The study was conducted on crossbred cows under the ICAR-ETT project, Post-graduate Institute, Department of Animal Reproduction and Gynaecology Dr. PDKV, Akola.Presynchronization of oestrus was done in cows by PGF2 alpha (Lutalyse) 25 mg administered im. Artificial insemination with frozen semen of progeny tested bull (H.F. x Gir 50 per cent) was carried on at an interval of 12 h. Flushing of the donor cows for embryo recovery was carried out on day 7 after last insemination.The time required for onset of superovulatory oestrus from last PGF2 alpha ranged from 38 to 44 h. with an average...