The effect of the nutritional energy concentration on embryonic and fetal losses in the female rabbit]

The laparoscopy technique was used to examine the effects of feeding 2 concentrations of energy and protein on the reproductive parameters in the doe rabbit. Forty-one does were laparoscopized on day 12 of gestation in order to estimate the ovulation rate and embryo number. Diets 1 and 2 contained 13.0 and 9.7 MJ digestible energy per kg DM and 159 and 135 g crude protein per kg DM respectively. The ovulation rate, number of implanted embryos at 12 d and total litter size at birth were similar for diets 1 and 2 (13.4 vs 14.2, 12.6 vs 12.8 and 9.1 vs 10.8), but the live litter size at birth was higher for diet 2 (7.1 vs 9.8). Laparoscopy is invaluable in determining the effects of diets on oestrus and birth rates in living and sexually active does.     

Detrimental effect on availability of buserelin acetate administered in seminal doses in rabbits

The study evaluated a seminal effect on the ability to induce ovulation of a synthetic GnRH analogue, buserelin acetate, administered by vaginal mucosa in rabbit does. In a first experiment, 751 receptive nulliparous and multiparous non-lactating does were randomly assigned to groups of different seminal doses (6, 12, 24, 50, and 100 million total sperm in 0.5 mL). All seminal doses contained 5μg of buserelin acetate to induce ovulation by vaginal mucosa absorption. Two hundred and six does from 751 were laparoscopized at 12^th days of gestation to evaluate ovulation induction, ovulation rate and implanted embryos, while pregnancy rate and total and live born were noted in all females. Results showed that the pregnancy rate was significantly affected by the seminal dose used (0.82 vs 0.72, 0.50, and 0.45, for 6, 24, 50, and 100 million of spermatozoa, respectively). Data from laparoscopized does showed significant differences between the group of 6 and 50 million sperm dose in the ovulation induction and consequently in the pregnancy rate (0.79 vs 0.52, 0.79 vs 0.48, respectively). Does from all groups had similar implanted embryos and litter sizes irrespective of seminal dose used. In a second experiment, inseminations were done without spermatozoa, 0.5 mL of two dilutions of seminal plasma (1/4 and 1/20) with 5μg of buserelin acetate were introduced into vagina from 71 receptive females and its results were compared to a control group (35 does) induced to ovulate with 1μg of buserelin acetate administered intramuscularly. Only 40% of females from 1/4 plasma dilution group became to ovulate. Consequently, the dilution rate of seminal plasma may reduce the availability rate of the GnRH analogue and the concentration needed to provoke the ovulation induction.     

Effects of insemination-ovulation interval on fertilization rates and embryo characteristics in dairy cattle

The objective of this study was to examine effects of the interval between insemination and ovulation on fertilization and embryo characteristics (quality scored as good, fair, poor and degenerate; morphology; number of cell cycles and accessory sperm number) in dairy cattle. Time of ovulation was assessed by ultrasonography (every 4h). Cows were artificially inseminated once between 36h before ovulation and 12h after ovulation. In total 122 oocytes/embryos were recovered 7d after ovulation. Insemination-ovulation interval (12h-intervals) affected fertilization and the percentages of good embryos. Fertilization rates were higher when AI was performed between 36-24 and 24-12h before ovulation (85% and 82%) compared to AI after ovulation (56%). AI between 24 and 12h before ovulation resulted in higher percentages of good embryos (68%) compared to AI after ovulation (6%). Insemination-ovulation interval had no effect on number of accessory sperm cells and number of cell cycles when corrected for embryo quality. This study showed that the insemination-ovulation interval with a high probability of fertilization is quite long (from 36 to 12h before ovulation). However, the insemination-ovulation interval in which this fertilized oocyte has a high probability of developing into a good embryo is shorter (24-12h before ovulation).     

Ovarian morphology,plasma progesterone concentrations and early embryo survival in the sow

Sixty-five Large White sows were used to examine relationships between ovarian morphology and embryo survival at 30 days gestation and plasma progesterone concentration before and after service.The total mass of luteal tissue was positively correlated with the number of corpora lutea on the ovaries (r = 0.68), and formed a fairly constant proportion of ovarian mass at 30 days gestation. The mean number of embryos per sow was 11.2 ± 0.76, and embryo survival rate was estimated to be 76.5%. There was a positive correlation between ovulation rate and number of embryos at 30 days of pregnancy (r = 0.39). The survival rate of embryos was inversely related (r = ?0.66) to the mean distance between embryos in the uterus. The means of plasma progesterone levels on days 11, 12 and 13 after service were positively correlated with the means of progesterone levels on days 9, 10, 11 and 12 of the cycle before service, the number of corpora lutea, the total mass of luteal tissue and the total mass of the ovaries, but not to numbers of embryos.     

