Onset of the preovulatory LH surge and of oestrus in intact ewes: Night is a preferred period

Oestrous cycles were induced in seasonally anoestrous ewes by introducing rams into the flock and giving to the ewes one intramuscular injection of 20 mg progesterone. At the second ovulation the onset of oestrus and the preovulatory surge of luteinizing hormone (LH) were recorded. It was found that the LH surge began in significantly more ewes during the night (79%) than during the day (21%). The onset of oestrus tended to follow a similar pattern. This temporal pattern was not related to the time of ram introduction, but may be the result of daily rhythms in ovarian activity. Furthermore, a preferred period for the LH surge indicates a preferred period for ovulation and this may be important in deciding when to begin artificial insemination.

Effect of coculture with oviduct epithelial cells on viability after transfer of vitrified in vitro produced goat embryos

This study evaluates the effect of coculture with goat oviduct epithelial cells (GOEC) on the pregnancy rate, embryo survival rate and offspring development after direct transfer of vitrified/thawed caprine in vitro produced (IVP) embryos. Oocytes were recovered from slaughterhouse goat ovaries, matured and inseminated with frozen/thawed capacitated semen, and presumptive zygotes were randomly cultured in synthetic oviduct fluid (SOF) (n=352) or GOEC (n=314). The percentage of cleaved embryos reaching the blastocyst stage was 28% and 20% in SOF and GOEC, respectively (P<0.05). Overall, 26 blastocysts of SOF were transferred freshly in pairs to recipient goats, whereas 58 of SOF and 36 of GOEC were vitrified and transferred directly in pairs to recipient goats after thawing without removal of cryoprotectants or morphological evaluation. The kidding rate was 92% for SOF fresh, 14% for SOF vitrified (P<0.001) and 56% for GOEC vitrified (P<0.05); the difference was also significant between vitrified groups (P<0.01). The embryo survival rate was 62% for SOF fresh, 9% for SOF vitrified (P<0.001) and 33% for GOEC vitrified (P<0.05) with a significant difference between vitrified groups (P<0.01). The results showed that the coculture of IVP goat embryos with GOEC significantly improves the pregnancy and embryo survival rates and leads to the birth of healthy offspring. However, further research using more defined GOEC coculture is required to confirm its capacity to increase the success rate of IVP embryo technology in goat.

Measurement of Ovine Pregnancy-Associated Glycoprotein (PAG) During Early Pregnancy in Lacaune Sheep

This study describes ovine pregnancy-associated glycoprotein (ovPAG) concentrations in 20 Lacaune sheep during early pregnancy. Measurements were performed by using semi-purified ovPAG as standard, tracer and immunogens for antibody production in rabbits. Antisera R780 (against ovPAG(57+59kDa)) and R805 (against ovPAG5(58+61kDa)) were used respectively in RIA-780 and RIA-805. Blood samples were collected at days 0, 18, 20, 22 and 25 after artificial insemination. From day 18 after breeding onward, the mean ovPAG concentration was significantly higher (p < 0.001) in plasma samples from pregnant ewes (n = 17) than in non-pregnant ones (n = 3). The specific activity of the tracer was 11 760 Ci/mmol in RIA-780 and 14 900 Ci/mmol in RIA-805. The minimal detection limits for RIA-780 and RIA-805 were 0.2 ng/ml and 0.3 ng/ml, respectively. The intra-assay CV of samples with low (1.0 ng/ml), medium (2.5 ng/ml) and high (4.0 ng/ml) PAG concentrations were 3%, 6% and 9% for RIA-780 and 8%, 9% and 5% for RIA-805. The inter-assay CV in the same samples were 13%, 12% and 7% for RIA-780 and 13%, 11% and 5% for RIA-805. The recovery was higher than 95% in both assays. No cross-reaction was observed with members of aspartic proteinase family as well as with other tested proteins. In both RIA-780 and RIA-805, inhibition of the binding of the tracer by antisera was parallel between standard curve and serial dilutions of pregnant ewe samples. In conclusion, the two homologous RIA systems are suitable for early quantification of ovPAG concentrations in ewe plasma samples from day 18 after breeding.

Improved vitrification method allowing direct transfer of goat embryos

The aim of this study was to design a vitrification method suited to field embryo transfer experiments in goat. In a first experiment, a standard vitrification protocol, previously designed for sheep embryos was compared to slow freezing of goat embryos. No significant difference was observed on kidding rate (48% versus 69%, respectively), nor on embryo survival rate (35% versus 45%). Second experiment: all embryos were vitrified. After warming, embryos were either transferred directly (direct transfer), or after in vitro dilution of the cryoprotectants (conventional transfer). The kidding rate was not affected by the transfer method (38% versus 23%, respectively). However, embryo survival rate tended to be higher after direct transfer (26% versus 14%). Third experiment: OPS vitrification was compared to standard vitrification. The kidding rate was not affected (22% versus 39%, respectively), but the embryo survival rate was lower after OPS (14% versus 28%). Fourth experiment: 0.4M sucrose was added with cryoprotectants in vitrification. The kidding rate after direct transfer was significantly enhanced after addition of sucrose (56% versus 27%, respectively), whereas embryo survival rate was not significantly affected (32% versus 18%). Fifth experiment: vitrification with sucrose supplementation was compared to slow freezing. No significant difference was observed after direct transfer on kidding rate (52% versus 31%, respectively), but embryo survival rate tended to be higher after vitrification (34% versus 21%). In conclusion, our results indicate that addition of 0.4M sucrose in association with direct transfer improves significantly the viability of goat vitrified embryos.

