Fertilization and embryo recovery rates in superovulated chios ewes after laparoscopic intrauterine insemination.

Forty superovulated dairy ewes of the Greek Chios breed were used in an experiment to evaluate the efficiency of laparoscopic intrauterine insemination on fertilization and embryo recovery rates as well as embryo quality. Estrus was synchronized by intravaginal progestagen impregnated sponges and superovulation was induced by administration of 8.8 mg o-FSH i.m. following a standard 8 dose protocol. A small volume (0.3 mL) of diluted fresh ram semen was deposited in each uterine horn 24 to 28 h after onset of the estrus by a laparoscopic technique. The animals were allocated randomly into two groups (Group A and B) of 20 animals each. In Group A, embryos were recovered 18 to 24 h after the intrauterine insemination and in Group B on Day 6. The average number of corpora lutea was 12.8 +/- 1.2 and 11.5 +/- 1.1 (+/- SEM); the overall embryo recovery was 66.4% and 57% and the percentage of recovered fertilized ova was 81% and 82.8% in Groups A and B, respectively. More fertilized ova were collected per ewe from Group A (P < or = 0.1). Results indicated that in Chios breed, superovulation using homologous FSH combined with laparoscopic AI leads to good ovarian response with satisfactory results in fertilization, embryo recovery and quality of embryos. This could lead to improved and more efficient methods for obtaining large numbers of high quality oocytes and embryos for embryo transfer programs which could contribute to genetic improvement and increase of the population size.     

No seasonal effect on embryo donor performance in the southwest region of the USA

Detailed superovulation and embryo collection records from this commercial transplant unit were statistically analyzed to evaluate seasonal effects, if any, on embryo donor performance. The raw data set included all the superovulation-collection attempts (n=1,029) by this unit on beef donor females during a 12-month interval (1982). Seasons (fall, winter, spring and summer), breed types (European and Brahman), FSH treatment schedules (A, B and C) and two-way interactions were evaluated by analysis of variance for an effect on mean corpora lutea (CL), ova collection rate, ova collected, fertilized ova, fertilization rate, embryo degeneration rate, transferable embryos and transferable embryo rate. Parameters were analyzed in two different data sets. First, Data Set I included records from all cows started on superovulatory treatments during a 12-month period whether or not they responded to treatment and whether or not ova were recovered at the time of collection. Mean values from this data set would be for all females started on superovulatory treatments and should be viewed only for their economic implications. A more realistic approach was made with Data Set II, which includes only those records from donors responded to superovulatory treatment and where at least one ovum was recovered at the time of non-surgical collection. Results showed that there was no season effect on superovulatory responses and ova parameters for beef donors in Data Sets I and II. When parameters were evaluated by breed type, European breed types produced more transferable embryos per donor (P<.05) and had a greater fertilization rate and transferable embryo rate (P<.001) than Brahman-type donors in both Data Sets I and II. However, Brahman-type donor animals produced more ova per collection (P<.05) than European donors in Data Set II. Season × Breed Type interaction was not different for superovulatory response or embryo parameters. This information further establishes a data base for stating that season does not affect embryo donor performance in the southwestern region of the USA.     

The biology of the stoat (Mustela erminea) in the National Parks of New Zealand IV. Reproduction

Abstract

The gonads of 528 female and 821 male stoats were examined. The weights of ovaries and testes in adults peaked simultaneously in October, the season of births and of post-partum oestrus. Of 73 females, 78% had even numbers of nipples, mostly 8 or 10. The mean number of embryos in 13 pregnancies was 8.8 (6–13), and embryo weights ranged from 0.005 g to 2.9 g. Of 11 pregnant females, 8 contained fewer embryos than corpora lutea, and there was evidence of transuterine migration of blastocysts in 6. All but 2 of 451 females caught in December–July inclusive carried corpora lutea of delay. Few adult and no young females were found in oestrus in September–October, though adult males were fertile from August to February (no first-year males were fertile). There was some evidence that the breeding season started later at more southerly latitudes in both males and females. The mean number of corpora lutea per female was 9.7 (n = 439), and there was a significant inverse correlation between counts for the 2 ovaries of one individual. There was generally no significant variation in fecundity of females with age, body weight, or year. Of 11 females which were considered to have lost their litters, 10 were collected in beech (Nothofagus) forests. Four females and 9 males had abnormal gonads; the most severe abnormality was an ovarian teratoma of unknown pathology.     

