1. Escuela Profesional de Ingeniería Agronómica, National University of Altiplano, Puno, Peru;
2. Animal Science Department, Federal University of Vicosa, Viçosa, Brazil;
3. Animal Science Department, Federal University of Rio Grande do Sul, Porto Alegre, Brazil;
4. Empresa Brasileira de Pesquisa Agropecuária Gado de Leite, Juiz de Fora, Brazil