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

Abstract

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 μg of the gonadotrophin-releasing hormone (GnRH) analogue buserelin given on Day 5 after ovulation (n = 12); or (v) the embryo was cooled to 4˚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 F_2α (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˚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-17β 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.