Investigation of factors affecting pregnancy rate after embryo transfer in the dromedary camel.

The uteri of 36 adult dromedary camels were flushed non-surgically three times each with 90-120 mL of embryo flushing medium 7 days after ovulation. A total of 242 embryos were recovered, of which 139 were transferred non-surgically to recipient camels that were either at different levels of synchrony with respect to the Day 7 donor (+1 to -3 days; n = 58), or were at Day 6 after ovulation, but received one of the following treatments: (i) none (controls, n = 15); (ii) 150 mg progesterone-in-oil injected intramuscularly once daily during Days 5-20 after ovulation inclusive (n = 16); (iii) 500 mg flunixin meglumine given intravenously 15 min before transfer of the embryo (n = 6); (iv) 20 microg of the gonadotrophin-releasing hormone (GnRH) analogue buserelin given on Day 5 after ovulation (n = 12); or (v) the embryo was cooled to 4 degrees C and held at this temperature in an insulated container for 24 h before being transferred (n = 32). Jugular vein blood samples, taken daily from all the recipient camels during Days 0-20 after ovulation, were assayed for progesterone concentration and closely timed serial samples taken from the camels receiving flunixin meglumine or GnRH were assayed for 13,14-dihydro-15-keto prostaglandin F2alpha (PGFM) or oestradiol concentrations. The pregnancy rate increased to a maximum of 67% when ovulation in the recipient was negatively synchronized to have occurred 1 day behind that in the donor, and it fell dramatically when the level of asynchrony between recipient and donor increased to +1 (9%) or -3 (10%) days. It was not improved by daily injections of progesterone (44%), flunixin meglumine given before transfer (16%), or GnRH given on Day 5 (33%). Of the 32 embryos that were cooled to 4 degrees C before being transferred to Day 6 recipients, 20 resulted in pregnancies (63%) to give a success rate similar to that attained with the control fresh embryos (67%). Serum progesterone concentrations in the recipients increased to a mean +/- SEM of 2.6 +/- 0.8 ng mL(-1) by Day 8 after ovulation and, in those that were pregnant, levels remained elevated at 3-5 ng mL(-1) for the remainder of the sampling period; in non-pregnant recipients the concentrations declined to <1 ng mL(-1) by Day 11. Plasma PGFM concentrations in the flunixin meglumine-treated camels remained low (40-90 pg mL(-1)) compared with those in the untreated control camels, in which peak values of around 180 pg mL(-1) were reached within 10 min after transfer after which a steady decline occurred until resting concentrations of 90-100 pg mL(-1) were reached by 110 min after transfer. Treatment with GnRH on Day 5 after ovulation produced a transitory increase in serum oestradiol-17beta concentrations for 24 h. However, from Day 8, oestradiol concentrations in both the GnRH-treated and the untreated camels increased steadily to reach 2.5-3.5 pg mL(-1) by Day 12.