In vitro and in vivo viability of vitrified and non-vitrified embryos derived from eCG and FSH treatment in rabbit does

This study aimed to evaluate the in vitro and in vivo viability of vitrified and non-vitrified embryos derived from eCG and FSH treatments in rabbit does. Ninety-six nulliparous does were randomly subjected to consecutive superovulation treatments with eCG (20 IU/kg body weight intramuscularly (i.m.), eCG group), FSH (3 x 0.6 mg/doe at 24 h intervals i.m., FSH group), or without superovulation treatment (control group). Does were artificially inseminated 3 days later and ovulation was induced immediately by hCG (75 IU/doe intravenous). Seven experimental groups were differentiated: first FSH and eCG treatment, second FSH and eCG treatment, eCG-interchanged group (does with previous FSH treatment), FSH-interchanged group (does with previous eCG treatments) and control group. Embryos were collected in vivo by laparoscopy 76-80 h post-insemination in the first and second recovery cycles and post mortem in the third recovery cycles. The ovulation rate was significantly higher in does treated with the first-FSH than in those treated with eCG or in control does (25.2+/-2.0 versus 19.2+/-1.4 to 11.0+/-1.5, and 12.2+/-1.2, first-FSH, first-eCG to second-eCG and control groups, respectively, P < 0.05). Significant differences were observed in the total recovery influenced by ovulation rate in each group (20.3+/-2.2 to 9.4+/-1.2, first-FSH to control groups). Embryo donor rate (donor with at least one normal embryo) was similar among groups with an overall of 75.1%. The number of normal embryos recovered per doe with at least one normal embryo increased significantly in relation to ovulation rate (17.7+/-2.2 to 8.41+/-3, first-FSH and control groups). The vitrification of embryos negatively affected their in vitro development to hatched blastocyst in all groups (88.1% versus 48%, P > 0.05). However, after embryo transfer, this negative effect was only observed in superovulated vitrified embryos (16.8 and 12.8% versus 39.4% total born rate from eCG, FSH and control vitrified groups, P < 0.05). Results indicated that the primary treatments with eCG or FSH increased the number of normal embryos recovered per donor doe, but these embryos are more sensitive to vitrification protocols.     

In vivo development of vitrified rabbit embryos: Effects on prenatal survival and placental development

The aim of this work is to study the effect of the vitrification procedure on prenatal survival and on placental development at the end of gestation in rabbits (Oryctolagus cuniculus). One hundred eighty-one females were slaughtered at 72 h of gestation. Morphologically normal embryos recovered at 72 h of gestation were kept at room temperature until transfer or vitrification. Vitrified embryos (320 embryos) were transferred into a total of 24 does and fresh embryos (712 embryos) were transferred into a total of 43 does. Females were induced to ovulate 72 h before transfer when fresh embryos were transferred and 60 to 63 h before transfer when vitrified embryos were transferred. Each recipient doe received eight embryos into the left oviduct and eight embryos into the right oviduct. The number of implanted embryos was estimated by laparoscopy as number of implantation sites at Day 14 of gestation. Recipient females were slaughtered by stunning and exsanguination 25 d after the transfer, and fetuses were classified according to their status. Live fetuses and fetal and maternal placenta were weighed Pregnancy rate was defined as the total number of females having at least one live fetus at Day 28 of gestation divided by the total number of females. Prenatal survival was estimated as live fetuses at Day 28 of gestation divided by the number of transferred embryos. The pregnancy rate after transfer of vitrified embryos (92%) was similar to that achieved with fresh embryos (86%), but prenatal survival was lower for vitrified than for fresh embryos (53% vs. 34%). We did not find differences in embryo survival from 72 h to implantation. Transfer of vitrified embryos reduced fetal survival from implantation to Day 28 (57% vs. 82%). Differences in the number of live fetuses at Day 28 of gestation were mainly due to the higher fetal mortality observed soon after implantation in pregnancies resulting from the transfer of vitrified embryos. A higher percentage of decidual reactions and atrophic maternal placentas (27.5% vs. 8.3%) and also of atrophic fetal and maternal placentas (12.1% vs. 5.3%) were observed after transfer of vitrified embryos. Both treatments showed similar percentage of dead fetuses (3.3% vs. 4%). Maternal placenta of the fetuses from fresh embryos was 15% heavier than maternal placenta of fetuses from vitrified embryos.     

