The effect of subluteal levels of exogenous progesterone on follicular dynamics and endocrine patterns during early luteal phase of the ewe

Effects of short and long - term nutrition and progesterone supplementation on the success of fixed - time artificial insemination in the ewe

The success of fixed - time artificial insemination (AI) in the ewe is variable due to poor synchrony of estrus. We examined the effects of long-term nutrition (LTN; low, medium, high - 6 months), short-term nutrition (STN; 1.0 M, 1.5 M - 14 days) and progesterone supplementation (P; single pessary, replacement on Day 9) on synchrony and reproductive outcomes. High LTN advanced (P < 0.05) estrus, increased (P = 0.06) pregnancy (range 71.1 - 81.1%) and improved (P < 0.01) litter size (range 1.30 - 1.50). STN increased (P < 0.05) pregnancy (79.0 versus 72.3%) but not litter size or timing of estrus. A LTN x STN interaction (P < 0.01) for time of estrus indicates that the effects of LTN were moderated by STN depending on the level of LTN. Pessary replacement delayed (P < 0.05) the onset of estrus, improved synchrony but did not affect pregnancy or litter size. High LTN increased (P < 0.05) the number of large (≥ 3.8 mm) and medium - size follicles (2.0 - 3.7 mm) but the diameter of large follicles tended to be reduced (P = 0.08) on Day 12. STN did not affect follicle number or size whilst P reduced (P < 0.05) the diameter of large follicles on Day 12 (4.83 versus 5.10 mm) and increased the number of medium - size follicles (3.56 versus 2.74 mm). In conclusion, both LTN and STN are major sources of variability in AI programs whilst pessary replacement has potential to reduce variability.

Effect of pre-synchronisation with progestogen and eCG on reproductive activity in synchronised ewes during anoestrous season

The objective of the study was to investigate the effect of pre-synchronisation on the occurrence of the oestrus and pregnancy rate after fixed time artificial insemination (FTAI) in synchronised ewes during the anoestrous season. Kivircik ewes (n = 84) were randomly assigned to one of the two treatment groups with (PRE; n = 42) or without (SYN; n = 42) pre-synchronisation. In the SYN group, the ewes were subjected to a 7-d short-term protocol (P4 insertion-6d-PGF2α-1d-P4 removal + eCG). In the PRE group, the same short-term protocol as in the SYN group was applied with 7 days apart for a pre-synchronised synchronisation protocol. A cervical FTAI was performed with fresh semen at 54 h after sponge removal. At the beginning of the synchronisation protocol, the oestrous response (66.7% vs. 0.0%) and cyclicity rates (64.3% vs. 14.3%) based on progesterone (P4) were higher in the PRE group compared to those in the SYN group, respectively (P < 0.01). However, the oestrous response after synchronisation was lower within 96 h (57.1% vs. 95.2%; P < 0.01) in the PRE group compared to that in the SYN group. Although the pregnancy rate after the FTAI was significantly (P < 0.05) lower in the PRE group (14.3%) than the SYN group (35.7%), the overall pregnancy rate after natural mating was not different (95.2%) between the groups. In conclusion, the pre-synchronisation decreased the oestrous response leading to a lower pregnancy rate after the FTAI in the synchronised ewes during the anoestrous season. Thus, attention should be paid to two consecutive administrations of eCG in a pre-synchronisation and synchronisation protocol in ewes.

Seventy years of progestagen treatments for management of the sheep oestrous cycle: where we are and where we should go

Management of the ovine oestrous cycle is mainly based on the use of exogenous hormones to mimic or enhance (progesterone and its analogues) or manipulate (prostaglandin F2α and its analogues) the activity of the corpus luteum, combined with the application of other hormones mimicking the pituitary secretion of gonadotrophins (e.g. equine chorionic gonadotrophin). These protocols have been applied without major change for decades but, now, there are two reasons to reconsider them: (1) our greatly improved knowledge of the dynamics of ovarian physiology, following the application of transrectal ultrasonography, indicates that modification of the protocols may improve fertility yields and (2) increasing concerns about animal health and welfare, food safety and the environmental impact of the treatments, as evidenced by public opinion and therefore market forces. Here, we offer an overview of these issues, introduce an updated protocol and suggest ways for future improvements to the protocols.

Luteotropic effects of human chorionic gonadotropin administered 7.5 days after synchronous estrous induction in Morada Nova ewes

