Detection of Mycotoxins in Fallow Deer Milk and Feces: Evidence of Climate-Driven Contamination in a Comparative Study of Two Weather-Divergent Years in Hungary

Extreme weather impacts the ecological niches of fungi, altering mycotoxin risks in wildlife. We analyzed mycotoxin carry-over into European fallow deer (<i>Dama dama</i>) milk across seasons and assessed how drought influences the shift from <i>Fusarium</i> to <i>Aspergillus</i> mycotoxins and affects physiological resilience. Samples were collected during 2021/2022 and a drought-stricken 2022/2023 from South Transdanubia and Northeastern Hungary. Aflatoxin B1/M1 (AFB1/AFM1), Fumonisin B1 (FB1), Deoxynivalenol (DON), Zearalenone (ZEN), and Body Condition Scores (BCS) were measured to evaluate the impact of exposure on health status. The severe drought significantly altered the mycotoxin profile: ZEN levels declined significantly (from a median of 0.28 to 0.00 ng/mL), consistent with the moisture requirements of <i>Fusarium graminearum</i>, whereas DON concentrations increased. Concurrently, AFM1 persisted, exhibiting increased variance and extreme outliers in the maize-dominated South Transdanubian region. Distinct pharmacokinetic patterns were observed, and positive correlations were observed between milk and feces for lipophilic toxins, validating milk as a possible biomarker. Hydrophilic DON showed no correlation despite its accumulation. Emergence of "Poor" BCS group carrying loads supports "condition-dependent foraging" hypothesis, as stressed individuals are forced to consume contaminated resources, exacerbating oxidative stress and metabolic deficits.