Superovulatory responses of Holstein cows

Approximately 1000 registered cows and heifers were superovulated one to 10 times. Nonsurgical embryo recoveries were performed on all donors which exhibited estrus. Healthy donors produced more total ova and cleaving embryos and had a higher ovum recovery rate, fertilization rate and pregnancy rate from embryos transferred than did cows classified as infertile. While ovum number was not affected during 10 repeated superovulations, fertilization rate and embryo number decreased. The number of ova recovered from healthy cows was affected by season, and from infertile cows by the day of the estrous cycle on which FSH was started and by the number of days since calving. More ova were recovered from infertile cows synchronized with prostaglandins prior to superovulation than following a natural estrous cycle. The number of embryos recovered from infertile cows was affected by age and from healthy cows by daily milk production. Fertilization rates in both healthy and infertile cows were affected by age, time since calving, daily milk production, day of cycle FSH was injected and season. There was no effect of the day of recovery on the number of ova or embryos recovered from healthy or infertile cows.     

Superovulatory responses in FSH- or Pergonal®-treated heifers

Follicle stimulating hormone (FSH) or human menopausal gonadotropin (Pergonal^®) were used in combination with prostaglandin F_2α (injected either intramuscularly or intravenously) to induce superovulation in 32 beef heifers. Two different transfer media (phosphate buffered saline [PBS] + 20% fetal calf serum, or PBS + 1.5% bovine serum albumin) and two different nonsurgical transfer instruments (stainless steel tube with polyethylene tubing and Cassou gun) were used to transfer embryos to recipient cows. There were no significant differences (P>0.10) in the number of corpora lutea, oocyte or embryos recovered, and transferable embryos (good morula and blastocysts) after superovulation with either gonadotropin. More pregnancies (P<0.10) resulted with non-surgical transfer of embryos from FSH- than Pergonal^®-primed donors (29% vs 13%, respectively). However, pregnancy rates were not affected by the two transfer media or transfer instruments used in this study.     

Superovulating cows with follicle stimulating hormone and pregnant mare's serum gonadotrophin

A total of 511 embryos was recovered non-surgically from nearly 100 superovulated or untreated donors. Superovulation with FSH-LH resulted in more corpora lutea, recovered ova, and pregnancies (P<.01) than superovulation with PMSG. No differences were observed in numbers of ovulations, embryos recovered, or pregnancies per donor when prostaglandin F_2α was given to donors 2 versus 3 days following gonadotrophin treatment.Pregnancy rates of 12, 31, 58, and 63% were obtained from groups of embryos classified morphologically as poor, fair, good, and excellent (P<.05). Morphologically normal embryos collected and transferred at 5 to 6 days of gestation resulted in more (P<.05) fetuses (75%) than morphologically normal embryos at 8 to 9 days of gestation (56%), but neither was significantly different from morphologically normal embryos at 6.5 to 7.5 days of gestation (61%). There was no difference (P>.05) between pregnancy rates when retarded embryos from untreated donors (12%) were compared to retarded embryos from superovulated donors (22%). However, a higher proportion of morphologically normal embryos from untreated donors developed into fetuses (71%) than did morphologically normal embryos from superovulated donors (59%, P<.05).     