This study was conducted in ewes to assess effects of human chorionic gonadotropin (hCG) administration after imposing an estrous induction treatment regimen. Ewes (n = 115) were treated with a 60 mg medroxyprogesterone-intravaginal-sponge for 6 d plus 200 IU of equine chorionic gonadotropin (eCG) im and 37.5 μg d-cloprostenol im 36 h before sponge removal (Day 0). After natural mating, ewes having at least one corpus luteum (CL; n = 108) were administered either 1 mL of saline (G-Control; n = 53) or 300 IU of hCG (G-hCG; n = 55) on Day 7.5 after sponge removal (Day 0). Ovarian ultrasonography and blood collection were performed on Days 7.5, 13.5, 17.5, 21.5, and 30.5. Accessory CL (aCL) were observed in 81.5 % (G-hCG) and 0.0 % (G-Control) of ewes (P = 0.0001). Diameter, area, and volume of luteal tissue were greater (P < 0.05) in G-hCG from Day 13.5 to 30.5. Progesterone (P4) concentrations were greater (P < 0.05) on Days 13.5, 17.5, 21.5 and 30.5 for ewes of the G-hCG group. Pregnancy percentage was similar (P = 0.25) between groups [47.1 % (G-control) compared with 60.0 % (G-hCG)], although total number of lambs produced by estrous synchronized ewes was greater (P = 0.005) in ewes of the G-hCG group (90.9 % compared with 66.0 %). In conclusion, hCG administration 7.5 days after sponge removal from Morada Nova ewes during the non-breeding season is an effective treatment to induce aCL formation, improve luteal tissue biometry and P4 concentrations, and to enhance the total number of lambs born.

Use of GnRH for Synchronization of the Follicular Wave in Assisted Reproductive Technologies in Sheep: A Preliminary Study

The present study aimed to set up a short-term protocol for synchronization of follicular wave emergence in sheep, concomitant with estrus synchronization, which would improve ovarian response in assisted reproductive technologies. Administration of a single GnRH dose, concomitant with the insertion of a progesterone-loaded CIDR device, caused regression of gonadotrophin-dependent follicles ≥4 mm in all the GnRH-treated sheep and in around 80% of the controls treated only with CIDR (p < 0.05). Similar percentages of ewes lost all follicles (around 70%) or only the largest one (around 30%) in both groups. Hence, 54.1% and 70% of the sheep lost all large follicles and initiated a new follicular wave in the control and GnRH groups, respectively (p < 0.05). The remaining sheep showed follicles that were still not dependent of luteinizing hormone (LH). So, in fact, all the sheep had non-dominant follicles after treatment. In conclusion, a treatment including GnRH at CIDR insertion would offer a time- and cost-efficient protocol for inducing follicular turnover and synchronizing a new follicular wave at any stage of the estrous cycle.

Intravaginal administration of progesterone using a new technique for sustained drug release in goats

The objective of the present study was to develop and evaluate a sustained release vaginal progesterone (P₄) capsule containing a mixture of mucoadhesive polymer and silicone fluid. Goats were administered a gelatin capsule containing 0.4 g of P₄ mixed in silicone fluid and either a hydroxypropylmethylcellulose (HM) or polyaclil starch (PA) base. The mean plasma P₄ concentrations at 2 and 12 h after administration were significantly higher in goats treated with PA capsules than in those with HM capsules. The plasma P₄ concentrations in goats treated with HM capsules increased and remained above 1.0 ng/ml for 96 h after administration, whereas the plasma P₄ concentrations in goats treated with PA capsules remained above 1.0 ng/ml for only 24 h after administration. In the next experiment, an HM capsule was attached to a silicone device and inserted in the vagina for 10 days. The plasma P₄ concentration remained similar to that of the natural luteal phase for 9 days. These results suggest that a mixture of mucoadhesive polymer and silicone fluid has the potential to be applied clinically as a sustained release base for estrus synchronization or hormonal therapy.

Effect of progesterone administration during growing phase of first dominant follicle on follicular wave pattern in buffalo heifers

In buffaloes, like other domestic mammals, antral follicles develop in a wave-like pattern. Factors predictive of a particular follicular wave pattern are yet to be identified. In this study, we examined the preponderance of 2- versus 3-wave patterns in 46 interovulatory intervals (IOIs) from 36 buffalo heifers, in which a subset of 10 heifers was scanned for 2 consecutive IOIs to record the repeatability of follicular wave pattern. Two-wave pattern was detected in 63.0% and 3-wave follicular pattern in 27.0% IOIs. The dominant follicles (DF) of both wave 1 as well as the ovulatory wave attained a smaller (P < 0.05) maximum diameter in 3-wave cycle as compared to 2-wave cycle. The mean duration of IOI was significantly shorter in 2-wave compared to three-wave cycles (20.5 ± 0.3 vs. 22.3 ± 0.2 days; P < 0.05). Out of 10 buffalo heifers, 7 displayed non-alternating patterns and 3 had alternating follicular wave patterns. We also tested the hypothesis that progesterone administration during early IOI results in increased preponderance of 3-wave pattern and heifers inseminated after ovulation of the third wave DF will have greater fertility. Sixteen heifers subjected to progesterone treatment from D0 (day of ovulation) in a decreasing dose until D5 were compared with control heifers (n = 10). Progesterone treatment significantly reduced the maximum diameter of DF of wave 1 (P < 0.001), whereas the mean duration of IOI remained unchanged (P > 0.05) between the two groups. Progesterone administration during early IOI significantly increased the proportion of 3-wave cycles as compared to control (P < 0.05). The hypothesis that progesterone administration during IOI results in increased preponderance of 3-wave pattern was supported. However, no change in fertility was recorded in progesterone-treated heifers (7 pregnant out of 16; 43.8%) as compared to untreated control heifers (4 out of 10 heifers; 40.0%). In summary, progesterone administration in buffalo heifers during the growing phase of wave 1 resulted in greater preponderance of 3-wave follicular patterns, with no significant effect on fertility.

