To verify the ovarian activity in respect to follicular dynamics and corpus luteum activity, 25 cows distributed in five experimental groups according to the crossbreeding level as: group 1: 1/2 Holstein x Zebu, group 2: 3/4 Holstein x Zebu, group 3: 15/16 Holstein x Zebu, group 4: crossbreed pure Holstein and group 5: 7/8 Holstein x Zebu, were daily monitored by ultrasonography examination during two estrous cycle after the second postpartum cycle. The average in days for the interovulatory period were respectively, for the first and second cycles: 21.76±3.33 and 21.94 ± 2.90. There was no difference between these values. The average for the interovulatory period between cycles was 22,08±2,46 days. In this experiment, the development of one (16%), two (78%) and three (16%) follicular waves was verified, with predominance of two follicular waves. The interovulatory period in three waves cycles (25.33±4.36 days) was longer when compared to one (16.0±3.6 days) and two (21.69±1.97 days) waves cycles. The follicular waves average length were: 11.0±3.69, 7.17±1.60 and 8.5±1.52 days, respectively, for the first, second and third follicular waves. In estrous cycles where only two waves occurred, the waves average length were: 11.15±1.65 and 12.07±2.82 days. The highest progesterone concentrations in the first and second estrous cycle were, respectively, in the 13.6±3.0 (7.29±4.3 ng/mL) and 11.8±3.4 (5.6±2.0 ng/mL) days and were not different among experimental groups and estrous cycle. After the analyses, it was concluded that the different experimental groups presented the same follicular dynamics behavior, and despite the differences in absolute numbers in progesterone concentration among the groups, they were indicative of normal luteal activity.
bovine; corpus luteum; follicular dynamics