Fertilized and unfertilized ova are transported at different rates by the hamster oviduct

To determine if the egg provides any clues for the regulation of ovum transport in the hamster, oocyte and embryo transport were compared. On the evening preceding ovulation, the animals were randomly assigned to one of five groups. They were caged overnight with a male of proven fertility (Group 1) or they were isolated (Group 2). Other females were artificially inseminated in both uterine horns at 2200 h either with fertile epididymal spermatozoa (Group 3), spermatozoa rendered infertile by freezing and thawing (Group 4), or with fertile spermatozoa in one uterine horn and infertile spermatozoa in the contralateral horn (Group 5). The number, condition, and distribution of ova in the genital tract were assessed at various intervals during the next 4 days. The rate of fertilization and normal development in females or sides inseminated with fertile or infertile spermatozoa was over 90% and 0% respectively. Embryos in Groups 1 and 3 reached the uterus 1 day earlier than unfertilized oocytes in Groups 2 and 4. In group 5, the transport of embryos resulting from insemination with fertile spermatozoa followed a pattern similar to those in Groups 1 and 3; the oocytes in the contralateral tract resembled those of Groups 2 and 4. The different transport rates of embryos and oocytes were not associated with the reproductive state of the female but with the condition of the ova. Moreover, the different transport rates were observed in animals transporting the two types of eggs simultaneously on different sides indicating that there is a local recognition of some unidentified factor unequally present in fertilized and unfertilized eggs.     

The use of embryo collection techniques in Holstein heifers: A model to study early embryonic death

Twenty-three cyclic Holstein heifers were purchased for use as embryo donors to study the effect of intrauterine exposure to Haemophilus somnus on the number, quality, and viability of embryos produced. Few problems were encountered using standard superovulation and nonsurgical embryo collection techniques on virgin heifers. Based on three or more ovulations, as determined by palpation per rectum of the ovaries at the time of embryo recovery, 28 of 30 heifers responded to the superovulation regimen. Of 29 nonsurgical recoveries, 27 produced one or more embryos. One hundred and seventy-six embryos and ova were collected from heifers synchronized, superovulated, and flushed 7 to 8 d after insemination.     

Induction of multiple follicular development and superovulation in the olive baboon, Papio anubis.

The objective of this study was to induce multiple follicular development and superovulation in the olive baboon. Beginning at menses, adult female baboons were treated with hMG for 10 days followed by hCG on day 11. Multiple follicular development was seen in all 19 animals; superovulation occurred in 11 of these. Serum E2 and P levels were consistent with multiple follicular and corpora lutea development, respectively. Ovulated ova were able to be fertilized. These results indicate that olive baboons can be superovulated using a regimen of hMG and hCG, however, development of antibodies against the human hormones precludes restimulation.     

Factors affecting spontaneous reduction of corpora lutea and twin embryos during the late embryonic/early fetal period in multiple-ovulating dairy cows

Spontaneous reduction of advanced twin embryos has been described in high-producing, Holstein-Fresian (Bos taurus) dairy herds. The first objective of the current study was to determine whether management and cow factors could have an effect on such a reduction in twin pregnancies during the early fetal period. Because loss of a corpus luteum was noted in cows suffering twin reduction, we expanded our study to include multiple-ovulating cows carrying singletons. Pregnancy was diagnosed and confirmed from Days 28 to 34 and 56 to 62 postinsemination. Sixty-nine (23.5%) of 293 pregnant cows with two corpora lutea carrying singletons and 132 (28.4%) of 464 twin pregnancies recorded on first pregnancy diagnosis subsequently lost one of the corpora lutea or one of the embryos, respectively. Thirty-four (25.8%) of the 132 twin pregnancies suffering embryo reduction lost one corpus luteum along with the embryo. Corpus luteum reduction always occurred in the ovary ipsilateral to the gravid horn suffering embryo reduction. Binary logistic regressions were performed considering corpus luteum and embryo reduction as dependent variables in single and twin pregnancies, respectively, and several management- and cow-related factors as independent variables. In cows carrying singletons, the risk of corpus luteum reduction was 14.3 (1/0.07) times lower for a given herd, whereas the interaction season by laterality significantly affected corpus luteum reduction such that in cows with two corpora lutea ipsilateral to the horn of pregnancy, the risk of reduction decreased during the winter period. In cows carrying twins, ipsilateral twin pregnancies were 3.45 (1/0.29) times more likely to undergo the loss of one embryo than bilateral twin pregnancies. As an overall conclusion, both corpora lutea and embryos were vulnerable to the effects of stress factors during the early fetal period in cows maintaining their pregnancies. A strong unilateral relationship between the corpus luteum and the conceptus was also observed.     

