The effects of treadmill exercise in the number and weight of mammary tumors chemically induced in female Sprague-Dawley rats: Preliminary results J. Oliveira * , C. Teixeira-Guedes, A. Faustino-Rocha, R. Soares-Maia, R. Arantes-Rodrigues, M. J. Pires, M. Ginja, P. Oliveira, R. Ferreira * UTAD, Dept. of Veterinary Sciences, Vila Real, Portugal