Ultrasound and endocrine evaluation of the ovarian response to a single dose of 500 IU of eCG following a 12-day treatment with progestogen-releasing intravaginal sponges in the breeding and nonbreeding seasons in ewes

Evaluation of the effect of melatonin implantation in rams and eCG dose in ewes synchronized by a CIDR-eCG protocol on reproductive performance of Lacaune sheep breed during non-breeding season

Sustainable production of milk is favorable in dairy sheep industry, which necessitates year-round reproduction of rams and ewes even during non-breeding season. Hence, protocols facilitating reproduction of rams and ewes during non-breeding season are of importance for this purpose. Therefore, the present study was conducted to investigate the effect of melatonin implantation in rams and administration of 400 IU eCG (E400) versus 300 IU eCG (E300) in ewes on reproductive performance of Lacaune sheep breed during non-breeding season. Rams were allocated to two groups including untreated (control, CON; n = 36) and melatonin-treated (MEL; n = 37). A subset of rams from CON (n = 7) and MEL (n = 7) groups were used for assessment of scrotal circumference, kinematic and functional characteristics of sperm, total antioxidant capacity (TAC) of semen and circulating testosterone on Days 0 (the beginning of study) and 60 (60 days after melatonin implantation). Further, the study had a 2 × 2 factorial design with four experimental groups including 1) ewes treated with E300 and introduced to CON rams (E300CON; n = 17 rams and 172 ewes), 2) ewes treated with E300 and introduced to MEL rams (E300MEL; n = 18 rams and 177 ewes), 3) ewes treated with E400 and introduced to CON rams (E400CON; n = 19 rams and 192 ewes), and ewes treated with E400 and introduced to MEL rams (E400MEL; n = 19 rams and 190 ewes). Melatonin implantation improved scrotal circumference, concentration, progressive motility, velocity, mitochondrial membrane potential and viability of sperm, TAC of semen, concentration of testosterone and fertility of rams (P < 0.05). Besides, E400 compared with E300 enhanced synchronization of estrus and fertility in ewes (P < 0.05). In conclusion, melatonin implantation promoted reproductive performance in Lacaune rams, and increase in dose of eCG improved reproductive performance in Lacaune ewes.

Ovarian Response and Fertility after Short-Term Progestagen/eCG Treatments Are Compromised in Nulliparous Sheep during Non-Breeding Season

The objective of this investigation was to determine the ovarian response, fertility, and prolificacy of nulliparous sheep when compared to multiparous sheep after a short-term (7 days) CIDR/eCG treatment which was administered during the non-breeding season. All the multiparous sheep, whereas only 54% of the nulliparous ewes, showed signs of estrus. However, 81.8% of the multiparous sheep and 100% of the nulliparous ewes ovulated. Fertility was also low after short-term progesterone treatments during the anestrous season in maiden sheep (30.8 vs. 72.7% in multiparous ewes). Such results indicate significant differences in the response to CIDR/eCG protocols for induction and synchronization of estrus and ovulation between nulliparous and multiparous sheep during the non-breeding season.

Approaches of estrous synchronization in sheep: developments during the last two decades: a review

The objective of the current review was to summarize the protocols used for estrous synchronization in ewes during the last two decades. Progesterone (P4) is a major hormone used in most protocols. P4 in the form of a controlled internal drug releasing (CIDR) device, medroxyprogesterone acetate (MAP), and fluorogestone acetates (FGA) has been used for estrous synchronization. Also, gonadotropins such as equine chorionic gonadotropin (eCG) and gonadotropin-releasing hormone (GnRH) are often administered at the end of P4-based protocols to improve fertility. Moreover, the administration of prostaglandins (PG) and ram effects have been used for estrus induction and synchronization of ewes. The findings of previous studies indicate that the outcome of administering various synthetics P4 analogues (CIDR, MAP, and FGA) in ewes is comparable in terms of estrous synchronization/induction. The supplementation of P4-based protocols with eCG, however, improves the estrus response and pregnancy rate during breeding and non-breeding season. On the other hand, PG is effective for successful estrous synchronization during the breeding season only. Often, two injections of PG are administered either 11 or 14 days apart along with P4-based protocols to lyse ovine corpus luteum (CL) when it is receptive to PG i.e., 3 days post-ovulation. Alternatively, the "ram effect" has been shown to improve the efficacy of P4-based protocols and can be used as an alternative to eCG in ewes. The current review describes the methods of synchronization and their outcomes during breeding and a non-breeding season in ewes.

Changes in ovarian morphology and hormone concentrations associated with reproductive seasonality in wild large Japanese field mice (Apodemus speciosus)

Wild large Japanese field mice (Apodemus speciosus) responses to cyclic seasonal changes are associated with physiological and behavioral changes. However, the detailed regulation of oogenesis in the ovary during the seasonal reproductive cycle in wild large Japanese field mice has not been studied. We assessed the dynamics and changes in ovarian morphology and hormone concentrations associated with reproductive seasonality throughout the year. The stages of the ovarian morphological breeding cycle of wild large Japanese field mice were classified as breeding, transition, and non-breeding periods during the annual reproductive cycle. Measurement of blood estradiol concentrations throughout the year showed that the levels in September and October were higher than those in other months. It is presumed that follicle development starts from a blood estradiol concentration of 38.4 ± 27.1 pg/mL, which marks a shift from the transitional season to the breeding season, followed by the transition to the non-breeding season at 26.1 ± 11.6 pg/mL. These results suggest that seasonal follicle development in wild rodents is correlated with estradiol regulation. We consider this species to be an alternative animal model for studying seasonal reproductive changes and the effects of environmental changes.