Factors affecting success of embryo collection and transfer in a transgenic goat program

During a goat transgenic program that took place in Israel from July 1995 to February 1996, Saanen (n = 343) and Nubian x Damascus (n = 378) crossbred goats of mixed ages were used as donors (n = 433) and recipients (n = 288). The effects of season, age, number of surgical procedures, previous hormonal treatments and ovulation rate on the number of microinjectable embryos collected were studied. Likewise, the effects of these parameters on the pregnancy rate as well as the number of embryos transplanted, endogenous progesterone concentrations and exogenous progesterone supplementation were studied in recipient does. Following superovulation with ovine follicle stimulating hormone, 85% of the does responded with 13.6 +/- 5.7 (mean +/- S D) ovulations/doe. Age, month and number of previous hormonal treatments significantly affected the ovulation rate. The average recovery rate was 70%, and it was affected only by the ovulation rate. Pronuclei were visualized in about 30% of the flushed embryos (including unfertilized ova), and those were microinjected with human serum albumin gene construct. About 68% of the injected embryos underwent at least one division during an overnight incubation, and those embryos were transferred, giving about 2.0 transferred embryos per ovulated donor. Of the recipients, 86% responded following synchronization with 3.1 +/- 1.6 (mean +/- S D) ovulations per doe. Breed and month had a significant effect on the ovulation rate. Two or three microinjected embryos were transferred to each recipient, resulting in more than a 40% pregnancy rate during September to November. Lower pregnancy rates were obtained before and after that period. By monitoring plasma progesterone concentrations in the recipients it was found that progesterone concentration was correlated with the ovulation rate. However, the pregnancy rate was not affected by progesterone concentration. During January and February, 30 to 50% of the recipients failed to develop functional corpora lutea (CL) following embryo transfer, which explained the lower pregnancy rate in those months. Of the 86 kids born 4 were transgenic.     

Effect of chlortetracycline supplementation during prebreeding and early gestation on age at puberty, ovulation rate, embryo survival and fetal development in gilts

A total of 166 crossbred gilts weighing approximately 87 +/- 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 +/- 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 +/- 1 or 71 d +/- 1 d of gestation for evaluation of reproductive performance. Age (190 +/- 3 d vs 195 +/- 3 d) and body weights (106 +/- 2 kg vs 106 +/- 2 kg) at puberty were similar for control and CTC-fed gilts, respectively. Although not significant (P > 0.05), ovulation rate was higher in CTC-fed than in control gilts as assessed at both 31 d (14.2 +/- 0.7 vs 12.9 +/- 0.9, P = 0.31) and 71 d (13.9 +/- 0.6 vs 12.4 +/- 0.5, P = 0.10) of gestation. There was an increase (P = 0.04) in the number of live embryos for CTC-fed gilts at 31 d (12.1 +/- 0.7 vs 9.7 +/- 0.7) but not at 71 d (10.0 +/- 1.1 vs 9.6 +/- 1.0) of gestation. The mean uterine length, placental length, placental weight, fetal length, fetal weight, and allantoic fluid volumes were similar between the control and CTC-fed gilts. Results indicated that feeding CTC during prebreeding and early gestation did not influence the proportion or age of gilts at puberty. However, CTC feeding may have influenced a trend to-ward an increased ovulation rate and increased number of live embryos in gilts.     

Lack of an effect of prostaglandin injection at estrus onset on the time of ovulation and on reproductive performance in weaned sows

We evaluated the effects of a PGF2alpha analogue on time of ovulation and reproductive performance in multiparous Camborough sows (n=47). At onset of first post-weaning estrus, sows received either an intravulval injection of 3.75 mg of prostaglandin analogue (PGF) or, served as a non-injected control (CON). Beginning 24 h after the onset of estrus, transcutaneous ultrasonography was carried out every six h to determine time of ovulation. At 36, 54, and 72 h after the onset of estrus, blood samples were taken for progesterone analysis. Weaning-to-estrus (WEI), duration of estrus, ovulation rate and number of live embryos at d 28 of gestation were recorded. Treatment had no effect (P > 0.05) on any parameters measured. Duration of estrus classified as less or greater than the overall mean also had no effect (P > 0.05) on any of the parameters measured. Results indicate that treatment did not advance ovulation nor did it improve reproductive performance in sows. Overall, a negative correlation of WEI with the ovulation rate (P = 0.0005, r = -0.54) was established.     

