Influence of GnRH administration on timing of the LH surge and ovulation in dwarf goats

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.

Protein and mRNA expression of follicle-stimulating hormone receptor and luteinizing hormone receptor during the oestrus in the yak (Bos grunniens)

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) have a central role in follicle growth, maturation and oestrus, but no clear pathway in the seasonal oestrus of yak (Bos grunniens) has been found. To better understand the role of FSH and LH in seasonal oestrus in the yak, six yaks were slaughtered while in oestrus, and the pineal gland, hypothalamus, pituitary gland, and gonads were collected. Using real-time PCR and immunohistochemical assays, we determined the mRNA and protein expression of the FSH and LH receptors (FSHR and LHR) in these organs. The analysis showed that the FSHR mRNA expression level was higher in the pituitary gland tissue compared with LHR (p < .01) during oestrus. By contrast, there was low expression of FSHR and LHR mRNA in the pineal gland and hypothalamus. FSHR mRNA expression was higher than that of LHR (p < .05) in the ovary, whereas LHR mRNA expression was higher than that of FSHR (p < .01) in the uterus. FSHR and LHR proteins were located in the pinealocyte, synaptic ribbon and synaptic spherules of the pineal gland and that FSH and LH interact via nerve fibres. In the hypothalamus, FSHR and LHR proteins were located in the magnocellular neurons and parvocellular neurons. FSHR and LHR proteins were localized in acidophilic cells and basophilic cells in the pituitary gland, and in surface epithelium, stromal cell and gland epithelium in the uterus. In the ovary, FSHR and LHR protein were present in the ovarian follicle. Thus, we concluded that FSHR and LHR are located in the pineal gland, hypothalamus, pituitary and gonad during oestrus in the yak. However, FSHR was mainly expressed in the pituitary gland and ovaries, whereas LHR was mainly expressed in the pituitary gland and uterus.

The timing of oestrus, the preovulatory LH surge and ovulation in Blanca Andaluza goats synchronised by intravaginal progestagen sponge treatment is modified by season but not by body condition score

The aim of this study was to determine whether a seasonal pattern of reproductive events is followed after synchronisation by intravaginal progestagen sponge treatment in female Blanca Andaluza goats, and whether the timing of these events is affected by body condition score (BCS). During seasonal anoestrus (March), and again during the breeding season (November), the same 32 does were distributed into four subgroups according to their BCS: ≤2.25, =2.50, =2.75, and ≥3.00 (n=8 in all cases). They were then synchronised using a commercial intravaginal sponge treatment. Every 4h over the 72h following sponge removal, oestrous activity, the LH concentration and each doe's number of follicles were followed by transrectal ultrasonography. The does synchronised during seasonal anoestrus produced more follicles than those synchronised during the breeding season (P<0.01). The time elapsed between sponge removal and the onset of oestrus, the LH surge and time of ovulation, was also shorter in these does (P<0.001). The BCS only modified the number of follicles present in the ovary just before ovulation; this number was significantly lower in the =2.50 BCS subgroup than in the other subgroups (P<0.05). The present results show that the time to ovulation, and all events around it, are modified by the season in which Blanca Andaluza does are synchronised, but not by BCS.

Induction/synchronization of oestrus and ovulation in dairy goats with different short term treatments and fixed time intrauterine or exocervical insemination system

