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

The present study compared the outcomes of in vivo embryo production in Morada Nova ewes subjected to either 9-day (G-9 , n = 21) or 12-day (G-12 , n = 21) progesterone (P )-based estruses synchronization protocol coupled with superovulatory treatment with decreasing doses of porcine follicle-stimulating hormone (133 mg of pFSH given over 3 days). Non-surgical embryo recovery (NSER) was performed 6-7 days 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-9 and G-12 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-12 (12.3 ± 1.7/12.1 ± 1.9) than in G-9 (7.9 ± 1.4/8.2 ± 1.6). Mean numbers of retrieved blastocysts and viable embryos were greater (p > .05) in G-12 (5.8 ± 1.9 and 3.7 ± 1.7) than G-9 (3.5 ± 1.1 and 0.8 ± 0.3 respectively). The total follicle count (all follicles ≥2 mm in diameter) at the sixth pFSH dose (at P -device removal) was positively correlated (p < .05) with the number of CL (r = .95) and viable embryos (r = .91) in G-12 . The ewes with ≥10 Cl (48% of all flushed donors) yielded 80.5% of viable embryos. In summary: (a) Morada Nova ewes from G-12 group had better superovulatory responses compared with G-9 group; (b) total follicle count at the last pFSH dose was a good predictor of superovulatory responses only in the ewes primed with P for 12 days; and (c) animals with ≥10 ovulations are main contributors to viable embryo production in Morada Nova ewes.