Gene transfer efficiency during gestation and the influence of co-transfer of non-manipulated embryos on production of transgenic mice

Litter size of DNA microinjected zygotes is lower than for non-manipulated zygotes. The rate of embryonic and fetal survival in early, mid and late gestation was determined to assess whether DNA integration was responsible for embryonic losses. Also, the effect of including non-microinjected embryos with injected embryos on pregnancy rate and transgenic pup production was determined. In Experiment 1, one-cell embryos from immature CD-1 mice were microinjected with a whey acidic protein promoter-human protein C gene construct. One hour after microinjection embryos were transferred to pseudopregnant recipients (45 transfers of 30 embryos each). Fifteen recipients were sacrificed on day 4, 12 and 18 of gestation and the embryos/fetuses analysed for the transgene. The percentage of embryos or fetuses that were positive for the transgene was not significantly different at any day. However, the number of viable embryos at day 4 was significantly greater than fetuses on days 12 or 18. In addition, a high degree of mosaicism was observed in day 18 fetuses and placentae recovered. In Experiment 2, one-cell embryos from CD-1 mice were microinjected and co-transferred with non-manipulated embryos (C57BL/6). Pregnancy rate and the total number of pups born were improved by addition of non-injected embryos. However, the number of transgenic mice produced was similar whether non-injected embryos were included or not. There were 32.2% (15/46) transgenic pups when 0 non-injected embryos were transferred compared with 15.1% (13/86) transgenic pups when 4 or 8 non-injected embryos were added to the transfers. In summary, a high degree of embryonic and fetal mortality occurs among microinjected embryos. Furthermore, since the percentage of transgenesis did not change throughout pregnancy, DNA integration does not appear to account for all of the embryonic losses. other factor(s) related to the microinjection procedure may be involved in the embryonic and fetal failure of microinjected embryos. Addition of non-injected embryos, although it increased pregnancy rate and the number of pups born from microinjected embryos, actually decreased the number of transgenic pups obtained per pregnancy.     

Fertility and blood progesterone levels following LHRH-induced superovulation in FSH-treated anestrous goats

Twenty mature, mixed-breed, seasonally anestrous female goats were used to study the effects of luteinizing hormone releasing hormone (LHRH) on ovulation rate, fertility, and blood progesterone levels following norgestomet-induced estrus and follicle stimulating hormone (FSH) treatments. Each goat received 6 mg norgestomet by subcutaneous (sc) implant and 3 mg intramuscularly, along with an intramuscular (im) injection of 5 mg estradiol valerate. Four injections of FSH were given for 2 d in divided doses of 10, 10, 5 and 5 mg im every 12 h, starting at 24 h before implant removal. The goats were randomly assigned to 1 of 2 equal treatment groups, and were treated with 2 intravenous (iv) injections of either 0.9% saline (control) or 300 ug LHRH at 24 and 48 h after the removal of the implants. All the goats exhibited estrus within 24 or 36 h of implant withdrawal and were mated to bucks of proven fertility. At laparotomy on Day 7 or 8 after the removal of the implants, the mean number of unovulated follicles was higher (P<0.05) in Group I than in Group II. The mean number of corpora lutea (ovulation rate), the total number of embryos and the number of normal embryos recovered were higher (P<0.05) in LHRH-treated does than in the controls. Treatment with LHRH resulted in 72.14% fertility (mean number of CL = 14) as compared with the controls with 64.29% fertility (mean number of CL = 2.8). The embryos obtained from goats in Group II were of more uniform developmental age regardless of the day of embryo collection, as compared with those of the controls. Plasma progesterone levels were significantly increased on Days 4 to 6 in both treatment groups. The results of this study have demonstrated that the FSH and LHRH treatment regimen increased follicular development, ovulation rate and blood progesterone levels in norgestomet-treated anestrous goats. Moreover, LHRH treatment enhanced fertility, and improved embryo quality as indicated by the significantly higher total number of embryos as well as the higher (P<0.05) number of normal recoverable embryos.     