Laparoscopic ovum pick-up and in vitro production of sika deer embryos: effect of season and culture conditions

Amongst the 200 deer subspecies worldwide, more than 40 are considered as endangered. In vitro embryo production may represent an efficient way to produce and disseminate offspring from sparse remaining individuals in these species. With a view to establishing a method of in vitro embryo production, we assessed the ovarian response after hormonal stimulation (oFSH), oocyte yield following laporoscopic ovum pick-up (LOPU) and oocyte developmental competence according to seasonal reproductive status in sika deer (Cervus nippon nippon). Twelve adult sika deer hinds were allocated between two groups and submitted weekly to oFSH follicular growth stimulation followed by LOPU. Hinds in Group A (n=6) were treated first during the breeding season (5 weeks), and then during the non-breeding season (3 weeks). Hinds in Group B (n=6) were submitted to similar procedures but in the reverse order (treated first during the non-breeding season). Cumulus-oocytes complexes (COC) recovered from Group B were allowed to mature in vitro for 24 h in TCM-199 medium supplemented with oFSH, goat follicular fluid and 100 microM cysteamine. In vitro fertilization was performed with frozen/thawed semen in SOFaa medium supplemented with 20% estrous sheep serum and presumptive zygotes were cultured in the presence or absence of ovine oviductal epithelial cell monolayer (oOEC) in SOFaa-BSA medium. Mean number of follicles aspirated per hind per session decreased significantly between breeding and non-breeding season in Group A (9.8+/-0.7 versus 3.2+/-0.7, mean+/-S.E.M., respectively, P<0.001) but did not change between the non-breeding and the subsequent breeding season in Group B (5.3+/-0.7 and 5.7+/-0.7, respectively, P>0.05). Irrespective of the season, good quality COC with complete and compact cumulus investments were recovered allowing a high cleavage rate after in vitro maturation and fertilization. Whereas development to the blastocyst stage did not occur in SOF medium alone, high development rates to the blastocyst stage were observed in oOEC co-culture regardless of season (22% and 34% of total oocytes in co-culture during non-breeding and breeding season, respectively).

Successful use of oviduct epithelial cell coculture for in vitro production of viable red deer (Cervus elaphus) embryos

Techniques for in vitro production (IVP) of viable embryos have been thoroughly developed in several domestic species in view to improve breeding efficiency. When applied to wild life, these techniques may also help the maintenance of biodiversity through amplification of sparse animals offspring and facilitation of genetic material exchange. During the successive steps of IVP, i.e. oocyte in vitro maturation (IVM), fertilization (IVF) and early embryo development (IVD) to the blastocyst stage, gametes and embryos are faced with unusual environment, including oxidative stress, known to be detrimental to their survival. In the present study, starting from methods developed in domestic species, we have adapted IVP to produce viable red deer embryos. In a first experiment, cumulus cells were removed from in vitro matured oocytes either before or after IVF. The presence of cumulus cells during IVF did not affect final cleavage or development rates. In a second experiment, in vitro matured oocytes were fertilized in the presence of cumulus cells and cultured in SOFaaBSA medium alone or in the presence of ovine oviduct epithelial cell (oOEC) monolayer. Whereas, oviduct cells did not improve the cleavage rate, they significantly increased the rate of embryos reaching the blastocyst stage (from 3 to 25% of total oocytes). Ten blastocysts from oOEC coculture were transferred after freezing and thawing to five recipient hinds and gave rise to three pregnancies. The three pregnant hinds gave birth to three live and normal calves.

Experimental infection of Black Belly and INRA 401 straight and crossbred sheep with trichostrongyle nematode parasites