Two experiments were carried out on Ionica dairy goats in order to test the efficiency of: (1) short term-5-day combined progestogen-PGF2α-GnRH treatments on induction/synchronization of oestrus and fertility after natural mating in lactating goats and during the transition period (Experiment 1); (2) short term-9-day FGA-PGF2α-eCG treatments on synchronizing oestrus and ovulation (Experiment 2.1) and artificial insemination (AI) fixed time system in synchronized does (Experiment 2.2), during the breeding season. In Experiment 1, four treatment groups (N=24) were considered: (1) FPe-11d - control, FGA intravaginal sponges (11 days)+PGF2α (9th d)+eCG (11th d); (2) FPe-5d, FGA (5 days)+PGF2α (5th d)+eCG (5th d); (3) PFe-5d, PGF2α (D0)+FGA (5 days)+eCG (5th d); (4) GPe-5d, GnRH (D0)+PGF2α (5th d)+eCG (5th d). Goats were checked for oestrus and naturally mated. The occurrence of oestrus was 75.0, 78.3, 86.4, and 58.3% for groups 1-4, respectively, with significant differences (P<0.05) between groups 3 and 4. Interval to oestrus was earlier (P<0.05) in GPE-5d than in FPe-11d control group. There were no differences between the groups (P>0.05) in fertility or in prolificacy. In Experiment 2.1, 22 goats were subdivided into two treatment groups (N=11): (T1) FPe-11d (control), FGA (11 days)+PGF2α (9th d)+eCG (11th d); (T2) FPe-9d, FGA (9 days)+PGF2α (7th d)+eCG (9th d). Oestrus and ovulation times were monitored every 4h; ovulation rate was also determined. The induction of oestrus ranged from 91 to 100% and all goats ovulated. Intervals to oestrus, from the onset of oestrus to ovulation, from sponge removal to ovulation, and ovulation rates were 28.2±4.9 and 26.0±4.0h, 25.3±9.2 and 28.9±7.4h, 53.5±7.6 and 54.9±7.1h, 3.7±1.6 and 2.4±1.4 corpora lutea (P<0.05) for T1 and T2, respectively. In T2 a great abnormal ovulatory response was observed. In Experiment 2.2, 48 goats were synchronized with FPe-9d treatment and subjected to AI, performed 50h after s.r. with frozen semen, and subdivided into 2 AI system groups (N=24): T3, exocervical AI (100×10(6)Spz/doe); T4, intrauterine AI (20×10(6)Spz/doe). Fertility rate was higher (P<0.05) in T4. It seems that short term-5-day combined progestogen-PGF2α-GnRH-eCG treatments need to be investigated for AI fixed time.

Day 0 Protocol: Superstimulatory treatment initiated in the absence of a large follicle improves ovarian response and embryo yield in goats

A new superstimulatory protocol (Day 0 Protocol) to initiate FSH treatment in the absence of a large follicle was compared to a traditional protocol in goats. The Day 0 Protocol (n=44) consisted of pre-treatment with progesterone and eCG to synchronize ovulation and the emergence of Wave 1, with FSH starting 84 h after the end of progesterone exposure (i.e., soon after ovulation). The traditional protocol (n=46) consisted of 11 d of progesterone exposure, with FSH treatment beginning 2 d before the end of progesterone exposure. Treatment with FSH was initiated in the absence of a large follicle in 37/44 and in 6/46 goats in the Day 0 Protocol and traditional protocol, respectively (P<0.01). There was more CL in the Day 0 Protocol than in the traditional protocol (breeding season: 9.6+/-0.6 and 6.3+/-0.8, P<0.05; non-breeding season: 14.3+/-1.5 and 10.7+/-1.5; P<0.05). More Grades 1 and 2 embryos were recovered in the Day 0 Protocol than in the traditional protocol (breeding season: 4.8+/-0.7 and 1.8+/-0.5, P<0.05; non-breeding season: 5.6+/-1.1 and 3.5+/-0.7, P=0.07). Similarly, the proportion of embryos that were Grades 1 and 2 was higher for the Day 0 Protocol than for the traditional protocol (breeding season: 81/114, 71%, versus 16/43, 37%, P<0.05; non-breeding season: 118/203, 58% versus 95/205, 46%, P<0.05). In summary, the Day 0 Protocol, was effective in initiating superstimulatory treatment in the absence of a large follicle, and compared to the traditional protocol, induced a higher ovulation rate and better embryo yield in goats.

