Rumensin (monensin) is the first ionophore to be approved by the Food and Drug Administration (FDA) for increased milk production efficiency. Monensin treatment at dose of 10 gm /ton in total mixed ration lead to increase both milk production and body weight through its effect on increase feed digestibility, microbial digestion and also decrease losses of nitrogen in feces which lead to decrease environmental hazards of nitrogen on both animal and public health. More over there is no cytotoxicity recorded due to monensin treatment at dose of 10gm/ton. Monensin treated animals showed significant increase in total protein serum level, globulin serum level, urea serum level, and cholesterol serum level level while had no effect on albumin, total bilrubin and glucose serum levels. Taken together, monensin is safe for use in dairy animals and has an environmental impact role.