Compared to INRA 401 lambs reared in France, Black Belly (BB) lambs reared in Guadeloupe (F.W.I.) were highly resistant to both primary and secondary experimental infection with Haemonchus contortus. To investigate this huge inter-breed difference, a nucleus flock of BB was constituted, and experiments were conducted to: (i) confirm this difference in lambs born in France, (ii) check whether it was similar for Trichostrongylus colubriformis and Teladorsagia circumcincta, and (iii) find out whether this difference was age-related. Forty BB lambs, 84 F1 lambs (BB siresxINRA 401 ewes) and 88 INRA 401 lambs born in two cohorts were used in an experimental design involving three host breeds, both genders and two age-groups (3.5- and 7-month-old when first infected). The limited availability of BB lambs made the study incomplete. Infection consisted of the administration of two doses of 10,000 infective larvae of one of the nematode species, separated by an anthelmintic treatment and an interval of 1 week before the second dose was administered. Fecal egg counts (FECs) were done on Days 28 and 35 after each infection; ewe lambs of the INRA 401 and F1 breeds were necropsied, the worm burden was established, the length of the female worms measured and the eggs in utero counted. For H. contortus and T. colubriformis, the FEC was lower in the BB than in the INRA 401 lambs, and the FEC found for the F1 lambs was intermediate. For T. circumcincta, only data for the F1 and INRA 401 lambs were available, and the FECs for these breeds were the same. In all three breeds, the FEC determined after the second dose was significantly lower than that found after the first dose in the ewe lambs, but not in the ram lambs. Infecting the lambs when they were 7- instead of 3.5-month-old significantly lowered egg excretion of both parasites in the F1 (P<0.0001), but not the INRA 401 lambs. Worm numbers in the F1 and in the INRA 401 ewe lambs confirmed the FEC data, many F1 lambs being free of T. colubriformis. The H. contortus female worms were shorter and had fewer eggs in utero in the F1 than in the INRA 401 lambs. A higher proportion of T. circumcincta was at the fourth larval stage in the F1 lambs. In conclusion, the BB breed is much more resistant than INRA 401 to H. contortus, with the F1 lambs being more like the BBs after the second dose. This difference was also found for T. colubriformis and, to a lesser extent, for T. circumcincta.

Current status of embryo technologies in sheep and goat

This review presents an overview of the technical bases of in vivo and in vitro embryo production in sheep and goat. The current limitations of in vivo production, such as variability of response to the hormonal treatment, fertilization failure in females showing a high ovulatory response, and the importance of premature regressed CL in the goat, are described along with possibilities for improvement. The new prospects offered by in vitro embryo production, by repeated ovum pick-up from live females and by juvenile breeding, are presented along with their limiting steps and research priorities. The recent improvements of embryo production and freezing technologies could be used for constitution of flocks without risks of disease transmission and will allow wider propagation of valuable genes in small ruminants populations in the future.

Successful direct transfer of vitrified sheep embryos

The use of a simple cryopreservation method, adapted to direct transfer of thawed embryos may help to reduce the costs of embryo transfer in sheep and increase the use of this technique genetic improvement of this species. Two experiments were made to test a vitrification method that is easy to apply in field conditions. All embryos were collected at Day 7 of the estrous cycle of FSH-stimulated donor ewes and were assessed morphologically, washed in modified PBS and incubated for 5 min in 10% glycerol, for 5 min in 10% glycerol and 20% ethylene glycol and were transferred into the vitrification solution (25% glycerol and 25% ethylene glycol). All solutions were based on mPBS. Embryos were loaded in straws (1 cm central part, the remaining parts being filled with 0.8 M galactose in mPBS) and plunged into liquid N2 within 30 sec of contact with the vitrification solution. The straws were thawed (10 sec at 20 degrees C) and the embryos were either transferred directly or after 5 min of incubation in the content of the straw (followed by washing in PBS) into the uterus of a recipient ewe. In Trial 1, the pregnancy rates at term (72 vs. 72%) as well as the embryo survival rates (60 vs 50% respectively) were not different between fresh (n = 48 embryos) and vitrified (n = 50) embryos. In a second trial no difference was observed between vitrified embryos transferred after in vitro removal of the cryoprotectant (n = 86 embryos) or directly after thawing (n = 72) both in terms of lambing rate (67 vs. 75%, respectively) and embryo survival rate (lambs born/embryos transferred; 49 vs. 53%). This method of sheep embryo cryopreservation provided high pregnancy and embryo survival, even after direct transfer of the embryos.

Mutation in bone morphogenetic protein receptor-IB is associated with increased ovulation rate in Booroola Mérino ewes

Ewes from the Booroola strain of Australian Mérino sheep are characterized by high ovulation rate and litter size. This phenotype is due to the action of the FecB(B) allele of a major gene named FecB, as determined by statistical analysis of phenotypic data. By genetic analysis of 31 informative half-sib families from heterozygous sires, we showed that the FecB locus is situated in the region of ovine chromosome 6 corresponding to the human chromosome 4q22-23 that contains the bone morphogenetic protein receptor IB (BMPR-IB) gene encoding a member of the transforming growth factor-beta (TGF-beta) receptor family. A nonconservative substitution (Q249R) in the BMPR-IB coding sequence was found to be associated fully with the hyperprolificacy phenotype of Booroola ewes. In vitro, ovarian granulosa cells from FecB(B)/FecB(B) ewes were less responsive than granulosa cells from FecB(+)/FecB(+) ewes to the inhibitory effect on steroidogenesis of GDF-5 and BMP-4, natural ligands of BMPR-IB. It is suggested that in FecB(B)/FecB(B) ewes, BMPR-IB would be inactivated partially, leading to an advanced differentiation of granulosa cells and an advanced maturation of ovulatory follicles.

