Comparative evaluation of the cost and efficiency of four types of sexing methods for the production of dairy female calves oleh Tomoko OBUCHI, Masahiro OSADA, Takeyuki OZAWA, Hiroshi NAKAGAWA, Michiko HAYASHI, Kiyoshi AKIYAMA, Nobutada SAKAGAMI, Ryotaro MIURA, Masaya GESHI, Hitoshi USHIJIMA