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Ecotoxicology (2017) 26:516–520
DOI 10.1007/s10646-017-1782-7
Aflatoxin contamination in corn sold for wildlife feed in texas
Nicholas R. Dunham
1
●Steven T. Peper
2
●Carson D. Downing
1
●Ronald J. Kendall
1
Accepted: 14 February 2017 / Published online: 27 February 2017
© Springer Science+Business Media New York 2017
Abstract Supplemental feeding with corn to attract and
manage deer is a common practice throughout Texas. Other
species, including northern bobwhites (Colinus virginia-
nus), are commonly seen feeding around supplemental deer
feeders. In many cases, supplemental feeding continues
year-round so feed supply stores always have supplemental
corn in stock. Fluctuating weather and improper storage of
corn can lead to and/or amplify aflatoxin contamination.
Due to the recent decline of bobwhites throughout the
Rolling Plains ecoregion of Texas, there has been interest in
finding factors such as toxins that could be linked to their
decline. In this study, we purchased and sampled supple-
mental corn from 19 locations throughout this ecoregion to
determine if aflatoxin contamination was present in indivi-
dual bags prior to being dispersed to wildlife. Of the 57
bags sampled, 33 bags (approximately 58%) contained
aflatoxin with a bag range between 0.0–19.91 parts per
billion (ppb). Additionally, three metal and three poly-
propylene supplemental feeders were each filled with
45.4 kg of triple cleaned corn and placed in an open field to
study long-term aflatoxin buildup. Feeders were sampled
every 3 months from November 2013–November 2014.
Average concentration of aflatoxin over the year was
4.08 ±2.53 ppb (±SE) in metal feeders, and 1.43 ±0.89
ppb (±SE) in polypropylene feeders. The concentration of
aflatoxins is not affected by the type of feeder (metal vs
polypropylene), the season corn was sampled, and the
location in the feeder (top, middle, bottom) where corn is
sampled. It is unlikely that corn used in supplemental fee-
ders is contributing to the bobwhite decline due to the low
levels of aflatoxin found in purchased corn and long-term
storage of corn used in supplemental feeders.
Keywords Aflatoxin ●Aspergillus spp. ●Corn ●Rolling
Plains ●Supplemental Feeder ●Texas
Introduction
Supplemental feeding with corn to attract white-tailed
(Odocoileus virginianus) and mule deer (Odocoileus
hemionus) is a common practice throughout Texas.
Ranchers, landowners, and hunters often consider supple-
mental feeding a necessary and beneficial management
technique (Perkins 1991). Some use supplemental feeding
to help influence hunting while others use it for some type
of active game management (Hernández and Guthery
2012). Corn is the primary feed of choice, many people also
use a protein based feed to help provide adequate nutrition
as well as to increase the antler size of their deer. In many
cases, supplemental feeding continues year-round so feed
supply stores always have deer corn in stock. Besides deer,
other species including northern bobwhites (Colinus virgi-
nianus) and scaled quail (Callipepla squamata) are com-
monly seen feeding around supplemental deer feeders. Both
northern bobwhites and scaled quail have been steadily
declining throughout all of Texas for decades (Church et al.
1993; Hernández et al. 2013). One of the major issues
*Ronald J. Kendall
ron.kendall@ttu.edu
1
The Wildlife Toxicology Laboratory, The Institute of
Environmental and Human Health, Texas Tech University, Box
41163, Lubbock, Texas 79409-1162, USA
2
Vector-Borne Zoonoses Laboratory, The Institute of
Environmental and Human Health, Texas Tech University, Box
41163, Lubbock, Texas 79409-1162, USA
related to supplemental feeding is the potential for wildlife,
especially quail, to be exposed to aflatoxin. Studies have
reported the incidence of aflatoxin contamination in corn
that is being used as bait for deer (Fischer et al. 1995).
Corn is known to constitute an important part of the diet
of bobwhite quail. Corn provides quail with digestible
carbohydrates and Vitamin A that play a key role in the
survival of quail during winter season (Nestler 1949). A
study by Korschgen (1948) has revealed that corn makes up
to 16.8% of the total diet of bobwhite quail in Missouri
during the late-fall and early-winter seasons (Korschgen
1948). More importantly, the opportunistic feeding of corn
in deer feeders by quail has been documented in the lit-
erature (Dietz et al. 2009).
Aflatoxin is a fungal metabolite that is produced by two
strains of mold (Aspergillus flavus and Aspergillus para-
siticus) which grows on corn and most types of grain
vegetables. Major crops that are affected by aflatoxin con-
tamination are peanuts (Arachis hypogaea), cotton (Gos-
sypium spp.), and corn (Zea mays) (Thompson and Henke
2000). Corn is especially vulnerable to contamination due to
cracked corn kernels that facilitate the invasion, germina-
tion, and growth of the fungus (Bingham et al. 2003).
