Aflatoxin contamination of commercial cottonseed in South Texas

Aflatoxins are toxic fungal metabolites produced by several members of Aspergillus section Flavi. U.S. federal regulations limit the use of aflatoxin-contaminated cottonseed. Cottonseed with aflatoxin content of 20 ng/g or higher may not enter the profitable dairy market. Between 4,472 and 9,949 truckloads of cottonseed from 31 to 35 gins in South Texas were analyzed for aflatoxin content each year from 1997 to 2001 upon receipt at the Valley Co-op Oil Mill in Harlingen, TX. The highest levels of contamination occurred in 1999, with an average aflatoxin content of 112 ng/g and 66% of the cottonseed truckloads exceeding 20 ng/g. Years 1997 and 2000 had the lowest aflatoxin levels, averaging 24 ng/g, with the lowest incidence (16%) of the truckloads exceeding 20 ng/g in 1997. In general, aflatoxin contamination increased as the ginning season progressed. Rainfall after boll opening correlated highly with aflatoxin content, with rainfall in July explaining over 50% of the observed variability in aflatoxin content. South Texas was divided into four regions: Rio Grande Valley, Coastal Bend, Upper Coast, and Winter Garden. Geostatistical analyses revealed recurrent patterns of high and low contamination. The greatest contamination occurred from the central Coastal Bend region through the southern Upper Coast region. The Rio Grande Valley region experienced the least contamination during the study period.