Successful in vitro production of embryos in the red deer (Cervus elaphus) and the sika deer (Cervus nippon)

The aim of our study was to define the conditions for IVM and IVF of oocytes in 2 common deer species as models for endangered related subspecies. Immature oocytes were recovered during the breeding season from postmortem ovaries (red deer) or by repeated laparoscopic follicular aspiration (sika deer). Oocytes were cultured for 24 h in IVM medium supplemented with EGF or FSH and follicular fluid. Stag semen was collected by electroejaculation (both species) or by epididymal flushing (red deer) and cryopreserved. For IVF, oocytes were exposed to different concentrations of thawed spermatozoa in a modified Tyrode albumin lactate pyruvate medium supplemented with 20% (v/v) estrus sheep serum for 18 h. After IVF, presumptive zygotes were allowed to develop in vitro for 7 days in synthetic oviduct fluid (SOF) supplemented with fetal calf serum (10%, v/v). In both species, the presence of ovine FSH and follicular fluid improved the in vitro maturation rate. In the sika deer, the optimal sperm concentration for IVF was 10(6)/mL and some fertilized oocytes reached the early morula stage (20 to 25 cells). In the red deer, after IVF with ejaculated or epididymal spermatozoa (2.0 x 10(6)/mL), 20% of zygotes developed to the blastocyst stage (50 to 80 cells).

Effect of growth factors, EGF and IGF-I, and estradiol on in vitro maturation of sheep oocytes

The objective of these experiments was to determine the effect of exogenous addition of insulin-like growth factor-I (IGF-I, 100 ng/mL), epidermal growth factor (EGF, 10 ng/mL) and estradiol (E2, 100 ng/mL) to the maturation medium of sheep oocytes on their subsequent development in vitro. Addition of IGF-I to the maturation medium did not improve nuclear or cytoplasmic maturation of sheep oocytes at the concentration tested. However, EGF improved significantly the resumption of meiosis (84% oocytes in metaphase II stage after IVM vs. 59% in medium alone). Cleavage rate and blastocyst development rates were improved (P<0.01) after addition of EGF (60% and 29%, respectively), as compared with maturation in TCM 199 alone (39% and 19%, respectively), but remained lower than rates observed after maturation in complete medium containing follicular fluid (FF, 10%) and FSH (81% and 35%, respectively). No additive effect of EGF over FSH was observed during these experiments. Addition of FF to FSH containing maturation medium improved significantly both cleavage (P<0.001) and blastocyst rates (P<0.05). Addition of E2 to the IVM medium is not required when medium already contains FF. However, in defined conditions supplementation of maturation medium with E2 had a positive effect. These results suggest that EGF, FSH and E2 may play an important role in the nuclear and cytoplasmic maturation of sheep oocytes in vitro.

Aspects of follicular and oocyte maturation that affect the developmental potential of embryos

The ability to mature, be fertilized and finally to develop into a viable embryo is acquired gradually by the oocyte during progressive differentiation throughout folliculogenesis. This process starts with oocyte growth during the first steps of follicular development. As the oocyte is close to its final size, other modifications occur, less spectacular but at least as important in determining the resulting ability of the oocyte to accomplish its reproductive purpose (developmental competence). These modifications, referred to as 'oocyte capacitation', are probably influenced by the follicle. The proportion of developmentally competent oocytes increases with follicular size. However, the relationship between follicular growth and oocyte competence is not very strict, since a given oocyte may acquire its competence at any stage of follicular growth and since some examples of functional disjunction between follicular size and oocyte competence are described. Follicular atresia may impair the acquisition of oocyte competence, as evidenced by the parallel study of follicular characteristics and of the developmental potential of their oocytes treated individually through in vitro maturation, fertilization and development. However, when atresia is experimentally induced in large preovulatory follicles, oocytes remain competent, indicating that once competence is acquired, it is no longer sensitive to atresia. Oocyte maturation represents only the end of this long and progressive process and validates the preparation of the oocyte by conferring its final developmental ability. As evidenced by recent cloning experiments, the cytoplasmic aspects of oocyte maturation are crucial for the acquisition of developmental competence. This cytoplasmic maturation may be activated in vitro by the use of complex media supplement (serum, follicular fluid) but the use of defined media for maturation allowed the identification of some active factors (such as epidermal growth factor, growth hormone, inhibin and activin). The study of some differential models of oocyte competence (follicular size and atresia, Booroola gene, prepubertal oocytes) will provide a better understanding of oocyte capacitation and maturation, and allow the improvement of in vitro methods for oocyte maturation, which represent the most limiting step of in vitro production of embryos in large mammals.

