Plasma progesterone concentration in relation to ovulation rate and embryo yield in Chios ewes superovulated with PMSG

• Published in: Animal reproduction science Vol. 39; no. 1; pp. 11 - 21
• Main Authors: Samartzi, F., Belibasaki, S., Vainas, E., Boscos, C.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.1995
• Subjects: ANIMAL EMBRYOS; BREBIS; EMBRIONES ANIMALES; Embryo yield; EMBRYON ANIMAL; Ewe; EWES; OVEJA; OVULACION; OVULATION; Ovulation rate; PMS; PROGESTERONA; PROGESTERONE; Progesterone concentration; SUPEROVULACION; SUPEROVULATION; Ewe; Progesterone concentration; Embryo yield; Ovulation rate; Superovulation
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/0378-4320(94)01372-S

The main purpose of this work was to investigate the relationship between plasma progesterone concentration and the number of ovulations and/or the number of embryos collected from Chios ewes induced to superovulate with various doses of PMSG. The oestrous cycles of the animals were synchronized by means of MAP intravaginal sponges for 14 days and PMSG was injected i.m. (1500 IU, Group 1; 1000 IU, Group 2; 750 IU, Group 3; 500 IU, Group 4; 0 IU, Group 5) at the time of sponge withdrawal. Seven days after sponge removal and 5 days after mating, mid-ventral laparotomy was performed and the uterine horns and/or oviducts were flushed. The number and diameter of corpora lutea (CL), the number of large (diameter > 0.5 cm) anovulated follicles and the total ovarian response (TOR = CL + large anovulated follicles) were recorded. The embryos were examined under a dissecting microscope and evaluated according to morphological criteria. Blood samples were collected once daily for 4 days starting on the day of sponge withdrawal. One more sample was taken on the day of embryo collection. Progesterone concentration was determined using a conventional ELISA. A significant positive correlation was found between plasma progesterone concentration and number of corpora lutea ( r = 0.61, P < 0.001), total diameter of corpora lutea ( r = 0.63, P < 0.001), total ovarian response ( r = 0.63, P < 0.001), number of eggs ( r = 0.51, P < 0.001), number of embryos ( r = 0.43, P < 0.001) and number of transferable embryos ( r = 0.36, P < 0.01) collected per ewe treated. A negative relation between progesterone concentration (≥ 2 ng ml −1) at the beginning of oestrus and number of corpora lutea (CL) was observed. The investigation of the relationship between ovulation rate and plasma progesterone concentration on the day of embryo collection resulted in the calculation of a formula for the prediction of the response of Chios sheep after superovulation with the specific hormonal regimen.