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Fertility of lactating dairy cows is associated with reduced progesterone (P 4 ) concentration compared with nonlactating animals. The objective of the current study was to determine whether P 4  during growth of the first follicular wave (FFW) affects embryo quality. Lactating Holstein cows at 33±3 days  post partum  were allocated to one of three treatments. Cows in the FFW and FFW with P 4  (FFWP) treatments started the superstimulation protocol on day 1 of the estrous cycle and second follicular wave (SFW) cows started the superstimulation protocol on estrous cycle day 7. Cows were superstimulated with 400 mg of NIH-FSH-P1 (FSH) given twice daily for 5 days, two prostaglandin F 2α  (PGF 2α ) injections given with the ninth and tenth injections of FSH, GNRH given 48 h after the first PGF 2α  injection, and timed insemination 12 and 24 h after the GNRH injection. Cows in the FFWP treatment received two intravaginal P 4  inserts during the superstimulation. Embryos were recovered 6.5 days after artificial insemination and excellent/good and fair embryos were frozen and transferred. Blood was sampled daily from estrous cycle day 0 until insemination from donor cows. During the superstimulation protocol, P 4  was ( P &lt;0.01) greatest for SFW cows followed by FFWP and FFW cows respectively. The percentage of embryos–oocytes from SFW and FFWP cows classified as excellent/good and fair embryos was ( P =0.02) greater than those of FFW cows. Pregnancy per embryo transfer was not ( P ≥0.73) affected by embryo donor treatment. Reduced embryo quality of cows induced to ovulate the follicles from the first follicular wave is a consequence of reduced P 4  during follicle growth.

reproduction

Reduced progesterone concentration during growth of the first follicular wave affects embryo quality but has no effect on embryo survival post transfer in lactating dairy cows