Intravaginal Device-Type and Treatment-Length for Ovine Estrus Synchronization Modify Vaginal Mucus and Microbiota and Affect Fertility

Simple Summary

This study examined the effects of different intravaginal device types used for estrous cycle management in sheep, and the timing of their insertion, on vaginal features (characteristics of vaginal mucus discharge, pH and microbiota) and fertility under field conditions.

Abstract

Induction and synchronization of estrus and ovulation in sheep is based on intravaginal progestagen-impregnated polyurethane sponges or progesterone-loaded silicon-based devices (CIDR), in either short- (6–7 days) or long-term (12–14 days) protocols. Bearing in mind that the use of intravaginal sponges in long-term protocols has been related to the presence of vaginitis at removal, we compared the effects of sponges and CIDRs, maintained during either 7 or 14 days, on vaginal features (characteristics of vaginal mucus discharge, pH and microbiota) and fertility under field conditions. Almost all the ewes treated with intravaginal sponges showed vaginal discharge at device withdrawal, which was purulent and/or bloody in around 15% and 80% of the females treated for 7 and 14 days, respectively. The vaginal pH and microbiota changed in both groups when compared to control sheep, especially in ewes treated for 14 days, which showed a pH value around 8 and a higher incidence of Salmonella spp. and Staphylococcus aureus. On the other hand, independently of the length of the treatment, only around 15–20% of the sheep treated with CIDRs evidenced vaginal discharge (p < 0.00005 when compared to sponge groups), and such discharge was scarce, clear, and showed no changes in vaginal pH and microbiota when compared to control sheep. Fertility yields were associated with vaginal features, being higher in both short-term treatments (75%) and the long-term CIDR-based treatment (70%) than in the long-term sponge-based treatment (45%).

The stimulatory effect of subluteal progesterone environment on the superovulatory response of passive immunization against inhibin in goats

The objective of the current study was to investigate the effect of subluteal progesterone environment on the efficacy of the ovarian responses in goats passively immunized against endogenous inhibin. Twelve cycling female Shiba goats were synchronized using two doses of prostaglandin F2α 11 days apart. After detection of ovulation (D0, by ultrasonography), goats were randomly assigned into 2 groups: (1) Subluteal P4 group (SLP; n = 6), treated with a previously once-used controlled intravaginal progesterone-releasing device (ou-CIDR) intravaginal from D 6 to D 12 concurrently with a luteolytic dose of PGF2α at D6 (2) Normal Luteal P4 group (NLP; n = 6), had neither ou-CIDR nor PGF2α. In both groups, goats were treated with an intravenous injection of 10 ml of inhibin antiserum at D10. After that, another luteolytic dose of PGF2α was administrated to goats in both groups at D12, and withdrawal of ou-CIDR in the SLP group. Detection of estrous behavior was checked again 24 h following PGF2α administration and or ou-CIDR withdrawal at 8 h intervals with a teaser buck. The follicle populations ≥4 mm in each goat were monitored through transrectal ultrasonography daily from 1 day after inhibin antiserum administration (0 h) and continued until ovulation had been detected (disappearance of large dominant follicles by ultrasonography). In addition, a repeated ultrasonographic scanning was performed 7 days after ovulation, and the ovulation rate had been estimated by counting the number of observed corpora lutea by ultrasonography. Blood samples were collected for measurement of plasma circulating inhibin binding activity, FSH, LH, estradiol (E2), and progesterone (P4) in both groups. Results revealed significant increases in maximum diameter of the preovulatory follicles (5.92 ± 0.17 mm vs 5.31 ± 0.26 mm; P < 0.05), and the mean maximum number of follicles ≥ 4 mm in diameter (18.45 ± 3.40 vs 12.15 ± 6.21; P < 0.05) in the SLP group compared with that of the NPL group. No significant differences were observed between both groups in term of inhibin binding activity %, and FSH. Following immunization, significant increases in the concentrations of circulating LH (at 72 h) and E2 (from 48 to 84 h) were noted in the SLP group as compared with the values obtained from the goats in the NLP group. Moreover, significant increases in ovulation rate (13.85 ± 1.40 vs 5.67 ± 2.10; P < 0.01) and subsequent P4 concentrations (from 192 to 288 h) were found in the SLP group as against those of the NLP group. In conclusion, maintaining a subluteal P4 environment concurrently with passive immunization against endogenous inhibin may improve the superovulatory response in female Shiba goats.

