Evaluation of nuclear abnormalities in buccal mucosa cells of grazing cattle from pastures routinely treated with 2,4-D: an exploratory field study.

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is widely used in agricultural systems, raising concerns about its potential genotoxic effects on non-target organisms. This cross-sectional observational field study evaluated nuclear abnormalities in exfoliated buccal mucosa cells from 36 grazing cattle maintained on a farm where 2,4-D was routinely used in Goiás, Brazil, and investigated their relationship with physiological variables, including rectal temperature, body weight, and body condition score (BCS). A total of 1,000 cells per animal (36,000 cells) were analyzed to quantify micronuclei and other nuclear abnormalities. Statistical analyses included the Shapiro-Wilk test, Mann-Whitney test, rank-biserial correlation, Spearman correlation, Benjamini-Hochberg correction for multiple comparisons, and multivariable Poisson regression with robust standard errors. Overall, low frequencies of micronuclei and other nuclear abnormalities were observed. Although nominal associations were identified in the unadjusted analyses, none remained statistically significant after Benjamini-Hochberg correction for multiple comparisons. In the multivariable Poisson regression model, body condition score remained inversely associated with micronucleus frequency (incidence rate ratio = 0.274; 95% confidence interval: 0.128-0.587; p = < 0.001). These findings suggest that physiological status may contribute to variation in cytological biomarkers under field conditions. Because individual exposure to 2,4-D was not directly measured and no untreated control group was included, the findings should be interpreted as exploratory. This study contributes to the use of cattle as sentinel organisms in environmental biomonitoring and reinforces the need for future studies incorporating direct exposure assessment and complementary biomarkers within the One Health framework.