Abstract
Aflatoxin is a widely occurring and dangerous mycotoxin, which can potentially affect wildlife that consumes contaminated grain.2,3,5 Unfortunately, grain that has been condemned for human and domestic animal consumption typically gets marketed as supplemental feed for wildlife.1 Avian species are exposed to aflatoxins from contaminated grain supplied at deer feeders and at backyard feeders.1-2 Because of the potential deleterious effects of aflatoxin (i.e., carcinogen, mutagen, teratogen),4 a limit of 50 parts per billion (ppb) of aflatoxin arbitrarily has been set for wildlife feed in Texas. Our objective was to determine the level of aflatoxin that negatively affects normal physiologic responses and induces acute morbidity and mortality in northern bobwhite (Colinus virginianus) and northern cardinals (Cardinalis cardinalis). Wild-caught, adult bobwhites (n=100) and cardinals (n=100) from southern Texas were maintained at the Texas A&M University-Kingsville aviary and were randomly assigned to a treatment group (2.5% fat diet for trial 1 and 5.0% fat diet for trial 2). Bobwhites were given 0, 100, 500, 1,000, and 2,000 ppb aflatoxin (trials 1 and 2); cardinals given 0, 100, 500, 1,000, and 2,000 ppb aflatoxin (trial 1) or 0, 25, 50, and 75 ppb aflatoxin (trial 2). Weekly bird weight and daily feed consumption were determined throughout each 28-day experiment. Blood plasma chemistries were determined at the onset and end of each 28-day experiment for bobwhites and only at the end of the experiments involving cardinals. Aflatoxin, derived from Parasiticus flavus, was orally administered once per week for 4 weeks. Control birds (0 ppb of aflatoxin) received an equivalent amount of aflatoxin solvent (dimethyl sulfoxide). A white blood cell proliferation test was conducted postmortem using spleen tissue to determine the effect that aflatoxin had on the function of the immune system.
Mortality due to aflatoxin was <20% in bobwhites and <20% in cardinals that received ≤100 ppb aflatoxin but >47% in cardinals that received >100 ppb aflatoxin. Aflatoxin did affect plasma parameters associated with liver, kidney, and immune system function. Beta globulins and creatinine decreased while gamma glutamyltransferase and uric acid increased in birds given aflatoxin. However, a dose-dependent effect with aflatoxin concentration was not evident in blood plasma parameters. Bird mortality during the study may have confounded this effect. White blood cell proliferation was greatly suppressed at aflatoxin concentrations as low as 50 ppb. Short-term, acute doses of aflatoxin are deleterious to the health of bobwhites and cardinals, and it potentially can cause death in immune-challenged birds.
Acknowledgments
Support was provided by the Ben and Rachel Vaughan Foundation, Tim Hixon, and the Caesar Kleberg Wildlife Research Institute.
Literature Cited
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