Differences in follicular development and repeatability of follicular growth pattern among Czech Fleckvieh (n = 20) and Holstein (n = 23) heifers were investigated. Follicular dynamics was evaluated by daily sonographic scanning during three interovulatory intervals. The mean duration of the interovulatory interval was 20.66 ± 0.32 days, no differences between breeds were observed. The proportion of the nonalterna-ting pattern was nearly the same as that of the alternating pattern (54% and 46%, respectively). The majority of IOIs ≤ 21 days were of the 2-wave pattern (71%) whereas only 29% of them were of the 3-wave pattern. Conversely, the majority of IOIs ≥ 22 days were of the 3-wave pattern (84%), whereas only 16% were of the 2-wave pattern. Differences could be observed in the Czech Fleckvieh heifers. Comparing 2-and 3-wave interovulatory intervals, 44.2% of the heifers exhibited 3 waves and 55.8% of the heifers exhibited 2 waves of follicular growth. The ratio of 3-to 2-wave heifers was about the same in the Holstein breed; in Czech Fleckvieh 2-wave cycles slightly dominated (11/12, 8/12; respectively). In Holstein heifers, the first follicular wave occurred 0.92 ± 0.15 days after ovulation in 2-wave interovulatory intervals, and the emergence of the first wave in 2-wave Czech Fleckvieh heifers appeared later (P < 0.05), 1.83 ± 0.3 days after ovulation. The maximal size reached by the dominant follicles in all animals and in the Czech Fleckvieh differed in the first and in the second wave of 2-wave cycles (P < 0.05). In 3-wave interovulatory intervals the dominant follicles in the second wave differed (P < 0.05) from the mean diameters of the first and the third wave in the Czech Fleckvieh. The ovulatory follicles were significantly (P < 0.05) smaller in 2-wave than in 3-wave interovulatory intervals among all animals and between the Holstein and Czech Fleckvieh heifers. In conclusion, we found a similar pattern of ovarian follicular dynamics in Czech Fleckvieh and Holstein heifers kept under identical nutritional and environmental conditions. Whether the significant difference in the emergence of the 1 st follicular wave in 2-wave IOIs between C and H heifers is of real biological significance is ambiguous.

ABSTRACT:The indicators of follicle development with regard to the growth wave order, the first ovulation, animal parity, and also with regard to the simultaneous presence or absence of a follicular cyst were determined in cows in the course of 60 days postpartum. Follicular dynamics were monitored daily by ultrasonography. The animals were assigned to three groups based on the time of the 1 st ovulation: G1 (n = 9) -the 1 st dominant follicle (DF) ovulated, G2 (n = 10) -ovulation occurred on the 2 nd or later follicular waves, and G3 (n = 5) -no ovulation occurred during the experimental period. G1 animals showed better fertility later (no cyst, less days open, P = 0.07, less hormonal treatment, P = 0.008). The rhythm of follicular wave development was generally similar in all the animals (based on emergence of the first follicular wave, the interval from emergence to deviation, and the number of all follicular waves). Nevertheless, emergence of follicular waves and deviation occurred by 0.5-0.9 day earlier in primiparous than in multiparous cows and in G1 vs. G2, or G3, respectively (in all P < 0.05). DF development was independent of parity as well as group effects, but the maximum size and growth rate (1.2 vs. 0.8 cm/day, P < 0.05) were higher in ovulatory follicles (OF) than in regressive ones (rDF). The presence of a growing cyst decreased the probability of rDF as well as OF development (P < 0.0001). The OF growth rate was faster in the milieu of a stagnating cyst than without any cyst (P < 0.04). Therefore, the development of follicles was dramatically suppressed beyond, but nor before, deviation in the milieu of a growing cyst. Cessation of the cyst growth accelerated the development of OFs. On the contrary, a cystic structure without any significant growth can persist for weeks with no effect on successful follicular development.

ABSTRACT:The objective of the present study was to examine if luteal blood flow (LBF) monitoring could be used as an additional prognostic tool for early pregnancy diagnosis, and we particularly focused on the differences in LBF between pregnant and nonpregnant mares. Furthermore, other possible developmental differences of corpus luteum (CL) between pregnant and nonpregnant mares were evaluated. The CL (n = 119) of 27 mares were monitored once daily in B-and Power-Doppler Mode on days 1, 2, 9, 12, and 16 after ovulation (day 0 = ovulation). The data were evaluated using the MIXED Linear Model with repeated measures, and parameters were estimated by the REML method. The course of LBF, area of CL, and pixel intensity differed in nonpregnant mares on a day-to-day basis in contrast to more stable values in pregnant mares. Further, the profiles of the courses were identical until day 9, but since day 12 the differences between pregnant and nonpregnant mares started to be prominent. The LBF, pixel intensity, and level of progesterone (P4) were similar in all mares until day 16, when smaller LBF, lower pixel intensity, and lower levels of P4 were found in nonpregnant mares (P = 0.04, P = 0.02, P < 0.05, respectively). In pregnant and nonpregnant mares the LBF was weakly (r = 0.29 in both) and pixel intensity strongly (r = 0.48 and 0.59, respectively) correlated to the levels of P4. LBF was strongly correlated to the area of CL in pregnant as well as nonpregnant mares (r = 0.72 and 0.64, respectively). In accordance with the results presented in our study we can state that LBF monitoring is not a suitable tool for early pregnancy diagnosis or prognosis as the differences between pregnant and nonpregnant mares are notable -similarly to other indicators of CL status -just after the onset of luteolysis (day 16) when embryo itself is detectable.