Scientific Reports · 10 authors, 7 centres
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This study found that European bison with more comorbidities had significantly different hepatic concentrations of copper, selenium, and zinc. Copper levels decreased with increasing number of lesions, while selenium and zinc increased, indicating that disease status affects mineral status. These findings highlight the need to consider health condition when assessing mineral status in wildlife populations.
**Background:** European bison (Bison bonasus) are a species of conservation concern, with health monitoring critical due to low genetic variability and susceptibility to diseases. Previous studies on trace element concentrations in this species rarely linked mineral status to disease burden. This study aimed to comprehensively investigate the relationship between comorbidities and hepatic concentrations of a wide spectrum of elements in European bison from the Bieszczady Mountains, Poland.
**Methods:** Liver samples were collected from 63 European bison (27 females, 36 males) culled between May 2020 and March 2022, primarily as part of thelasiosis control. Post-mortem examinations identified 10 types of anatomopathological lesions. Animals were grouped by number of clinical signs: group A (one type, n=?), group B (two types, n=?), group C (three or more types, n=?). Concentrations of 40 elements were measured using ICP-OES. Discriminant analysis was used to assess overall mineral status differences among groups. Linear models (general or generalized) were applied to 19 selected elements to evaluate associations with age, sex, and comorbidities. Further models tested the effect of specific lesions (lung nematodes, pneumonia, other lesions) on Cu, Se, and Zn.
**Key Results:** Discriminant analysis showed clear separation among groups A, B, and C based on hepatic mineral profiles (F1 eigenvalue 4.89, Wilk's lambda 0.059, p=0.011; F2 eigenvalue 1.87, Wilk's lambda 0.348, p=0.354). Of 19 elements analyzed, eight showed significant relationships with age, sex, or comorbidities. Only Cd increased with age. Six elements (Ca, Cu, Mg, Mo, Ni, Zn) differed by sex, with females having lower concentrations. Three elements—Cu, Se, and Zn—showed significant differences with comorbidities. Cu concentration decreased with increasing number of lesions (group A significantly higher than B and C). Se and Zn increased with more lesions (group A significantly lower than B and C for Se; for Zn, group A differed from B but not C). In models testing specific lesions, only lung nematodes significantly affected Se (F=7.549, p=0.008), and the 'other lesions' category significantly affected Zn (Wald chi²=20.750, p<0.001). Compared to cattle reference values, most animals had Cu and Se deficiency (61/63 Cu deficient, 53/63 Se deficient).
**Clinical Implications:** This study demonstrates that comorbidities significantly alter hepatic trace element concentrations in European bison, with Cu decreasing and Se and Zn increasing as disease burden rises. These changes likely reflect inflammation-induced redistribution of elements (e.g., Zn mobilization to liver, Cu release from liver). The findings underscore that health status must be considered when interpreting mineral status in wildlife populations, as random sampling from dead individuals may yield biased results. For conservation, this implies that mineral supplementation or habitat management to improve trace element availability could potentially reduce disease susceptibility. However, more research is needed to establish causal relationships and to develop non-invasive monitoring methods (e.g., hair analysis).