Estimation of oral exposure of dairy cows to the mycotoxin Deoxynivalenol (DON) through toxin residues in blood and other physiological matrices with a special focus on sampling size for future predictions

Abstract

Evaluation of dairy cow exposure to DON can generally be managed through analyses of feed or physiological specimens for DON residues. The latter enables a diagnosis not only on an individual basis but also on a herd basis. For this purpose, on the basis of published data, linear regression equations were derived for blood, urine, milk, and bile relating DON residue levels as predictor variables to DON exposure. Amongst the matrices evaluated, blood was identified to reflect the inner exposure to DON most reliably on toxicokinetic backgrounds, which was supported by a linear relationship between DON residues in blood and DON exposure. On the basis of this, and because of extended blood data availability, the derived regressions were validated using internal and external data, demonstrating a reasonable concordance. For all matrices evaluated, the ultimately recommended linear regression equations intercepted the origin and enabled the prediction of the DON exposure to be expected within the prediction intervals. DON exposure (µg/kg body weight/d) can be predicted by multiplying the DON residues (ng/mL) in blood by 2.52, in urine by 0.022, and in milk by 2.47. The span of the prediction intervals varied according to the dispersion of the observations and, thus, also considered apparent outliers that were not removed from the datasets. The reasons were extensively discussed and included toxicokinetic aspects. In addition, the suggestions for sample size estimation for future characterization of the mean exposure level of a given herd size were influenced by expectable variation in the data. It was concluded that more data are required for all specimens to further qualify the preliminary prediction equations.