The invention relates, in part, to antibodies with increased ADCC activity. Methods of producing such antibodies are also provided. The antibodies of the invention are produced in mammary epithelial cells, such as those in a non-human transgenic animal engineered to express and secrete the antibody in its milk. The antibodies or compositions comprising the antibodies can be used to treat disease in which ADCC activity provides a benefit. In one embodiment, therefore, the antibodies or compositions comprising the antibodies can be used to treat cancer, lymphoproliferative disease or autoimmune disease.