Abstract:

The objective of the study was to provide a reliable evidence for artificial insemination and multiple ovulation by the knowledge of characteristic of ovarian follicular waves and by determining whether the dynamic change existed in ovarian follicule (including recruitment, selection, dominance, atresia or ovulation) during the interovulatory interval (IOI). The ovarian follicles of 5 Dezhou donkeys with ten continuous estrous cycles were examined daily using rectal ultrasonography during the breeding season. Blood samples were drawn daily to measure serum concentrations of estradiol17β, LH, FSH and IGF1 by RIA for ten estrous cycles. The results of the research indicated that:（1）IOI in donkeys was (23.22±0.28)d .In the 10 estrous cycles evaluated, donkeys with two follicle waves exhibited a six minormajor waves and four majormajor waves pattern of follicle development. （2）The recruitment occurring of wave1 and wave2 began on the first and (10.2±1.4) days after ovulation，the numbers of follicles recruited were (5.2±1.2) and (4.0±0.3)，and the numbers of follicles selected were (2.3±0.5) and (2.5±0.4). The dominance of follicles at wave1 and 2 began on (5.8±0.6) and (18.1±1.4)days after ovulation. The mean days of the largest follicle occurred at (7.67±0.24) and (23.22±0.28)days and were (26.44±2.37) and (40.7±2.45)mm,with daily growth rate of (2.01±0.5) and (3.15±0.6) mm·d-1,respectively.（3）The average diameter of the biggest CL was (37.61±1.58)mm and the life length of CL was (17.30±1.62)d.（4）The high concentration of E2 ((46.47±9.53) pg·mL-1) lasted at from 3 d before to 2 d after ovulation ,and it reached the crest value((62.84±4.89) pg·mL-1) at 2 d befor ovulation. （5）The concentration of FSH declined significantly during the stage of the largest follicle at wave 1（7 d after ovulation）and wave 2（23 or 24 d after ovulation）with the negative feedback of E2.（6）The concentration of LH rose suddenly at several days before ovulation,and it reached the peak value((4.69±0.43) mIU·mL-1) at 2 d after ovulation. （7）The change in concentration of IGF1 was similar to E2, and it reached the crest value((47.9±3.91) ng·mL-1) at 1 d before ovulation. In conclusion, the results indicate that the follicular waves patterns exist in follicular development,and the occurrence of 2 follicular waves per cycle is a more common phenomena in Dezhou donkey ; and the ovulation occurr at 2 d before estrus ceased; E2, FSH, LH and IGF1 play important role in the change of folliculae wave, the recuitment and selection of small follicles, estrus and ovulation at wave 1 and wave 2.