الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
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Abstract
The present study was conducted on five experiments as follows:
Experiment I
- It aimed at studying the ovarian follicular dynamics and hormonal changes in goats during early pregnancy
- Ovaries of she-goats (n=8) were scanned daily for follicles ( ≥ 2 mm in diameter) and corpora lutea by transrectal ultrasound with blood sampling from jugular vein for hormonal RIA during the first thirty five days after mating.
- During early pregnancy three (37.5%), four (50%) and one goat (12.5%) showed nine, eight, seven waves of follicular development, respectively. The corpora lutea were detected as early as Day 3.61± 0.45, reached its initial maximum diameter on Day 7.80±0.41 post breeding, followed by a non significant reduction in size from Day 15.14±0.45 to 21.85±0.50, before re-increase again.
- A transient rise in FSH levels was temporally associated with the day of wave emergence (3 days prior to wave emergence). The plasma LH and estradiol levels were negatively correlated with progesterone concentration. The plasma inhibin levels were negatively correlated with FSH concentration and positively correlated with the number of large size follicles. The pattern of plasma inhibin changes during early pregnancy showed its tendency to decrease with the progression of pregnancy.
- This experiment supported the hypothesis that follicular development during pregnancy in she-goats showed a wave like pattern with predominantly eight waves until day 35 after breeding; the number of follicular waves could be predicted by the number of FSH peaks and the role of inhibin as one of the FSH regulators is sustained during pregnancy.
Experiment II
- It aimed at studying the profiles of circulating steroid hormones, gonadotrophins, immunoreactive-inhibin and prolactin during pregnancy in goats and immunolocalization of inhibin subunits, steroidogenic enzymes and prolactin in corpus luteum and placenta.
- Ten cyclic she-goats were used in the present study. Blood samples were collected through jugular vein weekly from five goats from day of estrus to 18 weeks of gestation. Ovaries were collected after animal scarification during mid luteal (day 10; n=2), and pregnancy (2, 3, 4 months) meanwhile the placenta were also collected at 3 months (n=1) and 4 months (n=1) for immunohistochemical localization of inhibin subunits, steroidogenic enzymes and prolactin.
- The present results revealed a marked decline in the pituitary secretion of FSH and LH to basal levels throughout the gestation period. The plasma levels of immunoreactive (ir-) inhibin showed a substantial decline until the 13th week of gestation, followed by a gradual increase with maximal levels at the 17th week.
- The plasma progesterone concentration following a gradual increase during the first week after mating remained at high values with minimal fluctuations throughout the pregnant period. The plasma concentrations of estradiol and prolactin during pregnancy showed nearly a similar pattern, where they declined to basal levels during the first 4-5 weeks postbreeding, then increased gradually, with maximal concentration during the late pregnancy.
- Immunohistochemical localization of inhibin α, βA, βB, and steroidogenic enzymes; cytochrome P450 aromatase, 3β-hydroxysteroid dehydrogenase, cytochrome 17α-ydroxylase P450, and cholesterol side-chain cleavage cytochrome P450 in the cyclic and pregnant goat corpus luteum and placenta; revealed positive immunoreactivity in luteal cells without difference between the luteal and pregnancy stages. Conversely, the placental syncytiotrophoblasts showed lack of positive staining to inhibin βA and 3β-hydroxysteroid dehydrogenase. In addition, the giant binucleate cells of goat placenta showed positive immunoreactions to prolactin.
- from this experiment, it can be concluded that the high plasma concentration of ir-inhibin, estradiol, and prolactin during the late pregnancy may be of placental origin and that the placenta may have a vital role in the maintenance of pregnancy and the regulation of mammary growth during this critical period in goats.
Experiment III
- It aimed at studying the physiological roles of inhibin in regulation of FSH secretion and follicular development during early pregnancy in goats.
- Eight goats were investigated sonographically on Day 19-21 (Day 0=Day of mating) for pregnancy check. On Day 25 postbreeding; animals received either 10 ml of normal goat serum (control group; n=3) or antiserum against [Tyr (30)]-inhibin alpha (1-30) (treated group; n=5). The ovaries of all animals were daily scanned with ultrasound for the present follicles (≥2mm in diameter) from 1 day before to 5 days after treatment. Jugular blood samples were collected every 6 hours (h) starting 24 h before and until 120 h after treatment.
- The plasma concentration of FSH increased at 6 h and remained at significantly high levels until 120 h in treated vs. control group. The plasma concentrations of estradiol showed a marked increase at 66 h, with peak levels at 120 h after treatment of antiserum. The basal concentrations of LH and the pattern of plasma concentrations of progesterone were not significantly different between the two groups.
- The number of medium sized follicles (3.5-5.0 mm) increased considerably from Day 2, whereas small sized (3.5 mm or less) and large sized (5 mm or more) follicles increased noticeably from Day 3, as compared with pre-treatment and controls.
- The present experiment clearly indicated that inhibin is a key hormone in regulation of follicular development through regulation of endogenous FSH secretion during the early pregnancy in goats.
Experiment IV
- It aimed at studying the effect of stage of lactation on the postpartum ovarian activity and hormonal profiles in goats.
- Six goats were ultrasonographically investigated daily with blood sampling during early (day 5-25after kidding) and late (day 40-60 after kidding) stages of suckling.
- The total number of follicles did not differ between the 2 stages of suckling, but the number of medium and large sized follicles increased significantly during late suckling period. Four goats showed a similar pattern of follicular development during the experimental period characterized by emergence of 5 and 6 waves during early and late stages of suckling, respectively.
- Although, the mean plasma FSH concentrations coincided with total inhibin secretion were higher during late suckling as compared with early suckling period; there was no difference in the total hormonal secretion of LH, estradiol and prolactin between the two stages.
- This experiment indicated that the stage of suckling has a detrimental role on the ovarian activity during early postpartum period in goats as a result of the suppressive effect of suckling stimulus on the hypothalamic-pituitary-gonadal axis, or through prolactin modulation of follicle maturation.
Experiment V
- It aimed at studying the ovarian events and hormonal changes around first postpartum ovulation in goats
- Six parturient goats were ultrasonographically examined daily for estrous behavior from Day 5 (Day 0=day of kidding) until Day 70 postpartum.
- Five goats (83.3%) showed at least one ovulation by the end of the monitoring period, and this was followed by a short luteal phase.
- The ovulatory and the first postovulatory waves emerged at 6.5±0.42 days before and day 0.2±0.31 after ovulation, and the maximum diameter was 7.27±0.25 mm and 6.65±0.34mm respectively. The first ovulation followed by short luteal phase ranged from 4-6 days (5.0±0.32 days). The maximal diameter of CL was 8.49±0.47mm attained on day 3.0±0.32.
- There was a clear negative correlation between plasma inhibin and FSH concentrations during the pre- and post ovulatory periods. LH showed a small increase above basal levels before and after ovulation. The plasma concentration of progesterone increased significantly after ovulation reach 0.78±0.17 ng/ml on Day 2.6±0.6 after ovulation.
- The ovulatory event associated with a slight decline in prolactin levels (≤100ng/ml) prior to the day of ovulation. The plasma estradiol concentrations increased noticeably by Day 4.4±0.51 post ovulation, reached 4.48±0.76 pg/ml and coincided with a decline in progesterone concentration.
- This experiment indicated that FSH and inhibin have a minimal role in induction of postpartum ovulation, while the decreased prolactin and the increased LH levels might be responsible for the onset of ovulatory event. The occurrence of postovulatory short-luteal phase in all ovulated goats, pointed out the role of progesterone priming in resumption of the normal ovarian activity.