| Summary: | Forty eight Friesian Holstein heifers were used in the study to improve reproductive status of bovine embryo transfer recipients by administration of gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin ( HCG ). Estrus of the recipient was induced by synchronization treatment using 15 nig luprostiol injected intramuscularly (estrus = Day 0). Thawed-frozen embryo was transferred into the apex of cornual horn of recipient at Day 7 of the cycle. Immediately after transfer sixteen recipient heifers were selected randomly as treated group 1 injected intramuscularly with 250 GnRH
(gonadorelin), other sixteen heifers as treated group 2 injected intramuscularly with 1,500 IU HCG, while the rest as control animals, given no treatment. Blood samples were collected from all recipients at Days 0, 7, 21, 42, 63 and 84. Blood plasma was separated immediately and stored at temperature of -20°C for quantitative progesterone determination using enzyme immunoassay (EIA) technique as well as for qualitative analysis. Rectal pregnancy examination of recipient heifers were carried out at Day 63, assisted with ultrasonographic examinations and confirmed further with progesterone determinations.
Conception rates of the treated and control animals were 50%, 50% and 31.25%, respectively. Blood plasma progesterone levels of the treated animals were consistently higher than that of the control at Days 21, 42, 63, and 84, were 6.12 ±0.98", 6.07 ± 1.08" and 4.43 ± 0.38'
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