Morphological evaluation of bovine embryos recovered non - surgically from superovulated dairy cows on days 6 1 / 2 to 7 1 / 2 : A field study

Ninety-two dairy cows milking 23 I milk/day at the time of superovulation and belonging to the main domestic breeds were used in this study. Their mean age was 5.5 years and they had calved a mean 3.6 times. In 71 animals the previous calving interval was 369 days, and the calving-superovulation interval was 126 days. The cows were superovulated with 1 500 to 3 000 IU of PMSG (mean of 2 400 IU) on days 8 to 13 of the estrous cycle (mean of 10.7 days), followed 48 to 60 hrs (mean of 52 hrs) later by cloprostenol treatment (0.5 mg). The mean interval from PMSG injection to heat was 4.1 days, and that from the cloprostenol treatment was 45.5 hrs. A total of 6.0 embryos/donor were nonsurgically recovered at the farm on days 6 to 8 (mean of 7.1 days). They were evaluated under a stereomicroscope and divided into the following groups : a) embryos with the appropriate (expected) age (developmental stage), showing no signs of degenera-