Effects of Equine Chorionic Gonadotropin on Ovulatory and Luteal Characteristics of Mares Submitted to an P4-Based Protocol of Ovulation Induction With hCG

The aim of this study was to evaluate the effect of equine chorionic gonadotropin (eCG) at the end of progesterone (P4) treatment on follicular and luteal characteristics during transition period (TP) and reproductive breeding season (RP). A total of 13 crossbred mares were distributed in two experimental groups in the spring and summer (n = 26). The animals received intravaginal P4 (1.9 g) releasing device from D0 to D10. On removal of P4 device, the mares received 400 IU of eCG (eCG group) or saline solution (control group). Human chorionic gonadotropin (hCG; 1.750 IU) was administered (DhCG) as soon as ovulatory follicle (OF) ≥35 mm was detected. Ovarian ultrasonography was performed from D0 until 15 days after ovulation. Blood samples were collected on D0, D5, D10, DhCG, 9 days after ovulation (CL9D), and 13 days after ovulation (CL13D). P4 and estradiol concentrations were assessed by chemiluminescence. Data were compared by Tukey test at P < .05. Ovulation rate was similar (P = .096) between seasons (RP = 100%; TP = 70%) but occurred earlier (P = .015) in RP (34.8 ± 10.1 hours) compared with TP (42.0 ± 10.4 hours). Interactions between season and treatment were observed for OF diameter (mm) (RP/control = 36.2 ± 1.8ab; RP/eCG = 32.9 ± 2.8 b; TP/control = 32.2 ± 1.2 b; TP/eCG = 37.2 ± 1.9a; P = .004) and for corpus luteum (CL) diameter (mm) on CL13D (RP/control = 25.4 ± 3.5a; RP/eCG = 22.5 ± 1.8ab; TP/control = 21.6 ± 4.9 b; TP/eCG = 27.4 ± 4.3a; P = .023), although no differences were observed for serum P4 on CL13D (RP/control = 6.0 ± 3.1 ng/mL; RP/eCG = 5.8 ± 0.9 ng/mL; TP/control = 3.6 ± 2.7 ng/mL; TP/eCG = 5.1 ± 2.3 ng/mL; P = .429) or for day of structural CL regression (RP/control = 12.8 ± 1.9; RP/eCG = 12.1 ± 1.1; TP/control = 11.0 ± 1.7; TP/eCG = 13.2 ± 2.0; P = .102). The application of eCG at the moment of P4 implant removal seemed to increase the capacity of luteal maintenance during spring TP. However, eCG treatment was worthless during the breeding season.

Efficiency of CIDR-Based Protocols Including GnRH Instead of eCG for Estrus Synchronization in Sheep

Simple Summary

This study examines the preovulatory and ovulatory events (in terms of the timing of onset of estrus behavior, preovulatory LH surge, and ovulation) and the yields obtained (in terms of ovulation rate, progesterone secretion, and fertility) after insertion of controlled internal drug release (CIDR) devices for 5 days and treatment with equine chorionic gonadotrophin (eCG) or gonadotrophin-releasing hormone (GnRH).

Abstract

The present study examined, for meat sheep (Segureña breed; 2–5-years old, mean body score of 3.5 ± 0.5), the timings of onset of estrus behavior, preovulatory luteinizing hormone (LH) surge and ovulation, and the ovulation rate and fertility obtained after insertion of controlled internal drug release (CIDR) devices for 5 days plus treatment with equine chorionic gonadotrophin (eCG; single dose at CIDR removal, n = 19 ewes) or gonadotrophin-releasing hormone (GnRH, either in a single dose at 56 h after CIDR removal, group CIDR-GnRH, n = 19 ewes; or in one dose at CIDR insertion and another dose 56 h after CIDR removal, group GnRH-CIDR-GnRH, n = 19 ewes). In all the ewes, the appearance of estrus behavior ranged between 84% and 90% and all females showing estrus signs had subsequent preovulatory LH peaks and ovulations. Onset of these events was earlier in the CIDR-eCG group than in the CIDR-GnRH and GnRH-CIDR-GnRH groups (p < 0.05). These differences were mainly determined by the onset of estrus behavior, since timing and intervals of LH peak and ovulation were similar among treatments. In fact, the range of ovulations was narrower in the GnRH-CIDR-GnRH group, which suggests better synchronization of follicular growth (p < 0.05). In conclusion, protocols with two doses of GnRH offer similar yields to eCG protocols.

Efficacy of the re-utilization of an ear implant impregnated with progestogen in estrus synchronization response and pregnancy in sheep

The goal of this study was to assess the efficacy of the re-utilization of an ear implant impregnated with norgestomet on estrus synchronization response and pregnancy rates in sheep. Fifty-five Texel ewes were classified according to body condition (3.5) and live weight (65 kg), and randomly assigned to two experimental groups: NORN-new (n = 30) and NORU-used (n = 25). The dose of norgestomet used in the treatments was half of that recommended for bovine (1.5 mg). The synchronization protocol consisted of an ear implant inserted on day 0 (beginning of the experiment) and kept for 6 days. The removal of the implant on day 6 was followed by an injection of a prostaglandin analogue (0.263 mg) and eCG (250 IU). Rams with paint applied to their chest were used to facilitate estrus detection for 5 days following implant withdrawal. Estrus behavior was observed in 93.3% (28/30) and 90% for NORN and NORU, respectively. Pregnancy rates for NORN were 73.3% and for NORU were 68%. Estrus behavior and pregnancy rates between treatment groups did not differ statistically. Therefore, the re-utilization of ear implants impregnated with norgestomet, in addition to eCG and a prostaglandin analogue in short-term estrus synchronization protocols, allow acceptable estrus response and pregnancy rates in sheep.