Effects of the Booroola Fec gene on ovarian follicular populations in superovulated Romanov ewes pretreated with a GnRH antagonist

Endocrine control of follicular growth was studied in mature Romanov ewes carrying (RF+) or not carrying (R+2) the Booroola Fec gene during an oestrous cycle after gonadotrophin-dependent follicles were suppressed by treatment with an antagonist of GnRH (Antarelix, 0.5 mg per day) and superovulatory treatment was administered. The left ovary was removed after 10 days of treatment (saline or Antarelix) and the right ovary was removed at the end of the superovulatory treatment. Ewes of both genotypes treated with Antarelix had lower plasma LH concentrations than did controls from day 0 to day 10. The inhibitory effect of Antarelix on LH concentration increased with day of treatment. The variability in FSH concentrations during the initial 10 days was reduced by Antarelix treatment in both genotypes. Plasma FSH concentrations were higher in RF+ ewes than in R+2 ewes. In both genotypes, FSH concentrations varied significantly with day of treatment, with the lowest concentrations at day 8 and the highest concentrations at day 5. RF+ ewes had a greater total and atretic number of antral follicles 0.62-1.12, 1.12-2.00 and 2.00-3.00 mm in diameter (classes 2, 3 and 4) than did R+2 ewes before and after superovulatory treatment. After superovulatory treatment, the total number of atretic and non-atretic follicles > 3.00 mm in diameter (class 5) increased in both genotypes. Superovulatory treatment also increased the number of total and atretic class 4 follicles in RF+ only. Conversely, superovulatory treatment decreased the mean number of class 3 follicles in both genotypes, while the number of atretic follicles was decreased only in R+2 ewes. Antarelix treatment significantly reduced the percentage of follicles > 2.00 mm in diameter in RF+ but not in R+2 ewes. Antarelix treatment before superovulatory treatment increased the total number of class 4 follicles in both genotypes but the increase was more significant in RF+ than in R+2 ewes. These results indicate that Antarelix pretreatment favours a greater superovulatory response in Romanov ewes carrying the Fec gene because ovulatory follicles are recruited from a wider range of follicular size classes.

Anti-PMSG antibody levels in sheep subjected annually to oestrus synchronisation

Estimation of the long-term consequences on reproduction performance of the oestrus synchronisation treatments that are annually applied to ewes was carried out on nine officially controlled dairy flocks in the Roquefort region of France. A hormonal treatment combining the insertion of a vaginal fluoro-gestone acetate (FGA) sponge for 14 days and the injection of about 500 IU of pregnant mare serum gonadotropin (PMSG) at withdrawal was applied to the ewes in seven of the nine flocks. The ewes in the two other flocks were used as controls. Blood samples were taken from each female just before the treatment (to test for the presence of residual antibodies) and 20 days after the PMSG injection. Anti-PMSG antibody binding rates were calculated for each blood sample. The residual binding rate increased with age and induce negative effects on the following years reproduction performances, i.e., they increased the probability that the ewes would not become pregnant.

Effects of the Booroola gene FecBB on somatic and germ cells of the fetal testis

The present study was conducted to compare in homozygous FecBBFecBB(BB) Booroola and ++ male fetuses, the body and the testicular growths and the tissular and cellular compositions of the testis between 60 and 140 days of gestation. To eliminate differences in growth due to uterine environment, single embryos have been transferred in recipient Mérinos d' Arles ewes. At 60 and 100 days of gestation, the body masses of BB fetuses were significantly lower than those of ++ foetuses (11 and 13%; P = 0.05); but their testis masses of their total contents of somatic (Leydig or Sertoli) cells did not differ significantly whatever the fetal age. At 100 and 140 days of gestation, testis and body masses were significantly correlated without difference between BB and ++ genotypes. In conclusion, the presence or absence of homozygous gene FecBB does not induce significant differences in somatic or germ cell composition of the testis between 60 and 140 days of gestation.

Role of the uterus in early regression of corpora lutea induced by the ram effect in seasonally anoestrous Barbarine ewes

The involvement of the uterus in early regression of corpora lutea induced by the ram effect was studied in seasonally anoestrous Barbarine ewes. In experiment 1, group I was only submitted to the male effect (control, n = 15) while group II (n = 14) was injected every 12 h with flunixin meglumine, a PGF2 alpha synthetase inhibitor (finadyne), from day 3 to day 6 (day 0: day of ram introduction). The preovulatory LH surge appeared at the same time (around 21 h after ram introduction) in both groups. Finadyne treatment significantly decreased 13-14-dihydro-15-keto-PGF2 alpha (PGFM) pulses (1.3 +/- 0.3 versus 0.4 +/- 0.2; P < 0.05), the number of short cycles (50 versus 14%, P < 0.05), and provided a single peak of oestrus, 15-16 days after the introduction of the rams, instead of between day 14 and day 23 (P < 0.01). In experiment 2, 17 hysterectomized ewes were allocated into two groups: group III (n = 8) was injected with oil and group IV (n = 9) received an intramuscular injection of 20 mg of progesterone immediately before introduction of rams. An additional group of intact ewes was used as control (group V, n = 9). Hysterectomy did not affect the ovulation response to the ram effect, but completely suppressed short cycles (0 versus 78%, P < 0.001). The preovulatory LH surge was delayed in hysterectomized females (36.0 +/- 14.1 versus 16.6 +/- 11.4 h; P < 0.004). Treatment with progesterone significantly (P < 0.01) increased the interval between introduction of rams and the preovulatory LH surge. In conclusion, suppression of short cycles by hysterectomy and an inhibitor of PGF2 alpha synthetase suggest that the uterus is essential for determining the lifespan of ram-induced corpora lutea and that premature release of PGF2 alpha is the cause of early luteal regression. The hypothesis that lower secretion of progesterone before D5 could be the initial cause of the premature induction of the luteolytic signal is discussed.