Surgical transfer of in vivo produced farmed European polecat (Mustela putorius) embryos

Surgical embryo transfer of farmed European polecat (Mustela putorius) was investigated as part of an ex situ preservation project. The long-term objective of the project is to develop effective technology for ex situ conservation of the European mink (Mustela lutreola), which is a highly endangered aboriginal European species. Twenty European polecat females, which served as a model species for the European mink, were humanely killed 4-9 days after first mating and embryos were recovered from oviducts and uteri. Donor-recipient pairs (n = 16) were generated by mating the donors (n = 20) once a day for 2 consecutive days with fertile males and by mating the corresponding recipients (n = 16) on the same days with vasectomized males. An embryo recovery rate of 70% (200 recovered embryos/284 corpora lutea) was achieved from 20 donors. Morulae and blastocysts were recovered between Days 5 and 9 after first mating and were regarded as the best developmental stages for uterine embryo transfer. A total of 172 embryos were transferred surgically under general anaesthesia into the ovarian third of the left uterine horn of 16 recipients with a thin glass capillary. Eleven recipients (69%) produced 72 pups equivalent to an average success rate of 42% (72 pups/172 transferred embryos). The average litter size was 4.5 (range 0-9). These results with this model species, farmed European polecat, demonstrate the potential of embryo transfer as an effective method for the preservation of the endangered European mink (M. lutreola). These species are closely related and have a similar reproductive physiology. However, success of applying embryo transfer in conserving European mink is still dependent on further studies both into its reproductive physiology and developing of improved flushing techniques for anaesthetized donors and the successful transfer of frozen-thawed embryos.     

Doppler sonography of the uterine arteries during a superovulatory regime in cattle. Uterine blood flow in superovulated cattle

Transrectal color Doppler sonography was used to investigate the effects of a gonadotropin treatment to induce superovulation on uterine blood flow and its relationship with steroid hormone levels, ovarian response and embryo yield in dairy cows. The estrous cycle of 42 cows was synchronized by using PGF(2alpha) during diestrus and GnRH 48 h later (Day 0). Cows were examined on the day of eCG (2750 IU)-administration (Day 10), 3 days after eCG (Day 13) and 7 days after artificial insemination (Day 22), including the determination of total estrogens (E) and progesterone (P(4)) in peripheral plasma. Eight days after insemination (Day 23) the uterus was flushed and the number of total ova and embryos as well as transferable embryos was determined. The ovarian response was defined by the number of follicles>5.0mm in diameter on Day 13 and the number of corpora lutea on Day 22. Uterine blood flow was reflected by the blood flow volume (BFV) and the pulsatility index (PI) in the uterine arteries. Both variables showed distinct changes throughout the superovulatory cycle: BFV increased by 94% and PI decreased by 30% between Days 10 and 22 (P<0.0001). On Day 13, BFV but not PI correlated with follicle numbers (r=0.35; P<0.05); no correlation was found with E and P(4) (P>0.05). On Day 22, BFV correlated positively and PI correlated negatively with the number of corpora lutea (r=0.45 and r=-0.37; P<0.05) and P(4) (r=0.39 and r=-0.30; P<0.05). The number of transferable embryos was solely related to BFV measured on Day 13 (r=0.32; P<0.05). Our results show for the first time that in cows a superovulatory treatment is associated with a marked increase in BFV and a marked decrease in PI in the uterine arteries, concurrent with the development of multiple follicles and corpora lutea. However, transrectal color Doppler sonography of the uterine arteries does not facilitate the prediction of embryo yields following superovulatory treatment.     

Successful embryo transfer in a small dasyurid marsupial, Sminthopsis crassicaudata

A technique for the transfer of early embryos from the uterus of donors to recipient females of a small dasyurid marsupial, Sminthopsis crassicaudata , is described. When the recipients were killed 3 to 5 d later, a few expanded blastocysts were found to be present in the uteri of most of the females provided that corpora lutea were present in the ovaries. This study demonstrates successful embryo transfer in a small marsupial species and supports the view that secretion of the endometrium due to luteal activity may be necessary for development of the expanded unilaminar blastocyst stage.     

