Environmental influences on development of aflatoxins in supplemental feed for wildlife

Aflatoxins are produced by toxigenic strains of Aspergillus flavus and A. parasiticus and among the most potent of all naturally occurring mycotoxins. Wildlife can be exposed to deleterious concentrations of aflatoxins in grains provided by humans at feeding stations and bait piles. Potential aflatoxin poisoning of wildlife from feeding stations is of management interest due to the popularity of this practice to attract wildlife. Although no direct link has been identified, aflatoxicosis is one of many hypotheses put forth to explain recent wild turkey ( Meleagris gallopavo ) population declines. We experimentally examined environmental factors that contribute to the development of aflatoxins in grains commonly provided at wildlife feeding stations. We conducted split‐plot greenhouse trials in Payne County, Oklahoma, USA using seeds of corn ( Zea mays ) and milo ( Sorghum bicolor ). In addition to the different grain stocks and duration of each trial, we varied disposition (broadcast versus piled), moisture (dry vs. wetted), and ambient temperature of each comparison. We relied on average ambient temperature for trials conducted during August (27 ° C), September (24 ° C), and December (16 ° C). Beginning with undetectable (0 parts per billion [ppb]) aflatoxin concentrations in the seeds, we tested weekly across 4 weeks per trial to quantify any increase in concentration. We detected aflatoxins in 53% of the 288 experimental units tested, with at least 26% exceeding the 20‐ppb standard for human consumption and 15% exceeding 1,000 ppb. Corn piled in wet conditions resulted in the greatest individual concentration of 3,230 ppb. At least 50% of trials with corn in August and September registered aflatoxin concentrations above the 100‐ppb threshold for deleterious effects in Galliformes. For individuals who provide supplemental feed, our results suggest that potential aflatoxicosis can be reduced by offering milo instead of corn, broadcasting grain instead of distributing in piles, limiting the length of time that grain persists before ingestion, keeping grain dry, and to refrain from feeding during warm periods (average daily temperatures >18°C).