Anthelmintic resistance against gastrointestinal nematodes in beef cattle: effect on liveweight gain of grazing livestock in Mexico

ABSTRACT This study aimed to determine the efficacy and parasite resistance of levamisole (LV) ivermectin (IVM) in beef cattle naturally infected with gastrointestinal nematodes, as well effect on liveweight gain a tropical wet region Oaxaca, Mexico. From November 2019 January 2020, sixty-six grazing calves were randomly allocated into three groups twenty-two animals each, treated LV or IVM an untreated control group (day 0). Feces collected 1 day before treatment 15 days after treatment. The from each animal was recorded at 0, 15, 30 45 post presented highest reduction eggs per gram (EPG) feces, followed by group. Resistance detected, although also suspected. had significantly higher effective 93.5%, resulting increase (P<0.05) 16.1kg, (92.4%) 17.1kg, compared A significant (P < 0.05) negative correlation observed between EPG weight for (�� = -0.46) -0.32). showed lack against adequate capacity but detrimental effects growth performance cattle.