Risk of transmission of Mycobacterium avium ssp. paratuberculosis by embryo transfer of in vivo and in vitro fertilized bovine embryos

Over a 5-year interval, experiments were conducted to determine if Mycobacterium avium ssp. paratuberculosis (Map) is associated with in vivo and in vitro fertilized (IVF) embryos and whether it can be transmitted by embryo transfer. The present studies included: collection of embryos from five asymptomatic, naturally infected donors and transfer to uninfected recipients; collection of oocytes from two naturally infected donors with overt clinical signs; exposure of in vivo and IVF embryos to Map and transfer to uninfected recipients; and the inoculation (transfer) of "clean" IVF embryos to the uterine lumen of infected cows. The presence of Map was confirmed in the uterine horns of all asymptomatic, infected donors. None of the tested embryos, which were not used for embryo transfer, or unfertilized ova (two per batch), were positive for Map, as determined by culture (n = 19) or by PCR (n = 13). However, all in vivo fertilized embryos exposed to Map in vitro (and subsequently sequentially washed) tested positive for Map, by both culture (12 batches) and PCR (15 batches), whereas IVF embryos treated in the same manner tested positive on culture (51%, 18/35 batches) and by PCR (28%, 20/71 batches). Transferring both in vivo embryos and IVF embryos potentially contaminated with Map into 28 recipients resulted in 13 pregnancies and eight calves born without evidence of disease transmission to either the recipients or the offspring over the following 5-year period. In samples collected from one of the clinically infected animals, two of seven (28%) cumulus oocyte complexes (COC) and follicular fluid tested positive by PCR and 10/10 cumulus oocyte complexes on culture for Map. From the second clinically infected cow, three of five batches of IVF embryos (n = 20) were positive on PCR and two of four batches containing unfertilized oocytes and embryos were positive on culture. Only 10% of embryos reached the morula and blastocyst stage 10 days after fertilization. In conclusion, Map is unlikely to be transmitted by embryo transfer when the embryos have been washed as recommended by the International Embryo Transfer Society.     

Good quality sheep embryos produced by superovulation treatment without the use of progesterone devices

Multiple ovulation and embryo transfer (MOET) is a very important tool for the genetic improvement and preservation of endangered livestock. However, the success of a MOET programme highly depends on the number of transferable embryos in response to a superovulation treatment. Thus, the aim of this study was to compare the number and quality of embryos produced during natural oestrus under porcine FSH treatment without the use of progesterone devices to more traditional protocols. Forty Sarda sheep were divided into 2 groups: without sponges (WS) (n = 20) and with sponges (S) containing 40mg FGA for 12 d (n = 20) (control group); 350 I.U. of porcine FSH per sheep was administered in eight decreasing doses twice daily starting four days after estrus was detected (Day 0) in group WS and 48 h before sponge removal in group S. A single i.m. dose of 125 μg of cloprostenol was administered on Day 6 after estrus in group WS to induce luteolysis. Sheep were naturally mated 24 h after cloprostenol injection or sponge removal. Seven days after mating, an inguinal laparotomy was performed and the number of corpora lutea (CL) recorded. Embryos were recovered surgically by flushing each uterine horn. A total of 38 fresh and 22 vitrified embryos were transferred in pairs into 3 groups of recipients seven days after estrus detection: fresh embryos from group S (S-F) (n = 9), fresh embryos from group WS (WS-F) (n = 10) and vitrified embryos from group WS (WS-V) (n = 11). Data on the number of corpora lutea (CL), recovered ova and embryos (OER), and quality 1-2 and 3 embryos (EQ_1-2, EQ₃) per ewe were analyzed by ANOVA. Recovery (RR), fertility (FR) and quality 1-2 embryo (Q_1-2R) rates per treatment were analyzed by a Chi Square analysis. A Chi Square analysis was also applied to pregnancy rate (PR), lambing rate (LR) and twinning rate (TR) of fresh and vitrified embryos in order to analyze embryo transfer results. Among all superovulation variables analysed, results show statistically significant differences in mean number of CL/ ewe (9.3 ± 3.9 vs 7 ± 3.2), RR (67% vs 80 %) and FR (100% vs 80%) (P < 0.05) between WS and S groups respectively. There were no significant differences in PR (78%, 70% and 82%), LR (67%, 60% and 59%) and TR (71%, 71% and 44.4%) among S-F, WS-F and WS-V groups respectively. In conclusion, it is possible to produce a good number of transferable embryos during natural oestrus avoiding the use of sponges.     