Oocyte developmental competence is improved by relatively greater circulating progesterone concentrations during preovulatory follicular growth

This study evaluated the effect of progesterone priming during follicular growth on oocyte competence to undergo oocyte cleavage and embryo development in sheep. Two experiments were performed on a total of 195 females that either received or did not receive a progesterone treatment (CIDR-type device) during the first follicular wave, beginning soon after ovulation (i.e., Day 0 of the experiment). On Day 3, the follicular population and oocyte quality (Experiment 1 and 2) and the competence of oocytes for cleavage and embryo development (Experiment 2) were evaluated after laparoscopic ovum pickup (LOPU) and in vitro fertilization. In Experiment 1, in a 2 × 2 factorial study the progesterone priming treatment (treated or not) was or was not associated with a single dose of FSH in a slow-release hyaluronic acid preparation given on Day 0. The follicular population on Day 3 and the number and morphology of recovered cumulus oocyte complexes (COCs) were not affected by the progesterone treatment (P = NS) but were improved by the FSH administration (P <  0.05). An interaction between both treatments was observed (P <  0.05), with more desirable outcome with the females that received both the progesterone and the FSH treatments. In Experiment 2, half of the females received the exogenous progesterone priming, and all females received FSH on Day 0. After follicular aspiration on Day 3, the cleavage rate and the embryo development rate following in vitro fertilization and culture were greater in those females that received the progesterone treatment (P <  0.05). In conclusion, these studies provide evidence that progesterone treatment during follicular growth affects oocyte competence, with the greater progesterone concentrations enhancing the oocyte's capacity to undergo cleavage and embryo development.

Ovarian follicular dynamics and endocrine profiles in Polwarth ewes with high and low body condition

In this investigation we tested the hypothesis that static body condition (BC) of the ewe affects oestradiol and FSH with implications for subsequent follicular growth and turn-over. Sixteen Polwarth ewes were selected from a flock according to their BC score (scale: 1 emaciated; 5 obese). High BC (HBC) ewes (no. = 8) had a BC score of 4·1 (s.e. 0·1) and low BC (LBC) ewes (no. = 8) had a BC score of 1·9 (s.e. 0·1). Daily ultrasound examinations were performed and blood samples for progesterone, oestradiol and follicle-stimulating hormone (FSH) determination were collected. All HBC ewes (8/8) exhibited three waves of follicular development, while four LBC ewes (4/8) had two waves and the other four (4/8) had three waves of follicular development (P ≤ 0·05) during the interovulatory period. Overall, the emergences of 33 out of 44 follicular waves were preceded by significant increases in FSH concentrations. Maximum FSH concentrations were detected 0·9 ± 0·2 days before wave emergence. Oestradiol concentrations increased significantly during the growing phase in 38 out of 44 large follicles. A negative correlation between oestradiol and FSH was observed in HBC ewes. A similar inhibitory effect of oestradiol on FSH was observed in LBC ewes, irrespective of whether they developed two or three follicular waves. However, a longer period with high FSH was needed to promote the emergence of the second follicular wave in two-wave LBC ewes. Four HBC ewes had twin ovulations but no LBC ewes did (P ≤ 0·05). In HBC ewes, the follicular phase was characterized by lower oestradiol (6·5 (s.e. 1·0) pmol/l) but higher mean FSH concentrations (2·4 (s.e.0·4) μg/l) than in LBC ewes (8·9 (s.e. 1·2) pmol/l and 2·0 (s.e. 0·3) μg/l, respectively; P ≤ 0·05). The present results suggest that BC influences the pattern of follicular dynamics through changes in the endocrine milieu. Higher FSH concentrations during the follicular phase in HBC ewes, which allowed an extended period of follicular recruitment from a significantly larger pool of small antral follicles could explain the higher ovulation rate observed in this group.

Effect of a new device for sustained progesterone release on the progesterone concentration, ovarian follicular diameter, time of ovulation and pregnancy rate of ewes

This study evaluated the effectiveness of a new progesterone intravaginal device (DPR) in ewes through four experiments: Experiment 1 compared the circulating progesterone concentration of ovariectomized ewes that received either a new or a re-used DPR. Experiment 2 compared the progesterone concentration between DPR-estrous-synchronized ewes and naturally estrous-cycling ewes. Experiment 3 evaluated the effect of new and re-used DPRs on ovarian follicular dynamics and time of ovulation of estrous cycling ewes. Experiment 4 compared the pregnancy rate after the use of a DPR and Controlled Internal Drug Releasing Device (CIDR). The mean concentration of progesterone released by the DPR device during its first use (New Group: 5.1 ± 0.5 ng/ml) was greater than that during the second use (Re-used Group: 2.4 ± 0.3 ng/ml). There was no difference between the animals that received DPR devices for first and second use in terms of ovulatory follicle diameter, follicular wave emergence day for ovulatory follicle and period of ovulatory wave of ovarian follicular development. However, there was a significant difference between groups regarding the time between DPR device removal and first ovulation (New Group: 71.7 ± 2.5h and Re-Used Group: 63.9 ± 2.7h). Pregnancy rates were similar between ewes with DPR and CIDR devices. It was concluded that DPR is effective in increasing and maintaining progesterone concentrations, controlling follicular dynamics, promoting synchronized times of ovulation from healthy follicles, promoting development of a competent corpus luteum and when used results in pregnancy rates similar to that with use of the CIDR.

Fertility in a high-altitude environment is compromised by luteal dysfunction: the relative roles of hypoxia and oxidative stress

BACKGROUND

At high altitudes, hypoxia, oxidative stress or both compromise sheep fertility. In the present work, we tested the relative effect of short- or long-term exposure to high altitude hypobaric hypoxia and oxidative stress on corpora luteal structure and function.