Synchrony of ovulation and follicular dynamics in merino ewes treated with GnRH in the breeding and non-breeding seasons

The effect of gonadotropin releasing hormone (GnRH) treatment on the time of ovulation and the occurrence of follicular dominance during the non-breeding and breeding seasons (experiment 1), and on fertility after artificial insemination (AI) in the non-breeding season (experiment 2), was examined in Merino ewes. Oestrus was synchronized in 40 nulliparous ewes (experiment 1; n = 20, in the non-breeding and breeding seasons) and in 79 multiparous ewes (experiment 2) using intravaginal sponges and pregnant mare serum gonadotropin. Thirty six hours after sponge removal (SR), half the ewes were injected (i.m.) with 40 microg of synthetic GnRH and the remainder used as controls. GnRH improved the synchrony of ovulation compared with the controls in the breeding (SD = 2.8 vs 5.7 days, p = 0.04) but not the non-breeding season (SD = 3.8 vs 4.4 days, p = 0.69), with ewes ovulating from 42 to 54 h (mean 50.4 +/- 4.08 h) and 42-60 h (mean 54.4 +/- 5.47 h) after SR for GnRH and control, respectively. For both treated and control ewes, ovulation occurred earlier in the non-breeding than the breeding season (50.1 vs 54.6 h; p = 0.002). GnRH had no effect on follicular dominance, as assessed by divergence (D: the time the ovulatory follicle exceeded the average size of the other non-ovulating follicles) or on the interval from D to ovulation (IDO). However, follicular dynamics differed between seasons. The mean follicle diameter increased at a faster rate up to 36 h after SR in the non-breeding compared with the breeding season and then rapidly declined, compared with a later peak (42 h after SR) in mean follicular size during the breeding season. IDO was shorter in the non-breeding than in the breeding season (26.7 +/- 4.30 h vs 39.6 +/- 4.53 h; p = 0.05). In experiment 2, ewes (n = 38 GnRH-treated, n = 40 controls) were inseminated in the uterus by laparoscopy 42 h or 48 h after SR with frozen-thawed sperm. The fertility of ewes treated with GnRH (nine of 39, 23%) was not different to the controls (eight of 38, 21%; p = 0.01). In conclusion the application of GnRH improved synchronization of ovulation but did not improve fertility rates after AI.

Advanced assisted reproduction technologies (ART) in goats

Assisted reproduction technologies (ART) are reviewed with special emphasis on goat genetic improvement programs. Estrous synchronization and artificial insemination are the most commonly used ART worldwide because of their simplicity and excellent cost/benefit, especially when proven sires are used. Multiple ovulation and embryo transfer (MOET) has not become widely used due to its unpredictability. In vitro embryo production using oocytes collected by laparoscopy from valuable donors has the potential to improve the results obtained from MOET and expand its applications (for example, using prepubertal donors). However, the costs and inefficiencies of the system might restrict its use to special situations. Finally, transgenesis and cloning are expected to have a significant impact on the future genetic improvement of livestock. However, because of low efficiencies and high costs, their present use is restricted to applications with high returns such as the production of recombinant proteins of pharmaceutical and biomedical interest.

New treatments associated with timed artificial insemination in small ruminants

Timed artificial insemination (TAI) is a very important tool in production systems, as it has a direct impact on cost-efficiency by reducing labour resulting from oestrus detection. However, to make TAI commercially feasible, hormonal treatments need to assure acceptable pregnancy rates and be economically viable. Recent advances in the knowledge of ovarian physiology (e.g. determination of follicular waves, sensitivity of the early corpus luteum) in small ruminants allowed the development of new treatments focused on an efficient estimation and synchronisation of the time of ovulation of the females of a treated flock/herd. In this review we summarise new information and concepts in the hormonal control of the life span of the corpus luteum, as well as methods to manipulate follicular growth in small ruminants. Additionally, we elaborate on recent studies concerning the use of TAI associated with short progestogen treatment in goats and the newly developed Synchrovine™ protocol (two doses of prostaglandin F2α given seven days apart) in sheep.