Superovulatory responses to eCG in llamas (Lama glama )

Llamas are copulation-induced single-ovulators, and multiple ovulation and embryo transfer (MOET) methods have not yet been developed for this species. Superovulatory responses to eCG given during an induced (Group A) or simulated (Group B) luteal phase were investigated using ultrasound to observe ovarian follicles and corpora lutea (CLs) and plasma progesterone was used to assess luteal function. Embryos were recovered nonsurgically. Group A (n = 19): donors were given 8 microg, im GnRH analogue (Day 0) to induce ovulation of a mature follicle, 1000 IU, im eCG (Day 7), and 250 microg PGF(2alpha) analogue (Day 9). Group B (n = 17): donors were given a subcutaneous progestagen implant (3 mg Norgestomet) at Days 0 to 7) and 1000 IU, im eCG (Day 5). When most (>65%) of the follicles in both Groups A and B had matured at 5 to 11 d post eCG, the donors were given 8 microg, im GnRH and mated once (n = 26) or twice within a 24-h interval (n = 10); embryos were recovered 6 to 9 d post ovulation. More follicles and corpora lutea were induced in Group B than in Group A, but a similar mean number of embryos were recovered (1.3 vs 1.6), and a similar proportion of donors yielded multiple embryos (35 vs 32%). The embryo recovery rate was similar for Groups A and B (39 and 37%), but it was higher (P < 0.001) with 2 (72%) rather than 1 (22%) mating, and it was negatively correlated with CL number (P < 0.05). Overall, 80% of the llamas had a precocious CL and elevated plasma progesterone concentrations when multiple follicles reached maturity. This was associated with increased subsequent superovulation and embryo recovery (P < 0.01). Peak plasma progesterone was positively correlated with the CL number (P < 0.05). From these results we conclude that superovulation may be achieved with eCG given during either an induced or a simulated luteal phase, that embryo recovery is improved following 2 matings rather than 1, and that MOET may indeed be feasible for use in the llama.     

Intrauterine transfer of early canine embryos

The success rate of in vitro fertilization (IVF) in dogs is low and only early embryos have been obtained. In the present study, we investigated the use of intrauterine transfer of early-stage canine embryos to obtain pups. Twenty-three female dogs, in which the date of ovulation (based on plasma progesterone concentrations) differed by +/-1 day, were used (10 donors and 13 recipients). The uterine tube was extirpated under general anesthesia 1-4 days after mating (5-7 days after ovulation), and descending perfusion was done to collect embryos. Embryos were examined and transferred into the uterine horn of a recipient, ipsilateral to the ovary with the most corpora lutea. Pregnancy was established in one of eight bitches that received early embryos (zygote to 4-cell embryos); she received two zygotes and one 2-cell embryo and delivered two puppies. Although intrauterine transfer of early embryos (zygote to 4-cell embryos) was difficult, pregnancy was achieved, suggesting that uterine tube transfer is appropriate for these early-stage embryos.     