METHODS

The growth dynamics of the corpora lutea during the estrous cycle were studied daily by ultrasonography in cycling sheep that were either native or naïve to high-altitude conditions and that were supplemented or not supplemented with antioxidant vitamins. Arterial and venous blood samples were simultaneously drawn for determination of gases and oxidative stress biomarkers and progesterone measurement. On day five after ovulation in the next cycle, the ovaries were removed for immunodetection of luteal HIF-1alpha and VEGF and IGF-I and to detect IGF-II gene expression.

RESULTS

The results showed that both short- and long-term exposure to high-altitude conditions decreased luteal growth and IGF-I and IGF-II gene expression but increased HIF-1 alpha and VEGF immunoexpression. The level of plasma progesterone was also increased at a high altitude, although an association with increased corpus luteum vascularization was only found in sheep native to a high-altitude location. Administration of antioxidant vitamins resulted in a limited effect, which was restricted to decreased expression of oxidative stress biomarkers and luteal HIF-1alpha and VEGF immunoexpression.

CONCLUSIONS

Exposure of the sheep to high-altitude hypobaric hypoxia for short or long time periods affects the development and function of the corpus luteum. Moreover, the observed association of oxidative stress with hypoxia and the absence of any significant effect of antioxidant vitamins on most anatomical and functional corpus luteum traits suggests that the effects of high altitude on this ovarian structure are mainly mediated by hypoxia. Thus, these findings may help explain the decrease in sheep fertility at a high altitude.

Comparison of the patterns of antral follicular development between hormonally synchronized and natural estrous cycles of non-seasonal, polyestrous goats in the tropics

The effects of estrus synchronization with prostaglandin F(2α) (PGF(2α)) and Controlled Internal Drug Release Device (CIDR) on ensuing antral follicular development were documented and compared to natural estrous cycles of non-seasonal tropical goats. Two to six follicular waves were observed, with the three-follicular wave pattern being most frequently observed (58%), followed by four follicular waves (31.6%) per estrous cycle. There were no significant differences (p>0.05) between the PGF(2α)- or CIDR-synchronized and natural estrous cycles nor between the synchronized and subsequent non-synchronized cycles in terms of the time of ovulation, the duration of inter-ovulatory intervals, daily numbers of antral follicles ≥3mm in diameter, and the number of follicular waves per cycle in the goats of the present study.

Ovarian response and embryo yield of Angora and Kilis goats given the day 0 protocol for superovulation in the non-breeding season

The aim of this study was to compare ovarian response and embryo yield of Day 0 protocol in Angora goats (AG) and indigenous Kilis goats (KG) in the non-breeding season. A total of 16 Angora goats (AG group) and 11 Kilis goats (KG group) were used in this study. In the synchronization process, after controlled internal drug release withdrawal, when estrus signs were observed, natural mating was performed. Ovarian response was determined by synchronized laparotomy 6 days after natural mating, and number of corpora lutea (CL) was recorded. Embryos were collected and morphologically evaluated by stereomicroscope. Synchronization rates did not differ between AG (88%, 14/16) and KG group (91%, 10/11). In AG and KG groups, the proportion of CL on the right (44% and 53%, respectively) and left (56% and 47%, respectively) ovaries were similar. The CL number per animal did not differ significantly between the two breeds and was determined as 4.4 ± 0.90 in AG group and 6.4 ± 1.44 in KG group. Transferable embryo yields were significantly higher in AG group (31/42, 74%) compared to KG group (16/46, 35%) in the non-breeding season (P < 0.01). In conclusion, it is suggested that the day 0 protocol can be used for goat superovulation in the non-breeding season; however, transferable embryo yields are affected by the breed.

Synchronization of oestrus and ovulation by short time combined FGA, PGF(2α), GnRH, eCG treatments for natural service or AI fixed-time

Two experiments were conducted in ewes in order to develop an oestrus-ovulation short time synchronization protocol based on combined FGA, PGF(2α), GnRH, eCG treatments, for use in dairy sheep before natural service (Experiment 1) or for fixed-time artificial insemination (Experiment 2), during the breeding season. In Experiment 1 seventy-five non-lactating dairy ewes were subdivided into 5 treatment groups (N=15): (1) Group Fe - control, which received FGA vaginal sponges (14 days)+eCG (Day 14); (2) Group FPe, FGA (5 days)+PGF(2α) (Day 5)+eCG (Day 5); (3) Group PFe, PGF(2α) (Day 0)+FGA (5 days)+eCG (Day 5); (4) Group PFG, PGF(2α) (Day 0)+FGA (5 days)+GnRH (30h after sponge removal, s.r.); (5) Group GPe, GnRH (Day 0)+PGF(2α) (Day 5)+eCG (Day 5). Ewes were checked for oestrus and hand-mated. Time of ovulation was recorded by laparoscopy for 10 animals from each treatment. The percentages of female in oestrus and the interval to oestrus (h after treatment), fertility and prolificacy rate were recorded. There were no treatment differences in the percentage of females in oestrus. The interval to oestrus was earlier in Fe Group and delayed in FPe Group (P<0.01). Ovulation time was earlier in GPe Group compared to FPe Group (P<0.05). Fertility rates were significantly different (P<0.05) between the PFe and the FPeG Groups compared with the PFG Group. No significant differences were observed in prolificacy among the treatments. In Experiment 2, sixty dry ewes were subdivided (N=20) into the following three experimental treatment groups: (1) Group FP, FGA (5 days)+PGF(2α) (Day 5); (2) Group FPG, FGA (5 days)+PGF(2α) (Day 5)+GnRH (30hs.r.); (3) Group FPeG, FGA (5 days)+PGF(2α) (Day 5)+eCG (Day 5)+GnRH (30hs.r.). These were further subdivided into two groups (N=10) corresponding to 52 and 60hs.r. fixed-time insemination. Laparoscopic intrauterine insemination was performed with frozen semen (80×10(6)spermatozoa/dose) and ovulation time was recorded in a subgroup (N=10). GnRH resulted in an earlier ovulation time (P<0.05) in FPG and FPeG Groups (53.0h vs 61.6h). Fertility rate was higher in FPeG treated ewes inseminated at 60hs.r. (60%, 6/10). In FP and FPG Groups fertility rates were higher following insemination at 52hs.r. (50.0 and 40.0%).

