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‐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 (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‐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 ≥2 mm 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 12 days; and (c) animals with ≥10 ovulations are main contributors to viable embryo production in Morada Nova ewes. [ABSTRACT FROM AUTHOR]