Superovulatory response and embryo quality in Katahdin ewes treated with FSH or FSH plus eCG during non-breeding season

The aim of this study was to evaluate the effect of a co-treatment of follicle-stimulating hormone (FSH) plus equine chorionic gonadotrophin (eCG) on serum insulin and insulin-like growth factor 1 (IGF-1) concentrations, superovulatory response, ovulatory rate, and number and production of embryos in Katahdin breed ewes during the non-breeding season. Twenty Katahdin ewes were synchronized with progestagens (CIDR) and assigned to two superovulation treatments (n = 10): (1): ewes treated with 200 mg ewe^-1 of FSH from day 5 to 8 after CIDR insertion at decreasing doses every 12 h (FSH group) and (2) ewes treated as FSH group plus 300 IU of eCG on day 5 after CIDR insertion (FSH + eCG group). Estrous behavior was monitored and direct mating was performed. On days - 7 (CIDR insertion), 0 (CIDR withdrawal), and 7 (embryo recovery), blood samples were collected to determine serum hormone concentrations. Co-treatment with eCG (FSH group) did not affect (P > 0.05) serum hormone levels. Superovulation response, ovulation rate, recovery rate, fertilization, and number of embryos were also similar (P > 0.05) between treatments. Compared with FSH group, FSH + eCG ewes had lower (P < 0.05) number of transferable embryos and higher (P < 0.05) number of oocyte and a tendency to increase the number of degenerated embryos (P = 0.07). Overall results suggest that the administration of eCG is not beneficial either to improve the ovulatory response or the amount of transferable embryos in Katahdin ewes superovulated with a protocol using progesterone and FSH at decreasing doses.

Effect of different dosages of PG-600 on ovulation and pregnancy rates in ewes during the breeding season

This study compared the reproductive effects of different dosages of PG-600 (Intervet/Merck Animal Health, Madison, NJ) during the breeding season of ewes. PG-600 is a single-dose injectable product labeled for estrous induction in swine, containing equine chorionic gonadotropin (80 IU/mL) and human chorionic gonadotropin (40 IU/mL). PG-600 is routinely used off-label for out-of-season estrous induction in sheep. However, at the most common dose administered to ewes (5 mL), PG-600 is likely to overstimulate the ovaries, resulting in reduced pregnancy rates. Following estrous synchronization with intravaginal progesterone and cloprostenol, Polypay ewes were treated with 5 mL PG-600 (T1; n = 8), 1.5 mL PG-600 (T2; n = 8), or 5 mL saline (C; n = 8) and then mated to rams. Jugular vein samples were collected prior to the PG-600 injection (0 hr) and at 2, 4, 8, 12, and 24 hr after injection. Serum estradiol-17β was determined by chemiluminescence and among groups using repeated measures analysis of covariance. Ovulation and pregnancy rates were determined by transrectal ultrasonography and compared by one-way ANOVA and chi-square, respectively. Estradiol-17β concentrations were greater in T1 compared to T2 and C (P < 0.001). Ovulation rate was greater (P < 0.001) but pregnancy rate was lower (P < 0.001) in the T1 compared to C and T2. These data confirm that a 5 mL dose of PG-600 administered to ewes during the breeding season overstimulates the ovaries, which may then reduce fertilization or embryo survival. Future research will focus on the effects of different dosages of PG-600 on pregnancy rate of ewes during the nonbreeding season.

Although it induces synchronized ovulation, hCG reduces the fertility of Santa Ines ewes submitted to TAI

ABSTRACT The aim of this study was to evaluate hCG treatment on ovarian response and on pregnancy rate using a 9-day oestrus synchronization protocol in Santa Ines ewes. On a random oestrus cycle day, ewes received an intravaginal progesterone device (Primer-PR®, Tecnopec, Brazil). Nine days later (Day 9), 30µg of d-cloprostenol (Prolise®, Syntex, Argentina) and 250IU of eCG (Folligon®, Intervet, Brazil) were administered and the progesterone device was removed. This moment, the ewes were randomly assigned on two groups: Control Group and hCG Group. In the hCG Group, the ewes received 500IU of hCG (Vetecor®, Hertape-Calier, Spain) 24h after device removal. In the Control Group, the ewes did not receive any ovulation inductor. Control and hCG Groups ewes were inseminated 60h and 48h after device removal, respectively. There was no difference between the groups regarding the first ovulatory follicle diameter and the second ovulatory follicle. hCG Group ewes had shorter interval between device removal and ovulation (Control: 79.9±15.4h and hCG: 54.7±4.9h; P=0.001) and more synchronized ovulations. However, the treatment with hCG decreased the pregnancy rate after TAI (P=0,009). In conclusion, hCG administration improves ovulatory synchronisation, but causes a decrease in the pregnancy rate.