LH pulse frequency and the emergence and growth of ovarian antral follicular waves in the ewe during the luteal phase of the estrous cycle

BACKGROUND

In the ewe, ovarian antral follicles emerge or grow from a pool of 2-3 mm follicles in a wave like pattern, reaching greater than or equal to 5 mm in diameter before regression or ovulation. There are 3 or 4 such follicular waves during each estrous cycle. Each wave is preceded by a peak in serum FSH concentrations. The role of pulsatile LH in ovarian antral follicular emergence and growth is unclear; therefore, the purpose of the present study was to further define this role.

METHODS

Ewes (n = 7) were given 200 ng of GnRH (IV) every hour for 96 h from Day 7 of the estrous cycle, to increase LH pulse frequency. Controls (n = 6) received saline. In a second study, ewes (n = 6) received subcutaneous progesterone-releasing implants for 10 days starting on Day 4 of the cycle, to decrease LH pulse frequency. Controls (n = 6) underwent sham surgery. Daily transrectal ovarian ultrasonography and blood sampling was performed on all ewes from the day of estrus to the day of ovulation at the end of the cycle of the study. At appropriate times, additional blood samples were taken every 12 minutes for 6 h and 36 min or 6 h in studies 1 and 2 respectively.

RESULTS

The largest follicle of the follicular wave growing when GnRH treatment started, grew to a larger diameter than the equivalent wave in control ewes (P < 0.05). Mean serum estradiol and progesterone concentrations were higher but mean serum FSH concentrations were lower during GnRH treatment compared to control ewes (P < 0.05). The increased serum concentrations of estradiol and progesterone, in GnRH treated ewes, suppressed a peak in serum concentrations of FSH, causing a follicular wave to be missed. Treatment with progesterone decreased the frequency of LH pulses but did not have any influence on serum FSH concentrations or follicular waves.

CONCLUSION

We concluded that waves of ovarian follicular growth can occur at LH pulse frequencies lower than those seen in the luteal phase of the estrous cycle but frequencies seen in the follicular phase, when applied during the mid-luteal phase, in the presence of progesterone, do enhance follicular growth to resemble an ovulatory follicle, blocking the emergence of the next wave.

Preovulatory follicle development in goats following oestrous synchronization with progestagens or prostaglandins

The study reports on differences in the dynamics of growth and functionality of preovulatory follicles in response to oestrous synchronization, either by the administration of two doses of prostaglandin or by an intravaginal progestagen sponge, in goats. The progestagen-treated group (n = 8) showed more follicles of preovulatory size (> or =5.5 mm) than the cloprostenol group (n = 8) during the follicular phase (4.5 +/- 0.6 vs 1.9 +/- 0.2, p < 0.01). The diameters of the largest follicles (LF1, LF2 and LF3) were also larger in the progestagen group (LF1, 7.8 +/- 0.3 vs 7.0 +/- 0.2 mm, p < 0.05; LF2, 6.7 +/- 0.2 vs 5.6 +/- 0.2 mm, p < 0.01; LF3, 5.5 +/- 0.3 vs 4.2 +/- 0.2 mm, p < 0.01). The study of the preovulatory follicles showed that 27.2% (3/11) of the follicles were in the static phase in the cloprostenol group, whilst 71.4% (10/14) were static in progestagen group (p < 0.05). Higher plasma oestradiol levels were recorded in the progestagen-treated goats during the 48 h prior to cloprostenol injection or progestagen withdrawal (4.2 +/- 0.4 vs 3.0 +/- 0.2 pg/ml, p < 0.05). In conclusion, goats with oestrus synchronized by progestagen showed a higher number of preovulatory-sized follicles, but a decreased oestradiol secretion when compared with does with oestrus synchronized by using prostaglandin analogues. These would support the development of alternative protocols for assisted reproduction.

