Biomarker-based evaluation of aflatoxin B1 exposure in cattle

Assessment of aflatoxin B1 (AFB1) exposure in cattle traditionally relies on feed analysis, which may not reflect chronic exposure or accurately indicate individual susceptibility. This study aimed to evaluate the utility of serum AFB1-albumin adducts and blood AFB1-DNA adducts as biomarkers for assessing individual chronic AFB1 exposure in cattle, irrespective of immediate feed contamination levels.

Blood samples were collected from 53 crossbred cattle from farms, clinical veterinary cases, and slaughterhouses in Puducherry, India. Feed samples (n = 40) from farm and clinical cases were analyzed for aflatoxin contamination using two-dimensional thin-layer chromatography. AFB1 exposure was quantified by measuring serum AFB1-albumin adducts and blood AFB1-DNA adducts using an indirect enzyme-linked immunosorbent assay. In addition, a novel method was developed to synthesize the aflatoxin B1-formamidopyrimidine (AFB1-FAPy) adduct in vitro and the synthesized adduct was characterized to serve as a standard for DNA adduct quantification.

AFB1 was detected in 50% of feed samples, with 70% of positive samples exceeding the maximum permissible limit of 20 μg/kg. Despite variable feed contamination, serum AFB1-albumin and blood AFB1-DNA adducts were consistently detected across all animal categories. Median AFB1-albumin adduct levels were similar among farm (0.730 pg/mg), clinical (0.670 pg/mg), and slaughterhouse (0.770 pg/mg) cattle (p = 0.731). Median AFB1-DNA adduct levels were highest in slaughterhouse cattle (18.33 pmol/μg DNA), followed by farm (14.76 pmol/μg DNA) and clinical cases (7.47 pmol/μg DNA), although differences were not statistically significant (p = 0.328). No significant correlation was observed between feed contamination levels and biomarker concentrations, highlighting the chronic nature of AFB1 exposure.

The consistent detection of AFB1-albumin and AFB1-DNA adducts in cattle, irrespective of detectable aflatoxin levels in feed, underscores the limitations of traditional feed analysis for monitoring chronic exposure. The novel synthesis and robust detection of AFB1-FAPy DNA adducts further enhance the reliability of these biomarkers. These biomarkers are minimally invasive, sensitive, and valuable for chronic aflatoxin exposure assessment, aiding proactive management strategies to safeguard animal health and public food safety.