by Dr. Dale Rollins
In his February 7, 2010 column, Dallas Morning News outdoor columnist Ray Sasser posed the question "is deer corn a quail killer?" Sasser is a well-respected writer, and perhaps the most vocal friend of quail in today's media. When he writes, people listen. Since that time, I've been flooded with e-mails and telephone calls seeking more information. Is aflatoxin-tainted corn the reason quail numbers have declined across much of Texas? It's certainly an attractive hypothesis.
aflacorn_cr.jpgAflatoxin is a naturally-occurring mycotoxin produced by two types of mold: Aspergillus flavus and Aspergillus parasiticus. While the presence of Aspergillus flavus does not always indicate harmful levels of aflatoxin, it does mean that the potential for aflatoxin production is present.
The occurence of aflatoxins is influenced by certain environmental factors; hence the extent of contamination will vary with geographic location, agricultural and agronomic practices, and the susceptibility of commodities to fungal invasion during pre-harvest, storage, and/or processing periods. As it is realized that absolute safety is never achieved, the Texas State Feed & Fertilizer Service attempts to limit exposure to aflatoxins by imposing regulatory limits on commodities intended for use as food and feed. These limits vary with the endpoint of the feed. For beef cattle the maximum allowable concentration of aflatoxin is 300 parts per billion (ppb), but for dairy cattle, poultry, and humans, the limit is 20 ppb. Feed intended for poultry (and by extension to quail) should not contain more than 20 ppb of aflatoxin.
For sure there's a lot of deer corn fed in Texas. Back in 1999, my Extension colleagues and I purchased 100 bags of deer corn from retail outlets across the state. We estimated that six million 50-pound bags of deer corn were fed in Texas during 1999. My colleague Dr. Neal Wilkins summarized the aflatoxin issue in 1999 in Aflatoxins: A Concern for Quail Managers? Therein Wilkins stated "it is not yet known through any field reports, or through research, whether or not bobwhites are impacted by aflatoxins to a degree that would impact local populations."
By law, "deer corn" in Texas cannot exceed 50 ppb. At the time of the 1999 surveys, the legal limit was 100 ppb. Forty-four percent of the deer corn samples were above 20 ppb, and another 20 percent was above 100 ppb. Aflatoxins can occur in grains besides corn, including milo, wheat, and peanuts, but among wildlife feedstuffs, it tends to be most pronounced in corn. There are at least 13 different types of naturally-occurring aflatoxins-the most toxic is aflatoxin B1.
Dr. Brad Dabbert and graduate student DeAnna Oberheu at Texas Tech studied the aflatoxin level in quail about 10 years ago in Wheeler County (and also just across the OK line in Roger Mills County). They removed the crop contents from hunter-killed quail during the 1996 and 1997 hunting to determine if they were exposed to aflatoxin by consuming either wild or supplemental food. Crop contents were segregated into three categories based upon their contents: all wild seeds (n=11), all supplemental foods (n=21), and mixed foods (n=18). Contents were then analyzed for AF concentration. Mean (±SE) AF concentration (ppb) of wild seeds was 2.44±0.54; supplemental foods, 0.12±0.41; and mixed foods, 0.53±0.40. Wild seeds had higher AF concentrations than either the supplemental or mixed categories. None of their samples were above concentrations found to cause damage to northern bobwhite.
To date, aflatoxicosis has not been implicated in massive die-offs in wild birds.PICT0200_cr.jpg Nevertheless, aflatoxin is an extremely potent toxin, and its potential to cause subclinical yet debilitating effects must be respected. Aflatoxin could affect quail by causing immune suppression which would predispose animals to covert losses from other disease processes (i.e., aflatoxin exposure compounded the effects of coccidiosis in Japanese quail). Who knows maybe "low-path" avian influenza could become more "high path" in an aflatoxin-rich environment). Also, low-grade debilitation due to poor liver function could enhance predation. Such indirect, sublethal effects would be difficult (if not impossible) to detect in a wild quail population.
Deana Moore, a graduate student at Texas A&M University-Kingsville, tested the acute effects of administering bobwhites with 0, 100, 200, 500, 1,000, or 2,000 ppb of aflatoxin. Mortalities were observed at all levels of aflatoxin ingestion, but only 14 % of the bobwhites died during the trials. Immunosuppression was the most notable effect of aflatoxin exposure.
I often ponder the potential role of aflatoxin in the apparent decline of bobwhites (and blue quail). The hypothesis that deer corn is a quail killer is trendy, and "sexy." But I offer three counter instances that may place the hypothesis in context.
* First, was deer corn being fed in 2005? Of course it was, and yet quail were abundant then (maybe the 2005 crop of deer corn was "cleaner", i.e., had lower aflatoxin levels overall);
* Second, if it was as big a deal as some would tout, there wouldn't be a turkey left in the Edwards Plateau (i.e., turkeys are notorious "corn Hoovers". And the apparent dearth of quail spans both fed and unfed areas in west Texas.
* Finally, not everybody feeds deer corn, but quail numbers are down pretty much across the board. E.g., RPQRR has only one deer feeder, but quail numbers are down 50 to 70% across the ranch. Incidentally,there are (still) at least 2 nice coveys that frequent the deer feeder.
My opinion? Aflatoxin may be a contributing factor, but it's not the big one.
Dr. Scott Henke of the Caesar Kleberg Wildlife Research Institute monitored aflatoxin levels in corn stored in various types of containers to determine if aflatoxin levels increased over time. His research concluded that managers can limit their risk of feeding aflatoxin-contaminated grain by first testing the grain at the time of purchase and by not storing grain for longer than two months. A listing of testing facilities can be found at http://www.rma.usda.gov/fields/ok_rso/2009/2009aflatoxin.pdf.
Aside from the aflatoxin concerns, there other mechanisms via which feeders may impact quail negatively, including:
* Higher incidence of nest depredation near feeders;
* Higher incidence predation or parasitism;
* Higher harvest rate because birds are more predictable and localized near feeders;
* Higher populations of nest predators through a "flushing" effect (i.e., feeding a high energy feed just prior to ovulation in mammals increases ovulation rate."