informal, 

and simply aims to encourage consideration of the full risk pathway from seed to feed. 

Experts will be asked to ”imagine that you were asked to predict whether a particular NOFI 

shipment would, or would not, pose substantive risk of introducing ASF to the United States. 

What would you want to know about the shipment to best inform your estimate?” To ensure 

that results are generalizable to a broad range of countries and NOFIs, we will ask that

particular NOFIs, countries, companies or distributors are not named. The product of Step 2 

will be a list of factors, and their component response levels (e.g., present yes/no, or 

above/below a target temperature/time, etc.), that may indicate whether a particular NOFI 

shipment represents a risk for pathogen introduction. 

EXPERT ELICITATION 

METHOD
STEP 3: FORMAL PANEL SELECTION

Five to nine experts with expertise covering critical themes (per the output of the initial 

interviews) will be selected to rank risk factors. Selection at this stage will be based on 

knowledge and interest exhibited during Step 2, and aim to comprise diverse affiliations 

(approximately equal representation of government, industry and academia).

STEP 4: SECONDARY INTERVIEWS 

The first task will be to shape the results from Step 2 into a shortened subset of key, 

conditionally-independent factors, each with 2-3 mutually exclusive response levels. Much 

of this process will take place via email, though individual phone calls with each expert may 

also be required. Once everyone is comfortable with the final list, experts will each 

independently rank the factors in order from greatest to least predictive strength. 

Descriptive statistics of group results will be presented to the panel during a conference call 

in which discussion of results and discrepancies will be encouraged. Finally, experts will be 

given an opportunity to clarify and revise their individual rankings, if they choose. The 

outcome of this step will be a ranked list of key factors considered predictive of NOFI 

shipment contamination with ASF. 
Unique product 

type descriptions 

(Lines) a

Top exporting 

countries (% of 

shipments imported) b

Percent of shipments imported

ASF-free 

Countries

ASF-affected 

Countries c

ASFregionalized 

Countries

Canola Meal 

(137,121)

Canada (99.7%) 99.9% 0.095% <0.01%

Corn Ground 

Grains (32,538)

Canada (97.4%) 99.2% 0.36% 0.49%

Alfalfa Hay (21,711) Canada (65.8%)

Mexico (33.6%)

99.8% 0.21% <0.01%

Oats Ground 

Grains (17,537)

Canada (99.8%) 100% 0 0

Soybean Meal 

(15,383)

Canada (87.6%)

India (4.7%)

China (5.1%)

94.9% 5.1% 0.03%

Corn, Whole 

Grains (15,138)

Canada (94.9%)

Romania (2.0%)

Turkey (1.9%)

98% 0.01% 1.98%

Soybeans, 

Soybean Meal 

Ground Grains 

(14,820)

Canada (58.1%)

India (26.1%)

China (11.2%)

88.2% 11.7% 0.14%

Brewery/Distillery 

Byproduct (13,628)

Canada (78.6%)5

Brazil (12.9%)

Belgium (3.8%)

82.6% 4.5% 12.9%

Timothy Hay** 

(11,914)

Canada (99.8%) 99.9% 0 <0.01%

Corn Gluten 

(11,375)

Canada (99.9%) 100% 0 0

a In the FDA database, a “line” entry designates a shipment of a unique product type. A shipment containing different 

products are separated into lines to that designate unique product types. The size of the shipment is not specified 

and varies widely.

b Top 3 countries among those countries exporting at least 1% of total imports

c

 ASF-affected countries as of December 2018. Countries exporting lines to US may have been designated free at 

the time of shipment.

d Straw, hay, and grass is allowed to be imported from countries affected by pathogens of concern if processed by 

pelletizing or other process that effectively inactivates hazards

Table 1. Ten most frequently imported non-animal origin feed ingredients to U.S., 2015-

2018 by ASF country status based on data on animal feed ingredients provided by the 

Food and Drug Administration. 
HTS Product Description

(description of product processing) 

FDA Product 

Category

Number of 

shipments 

imported

(by 

country) 

Percentage of 

shipments from 

ASF countries 

among shipments 

from all countries

High starch vegetables: cassava, 

arrowroot, salep, Jerusalem artichokes, 

sweet potatoes, and similar roots. Also 

sago pith. 

(fresh or dried)

Animal Feeds 20 (China) 100%

Ginger, saffron, turmeric, thyme, bay 

leaves, curry and other spices.

