Microcystin (MC) toxin produced by cyanobacteria has become a significant concern for societies worldwide. The
risk of MC in drinking water has been assessed to human health. Nonetheless, its risk to animal health has not
been thoroughly evaluated. This study investigated MCs in irrigation water and alfalfa plant from nearby
farmlands. Both irrigation water and alfalfa shoots contained greater MC concentrations (1.8–17.4 μg L􀀀 1 and
0.053–0.128 μg g􀀀 1) during summer than winter (2.4 μg L􀀀 1 and 0.017 μg g􀀀 1). These MC concentrations showed
a correlation with the predominance of cyanobacteria in the sites, triggering the potential risk of these microorganisms
in irrigation waters. Accordingly, there would be a high risk (risk quotient, RQ > 1) during summer
and a moderate risk (0.1<RQ < 1) during winter for cattle and sheep that drink polluted irrigation water or eat
contaminated alfalfa plants. Therefore, the study suggests that cyanotoxins in forage plants and irrigation water
sources should be regularly monitored to protect animals from consuming contaminated food and water.