[In vitro oocyte maturation in domestic ruminants]

In vitro maturation represents the first step towards the in vitro production of embryos in domestic species. This production is of great interest from both zootechnic and basic points of view. Beyond nuclear aspects of maturation (progression of meiosis to metaphase II) cytoplasmic aspects confer to oocytes their potential to be fertilized and to develop normally. The culture medium used for maturation could influence this competence. Furthermore, the origin of oocytes (physiologic and genetic status of the oocyte donor, characteristics of the follicle) could also be determinant. The improvement of in vitro maturation techniques will certainly require a better understanding of these different aspects. Additionally, the maintenance of the oocytes in meiotic block during a pre-maturation in vitro culture will allow them to complete the storage of molecules necessary for fertilization and development.

The ovarian secretion of androstenedione and oestradiol during late pregnancy and the early postpartum period in sheep with an autotransplanted ovary

During late pregnancy in the ewe, ovarian function is suppressed by placental steroids and following parturition ovarian function is restored. This experiment determined the ovarian secretion of oestradiol and androstenedione during late pregnancy and the early postpartum period in ewes. Six ewes with ovarian autotransplants were transplanted with three day 6 embryos and three gave birth on day 147. Ovarian and jugular blood sampled were collected on three different occasions. On each occasion a 4 h period of sampling was followed by a 6 or 8 h period during which the ewes were challenged with 150 ng of gonadotropin-releasing hormone (GnRH). Basal secretion of oestradiol and androstenedione was 0.3 +/- 0.1 and 10.5 +/- 3.0 ng min-1, respectively, on day 120 of pregnancy. Oestradiol secretion remained low on days 7 and 21 postpartum (0.4 +/- 0.3 and 0.3 +/- 0.1 ng min-1, respectively). Androstenedione secretion (ng min-1) on days 7 and 21 postpartum was 2.5 +/- 0.5 and 4.1 +/- 1.8, respectively. The injection of GnRH on day 121 of pregnancy produced luteinizing hormone (LH) release with a peak concentration of 0.6 +/- 0.1 ng mL-1, that did not stimulate steroid secretion. On day 8 postpartum GnRH injection induced LH release with a peak concentration of 3.9 +/- 1.1 ng mL-1 that stimulated secretion of oestradiol (0.2 +/- 0.1 to 2.1 +/- 0.9 ng min-1; P < 0.01) and androstenedione (2.3 +/- 0.6 to 17.1 +/- 6.9 ng min-1; P < 0.001). Similar effects were seen on day 22 postpartum; GnRH injection induced LH release with a peak concentration of 4.7 +/- 1.4 ng mL-1 that stimulated secretion of oestradiol (0.2 +/- 0.1 to 3.7 +/- 1.1 ng min-1; P < 0.001) and androstenedione (4.2 +/- 2.6 to 29.5 +/- 9.2 ng min-1; P < 0.01). These results suggest that the suppression of ovarian function during late pregnancy in the ewe is reversed by 7 days postpartum.

[Control of terminal follicular maturation during the follicular phase in domestic mammals]

Terminal follicular maturation in the ovine and the bovine species involves growth and differentiation processes in follicles between 1-2 mm diameter and the preovulatory stage. During this maturation, the follicle acquires the ability to ovulate and the oocyte becomes able to be fertilized and to develop after fertilization. Selection of ovulatory follicles results from the integration of different parameters such as the circulating levels of gonadotropins, the structure of follicular populations and the sensitivity of the hypothalamo-pituitary axis to ovarian hormones. Differences between follicles for FSH and LH responsiveness can be amplified by paracrine intrafollicular regulations. These mechanisms are probably determinant for selection of ovulatory follicles.