Time of ovulation and pregnancy outcomes obtained with the prostaglandin-based protocol Synchrovine for FTAI in sheep

The objective of the present study was to determine the ovarian response induced with the prostaglandin-based protocol Synchrovine (two doses of PGF_2α given 7 d apart), as well as the fertility after FTAI. In Experiment 1, 15 females received the Synchrovine protocol using two different PGF_2α analogues (Delprostenate vs. D-Cloprostenol). No differences in estrus response, time of ovulation and follicular dynamics were found between both groups (P < 0.05). The ovulation after Synchrovine was synchronized in a similar mean interval (68.8 ± 7.1 h) than when the females received a single dose of PGF_2α (70.2 ± 20.7 h; P=NS), but the dispersion between the first and the last ovulation was reduced with this protocol (range 60-84 h vs. 24-96 h, respectively; P < 0.05). In experiment 2, 318 ewes were treated with the Synchrovine protocol and cervical FTAI was performed using different sperm cell concentrations. Pregnancy rate was higher using 200 × 10⁶ and 100 × 10⁶ sperm cells (38.2%, 39/102; and 34.9%, 38/109, respectively) than using 50 × 10⁶ (23.4%, 25/107, P < 0.05). In Experiment 3, 444 ewes received the Synchrovine protocol and were assigned to receive 300 IU of eCG or not at the moment of the second dose of PGF_2α, and cervical FTAI was performed 42 h or 48 h after the second dose of PGF_2α. No effect was found related to the eCG administration nor the time of insemination. In Experiment 4, 342 received cervical or intrauterine insemination after treatment with the Synchrovine protocol, resulting in greater pregnancy rate for intrauterine insemination than cervical insemination (52.5%, 90/171 vs. 31%, 53/171, P < 0.05). These experiments demonstrate that the Synchrovine protocol effectively induces luteolysis, estrus and ovulation in most of the treated females, and ovulation is synchronized into a narrow window of 24 h. Pregnancy rate obtained with cervical FTAI is around 30-45%, with similar results using 100 × 10⁶ or 200 × 10⁶ sperm cells, the eCG administration seems not to be necessary, the type of PGF2α analogue does not appear relevant, and fertility is improved with intrauterine semen deposition.

Effect of feeding greater amounts of dietary energy for a short-term with or without eCG injection on reproductive performance, serum metabolites and hormones in ewes

This study was conducted to compare the effect of transient high-energy diet in a short-term period with or without eCG injection on ovarian follicle development, twining rate, serum metabolites and hormones in ewes. A total of 45 estrous cyclic Naeini ewes were randomly assigned to three experimental groups: 1-Control (control), 2-High energy short-term feeding (HE), and 3-high energy short-term feeding + eCG injection (HEe). Ewes were housed in individual pens with free access to feed and water. The stage of the estrous cycle of all ewes was synchronized by insertion of intravaginal progesterone sponges. Focus feeding started from 4 days before until 1 day after sponge removal. Follicle development was monitored from 4 days before until 1 day after sponge removal and blood samples were taken during this time. Results showed that ewes fed high energy diets (HE and HEe) had greater (P < 0.05) large follicle numbers compared with the control group. Feeding high energy diets increased (P < 0.05) serum glucose, cholesterol and insulin, but had lesser (P < 0.05) serum urea nitrogen concentrations near the time of ovulation. After the start of experiment, ewes fed high energy diets had less (P < 0.05) serum estradiol. However, 1 day after sponge removal, serum estradiol in HE and HEe groups increased (P < 0.05). It was concluded that short-term (6-day) changes in amount of dietary energy with or without eCG injection increased twin births and had beneficial effects on the blood metabolites and hormone concentrations in Naeini ewes.

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.

Efeito do flushing sobre o desempenho reprodutivo de ovelhas Morada Nova e Santa Inês submetidas à inseminação artificial em tempo fixo

O objetivo do estudo foi analisar o efeito do flushing, do protocolo hormonal para sincronização de estro e da IATF sobre o desempenho reprodutivo de ovelhas Morada Nova (MN) e Santa Inês (SI). Foram utilizadas 27 ovelhas SI e 24 ovelhas MN suplementadas com concentrado (1% do peso vivo, em média) durante 75 dias de estação reprodutiva. Após 30 dias de suplementação, as ovelhas foram sincronizadas com protocolo hormonal (PH) à base de progestágeno, eCG e cloprostenol. A observação de estro foi realizada após 12, 24, 36 e 48 horas do término do PH, com o auxílio de dois rufiões, e a IATF foi realizada aproximadamente 55 horas após o final do PH. Do 20º ao 45º dia após o início do PH, realizou-se o repasse com um reproduto Dorper. O diagnóstico de prenhez foi realizado 70 dias após a IATF. Foi analisado o peso, escore da condição corporal (ECC), taxa de apresentação de estro, taxa de prenhez e prolificidade, testando-se os efeitos da raça, semana de suplementação (SS) e classe de ECC. O peso e ECC das ovelhas variaram em função da SS. Foi observada taxa de estro de 88,2%, sendo que 43,2% das ovelhas apresentaram estro até 24 horas do final do PH. A taxa de prenhez por IATF foi de 31,4% e a de prenhez após repasse foi de 50,0%, sendo que a classe de ECC interferiu nas taxas de prenhez. Obteve-se maior porcentagem de partos múltiplos de ovelhas prenhes por IATF do que por monta natural no repasse. Conclui-se que o flushing resultou em ganho de peso e aumento do ECC, o que garantiu a padronização do rebanho para a estação reprodutiva e, consequentemente, melhorou o desempenho reprodutivo. O PH utilizado aumentou a prolificidade e adiantou o início do estro; porém, não foi eficiente na sincronização de ovelhas deslanadas.

