الفهرس 
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Abstract
A total number of 100 lactating multiparous dairy cows were used during this experiment. Cows were superovulated using two regimens. A total dose of 400 mg FSH administrated twice daily in decreasing doses over 4 consecutive days. Donor cows were inseminated with double straws of frozen- thawed semen from proven sires. Embryos were recovered non-surgically 7.5 days after the onset of estrus using a 2-way catheter. The effect of donor’s breed, age, body condition score, time of superovulation, parity, milk production, days in milk, regimen of superovulation and feeding propylene glycol on ovarian response, embryo production and quality was investigated.
The results showed that donor’s age has a significant effect on the ovarian response to the superovulatory treatment and embryo production. Higher superovulatory response was observed during December and April than in January, February and March.There was a negative significant correlation between milk production and embryo yield. The highest values of embryo recovery as well as the transferable embryos were obtained in cows of the minimum daily milk production (20-25 and 25-30 kg. groups). Concerning feeding propylene glycol, the results showed that the number of total ova/ embryos recovered and the number of transferable embryos were significantly higher in the PG group compared with control group (P < 0. 05; P < 0.01, respectively). In conclusion, understanding of some factors which may affect the ovarian response and embryo production (e.g. age, season, parity, nutrition and milk production of the donor cows) as well as feeding PG before superovulation treatment may improve these traits in the highly lactating cows.