Short- and long-term effects of unilateral ovariectomy in sheep: causative mechanisms

The mechanisms of ovulatory compensation following unilateral ovariectomy (ULO) are still not understood. In the present study, we investigated the short- and long-term effects of ULO in sheep using transrectal ovarian ultrasonography and hormone estimations made during the estrous cycle in which surgery was done, the estrous cycle 2 mo after surgery, and the 17-day period during the subsequent anestrus. The ULOs were done when a follicle in the first follicular wave of the cycle reached a diameter > or =5 mm, leaving at least one corpus luteum and one ovulatory-sized follicle in the remaining ovary. Ovulation rate per ewe was 50% higher in the ULO ewes compared with the control ewes at the end of the cycle during which surgery was performed, but it did not differ between groups at the end of the cycle, 2 mo later. This compensation of ovulation rate in ULO ewes was due to ovulation of follicles from the penultimate follicular wave in addition to those from the final wave of the cycle. Ovulation from multiple follicular waves appeared to be due to a prolongation of the static phase of the largest follicle of the penultimate wave of the cycle. Interestingly, the length of the static phase of waves was prolonged in ULO ewes compared with control ewes in every instance where the length of the static phase could be determined. Changes in follicular dynamics due to ULO were not associated with alterations in FSH and LH secretion. In conclusion, ovulatory compensation in ULO sheep involves ovulation from multiple follicular waves due to the lengthened static phase of ovulatory-sized follicles. These altered antral follicular dynamics do not appear to be FSH or LH dependent. Further studies are required to examine the potential role of the nervous system in the enhancement of the life span of the ovulatory-sized follicles leading to ovulatory compensation by the unpaired ovary in ULO sheep.

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.

Developmental programming: follicular persistence in prenatal testosterone-treated sheep is not programmed by androgenic actions of testosterone

Testosterone (T) treatment during early-midgestation (30-90 d; term is 147 d) leads to reproductive cycle defects. Daily ultrasonography in prenatal T-treated female sheep during the first two breeding seasons revealed an increase in the number of large follicles and follicular persistence. The objective of this study was to determine whether follicular persistence in prenatal T-treated females was programmed by the androgenic actions of T. Pregnant Suffolk ewes were injected with 100 mg (im; twice weekly) of T propionate or dihydrotestosterone (DHT, a nonaromatizable androgen) in cottonseed oil from d 30 to d 90 of gestation. Prior to daily transrectal ovarian ultrasonography, estrus was synchronized with two injections of 20 mg of prostaglandin F2alpha (PGF2alpha) given 11 d apart in two consecutive years. In yr 1 ultrasonography began 14 d after PGF2alpha, during the presumptive luteal phase, and continued until subsequent ovulation and corpora lutea were detected (10-13 d). In yr 2, ultrasonography began 2 d before the last PGF2alpha injection and concluded 25 d after the last PGF2alpha injection. Daily changes in appearance and disappearance of ovarian follicles and follicular sizes were assessed. Prenatal DHT, but not prenatal T, treatment increased the total number of follicles by increasing the number of small follicles. Prenatal T, but not DHT, treatment increased (P<0.05) the number of large follicles with the majority of prenatal T-treated females manifesting follicular persistence. The data indicate that occurrence of large-sized follicles and follicular persistence in prenatal T-treated females are not programmed by androgenic actions but likely are programmed by estrogenic actions stemming from aromatization of T to estradiol.

Endocrine, luteal and follicular responses after the use of the short-term protocol to synchronize ovulation in goats

The effect of the so-called Short-Term Protocol (5-day progesterone treatment+PGF(2)alpha) on ovarian activity and LH surge was studied in goats. The goats received 250IU eCG at the time of device withdrawal (eCG group; n=7), or 200microg of EB (estradiol benzoate) 24h after device withdrawal (EB group; n=8), or received neither eCG nor EB (control group; n=8). The Short-Term Protocol induced greater (4.1+/-1.1ng/ml) progesterone serum concentrations at 24h after start of the treatment, that declined to 0.2+/-0.1ng/ml at 12h after device withdrawal. In all of the groups, the maximum concentration of estradiol-17beta was reached at about 36h after device withdrawal. Maximum concentration was greater in the EB group (76.9+/-24.6pmol/l) than in the control group (41.8+/-9.0pmol/l; P<0.01), with the eCG group showing intermediate concentration (70.3+/-32.5pmol/l; P=NS). The LH peak occurred earlier in the eCG group (38.4+/-2.0h after device withdrawal) and in the EB group (41.0+/-4.1h), than in the control group (46.3+/-5.1h; P<0.05). Ovulation occurred earlier in the eCG group (5/7) and in the EB group (8/8) (58.8+/-2.7h and 63.0+/-5.6h, respectively), than in the control group (7/8) (70.2+/-8.3h; P<0.05). In summary, the Short-Term Protocol induced similar concentrations of progesterone among treated goats. In addition, eCG or EB resulted in a similar increase in estradiol-17beta and a similar LH surge, which induced ovulation in most females (86.7%) in a consistent interval (about 60h) after the end of progesterone exposure.

Does injection of prostaglandin F2α (PGF2α) cause ovulation in anestrous Western White Face ewes?