Follicular dynamics, interval to ovulation and fertility after AI in short-term progesterone and PGF2α oestrous synchronization protocol in sheep

The study was aimed to assess the influence that short-term progesterone treatments have on follicular dynamics, oestrus and ovulation in sheep. The treatment was tested thereafter in a field trial to assess its fertility after AI with fresh semen. In a first experiment, 12 ewes without CL were grouped to receive a new (n = 6) or used CIDR (n = 6) for 7 days and blood samples were obtained to follow plasma progesterone profiles. In a second experiment, 39 cycling ewes were synchronized by a 7-day P4+PGF2α protocol using a new (n = 20) or a 7-day used CIDR (n = 19). Half of both groups received 400 IU eCG and half remained untreated as controls. Ultrasound ovarian examination and oestrous detection were used to compare follicular dynamics, oestrus and ovulation in both groups. In a third experiment, 288 ewes in 3 farms were synchronized by the short-term P4+PGF2α+eCG protocol and ewes were AI with fresh semen 24 h after oestrous detection. Lambing performance was used to test the fertility of the treatment. In Experiment 1, ewes with new inserts presented higher P4 concentration than ewes with used inserts throughout the sampling period (p < 0.05) and exhibited a P4 peak at days 1-2 of the treatment that was not observed in ewes with used inserts. In Experiment 2, ewes treated with new and used inserts show similar ovarian and behavioral traits (p > 0.10). However, ewes treated with eCG show shorter interval to oestrus (p = 0.004) and tend to have larger mature CL (p = 0.06). In Experiment 3, oestrous presentation and lambing performance after AI with fresh semen was considered normal compared to published results. Results suggest that the oestrous synchronization protocol based on P4+PGF2α allows little control of follicular dynamics without compromising fertility after AI with fresh semen provided that eCG is added at the end of the treatment.

The effects of time and dose of pregnant mare serum gonadotropin (PMSG) on reproductive efficiency in hair sheep ewes

The aim of this study was to evaluate the effects of dose and application time of pregnant mare serum gonadotropin (PMSG) on reproductive performance of hair sheep ewes synchronized with fluorogesterone acetate (FGA) under tropical conditions of Northeastern Mexico. Ninety-nine hair ewes (63 Blackbelly and 36 Pelibuey) were treated with intravaginal sponges during 10 days. After insertion of FGA sponges, ewes were divided into four groups, and PMSG was injected intramuscularly at doses of 100, 200, and 400 IU. Relative to FGA sponge removal, PMSG was administrated at -48 h, -24 h, and at sponge removal. PMSG was not administered to the control group. Control ewes had similar (P > 0.05) lambing rate, fertility, and fecundity than those treated with 100 IU of PMSG, but lower (P < 0.05) percentages to these variables than those treated with 200 and 400 IU of PMSG. Time to estrus decreased linearly, and ovulation rate increased quadratically as PMSG dose increased (0 to 400 IU). Administration of PMSG before sponge removal increased (P < 0.01) response to estrus and decreased (P < 0.01) interval to estrus compared with control. Ovulation rate, lambing rate, fertility, and fecundity were not affected (P > 0.05) by administration time of PMSG. Both dose and time of PMSG application did not affect (P > 0.05) pregnancy rate, percentage of single and multiple lambing, and prolificacy. In conclusion, results show that the dose of 400 IU of PMSG administered before sponge withdrawal in an estrus synchronization protocol improved reproductive efficiency of hair sheep ewes.

The effects of a low therapeutic dose of βCG fragment-lytic peptide conjugates on ovarian function and gonadotropin secretion in ewes: a randomized controlled trial

The main objective of this experiment was to determine and compare the effects of two lytic peptide conjugates, Phor21-ßCG(ala) and ßCG(ala)-Phor21, at a low therapeutic dose (0.2 mg/kg body weight i.v.), on periovulatory ovarian and endocrine activity, and ensuing luteal function in an ovine experimental model. We hypothesized that the dense expression of LH/hCG receptors on the preovulatory follicle would present an appropriate target for the drugs and disrupt normal ovarian dynamics in sheep. Serum levels of reproductive hormones and ultrasonographic images were used for the assessment of periovulatory events following drug administration in 14 Rideau Arcott ewes; seven animals served as controls. Ovulations were synchronized with intravaginal progestogen-releasing sponges (medroxyprogesterone acetate, 60 mg) that were left in place for 12 days and a single i.m. injection of 750 IU of equine chorionic gonadotropin (eCG) given at sponge withdrawal. Both drugs were administered by i.v. injection 36 h post sponge removal/eCG injection, during the period of increasing LH responsiveness of potential ovulatory follicles and around the expected onset of the preovulatory surge of gonadotropins. No difference (p>0.05) was detected in the number of luteal structures per ewe in control versus treated animals during early luteogenesis. After drug administration, peak FSH concentrations were higher (p<0.05) in Phor21-ßCG(ala)-treated compared to control ewes and circulating estradiol concentrations were lower (p<0.05) in ßCG(ala)-Phor21-treated animals. Mean serum progesterone concentrations were lower (p<0.05) in ßCG(ala)-Phor21-treated than control ewes during the luteal phase post-treatment. There were no differences (p>0.05) in the percentage of ewes that lambed or lamb characteristics between the three groups at lambing 9 months post-treatment. In summary, neither Phor21-ßCG(ala) nor ßCG(ala)-Phor21 demonstrated adverse effects on the ovulatory process but the treatment with ßCG(ala)-Phor21 significantly depressed follicular and luteal steroidogenesis. With a lack of evidence for disruptive effects on endocrine function and fertility, these obsevations support the use of Phor21-ßGG(ala) as a cancer pharmaceutical.