In vitro maturation and fertilization of goat oocytes

Follicular cumulus-enclosed goat oocytes were matured in vitro in the presence of granulosa cells, follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol-17beta. While 86% of the oocytes from follicles 2 to 6 mm in diameter achieved meiotic maturation, only 24% of the oocytes from follicles 1 to 2 mm in diameter progressed to Metaphase II. Exposure of follicle-enclosed cumulus-oocyte complexes to 20 degrees C prior to culture resulted in 11.5% of the oocytes exhibiting abnormal meiotic spindle. This indicated that immature goat oocytes are particularly sensitive to temperature. Ejaculated spermatozoa were capacitated according to the technique previously proposed for ram sperm (1). The fertilization rates of ovulated and mechanically denuded in vitro-matured oocytes were 85 and 82.8%, respectively; 59.7% of ovulated and 57.1% of in vitro-matured oocytes were normally fertilized, as shown by the presence of both the female and the male pronucleus as well as by the remnants of the sperm tail in the ooplasm, 17 hours after insemination. Polyspermy was the main abnormality detected, and it affected almost 20% of the inseminated oocytes. The cleavage rate (two to fourcell stage) 41 hours after insemination of in vitro-matured and fertilized oocytes was 58%.

Resumption of gonadotrophin release during the post-partum period in suckling and non-suckling ewes

The post-partum secretion of LH, FSH and prolactin was monitored in 15 suckling and 6 non-suckling Préalpes du Sud ewes lambing during the breeding season by measuring plasma hormone concentrations daily at 6-h intervals and also weekly at 20-min intervals for 6 h from parturition to resumption of regular cyclic ovarian activity. There was a constant phenomenon in the resumption of normal patterns of FSH and LH secretion: there was a rise in FSH values culminating on average on Day 4 post partum and returning subsequently to values observed during the oestrous cycle, and concurrently an increase in the frequency and amplitude of LH pulses more progressive in suckling than in non-suckling ewes which led to an elevation of LH mean concentrations and occurrence of an LH surge. Since neither the FSH secretory pattern nor FSH mean values differed between suckling and non-suckling ewes, the results suggested that LH pulsatile pattern was a major limiting factor for the resumption of normal oestrous cycles. Before regular oestrous cycles resumed other changes in preovulatory LH surges also occurred: (i) they increased in duration and probably in amplitude; (ii) they were preceded by an acceleration in LH pulse frequency and a large decrease in FSH values as in normal cyclic ewes; and (iii) at least in non-suckling ewes they occurred concurrently with a prolactin surge.

Lamb production using superovulation, embryo bisection, and transfer

In this study, 39 embryos from donor ewes superovulated with follicle stimulating hormone-pituitary (FSH-P) were bisected to produce pairs of monozygotic twin lambs for experimentation. Each pair obtained by bisecting 8-, 9- or 10-day-old embryos was immediately transferred surgically into a recipient ewe at the same physiological stage. Of the 39 recipients which received a pair of half-embryos by transfer into the uterine horn ipsilateral to the corpus luteum, 28 (72%) lambed. Eighteen of 28 recipients lambing (64%) produced pairs, i.e., 7 male and 11 female pairs. Ten of 28 lambings produced a single lamb, i.e., six males and four females. Overall yield (the number of lambs produced in relation to the number of embryos used) was 118%. This percentage tended to increase, depending on the day of collection (Day 8, 100%; Day 9, 118%; and Day 10, 131%).

Transfer of superovulated sheep embryos obtained with different FSH-P

Embryo transfer is one way of accelerating genetic improvement in sheep. One of the main obstacles has been the production of good-quality embryos. The use of progestagens and the stimulation of ovulation with follicle stimulating hormone pituitary extract (FSH-P) has permitted the superovulation of donor and recipient ewes and the synchronization of their cycles. The injection of 16 mg FSH-P at the end of progestin treatment gave means of 9 +/- 1.5, 12 +/- 1.5, and 19.5 +/- 2.6 corpora lutea per ewes in the Préalpes, Lacaune, and Romanov x Préalpes breeds respectively (this last breed is particularly prolific). Twenty Préalpes donor ewes produced 133 embryos that were recovered surgically at Day 6 of gestation; of these, 99 morulae were transferable. Forty-five morulae transferred surgically into 24 Préalpes recipient ewes yielded 16 pregnant ewes and 27 lambs (1.7 per ewe). Twenty-two Lacaune ewes yielded 204 embryos, of which 152 morulae were transferable. Of 76 recipients, 58 became pregnant and gave birth to 97 lambs (1.7 per ewe). During anoestrus, the mean ovulation rate decreased from 11.2 to 8.4; 40.6% of the embryos recovered were of transferable quality versus 74.5% during the normal breeding season. An improved superovulation technique, based on the use of FSH-P with a known follicle stimulating hormone to luteinizing hormonal (FSH/LH) ratio, provided us with good-quality embryos. This treatment must be adapted to the season.