Exposure to aflatoxin can be harmful to both humans and
wildlife (Stoloff 1980) because it is a known carcinogen and
has been documented to cause excessive weight loss, liver
damage, impaired immune systems, and mortality to avian
species, including quail (Thaxton et al. 1973; Pier 1992;
Ruff et al. 1992; Quist et al. 2000). Some of these negative
effects have been documented in bobwhite quail with afla-
toxin levels as low as 100 parts per billion (ppb) (Moore
et al. 2013).
Many factors contribute to the production of aflatoxin on
grain products, including moisture level of feed, tempera-
ture, pH, relative humidity, and a variety of plant stressors
such as damaged kernels and insect infestation (Jacques
1988). Aspergillus infection and aflatoxin contamination of
corn kernels is predominantly observed during high tem-
perature (>90 °F with warm nights) and drought conditions
(Vincelli et al. 1995). Aflatoxin can infect agricultural and
wild plants in the field, or while in storage, regardless of
storage system, time of year, or environmental condition
(Thompson and Henke 2000). Aflatoxin growth on stored
grains has contributed to most of the recorded animal
aflatoxin poisoning incidents (Jacques 1988). Given the
duration of growth when conditions are optimal, and
the variety of plants that aflatoxin can infect, quail have the
potential to be exposed to aflatoxin through much of their
diets (Oberheu and Dabbert 2001a).
Because aflatoxin contaminated grain has been docu-
mented to cause a variety of negative effects to humans and
domestic animals, the U.S Food and Drug Administration
(US FDA) has implemented a <20 ppb aflatoxin level in
grains used for human consumption and strict regulations
for domestic animals (US FDA 1979). Supplemental feed
for wildlife species is not governed by these federal reg-
ulations, but some state governments have implemented
their own regulations. In Texas, corn sold for the sole
purpose of supplemental wildlife feeding activities is
required to have <50 ppb of aflatoxin prior to being bagged
and sold to consumers (Texas Commercial Feed Control
Act 2011). Additionally, supplemental wildlife feed com-
panies have their corn tested and guarantee that the corn
“Meets the Texas <50 ppb standard for wildlife feed”;
however, most companies ensure that they meet the <20
ppb aflatoxin standards to ensure they are safe for wildlife
consumption.
Feeding aflatoxin contaminated grain may increase their
risk of contamination and potentially diminish any realized
benefit from supplemental feeding (Perez et al. 2001). With
stores having deer corn available year round there is a
concern of amplification of aflatoxin production within each
bag. This is also alarming due to many of these feed/seed
stores storage practices. Many of these stores have grain
stored on the floor of an unventilated steel building or stored
outside of a store where they are constantly being exposed
to various weather conditions (Wildlife Toxicology
Laboratory, personal observation). Henke et al. (2001)
reported aflatoxin in wild bird seed purchased throughout
Texas, of which 83% contained corn as an ingredient.
Additionally aflatoxin was not detected in bags of supple-
mental feed prior to them being used to fill feeders but
aflatoxin production in the feeders increased overtime ran-
ging from 0.57 to 15.47 ppb (Oberheu and Dabbert 2001b).
While aflatoxin is not be the sole contributor to the decline
of quail in Texas, it may influence and/or be a confounding
factor.
Since aflatoxin can grow fast given the right environ-
mental conditions, the goals of this study were to: (1)
Follow-up on two of Oberheau and Dabbert (2001a, 2001b)
studies that documented aflatoxin production in supple-
mental feed bags and aflatoxin production in metal sup-
plemental feeders to understand if storage practices and
overall cleanliness has reduced contamination and (2)
Examine if aflatoxin production varied between two com-
mon supplemental wildlife feeders types used throughout
the Rolling Plains of Texas.
Materials and methods
Supplemental corn collection
Bags of deer corn (n=57) were purchased from opportu-
nistically selected stores throughout the Rolling Plains of
Texas from October–December 2013. At the time of
Aflatoxin contamination in corn sold for wildlife feed in texas 517
purchase, the clerk was asked to sell us the most “popular”
selling brands of deer corn. Three 18.14 to 22.68-kg bags of
deer corn were purchased from each location based on the
recommendations of the store clerk. All corn was labelled
“recleaned”or “triple cleaned”meaning that the husk, debris,
and other organic products are removed, leaving only dry
corn. Additionally, all bags were labeled as tested to ensure
<20 ppb of aflatoxin contamination prior to being pack-
aged. Corn was returned to Texas Tech University and
approximately 250 g of corn was sampled from the top,
middle, and bottom of each individual bag. Aflatoxin con-
tamination is usually localized in nature and does not occur
uniformly throughout a given bag. Hence, composite sam-
pling of the bag is recommended (Aflatoxins in Corn,
2017). To simulate composite sampling, corn was sampled
from the top, middle, and bottom portions of each bag. All
corn was sampled within 2 days of purchase. Subsamples
from each bag (n=3) were later pooled together to get an
average aflatoxin concentration in a bag. Individual sub-
samples were placed into a plastic freezer bag and stored at
−80 °C until analysis.