Fertility Rates of Ewes Treated with Medroxyprogesterone and Injected with Equine Chorionic Gonadotropin plus Human Chorionic Gonadotropin in Anoestrous Season

The aim of the present paper was to investigate the efficiency of the equine chorionic gonadotropin (eCG) plus human chorionic gonadotropin (hCG) associated with medroxyprogesterone acetate (MAP) to estrous ewes synchronization. Ninety Texel ewes were investigated during seasonal anoestrous. The ewes received intravaginal sponges containing MAP (60 mg) for nine days. At the time of sponges' withdrawal, the ewes were divided into three groups (G): (1) receiving 2 mL of saline i.m. (n = 30), (2) receiving eCG 400 IU i.m. (n = 30), and (3) receiving eCG 400 IU plus hCG 200 IU i.m. (n = 30). Twelve h after sponges' removal, teaser rams were used to estrus check and remained with the ewes for 96 h. The artificial insemination was made with fresh semen 10 h after estrus detection. The effect of the treatment was not significant for the estrous rates among the groups: 73%, 90%, and 86%, respectively. The main effect was observed in the pregnancy and lambing rates among the groups: 70%, 86%, 56%, and 80%, 120%, 56%, respectively. Based on these results from our study, the use of the MAP—eCG is the best choice to improve the fertility rate on ewes.

Progesterone treatment, FSH plus eCG, GnRH administration, and Day 0 Protocol for MOET programs in sheep

The effect of various superstimulatory treatments on the number of corpora lutea, fertilization rate, and embryo yield was studied in sheep. Overall, data from 708 Merino donors and 4262 embryos were analyzed in four experiments. In Experiment 1, varying intervals of progesterone treatment (5 to 14 d) before follicle-stimulating hormone (FSH) administration did not significantly affect the proportion of responding donors, the mean number of corpora lutea, or the mean number of recovered and transferable embryos per donor. In Experiment 2, a single dose of equine chorionic gonadotropin (eCG, 200 or 300 IU) combined with the FSH treatment (i.e., given at CIDR removal) reduced the number and the quality of embryos compared with that for not giving eCG (P<0.05). In Experiment 3, one dose of gonadotropin-releasing hormone (GnRH) given 24h after CIDR removal improved the number of transferable embryos compared with that for not giving GnRH (P<0.05). In Experiment 4, the new superstimulatory Day 0 Protocol, which includes starting FSH treatment at the emergence of Wave 1 (i.e., soon after ovulation, in the absence of a large follicle), improved ovarian response, with a tendency to produce more embryos compared with that for the Traditional Protocol. In summary, this study, analyzing data from various pharmacologic treatments, allows an improvement from four to eight transferable embryos per treated donor in multiple ovulation and embryo transfer programs in sheep.

The effect of dietary supplementation with calcium salts of long chain fatty acids and/or L-carnitine on ovarian activity of Rahmani ewes

This study investigated the effect of dietary supplementation with calcium salts of long chain fatty acids with or without of l-carnitine on ovarian activity using 24 Rahmani ewes randomly allocated to four treatments. Control animals (n=6) were fed a basal diet of hay (64.2%) and barley grain (35.0%) plus minerals and vitamins (0.8%). Ewes on the three treatments received the same basal diet supplemented with calcium salts of long chain fatty acids (CSFA) at 3% of the basal diet dry matter intake (1.4 kg/ewe/d); 250 ppm l-carnitine (LC); or both these supplements (CSFA+LC). All use exhibited natural estrus on one or two occasions and were weighed at the start and the end of the study as well as body condition score was assessed at the end of study. All ewes were then synchronised for estrus using intravaginal sponges for 12 d prior to the start of the nutritional treatments and three weeks after the nutritional treatments began. The nutritional treatments were imposed for a total of 8 weeks. Blood samples were collected prior to the start of treatments and every two weeks thereafter except after sponge removal of first and second synchronisation where the blood samples were collected daily for progesterone assay. The results revealed that Rahmani ewes received basal diet (control) and l-carnitine had significantly decrease final body weight and body condition score (36.3+/-0.4; 36.8+/-0.3; 2.2+/-0.04; 2.1+/-0.05; p<0.05, respectively) than those on CSFA and CSFA+LC (38.6+/-0.9; 39.5+/-0.6; 3.3+/-0.07; 3.4+/-0.06; respectively). At the second ultrasound examination, the control animals had significantly fewer total follicles (7.3+/-0.8; p<0.05) than those on the CSFA (8.4+/-0.8), l-carnitine (8.7+/-1.5) and CSFA+LC (8.0+/-0.6) treatments. The increased numbers occurred in the medium and large categories of follicles. In addition, the ovulation rates were significantly lower (p<0.05) for control (1.3+/-0.2) and l-carnitine (1.5+/-0.00) than for CSFA (2.5+/-0.3) and CSFA+LC (2.3+/-0.2). Furthermore, serum progesterone concentrations had risen and were significantly higher (p<0.05) for CSFA (2.5+/-0.3 ng/ml) and CSFA+LC (2.7+/-0.1 ng/ml) than for control (1.1+/-0.7 ng/ml) and l-carnitine (1.5+/-0.4 ng/ml). It was concluded that supplementation of the basal diet with l-carnitine alone did not improve performance of ewes or the ovarian response. However, the addition of calcium salts of long chain fatty acids to the basal diet alone or in combination with l-carnitine significantly improved the number and size of ovarian preovulatory follicles, and the ovulation rate of Rahmani ewes. Further evidence was required to study their influence on follicular atresia.

