Study of the factors affecting embryo yields and quality in superovulated Morada Nova ewes that underwent non-surgical uterine flushing.

Abstract

The present study compared the outcomes of in vivo embryo production in Morada Nova ewes subjected to either 9-day (G-9SOV , n=21) or 12-day (G-12SOV , n=21) progesterone (P4 )-based estruses synchronization protocol coupled with superovulatory treatment with decreasing doses of porcine follicle-stimulating hormone (133mg of pFSH given over 3days). Non-surgical embryo recovery (NSER) was performed 6-7days after the onset of oestrus. Total antral follicle count doubled from the first to the sixth pFSH dose in both groups (p<.05). Oestrus responses did not vary between the two groups of animals (95.2%). Corpora lutea (CL) were detected in 85.0% and 60.0% of ewes that previously manifested oestrus behaviour in G-9SOV and G-12SOV respectively. NSER was successfully completed in 86.2% of ewes that had CL (p>.05). The mean number of CL per ewe/successfully flushed donor ewe was greater (p<.05) in G-12SOV (12.3±1.7/12.1±1.9) than in G-9SOV (7.9±1.4/8.2±1.6). Mean numbers of retrieved blastocysts and viable embryos were greater (p>.05) in G-12SOV (5.8±1.9 and 3.7±1.7) than G-9SOV (3.5±1.1 and 0.8±0.3 respectively). The total follicle count (all follicles ≥2mm in diameter) at the sixth pFSH dose (at P4 -device removal) was positively correlated (p<.05) with the number of CL (r=.95) and viable embryos (r=.91) in G-12SOV . The ewes with ≥10 Cl (48% of all flushed donors) yielded 80.5% of viable embryos. In summary: (a) Morada Nova ewes from G-12SOV group had better superovulatory responses compared with G-9SOV group; (b) total follicle count at the last pFSH dose was a good predictor of superovulatory responses only in the ewes primed with P4 for 12days; and (c) animals with ≥10 ovulations are main contributors to viable embryo production in Morada Nova ewes.