A Preliminary Study On The Early Developmental Pattern Of Ovarian Follicles From Ducks And Geese

As the basis for avian reproductive activities,the developmental potential of ovarian follicles at early stages of growth determines the reproductive abiliity offemale poultry.Considering the big difference in the egg-laying performance between ducks and geese,investigations of the early developmental patterns of their ovarian dollicles will be helpful for exploring the underlying genetic causes as well as the regulatory mechanisms.Therefore,in the present study,ovaries from bothSichuan White Goose and Nong-hua Duck at the postnatal age of 1-6 weeks were used as the experimental material.By carrying out the H-E staining of tissue sections and determing the mRNA expression of several follicle development-related genes using Q-PCR method together with respective correlation analysis,the developmental patterns of ovarian follciles were preliminarily revealed in both ducks and geese during the early postnatal period.The principle results were listed as follows:(1)A greater number of follicles were observed in ovarian cortex of both ducks and geese,and ovarian surface epithelial cells ovarian follicle development.However,ovaries from ducks during early growing phase had a relatively faster developmental speed than those from geese.In particular,ovarian cortex sulcus from 1 to 6-week-old geese growed more slowly than that from ducks,and the growth rate of both the transverse and anteroposterior diameter of ducks at the age of 5-6 weeks was faster than that of geese.Additionally,the developmental degree of goose ovarian medulla was also lower than that of duck in the same week.(2)The histological structure of ovaria folliles was similar between ducks and geese at the age of postnatal 1-6 weeks,and both exhibited a similar follicular developmetal pattern.Neverthelss,differeces were also present such as that the ratio of primary and secondary follicles was higher in ducks than in geese.Besides,compared to ducks the secondary follicles from geese ovaries growed much more slowly,showing a lower ratio,smller diameter and inadequate increment of secondary follicles.(3)Transcripts of follicle recruitment-related genes(i.e.FHSR,GDF-9,AMH)were widely expressed in all developmental staged ovarian follicles in both ducks and geese but exhibited species/stage-specific expression patterns,indicating that there may be differences in their roles during early follicular development.GDF9 and AMH might regulate duck follicualr development by influencing the follicular diameter,while FSHR took parts in the development of goose folliclesthrough controlling the number of follicles.(4)Abundance of several steroidogenesis-related genes in ovarian follicles from ducks and geese at the ages of 1-6 weeks suggested that the procress of steroid homorne synthesis and secretion was very active during the early growing phase.Nevertheless,the expression peak of StAR/3?-HSD/CYP17/CYP19 mRNA varied between ducks and geese,for example,their mRNA levels droped dramatically in ovarian follicles of the 4-6-week-old geese.(5)Caspase-3 and BCL2 were involved in the folluclar atresia of both ducks and geese by affectig the follicular diameter.Futhermore,the distinct extent of follicular atresia between ducks and geese may be attributed to the different growth rate of their early growing follicles and the different expression patterns of Caspase-3 and BCL2 during follicle development.