Supplemental feeder collection
From November 2013–November 2014, three 97.72-kg
capacity metal (Moultrie Pro-Hunter Tripod Feeder; Calera,
Al, USA) and three 136.1-kg capacity polypropylene/PP
(Wildgame Innovations Poly Barrel Feeder; Grand Prairie,
TX, USA) supplemental feeders were each filled with
45.36-kg of triple cleaned deer corn, certified at <20 ppb,
purchased from the local feed store. Feeders were placed in
an open field in Lubbock County, TX (33°35’14.2”N, 102°
01’52.6”W) for the duration of the experiment. Bottom feed
ports of each feeder were left open but modified with a
screen so corn would not dispense but allow for normal
exposure conditions. Three 250 g samples from each feeder
(top, middle, bottom) were collected every 3 months i.e.
November 2013, February 2014 (Spring), May 2014
(Summer), August 2014 (Fall), and November 2015
(Winter). Sampling at these time periods would give us a
good chance to investigate the seasonal variations in afla-
toxin contamination. Samples were collected on the same
day every 3 months over the duration of the study. Indivi-
dual subsamples were placed into a plastic freezer bag and
stored at −80 °C until analysis.
Sample analysis
Each subsample was analyzed for aflatoxin contamination
using the FluoroQuant® Afla Test kit (Romer Labs Inc.,
Union, MO 63084, USA), which could detect aflatoxins in
the range of 0 to1000 ppb. We followed the Romer Labs
Inc. instructions which included grinding corn enough to
pass through a #20 size mesh sieve, and then combining
ground corn with 100 ml methanol/water (80:20) in an
extraction container. Contents were blended for 1 min and
then filtered into a polypropylene container. Next, 1 ml of
extract was pipetted into a column (SolSep® 2001 Afla-
toxin column) and mixed with 1 ml of diluent. The extract
was slowly pushed through the column and a total of 500 µl
of sample extract was then pipetted and transferred into a
clean, scratch-free 12 ×75 mm cuvette. One ml of prepared
developer was then added to purify the extract. The cuvette
was capped and vortexed for 5 sec then wiped clean and
inserted into the calibrated fluorometer (Romer Series III,
Model RL100) to determine level of aflatoxin contamina-
tion. Fluorometer was recalibrated daily using the calibra-
tion standards provided by Romer Labs Inc.
Data analysis
One-way ANOVA was performed using MINITAB 17
(2010) to detect any significant differences in afltaoxin
concentrations from the top, middle and bottom sub-
samples of all 57 bags. This was conducted to check if
the aflatoxin concentrations varied among the sampling
locations (top, middle and bottom) of each bag.
A model was employed to determine if the aflatoxin
concentrations in supplemental feeders are influenced by the
type of feeder (metal vs PP) and the season/time during
which corn was sampled. The model consisted of two fixed
factors, container type (metal vs PP) and the season. A
random factor, i.e. container number (1, 2, and 3) is nested
within the type of container. An ANOVA was run on
MINITAB 17 on the aflatoxin concentrations that were
determined to be positive.
Binary logistic regression on SAS (Version 9.3) was
used to account for the samples with no aflatoxins (zero
aflatoxin concentrations). The response was considered to
be zero if the concentration of aflatoxin in the sample is 0.
The response is considered to be 1 if the concentration of
aflatoxin in the sample is greater that zero. SAS (version
9.3) was employed to perform the binary logistic regression,
as MINITAB does not allow nested or random factors in
logistic regression.
Significance was inferred at a p-value ≤0.05. The afla-
toxin concentrations are reported a mean ±standard error
(SE).
Results/Discussion
Of the 57 bags of supplemental corn purchased from feed
stores throughout the Rolling Plains, aflatoxins were found
in 33 (58%) of the bags. The average aflatoxin concentra-
tion in the 57 bags ranged from 0.00–19.71 ppb. Of the
518 N. R. Dunham et al.
171 sub-samples, only three sub-samples had an aflatoxin
concentration greater than 20 ppb (59.13, 47.84, 21.65 ppb,
respectively), confirming that aflatoxin contamination, if
any, is localized within a given region in the bags. No
significant difference in the concentration of aflatoxins
between the top, middle and bottom locations of the bag
was observed (One-way ANOVA, p=0.328). The low
levels of aflatoxins in the corn bought from the stores are
expected because it is “recleaned”or “triple cleaned”and is
sampled within 2 days of purchase.
