1. University of Brasília, Brasília, CEP 70919-970, Brazil.
2. Laboratory of Animal Reproduction, Center for Technology of Zebu Dairy Breeds-CTZL, Embrapa Cerrados, Brasília, CEP 72668-900, Brazil.
3. Laboratory of Animal Virology and Cell Culture, UNESP–University of São Paulo State, Araçatuba, São Paulo, 16050-680, Brazil.