Effect of synchronization protocols and GnRH treatment on the reproductive performance in goats

Ovarian Dynamics and Changes in Estradiol-17β and Progesterone Relationship with Standing Estrus, Preovulatory Follicles, and Ovulation Using Single Prostaglandin F2α Injection in Barbari Goats

The purpose of the present research was to define ovarian follicular dynamics and plasma endocrine profiles in response to a single PGF2α injection, administered indiscriminately during the breeding season of Barbari goats. Ovarian dynamics were observed at every 12 h interval by using B mode ultrasonography, blood samples for hormonal analysis such as estradiol 17β and progesterone were collected at every 12 h interval, and bucks with aprons were used to identify standing estrus at every 6 h interval. Relative to PGF2α, the start of standing estrus and ovulation differ (p < 0.05) between early- (n = 7), intermediate- (n = 6), and late-responding (n = 6) goats. The highest plasma level of estradiol 17β was detected 12 h prior to ovulation. The average diameter of the ovulatory follicle and length of standing estrus were comparable (p > 0.05) between the goats. The corpus luteum degenerated more quickly (p < 0.05) in early- than intermediate- and late-responding goats. Dominant follicle diameter and estradiol 17β concentration also differ (p < 0.05) among groups. Although the plasma level of progesterone did not vary (p = 0.065), the variation in progesterone concentration with time differed (p < 0.05) amongst the goats. As a result, this research indirectly reveals that the beginning of standing estrus, end of estrus, and ovulation after PGF2α might fluctuate in Barbari goats because of follicular and hormonal dynamics during the luteal phase.

Reproductive performance of goats treated with free gonadorelin or nanoconjugated gonadorelin at estrus

The reproductive performance of goats that received a GnRH analog (gonadorelin) fabricated with or without chitosan-sodium tripolyphosphate (TPP) nanoparticles on the day of estrus (day 0) was evaluated. The chitosan-TPP polymer was conjugated with gonadorelin using an ionic gelation method. Thirty-three multiparous Zaraiebi goats were synchronized for estrus with 2 intramuscular (im) injections of 125 μg prostaglandin F_2α 14 d apart. Goats showing signs of estrus were divided equally into 3 experimental groups and received a single im injection of 1 mL physiological saline (placebo; control), 50 μg/mL gonadorelin (GnRH), or 12.5 μg (quarter of GnRH dose)/mL chitosan-TPP-conjugated gonadorelin nanoparticles (NGnRH). Each goat underwent ultrasound imaging of their ovaries at day 0 and at day 10 after mating, and pregnancy was diagnosed 28 and 45 d after mating. The concentrations of estradiol (E₂) and progesterone (P₄) were determined at day 0 and at days 7, 14, 21, and 42 after mating. NGnRH size, polydispersity, and zeta potential were 93.91 nm, 0.302, and 11.6 mV, respectively. Chitosan-TPP nanoparticles showed 91.2% entrapment efficiency for GnRH. No differences in estrus rate, interval to estrus, or ovarian structure at day 0 were observed among the experimental groups, but the GnRH and NGnRH treatments significantly decreased the duration of estrus compared with the control. At day 10 after mating, both GnRH and NGnRH increased (P = 0.011) the number of corpora lutea compared with the control. Treatment with GnRH increased (P = 0.023) serum E₂ concentrations from day 7 to 42 after mating compared with NGnRH and control treatments. The highest (P = 0.043) serum P₄ concentration was observed in the GnRH group, followed by the NGnRH and control groups. The increase in serum P₄ concentration started earlier a on day 7 in the GnRH group but later on day 14 in the NGnRH group. Compared with the control, GnRH resulted in a higher (P = 0.041) P₄-to-E₂ ratio, followed by NGnRH. Both gonadorelin treatments significantly increased the twinning rate, the number of embryos at days 28 and 42, and prolificacy and decreased pregnancy losses compared with the control. In conclusion, the administration of GnRH at the time of estrus improved the prolificacy of goats by increasing both the ovulation rate and the number of embryos. In addition, the nanoformulation developed in this study allowed a 75% reduction in the conventional dose of gonadorelin without affecting the fertility and prolificacy of goats, indicating the bioavailability of the reduced GnRH dose after conjugation with developed nanoformula.