Many feed stores throughout the Rolling Plains store
their grain products in a variety of storage areas that often
do not have a consistent temperature or proper ventilation
(Wildlife Toxicology Laboratory, personal observation).
These storage locations would range from the floor of a
warehouse, stacked up in a steel building, or simply placed
outside of a store for a costumer to purchase. Due to these
inconsistencies, we expected to see higher aflatoxin levels
within corn bags purchased throughout the region; however,
aflatoxin was found to be extremely low and nowhere near
the 50 ppb wildlife feed standard or even the “20 ppb bag
guarantee”listed on the label. Reducing the amount of
organic matter and drying the corn kernels prior to bagging
is likely helping reduce the amount of aflatoxin production
within each supplemental corn bags. It is possible that
aflatoxin may not have been found within each bag because
this corn may have been newly packaged. Unfortunately,
the date of packaging was not recorded for each of these
bags sampled.
Aflatoxin contamination was observed in the feeders
(both metal and PP) during every season the corn was
sampled, in agreement with the results of Oberheau and
Dabbert (2001b). The average level of aflatoxins in the
supplementary feeders during a given season is summarized
in Fig. 1. Over the time frame of November 2013 through
November 2014, the level of aflatoxins in the metal feeders
ranged from 0.00–114.44 ppb with an average aflatoxin
concentration of 4.08 ±2.53 ppb. During the same time
frame, the level of aflatoxins in the PP feeders ranged from
0.00–40.68 ppb with an average aflatoxin concentration of
1.43 ±0.89 ppb. Neither the fixed factors (type of container
and the season during which corn was sampled) nor the
random factor (container number nested within the type of
container) affected the concentration of aflatoxins in the
feeders (ANOVA, p>0.05). Results from the binary logistic
regression analysis also suggested that the aflatoxin con-
centrations in the feeders is not affected/influenced by the
type of container, the season during which corn was sam-
pled, and the location of corn in the feeder (top, middle, and
bottom).
Fluctuating weather and long-term storage of corn was
expected to increase the amount of aflatoxin contamination
within the feeders. Over the course of our study, the loca-
tion of these supplemental feeders experiences more than
25.4 cm higher precipitation than each of the 3 years prior
(NOAA 2016). Optimal aflatoxin production happens when
relative humidity is between 70–90% and temperature range
between 36–38 °C, but it can grow at temperatures as low as
6 °C (Salunkhe et al. 1987). The conditions in which this
fungus can grow are commonly experienced throughout
Texas, including Lubbock County and throughout the
Rolling Plains ecoregion.
While aflatoxin may not have been found at alarming
levels during the long-term storage of triple cleaned sup-
plemental deer corn, many landowners and hunters will
often supplement with a mixed grain (corn, milo, soybeans,
sunflowers, etc.) feed. These mixed grain feeds contain
many forms of organic products that are not triple cleaned
which may increase in its susceptibility to aflatoxin pro-
duction. Much like supplemental corn, these mixed grain
feeders are also used to supplement for wildlife all year long
but monitoring production in mixed grains were out of the
scope of the present study. Future research is needed to
investigate the difference in corn versus mix grain supple-
mental feed aflatoxin production.
Aflatoxin can grow on nearly all agricultural and wild
foods (Salunkhe et al. 1987; Oberheau and Dabbert 2001a)
but contamination was not found at alarming levels
throughout this entire study. Given the results of the study,
aflatoxin contamination is likely not impacting northern
bobwhites and or other wildlife species throughout the
Rolling Plains of Texas. Additional research is needed to
determine if aflatoxin poses a risk in mixed grain supple-
mental feed and if aflatoxin is problematic in other regions
of the United States.
Acknowledgements Funding for this research was provided by Park
Cities Quail and the Rolling Plains Quail Research Foundation. We
would like to sincerely thank Professor James Surles at the Texas Tech
University Department of Mathematics and Statistics for his help with
the data analysis. We thank members of the Wildlife Toxicology
Laboratory for all of their help sampling and processing the
Fig. 1 Mean aflatoxin production (±SE) in metal and polypropylene
supplemental wildlife feeders from November 2013–November 2014
Aflatoxin contamination in corn sold for wildlife feed in texas 519
supplemental feed during this experiment. We also would like to thank
the reviewers for their time and valuable input regarding this
manuscript.
Compliance with ethical standards
Conflict of interest The authors declare that they have no competing
interests.
Ethical approval This article does not contain any studies with
human participants or animals performed by any of the authors.
Informed consent Informed consent was obtained from all indivi-
dual participants included in the study.
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