Production, freezing and transfer of embryos from a bluetongue-infected goat herd without bluetongue transmission

In order to import non-seasonal Creole goats from the Carribean to Europe for an experimental purpose, thirty Creole goats were treated with 10 mg of FSH; embryos were collected at slaughter, washed and deep frozen. After rapid thawing, they were reimplanted surgically into European dairy goats. Twenty-four females ovulated but only 17 of the ovulating females had functional corpora lutea (CL) at collection. Ovulation rate (CL goat ) and recovery rate (embryo CL ) were 13.8 and 78% for females with functional CL. Of 191 embryonic structures collected, 79% were considered suitable for deep freezing: 23% were young blastocysts, 47% were expanded blastocysts, and 30% were zona-pellucida (zp)-free and zp-damaged embryos. Seventy-eight embryos were thawed and 63 were reimplanted. Sixty-eight percent of the recipient females delivered 19 kids. The percentage of kids born relative to good-quality re-implanted embryos was higher for zp-free embryos (64%) than for young and expanded blastocyts (36%). Forty-seven percent of the donor females had strong positive serological reactions for bluetongue virus antibodies against serotypes 6 and 14. However, no recipient goats or newborn kids were positive. Virus isolation attempts on the collection media and last embryo washes were negative.

Diurnal variation in the response of anoestrous ewes to the ram effect

The re-introduction of rams after a period of separation was used to stimulate LH secretion and induce ovulation in seasonally anovulatory ewes maintained under natural photoperiod. In 2 experiments, the rams were introduced in the morning or the evening to test for diurnal variations in responsiveness to the treatment. In the first experiment, with Romanov ewes, the ram-induced increase in tonic LH secretion was significantly earlier in the ewes treated (N = 6) at 07:30 h (mean +/- s.e.m. delay to first pulse: 20 +/- 6 min) than in those (N = 5) treated at 19:30 h (66 +/- 15 min; P = 0.006). The pulse interval after the ram effect was significantly shorter in ewes that subsequently ovulated (120 +/- 10 min) than in ewes that did not ovulate (288 +/- 108 min; P = 0.043). There was a significant decline in pulse amplitude from 6.7 +/- 1.2 to 3.4 +/- 0.6 ng/ml (both groups combined) after the introduction of rams (P = 0.040). Of the 11 ewes, 7 subsequently ovulated and a preovulatory LH surge was observed in 6 of these 30-36 h after ram introduction. In the second experiment, with seasonally anoestrous Préalpes-du-Sud ewes, the effect of the timing of the introduction of rams on the periovulatory events was tested. The delay to the onsets of oestrus and the LH surge was not affected, but the ovulation rate was higher after ram introduction in the morning (1.42) than in the evening (1.14). In the 12-h period before the introduction of the rams in the first experiment, there was a difference between the groups in the secretion of LH, but the existence of diurnal rhythms in the concentrations of LH or FSH were not confirmed in a later study in which 7 ewes were sampled every 20 min for 36 h. In contrast, there was a distinct diurnal variation in the secretion of prolactin, with the highest values being recorded at night and the lowest around midday (P = 0.025). The rise and fall in prolactin values did not appear to coincide with dawn or dusk.(ABSTRACT TRUNCATED AT 400 WORDS)

[Progesterone secretion during male-induced cycle in the Creole goat in anestrus: seasonal effects]

Plasma progesterone levels during male-induced ovarian cycles were measured at three periods (March, July, November) in Creole goats. For the females experiencing a cycle of normal duration, plasma progesterone reached 2.0 ng/ml six days after male introduction. For the females experiencing a short cycle, a brief (one day) and slight (0.5 to 1.0 ng/ml) secretion of progesterone was observed during this cycle. A seasonal variation in the interval between male introduction and maximum level of progesterone during the short cycle was demonstrated (March: 4.7 days; July: 5.6 d. and November: 3.1 d.), but the maximum level reached did not vary with season (0.6; 0.9 and 0.6 ng/ml).

Superovulation and egg transfer in the ewe

102 Prealpes du Sud donor ewes were superovulated by a treatment with vaginal sponges impregnated with 40 mg of FGA. When the sponges were withdrawn at 14 days, follicular maturation was stimulated in these ewes with 12 mg of porcine pituitary extract (pFSH). The recipient ewes were treated i.m. with 500 IU of PMSG. Different batches of pFSH (batch pFSH1/Group A; batch pFSH2: groups B and C) were used; a total of 12 mg was given in 4 injections of 3 mg each (groups A and B) or in decreasing doses of 5, 3, 2, and 1 mg (group C). The embryos were recovered at D6 and transferred after 1 or 5 h of storage in medium 199 or medium B2 (Ménézo, 1976) + 10% FCS at either 37 or 20 degrees C (B only). Surgery was used to recover the embryos and place them (one per uterine horn) in the recipients. pFSH1 induced estrus 24 h after sponge withdrawal in 100% of group A ewes. When the LH level was lower (pFSH2; groups B and C), only 62.5% of the ewes came on heat at 24 h. pFSH2 induced 8.1 corpora lutea per ewe (groups B and C) vs 4.6 in group A (pFSH1) and twofold more viable embryos were recovered in groups B and C than in group A (6.1 vs 2.7). In relation to the number of corpora lutea, 59, 69, 80% of viable embryos were recovered in groups A, B, and C, respectively. There was a positive correlation between the number of corpora lutea and the number of morulae recovered.(ABSTRACT TRUNCATED AT 250 WORDS)