Effect of recombinant bovine somatotropin on superovulatory response and recipient pregnancy rates in a commercial embryo transfer program

Recombinant bovine somatotropin (rbST) has been shown to increase follicular growth in cattle and some studies have demonstrated an increase in superovulatory response for rbST-treated cows. Pregnancy rates have also been shown to increase when rbST was administered around the time of insemination or prior to embryo transfer. The application of rbST for the purpose of increasing superovulatory responses of donor cows and increasing pregnancy rates of recipient heifers was tested in a commercial embryo transfer program. In Experiment 1, embryo donor cows (n = 56) underwent three cycles of control superovulation (two before and one after weaning) and subsequently underwent up to four additional superovulations while being treated with either rbST (500 mg sustained-release rbST; Posilac, Monsanto, St. Louis, MO; n = 28) or excipient (control; n = 28) once every 14 days. In Experiment 2, lactating embryo donor cows (n = 37) underwent a control superovulation and then underwent a superovulation while lactating and being treated with either rbST (n = 16) or excipient (n = 21). In Experiment 3, embryo recipient heifers that were being implanted with either in vitro or in vivo produced embryos were treated with either rbST (n = 146) or excipient (n = 143) at the time of embryo transfer. Treatment of non-lactating (Experiment 1) or lactating (Experiment 2) donor cows with rbST during repeated superovulation did not affect the number of corpora lutea, the sum of transferable embryos, degenerate embryos, and unfertilized oocytes, or the number of transferable embryos. Treatment of recipient heifers with rbST (Experiment 3) did not affect pregnancy rates for either in vitro or in vivo produced embryos. We conclude that superovulatory response and pregnancy rates (respectively) are similar to control for rbST-treated cows undergoing repeated superovulations and rbST-treated recipient heifers treated at the time of embryo transfer.     

Superovulation of beef heifers with Folltropin: A new FSH preparation containing reduced LH activity

The optimum superovulatory dose of Folltropin was determined and compared with a standard 28 mg dose of FSH-P in beef heifers. In Experiment 1, mean numbers of corpora lutea (CL) did not differ among the groups treated with 10, 20, 30 or 40 mg Folltropin or FSH-P, and the mean CL number was reduced (P<0.05) only in the 5 mg Folltropin group. Mean numbers of ova/embryos recovered, fertilized and transferable were greater (P<0.05) for the 10, 20 and 30 mg Folltropin groups than for the 5 mg group. The 40 mg Folltropin group and the FSH-P group were intermediate. The percentage of fertilized and transferable embryos did not differ over the dosages used in this experiment. In Experiment 2, mean numbers of CL were greater for the 9, 18 and 36 mg Folltropin groups than for the 4.5 mg group, with the 9 mg group being lower than the 36 mg group (P<0.05). The 18 mg group was intermediate and did not differ. Mean numbers of ova/embryos recovered and fertilized ova were greater for the 9, 18 and 36 mg groups (P<0.05) than for the 4.5 mg group. The percent of fertilized and mean number and percentage of transferable embryos did not differ among treatments. We conclude that Folltropin may be a satisfactory superovulatory replacement for FSH-P and that a dose of 18 to 20 mg Folltropin may be within the optimum superovulatory dosage range for beef heifers. Dosages of Folltropin of more than twice the optimum did not result in deterioration of ova/embryo quality.     

Surgical recovery and successful surgical transfer of conventionally frozen-thawed embryos in the farmed European polecat (Mustela putorius)

Surgical transfer of in vivo produced conventionally frozen-thawed embryos of farmed European polecat (Mustela putorius) was investigated as a part of an ex-situ preservation program which has the long-term aim of developing a genome resource bank for the endangered European mink (Mustela lutreola). Eighteen oestrous yearling European polecat donors were mated once daily on two consecutive days using 13 fertile males. The donors were surgically flushed for embryos 8-9 days after the first mating. The embryo recovery rate was 60% (116 embryos/193 corpora lutea). The embryos were cryopreserved with 1.5 M ethylene glycol in a programmable freezer using a conventional slow freezing protocol. The thawed embryos were surgically transferred either after dilution with 0.5 M sucrose or directly without removal of ethylene glycol. To induce ovulation, eight recipient females were mated once daily on two consecutive days with vasectomized males starting 7 or 8 days before embryo transfer. The recipients received 7-11 embryos each and three recipients delivered a total of nine pups after a gestation length of 44-46 days. The embryo survival rate was 10% (9 pups/93 frozen embryos). This report describes the first successful cryopreservation of embryos in the Mustelidae family resulting in viable offspring. The low embryo survival rate, however, indicates that the freezing-thawing protocol needs to be improved.