Wilson Gonçalves Viana

Ovarian follicular dynamics during the estrous cycle in buffalo ( Bubalus bubalis )

The growth, selection, regression and ovulation of ovarian follicles was ultrasonically monitored in 30 Murrah buffalo throughout a spontaneous estrous cycle during the breeding season (autumn). Examinations revealed that follicular growth during the estrous cycle occurs in waves; the buffalo showed 1-wave (3.3%, n = 1), 2-wave (63.3%, n = 19) or 3-wave (33.3%, n = 10) follicular growth. The first wave began at 1.00, 1.16 +/-0.50 and 1.10 +/- 0.32 d in buffalo with 1, 2 and 3 waves, respectively (ovulation = Day 0). The second wave appeared at 10.83 +/- 1.09 and 9.30 +/- 1.25 d (P < 0.01) for the 2 and 3 wave cycle animals, respectively. The third wave started at 16.80 +/- 1.22 d. Structural persistence of the first dominant follicle was longer in the 2- than 3-wave cycles (20.67 +/- 1.18 vs 17.90 +/- 3.47 d ; P < 0.05). The duration of the growth and static phases of the first dominant follicle differed between the 2 and 3 wave cycles (P < 0.05), whereas there were no differences in linear growth rates (cm/d). Two and three wave cycles differed (P < 0.05) with respect to the maximum diameter of both the first dominant follicle (1.51 +/- 0.24 vs 1.33 +/- 0.18 cm) and the ovulatory follicles (1.55 +/- 0.16 vs 1.34 +/- 0.13 cm). No relationship was found between dominant follicle development and the presence of either a CL or a previous dominant follicle in either ovary. Two and three wave cycles also differed with respect to the mean length of intervals between ovulation (22.27 +/- 0.89 vs 24.50 +/- 1.88 d; P < 0.01) and the mean length of luteal phases (10.40 +/- 2.11 vs 12.66 +/- 2.91 d; P < 0.05). These results demonstrate that buffalo have estrous cycles with 1, 2 or 3 follicular waves; that 2-wave cycles are the most common; and that the number of waves in a cycle is associated with the luteal phase and with estrous cycle length.

Sincronização de estro e dinâmica folicular de éguas Crioulas submetidas a tratamentos com norgestomet, acetato de melengestrol e altrenogest

21 Crioulo mares on reproductive age were grouped into 3 groups (I, II e III) with 7 animals each; group I was treated with unique 3 mg norgestomet + 5 mg estradiol valerate intramuscular injection and a subcutaneous implant of norgestomet during 9 days; group II received unique 5 mg of 17-b estradiol intramuscular injection and 0,5 mg of melengestrol acetate given orally during 9 days; group III consisted on mares given 0,045 mg/kg altrenogest orally during 9 days. At progestogen treatment removal (9th. day), all mares from the 3 groups received luteolytic dose of luprosteol and 3.000 UI of hCG when dominant follicle was ultrasonographically detected in ovulatory conditions . All mares were daily evaluated by rectal palpation and ultrasound examination for retrospectively measurement of the largest and second largest follicles, and mated by tested stallions closed to ovulation. Follicular development was not observed on group II (MGA). Considering 5 days post PGF2a-analogue administration, synchronization rates for groups I and III were, respectively, 85.71% and 66.70% (p > 0.05). Porcentage of oestrus supression for these groups were, respectively, 85.71% and 100.00% (p > 0.05). Pregnancy rate was not significantly different between the two groups (I, 100% and II, 85.71%; p > 0.05). Results were based on mares showing response to the synchronization regimen. PGF2a-oestrus, PGF2a-hCG, hCG-ovulation and PGF2a-ovulation intervals for groups I and III were 4.5 ± 0.80 and 4.2 ± 0.8 (p > 0.05), 8.0 ± 1.41 and 6.17 ± 0.6 (p > 0.05), 1.5 ± 0.22 and 2.28 ± 0.28 (p > 0.05) and 9,8 ± 1,02 and 8,6 ± 1,32 (p > 0.05) days respectively. The results prove the eficiency of oestrus synchronization regimens by norgestomet implant and oral administration of altrenogest, with tendency to higher synchronization rate to norgestomet system, although no significantly diferences were observed concerning to reproductive parameters and follicular dynamics data, with exception to the minor largest diameter of dominant follicles and ocurrence of only one major wave for supressed cycles by progestogen-estradiol regimen.