Wpływ egzogennych hormonów i efektu kozła na wzrost pęcherzyków jajnikowych kóz w sezonie spoczynku płciowego
AbstractContemporary methods of estrus synchronization with exogenous gestagens and gonadotropins in the goat are commonly used around the world due mainly to their practicality and usefulness in animal breeding and production. However, their effectiveness is highly variable and frequently below expectations. This variability appears to be caused by our insufficient knowledge of the specific physiology of growth of ovarian antral follicles, which was not very well known at the time when those methods had been developed. Many years of research and testing in production systems, on a large scale, have shown that each of the currently used estrus synchronization procedures has its limitations, whose elimination could potentially lead to increased fertility and production rates of animals. Therefore, the primary aim of this study was to document the dynamic changes in ovarian activity in seasonally anovular goats subjected to hormonal stimulation with exogenous hormones or the male effect, namely the impact of long-term progestagen priming, exogenous gonadotropins (cCG and hCG) or GnRI-I analogue (buserelin acetate), and of the buck introduction on ovarian antral follicular dynamics and reproductive hormone secretion. The author of the study have evaluated, in a series of experiments, the effects of a gonadotropin (200 IU) and GnRII (gonadotropin releasing hormone; 0.01125 mg) on the single dose of cCG (equine chorionic gonadotropin, 500 IU), hCG (human chorionic ovarian function and circulating concentrations of estradiol, lulcinizing hormone (LH) and progesterone in anestrous White Polish goats with or without. In the last experiment, changes in the ovarian activity and serum concentrations of LII and ovarian steroids in response to the buck effect were evaluated. Each experiment was performed on 12 sexually mature, clinically healthy anestrous goats. Animals were divided into equal groups (n = 6). The first group of animals received vaginal sponges soaked with fluorogestone acetate (FGA, 45 mg) and the other group served as untreated controls. All animals underwent daily transrectal ultrasonography of the ovaries for the entire duration of the study to visualize and measure all antral follicles > 2 mm in diameter and luteal structures. Ultrasonographically detected ovarian follicles were classified into one of the three size classes: small (< 4 mm), medium (from 4 to 5 mm) and large (> 5 mm in diameter) and grouped into the waves of follicular growth. Follicular wave characteristics and hormonal profiles were monitored over the two 21 days consecutive periods separated by the occurrence of ovulation. The present results revealed the modulatory effects of fluorogestane acetate on ovarian antral follicle recruitment and growth in anestrous goats. In goats not pretreated with FGA there were significantly more follicles greater than 5 mm and follicle diameter was greater in the ovulatory wave after eCG, hCG or GnRH administration but there were fewer ovulations compared with FGA-pretreated goats. FGA also suppressed the pulsatile LH secretion in seasonally anovular goats during the first 4 hours after buck introduction, but the time of occurrence of the preovulatory LH surge was similar to that in a group of control animals. Furthermore, a greater number of growing antral follicles in FGA-pretreated goats was accompanied by higher circulating concentrations of estradiol in comparison to that had not been pre-stimulated goats. Treatment of anestrous goats with the progestagen did not affect the number of emerging follicular waves. In this study, all goats pre-stimulated with FGA before the treatment with eCG, hCG or GnRI I developed fully functional corpora lutea post-ovulation. However, all goats that had not been pre-treated with FGA before receiving eCG, hCG or GnRH developed short-lived corpora lutea. Only in the groups of goats stimulated to ovulate with the buck effect, both short-lived and normal corpora lutea have been observed, regardless of whether or not the females had previously been prestirnulated with FGA. The greatest number of growing antral follicles was recorded in the ovulatory wave of eCG-stimulated, FGA-primed anestrous goats and in this group of the highest ovulation rate was observed. Interestingly, in goats that had not been pre-stimulated with FGA, the number of follicles in the ovulatory wave of eCG-treated goats did not vary from those seen in other groups of animals (i.e., hCG- and GnRH-treated or following the buck introduction). The numbers of antral follicles in the first wave after ovulation were significantly greater following an application of hCG or GnRH to the anestrous goats. In addition, persistent ovarian follicles were detected ultrasonographically in goats that received eCG or hCG, but not after GnRH or in response to the buck effect. Following the eCG-, hCG- or GnRII-induced ovulations and luteal phases in the goals of the present study, the next ovulation did not occur. However, in all of the goats after the introduction of the buck to the herd, the induced ovulations and luteal phases, both shortened and full-length, were followed by the next ovulatio suggesting the resumption of the regular cyclic ovarian function.
|Other language title versions||Influences of exogenous hormones and of the buck effect on the growth of caprine ovarian follicles during the non-breeding season|
|Publisher||Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW |
|Publishing place (Publisher address)||Kraków Kraków|
|Book series /Journal (in case of Journal special issue)||Zeszyty Naukowe Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Rozprawy, ISSN 1899-3486, (0 pkt)|
|Publication size in sheets||5.45|
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