Data/hora: 10/06/2024 03:59:33

Biblioteca(s): | Embrapa Caprinos e Ovinos.
Data corrente: | 23/03/2005
Data da última atualização: | 10/06/2011
Autoria: | EVANS, A. C. O.; DUFFY, P.; HYNES, N.; BOLAND, M. P.
Título: | Waves of follicle development during the estrous cycles in sheep.
Ano de publicação: | 2000
Fonte/Imprenta: | Theriogenology, v. 53, n. 3, p. 699-715, 2000.
Idioma: | Inglês
Conteúdo: | The pattem of ovarian follicle development in maiden cyclic lambs was characterized using the definition of a follicle wave as the changes in the number of follicles among the days of the estrous cycle, as originally defined in cattle by Rajakoski in 1960. We also examined the steroid content relationships among follicleson Days 5 (Wave 1) and 14 (Waves 2 and 3) of the estrous cycle. In Experiment I, the avaries of 20 cyclic lambs (40 to 45 kg) were examined daily using transrectal ultrasonography for 1 or 2 estrous cycles (n = 31 cycles). The number of small (2 and 3 mm in diameter), medium (4 and 5 mm) and large (³6 mm) follicles were aligned with the beginning and end of the average length estrous cycle and then compared among days. Identified follicles were defined as those that grew to ³ 4 mm and remained at ³3 mm for ³3 d. The number of  identified follicles emerging (retrospectively identified at 2 or 3 mm) per ewe per day was algo aligned with the average length estrous cycle. In Experiment 2, ewe lambs were ovariectomized on Day 5 (n = 6) or 14 (n = 5) of the estrous cycle, then follicle diameters and follicular fluid concentratiops of estradiol and progesterone were compared among follicles. Data were analyzed by repeated measures ANOVA and compared among days using Fisher's LSD. In Experiment 1, either 2 (n = 10 cycles), 3 (n = 20 cycles) or 4 (n = 1 cycle) periods of emergence of identified follicles occurred during individual cycles, with estrous cycle lengths of 15.6+1.6, 16.1+ 1.1 and 17 d respectively. In animaIs with 2 or 3 periods of emergence of identified follicles, the total number of small, medium and large follicles differed (P<0.05) among days of the estrous cycle showing a wave-like pattem. In Experiment 2, a single follicle collected on each of Days 5 and 14 of the cycle (6.2+0.2 and 3.9+0.2 mm in diameter) had a higher (P<0.05) concentration of follicular fluid estradiol (36.2+4.4 and 50.9+21.6 ng/mL) than other follicles collected on the same day (next largest follicle: 4.3+0.3 and 3.5+0.4 mm; 4.3+0.9 and 18.2+6.7 ng/mL estradiol). The results showed that 1) there was a synchronous emergence of follic1es associated with fluctuations in the number and size of follicles during the estrous cycle; 2) within a wave there was a hierarchy among follicles for diameter and steroid content; 3) ovarian follicle growth in ewe lambs occurred in 2 or 3 organized waves during the estrous cycle.
Palavras-Chave: | Dinâmica folicular; Onda folicular; Ovariectomia; Ultra-som.
Thesagro: | Ciclo Estral; Endocrinologia; Ovino; Reprodução Animal.
Categoria do assunto: | --
Registro original: | Embrapa Caprinos e Ovinos (CNPC)
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