Animal Feeds 1 (China) 12.5%

Leguminous vegetables

(dried shelled)

Animal Feeds 1 (China) 0.02%

Minimally processed vegetables

(dried, whole, cut, sliced, broken, or in 

powder but not further prepared)

Animal Feeds 11 (China) 39%

Sweet Corn Silage 1 (China) 100%

Corn/maize Corn Ground 

Grains Animal

1 (China) 0.004%

Flaxseed/linseed

(whether or not broken)

Oilseed Byproduct 2 (China) 5%

Whole Grains 

Animal

3 (China)

6 (Russian 

Fed.)

1.2%

2.4%

Flours and meals: dried leguminous 

vegetables (HD. 0713), sago or roots (HD. 

0714), fruit and nuts (Ch. 8)

(flours and meals)

Animal Feeds 225 

(China)

86%

Potato Meal/Pulp 

Potato Veg 

Byproduct

235 

(China)

99%

Flours and meals: oilseeds, oleaginous 

fruits other than those of mustard

(flours and meals)

Soybean Meal 33 (China) 35%

Soybeans, 

Soybean meal, 

Ground grains 

Animal

17 (China) 4.3%

Locust beans, seaweeds etc., sugar beet 

and sugar cane, fruit stones and kernels, 

other vegetable products used for 

human consumption, NESOI

Animal Feeds 29 (China)

1 (South 

Africa)

12.3%

4.3%

Table 2. The frequency of imports of non-animal origin feed ingredients originating 

from ASF affected countries among imports of non-animal origin feed ingredient from 

all countries (2015-2018), from data provided by the FDA.

(FDA data was cross-referenced to the import category code descriptors listed in the 

Harmonized Tariff Schedule to provide the HTS product description)
Oil seeds and oleaginous fruits, NESOI

(whether or not broken)

Animal Feeds 2 (China)

32 

(Ethiopia)

0.23%

3.6%

Forage products: rutabaga, mangolds, 

hay, alfalfa/lucerne, clover, forage kale, 

lupines, and similar products

(whether or not in the form of pellets)

Alfalfa Hay 38 (China) 0.18%

Mixed Hay 1 (Gabon) 0.01%

Seeds, fruit, and spores

(whole, of a kind used for sowing)

Animal Feeds 2 (China) 50%

Soybeans

(whether or not broken)

Animal Feeds 5 (China)

117 

(Ukraine)

2.7%

64%

Ground Grains 

Animal

1 (China)

1 (Ethiopia)

0.59%

0.59%

Soybean Meal 1 (China) 33%

Soybeans, 

Soybean Meal 

Ground Grains 

Animal

87 (China)

6 (Ethiopia)

9 (Russian 

Fed.)

51 

(Uganda)

6 (Ukraine)

1.5%

0.11%

0.16%

0.90%

0.11%

Soybeans, Whole 

Grains Animal 

234 

(China)

7 (Ethiopia)

36 

(Russian 

Fed.)

8 (Ukraine)

10.7%

0.32%

1.7%

0.37%

Starches and inulin Corn Ground 

Grains Animal

99 (China) 61%

Vegetable saps and extracts: Pectic 

substances, pectinates, pectates, agaragar and other mucilages and thickeners

(derived from vegetable products)

Animal Feeds 1 (China) 4.52%

Wheat gluten

(whether or not dried)

Mixed Feed 

Ration for Animals

1 (China) 100%

Wheat Gluten 2 (China)

383 

(Russian 

Fed.)

0.045%

8.6%

Bran, sharps, and other residues Flour Mill 

Byproducts

2 (China) 100%
(in pellets or not; derived from shifting, 

milling, or other working of cereals or 

leguminous plants)

Mixed Feed 

Ration Used for 

More than One 

Species

5 (Nigeria) 100%

Food preparations Brewery/Distillery 

Byprod

1 (China) 0.076%

Veg Byprod 5 (China) 0.41%

Fruit, nuts, and other edible parts of 

plants NESOI

(otherwise prepared or preserved, 

whether or not containing added 

sweetening or spirit)

Soybeans, 

Soybean Meal 

Ground Grains 

Animal

1 (South 

Africa)

4.8%

Oilcake and other solid residues, NESOI

(in pellets or not; resulting from the 

extraction of vegetable fats or oils, 

except from soybean or peanuts)

Canola Meal 105 

(China)

24 

(Russian 

Fed.)