In a previous study in our laboratory, treatment of non-prolific Western White Face (WWF) ewes with PGF(2 alpha) and intravaginal sponges containing medroxyprogesterone acetate (MAP) on approximately Day 8 of a cycle (Day 0 = first ovulation of the interovulatory interval) resulted in ovulations during the subsequent 6 days when MAP sponges were in place. Two experiments were performed on WWF ewes during anestrus to allow us to independently examine if such ovulations were due to the direct effects of PGF(2 alpha) on the ovary or to the effects of a rapid decrease in serum concentrations of progesterone at PGF(2 alpha)-induced luteolysis. Experiment 1: ewes fitted with MAP sponges for 6 days (n = 12) were injected with PGF(2 alpha) (n = 6; 15 mg im), or saline (n = 6) on the day of sponge insertion. Experiment 2: ewes received progesterone-releasing subcutaneous implants (n = 6) or empty implants (n = 5) for 5 days. Six hours prior to implant removal, all ewes received a MAP sponge, which remained in place for 6 days. Ewes from both experiments underwent ovarian ultrasonography and blood sampling once daily for 6 days before and twice daily for 6 days after sponge insertion. Additional blood samples were collected every 4 h during sponge treatment. Experiment 1: 4-6 (67%) PGF(2 alpha)-treated ewes ovulated approximately 1.5 days after PGF(2 alpha) injection; these ovulations were not preceded by estrus or a preovulatory surge release of LH, and resulted in transient corpora hemorrhagica (CH). The growth phase was longer (P < 0.05) and the growth rate slower (P < 0.05) in ovulating versus non-ovulating follicles in PGF(2 alpha)-treated ewes. Experiment 2: in ewes given progesterone implants, serum progesterone concentrations reached a peak (1.7 2 ng/mL; P < 0.001) on the day of implant removal and decreased to basal concentrations (<0.17 ng/mL; P < 0.001) within 24 h of implant removal. No ovulations occurred in either the treated or the control ewes. We concluded that ovulations occurring after PGF(2 alpha) injection, in the presence of a MAP sponge, could be due to a direct effect of PGF(2 alpha) at the ovarian level, rather than a sudden decline in circulating progesterone concentrations.

Reproductive Performance of Ewes after 5-Day Treatment with Intravaginal Inserts Containing Progesterone in Combination with Injection of Prostaglandin F2alpha

Three experiments were conducted with a total of 1579 ewes to examine reproductive performance in response to synchronization of oestrus during the breeding season, using controlled internal drug releasing (CIDR-G) inserts in regimens designed to provide high concentrations of circulating progesterone. In experiment 1, treatment with two CIDR-G inserts for 12 days produced conception rate (79%) and prolificacy (1.9) to first service equivalent to breeding at natural oestrus (56% and 2.0, respectively). Pregnancy rates to two service periods were 90 and 79%, respectively. In experiments 2 and 3, progesterone was delivered by a single CIDR-G insert for 5 days in combination with prostaglandin F2alpha (PGF2alpha; 5 mg i.m., twice, 3 h apart) the day before (experiment 2), or at insert removal (experiment 3). The combined treatments improved rates of synchronization of oestrus (p<0.01) by 23 and 20% points, respectively, and pregnancy rates to the first service period by 19 (p<0.05) and 13 (p<0.01) percentage points, respectively, compared to treatment with PGF2alpha alone. It is concluded that the combination of treatment for 5 days with a CIDR-G insert and two injections of 5 mg PGF2alpha, the day before, or the day of insert removal, were effective treatments to obtain high fertility at synchronized oestrus in ewes during the breeding season.

Fetal programming: prenatal testosterone treatment leads to follicular persistence/luteal defects; partial restoration of ovarian function by cyclic progesterone treatment

Prenatal testosterone (T) excess during midgestation leads to estrous cycle defects and polycystic ovaries in sheep. We hypothesized that follicular persistence causes polycystic ovaries and that cyclic progesterone (P) treatment would overcome follicular persistence and restore cyclicity. Twice-weekly blood samples for P measurements were taken from control (C; n = 16) and prenatally T-treated (T60; n = 14; 100 mg T, im, twice weekly from d 30-90 of gestation) Suffolk sheep starting before the onset of puberty and continuing through the second breeding season. A subset of C and T60 sheep were treated cyclically with a modified controlled internal drug-releasing device for 13-14 d every 17 d during the first anestrus (CP, 7; TP, 6). Transrectal ovarian ultrasonography was performed for 8 d in the first and 21 d in the second breeding season. Prenatal T excess reduced the number, but increased the duration of progestogenic cycles, reduced the proportion of ewes with normal cycles, increased the proportion of ewes with subluteal cycles, decreased the proportion of ewes with ovulatory cycles, induced the occurrence of persistent follicles, and reduced the number of corpora lutea in those that cycled. Cyclic P treatment in anestrus, which produced one third the P concentration seen during luteal phase of cycle, did not reduce the number of persistent follicles, but increased the number of progestogenic cycles while reducing their duration. These findings suggested that follicular persistence might contribute to the polycystic ovarian morphology. Cyclic P treatment was able to only partially restore follicular dynamics, but this may be related to the low replacement concentrations of P achieved.