Corticosterone is conserved across all species and the antibody provided in the kit will bind to corticosterone independently from the species it comes from. Therefore the product is basically “species-independent”. There is however one issue to consider if the sample is from sheep and contains IgG (like in serum or plasma samples): The plate provided with the kit is pre-coated with an antibody that captures sheep IgG and therefore samples containing endogenous sheep IgG will likely cause interference.