Relationships of changes in ultrasonographic image attributes to ovulatory and steroidogenic capacity of large antral follicles in sheep

Ovarian steroidogenesis and antral follicular development in ewes, following the treatment with medroxyprogesterone acetate (MAP) and equine chorionic gonadotrophin (eCG), are affected by the reproductive season. The objective of this study was to compare the ultrasonographic attributes of large antral follicles between cyclic (December) and seasonally anovular (June-July) ewes, after a 12-day treatment with MAP-soaked intravaginal sponges, with or without the administration of 500IU of eCG at sponge removal, and to determine whether there is a correlation between the ultrasonographic attributes of the follicular wall and serum concentrations of oestradiol. Digital images of ovulatory follicles from cyclic ewes and eCG-treated anoestrous ewes (n=34 follicles), and of anovulatory follicles attaining > or =5mm in control anoestrous ewes (n=8 follicles), were analysed using the spot and line techniques designed to determine the echotextural characteristics of the follicular antrum (central and peripheral), follicular wall and perifollicular ovarian stroma. The mean diameter of ovulatory follicles was greater (P<0.001) in cyclic than anoestrous ewes, with or without the eCG treatment. The mean pixel heterogeneity (SD of numerical pixel values) of the follicular antrum (P<0.05), as well as mean pixel intensity and heterogeneity of the peripheral antrum, follicular wall proper and perifollicular ovarian stroma (P<0.05), were consistently greater in anoestrous than cyclic ewes at the time of sponge removal and 24h after the treatment with MAP sponges or MAP/eCG. Mean oestradiol concentrations were greater (P<0.05) in cyclic compared to anoestrous ewes in both MAP- and MAP/eCG-treated animals, from 1 to 2 days after sponge withdrawal. There was a moderate negative correlation (r(2)=0.12, P<0.05; Pearson's Product Moment and r(2)=0.23, P<0.05; ANCOVA) between mean pixel heterogeneity (standard deviation of mean pixel values) of the follicular wall proper (all follicles > or =5mm in diameter) and serum concentrations of oestradiol after sponge withdrawal. Our results indicate that large antral follicles from cyclic and seasonally anovular ewes exhibit distinctive ultrasonographic characteristics. The differences in follicular echotexture appear to be related mainly to seasonal variations in ovarian follicular morphology and oestradiol production.

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.

Ultrasonographic characteristics of ovulatory follicles and associated endocrine changes in cyclic ewes treated with medroxyprogesterone acetate (MAP)-releasing intravaginal sponges and equine chorionic gonadotropin (eCG)

The aim of this study was to assess the ultrasonographic characteristics of ovulatory follicles in cyclic Western White Face ewes (December) that had received intravaginal sponges containing medroxyprogesterone acetate (MAP; 60 mg) for 12 days, with or without an injection of 500 IU of equine chorionic gonadotropin (eCG) at sponge removal. We hypothesized that quantitative echotextural attributes of the follicles in ewes treated only with MAP would differ from those in MAP/eCG-treated ewes, reflecting the increased antral follicular growth and secretory function under eCG influence. Digital images of ovulatory follicles obtained at 0 and 24 h after MAP sponge removal and at 24 h before ovulation in the eCG-treated (five ewes, 13 follicles) and control (six ewes, 9 follicles) animals, were subjected to computerized analyses. The mean diameter of ovulatory follicles increased (p < 0.001) 24 h after eCG treatment. The mean pixel intensity and heterogeneity of the follicular antrum (p < 0.001), as well as mean pixel intensity of the follicular wall and perifollicular ovarian stroma (p < 0.05), were greater in eCG-treated animals compared with control ewes 24 h after sponge removal and at 24 h before ovulation. Mean serum concentrations of oestradiol-17beta tended to increase (p = 0.06) 24 h after eCG treatment and the eCG-treated ewes exceeded (p < 0.05) control animals in progesterone concentrations from days 9-15 after ovulation. Our results support the hypothesis that large antral follicles in eCG-treated ewes exhibit distinctive echotextural characteristics. Follicular image attributes in eCG-treated ewes appear to be indicative of the changes in follicular morphology and secretory activity caused by the administration of the exogenous gonadotropin, which has both FSH- and LH-like activities.

Ultrasonographic image attributes of non-ovulatory follicles and follicles with different luteal outcomes in gonadotropin-releasing hormone (GnRH)-treated anestrous ewes

Ultrasonographic images are composed of multiple square picture elements called pixels. Quantitative changes in numerical pixel values (echotexture) determined by computer-assisted analysis of digital images reflect discrete changes in the microscopic structure and physiological status of ovarian antral follicles. The objective of the present study was to determine and compare the ultrasonographic attributes of non-ovulatory antral follicles that grew to an ostensibly ovulatory diameter (> or =5mm) and follicles with different luteal outcomes in response to gonadotropin-releasing hormone (GnRH) in anestrous Western White Face ewes (n=34). All animals received GnRH injections (250ng i.v. every 2h for 24h) followed by a bolus injection of 125microg of GnRH i.v. Ovarian images obtained by repeated transrectal ultrasonography were digitized and subjected to computerized analyses to determine the changes in follicular size and echotexture of the follicular antrum and wall. At the beginning of GnRH treatment, follicles that formed inadequate corpora lutea following ovulation (ICL; n=22) had higher (P<0.001) pixel intensity of the central and peripheral antrum compared with non-ovulatory follicles (n=40). Pixel intensity of the central follicular antrum was greater (P<0.01) in follicles that formed ICL compared with follicles that formed normal (full-lifespan) CL post-treatment (NCL; n=20) and mean pixel heterogeneity of the follicular wall was greater (P<0.05) in non-ovulatory follicles compared with follicles that gave rise to NCL. At the time of GnRH bolus injection (i.e., induction of a synchronous LH surge), the mean diameter of non-ovulatory follicles was greater (P<0.01) than that of all ovulating follicles, and pixel heterogeneity of the central follicular antrum was lowest (P<0.05) in non-ovulatory follicles. The mean diameter of luteinized unovulated follicles (n=9) tended to be greater (P<0.10) at 2.5 and 3 days after emergence, and pixel intensity of the follicular wall was lower (P<0.05) compared with non-luteinized follicles (n=8) at 1.5 and 2.5 days after emergence (beginning of the growth from approximately 3mm onwards). In conclusion, ovarian antral follicles with different outcomes after GnRH treatment (in seasonally anestrous ewes) had distinctive ultrasonographic characteristics.