0.077%

0.018%

Ground Grains 

Animal

17 (China) 7.8%

Linseed Meal 12 (China) 2%

Soybeans, 

Soybean Meal 

Ground Grains 

Animal 

2 (China) 67%

Peanut oilcake and other solid residues

(resulting from the extraction of peanut 

oil; whether or not ground or in pellets)

Peanut Meal 2 (China) 100%

Preparations of a kind used in animal 

feeding

Alfalfa Hay 5 (China) 50%

Beet Molasses 

Veg Byproduct

5 (Russian 

Fed.)

100%

Brewery/Distillery 

Byprod

9 (China) 29%

Canola Meal 1 (China) 3.6%

Corn, Whole 

Grains Animal

2 (China) 50%

Rice Ground 

Grains Animal

2 (China) 4.8%
Silage 1 (Ukraine) 50%

Soybean Meal 55 (China) 98%

Soybeans, 

Soybean Meal 

Ground Grains 

Animal 

129 

(China)

25%

Soybeans, Whole 

Grains Animal

8 (China) 89%

Wheat Gluten 10 (China) 100%

Provitamins and vitamins

(natural or synthetic; derivatives 

therefore used primarily as vitamins, and 

intermixtures of the foregoing)

Brewery/Distillery 

Byprod

22 (China) 100%

Residues and waste of sugar 

manufacture, starch manufacture, 

brewing, or distilling.

(whether or not in pellets)

Animal Feeds 291 

(China)

25%

Brewery/Distillery 

Byprod

30 (China) 0.28%

Corn Ground 

Grains Animal

17 (China) 4.2%

Mixed Grains, 

Feeds Ground 

Grains Animal

9 (China) 47%

Silage 23 (China) 100%

Veg Byprod 1 (China) 1.8%

Soybean oilcake and other solid 

residues

(resulting from the extraction of soy 

bean oil; whether or not ground or in the 

form of pellets)

Animal Feeds 54 (China) 16%

Soybean Meal 688 

(China)

5.3%

Soybeans, 

Soybean Meal 

Ground Grains 

Animal

1425 

(China)

3 (Nigeria)

18.9%

0.40%

Soybeans, 

Soybean Meal 

Whole/Ground 

Grains Animal

1 (China) 100%
Soybeans Whole 

Grains Animal

3 (China) 75%

Vegetable residues, waste, and byproducts used in animal feeding, NESOI

(in pellets or not)

Animal Feeds 493 

(China)

40%

Corn Cobs 74 (China) 99%

Pea Vine Silage 

Veg Byprod

30 (China) 15.7%

Vegetables, other than tomatoes, 

mushrooms, and truffles

(prepared or preserved otherwise than 

by vinegar or acetic acid, not frozen)

Sweet Corn Silage 

Veg Byprod

8 (China) 73%

Enzymes and prepared enzymes, NESOI Corn 

Products/Byprod

4 (China) 100%

Peptones and derivatives; other proteins 

and derivatives NESOI; hide power

(chromed or not)

Pea Vine Silage 

Veg Byprod

9 (China) 100%

Rice Protein 1 (China) 100%
Dee, S.A., Bauermann, F.V., Niederwerder, M.C., Singrey, A., Clement, T., de Lima, M., Long, 

C., Patterson, G., Sheahan, M.A., Stoian, A.M.M., Petrovan, V., Jones, C.K., De Jong, 

J., Ji, J., Spronk, G.D., Minion, L., Christopher-Hennings, J., Zimmerman, J.J., Rowland, 

R.R.R., Nelson, E., Sundberg, P., Diel, D.G., 2018a. Survival of viral pathogens in 

animal feed ingredients under transboundary shipping models. PLoS One 13, e0194509.

Dee, S.A., Bauermann, F.V., Niederwerder, M.C., Singrey, A., Clement, T., de Lima, M., Long, 

C., Patterson, G., Sheahan, M.A., Stoian, A.M.M., Petrovan, V., Jones, C.K., Jong, J., Ji, 

J., Spronk, G.D., Minion, L., Christopher-Hennings, J., Zimmerman, J.J., Rowland, 

R.R.R., Nelson, E., Sundberg, P., Diel, D.G., 2018b. Correction: Survival of viral 

pathogens in animal feed ingredients under transboundary shipping models. PLoS One

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