Ovarian follicular dynamics after cauterization of the dominant follicle in anestrous ewes

An experiment was conducted to ascertain if follicles could reach ovulatory size after the largest follicle (dominant) has been removed at different times during a progestin treatment in anestrous ewes, and secondly to determine if these new follicles could respond to an hCG-induced ovulation and have similar function as corpora lutea. Mature crossbred sheep (n=44) in anestrous were treated with an intravaginal sponge containing 40 mg of FGA (day 0=sponge insertion) for 9 days. Treatments consisted of cauterization of the largest follicle on the experimental day 3 (T1), day 6 (T2) and day 9 (T3); day 12 to ascertain the size of the largest follicle in control ewes. During laparotomies, the diameters of the largest follicle (DF), and those of the second and third largest follicles (SF1 and SF2, respectively) were determined. On day 12, a second laparotomy was performed for those ewes which had their DF cauterized on days 3, 6 and 9, a fourth group was left intact and only laparotomized on day 12. At this time, the size of the new DF, SF1 and SF2 were determined. Immediately after the laparotomy on day 12, all the ewes were treated with 1000 i.u. of hCG to induce ovulation. Blood samples were collected daily from day 0 to 50 and samples were analyzed for progesterone concentrations. The size of the DF at the time of sponge removal was smaller that those observed on day 3 or 6 of sponge suggesting that follicles in ewes treated with this progestin regress and a new wave of follicular development ensues between day 6 and the time of sponge removal. The size of the DF on day 12 was also smaller in ewes that have the largest follicle removed at the time of sponge removal reflecting that these follicles had a shorter period of growth; however, the rate of growth was greater for these follicles than for follicles arising after cauterization on day 3 or 6 after sponge insertion. There were no differences among treatments, in the number of ewes that formed a corpus luteum (CL) in response to hCG. Life span of the corpora lutea did not differ among ewes having their DF removed on day 6 or 9 or those that served as controls, however, ewes that had their DF removed on day 3 developed longer lived CL in a larger proportion of animals. Average progesterone concentration during the life span of the induced corpora lutea was greater in control ewes than in any other experimental group. These observations allow us to conclude that, (a) the follicular dynamics observed in anestrous ewes treated with a progestin intravaginal sponge resembles that observed during the normal estrous cycle in the ewe; (b) the effects of progesterone on life span of the corpus luteum could not be only related to direct effects at the follicle but also involve changes in other components of the uterine-ovarian-hypothalamic axis; (c) the mechanisms controlling luteal life span seem to be different to those mechanisms controlling the function of the induced corpus luteum.

Comparison of Estrus Induction and Subsequent Fertility with Two Different Intravaginal Devices in Ewes during the Non-Breeding Season

Two experiments were conducted to compare the effect of estrus induction by controlled internal drug release (CIDR) and intravaginal cream containing 500 mg progesterone (P cream) in ewes during the non-breeding season. In the first experiment, twenty-four ewes were randomly grouped for two treatments with the different intravaginal devices for 12 days: Group A was the CIDR group and Group B was the P cream group. Blood was collected from all treated ewes, and progesterone (P(4)), estradiol 17-beta (E(2)) and luteinizing hormone (LH) concentrations were measured by enzyme immunoassay. In the second experiment, the conception rates from natural mating, estrus-detected AI (inseminated 12 h after estrus detection), or fixed-time AI (inseminated 42 h after removal of an intravaginal device) in 127 ewes treated with CIDR or P cream were compared. In Experiment 1, the rate of estrus induction and the time of estrus onset after device removal were 91.7% and 36.3 +/- 15.7 h in Group A, and 100% and 35.0 +/- 12.6 h in Group B, respectively. There were no significant differences between the devices. The mean plasma P(4) concentration in Group B was significantly (P < 0.01) lower than Group A between day -9 and day -1 (Day 0: the day of device removal). However, no significant differences were found in the mean E(2) concentrations of the two groups after treatment. The mean time of estrus onset in ewes with an observed LH surge and the time of LH surge after treatment were 23.3 +/- 8.7 h and 30.3 +/- 5.0 h for Group A and 27.6 +/- 6.5 and 26.3 +/- 8.0 h for Group B, respectively, and there were no significant differences. However, a significant difference (P < 0.05) was found in the mean time from the time of estrus onset to LH surge between Group A (6.4 +/- 6.7 h) and Group B (-1.3 +/- 4.1 h). In Experiment 2, the conception rates for natural mating, estrus-detected AI, and fixed-time AI were 55.0, 29.4, and 25.0% for Group A and 40.7, 25.0, and 42.1% for Group B, respectively, and there were no significant differences. These results suggest that the effect of induction of estrus and ovulation and the rate of conception after treatment were comparable to CIDR even though the plasma P(4) concentration of the P cream method tended to be low during the insertion period.

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.