Factors affecting pregnancy rates and early embryonic death after equine embryo transfer

In the present study, 638 embryo transfers conducted over 3 yr were retrospectively examined to determine which factors (recipient, embryo and transfer) significantly influenced pregnancy and embryo loss rates and to determine how rates could be improved. On Day 7 or 8 after ovulation, embryos (fresh or cooled/transported) were transferred by surgical or nonsurgical techniques into recipients ovulating from 5 to 9 d before transfer. At 12 and 50 d of gestation (Day 0 = day of ovulation), pregnancy rates were 65.7% (419 of 638) and 55.5% (354 of 638). Pregnancy rates on Day 50 were significantly higher for recipients that had excellent to good uterine tone or were graded as "acceptable" during a pretransfer examination, usually performed 5 d after ovulation, versus recipients that had fair to poor uterine tone or were graded "marginally acceptable." Embryonic factors that significantly affected pregnancy rates were morphology grade, diameter and stage of development. The incidence of early embryonic death was 15.5% (65 of 419) from Days 12 to 50. Embryo loss rates were significantly higher in recipients used 7 or 9 d vs 5 or 6 d after ovulation. Embryos with minor morphological changes (Grade 2) resulted in more (P<0.05) embryo death than embryos with no morphological abnormalities (Grade 1). Between Days 12 and 50, the highest incidence of embryo death occurred during the interval from Days 17 to 25 of gestation. Embryonic vesicles that were imaged with ultrasound during the first pregnancy exam (5 d after transfer) resulted in significantly fewer embryonic deaths than vesicles not imaged until subsequent exams. In the present study, embryo morphology was predictive of the potential for an embryo to result in a viable pregnancy. Delayed development of the embryo upon collection from the donor or delayed development of the embryonic vesicle within the recipient's uterus was associated with a higher incidence of pregnancy failure. Recipient selection (age, day after ovulation, quality on Day 5) significantly affected pregnancy and embryo loss rates.     

The influence of insulin administration after weaning the first litter on ovulation rate and embryo survival in sows

Primiparous crossbred sows (n = 43), lactating for an average of 21.1 +/- 0.1 d and weaning 8.7 +/- 0.1 pigs, were used to evaluate the influence of insulin on ovulation rate and embryo survival. The sows were maintained on 2.3 kg/head/d of a 14% protein gestation diet during pregnancy, fed ad libitum during lactation, given 2.7 kg/head/d from weaning until re-breeding and fed 2.3 kg/head/d after mating. Beginning the day after weaning (Day 0) sows were treated with 0.4 IU/kg body weight (BW) insulin (n = 21) or were administered an equivalent volume of saline (n = 22) for 4 d. Beginning on Day 3 and continuing until Day 14 after weaning, the sows were checked for estrus twice daily and were artificially inseminated using pooled semen from 2 fertile boars. At slaughter (days 30 to 40 of gestation), ovaries and uteri were collected, and the ovulation rate, embryo number and viability, and uterine weight and length were evaluated and recorded. Use of insulin decreased the average interval from weaning to estrus compared with saline by increasing percentage in estrus by Day 14 after weaning (5.0 +/- 0.57 vs 6.9 +/- 0.56 d, respectively; P < 0.03). Ovulation rate, number of embryos, embryo survival, and average uterine length and weight were not influenced by insulin treatment. Overall, insulin affected reproductive efficiency in primiparous sows by increasing the percentage of sows in estrus.     

Effect of time of artificial insemination on embryo sex ratio in dairy cattle

The objective of the present study was to examine whether different intervals between insemination and ovulation have an influence on the sex of seven-day-old embryos in dairy cattle. Cows were inseminated once with semen of one of two bulls of proven fertility between 36 h before ovulation and 12 h after ovulation. Time of ovulation was assessed by ultrasound at 4-h intervals. In total, 64 embryos were determined to be male or female. Of these 64 embryos, 51.6% were female. The sex ratio in the various insemination-ovulation intervals (early: between 36 and 20 h before ovulation; intermediate: between 20 and 8 h before ovulation; late: between 8 h before and 12 h after ovulation) did not significantly differ from the expected 1:1 sex ratio (50, 50 and 55% females, respectively). Bull (Bull A and B) and Parity (primiparous and multiparous) had no influence on the expected 1:1 sex ratio either. The number of cell cycles was similar for male and female (P = 0.23) embryos when quality of the embryo (P < 0.0001) was included in the model. The results of this study indicate that, in cattle, the interval between insemination and ovulation does not influence the sex ratio of seven-day-old embryos.     

Effect of eCG dose and ovulation induction treatments on embryo recovery and in vitro development post-vitrification in two selected lines of rabbit does

The aim of this work was to evaluate the effect of different doses of eCG administered subcutaneously (0, 50 and 200 IU) and the hormonal induction of ovulation (GnRH or hCG) on embryo recovery and in vitro development of embryos post-vitrification in two selected lines of rabbit does. The two selected lines were line V (selected for the litter size at weaning) and line R (selected for growth rate). Administration of 200 IU of eCG significantly increased ovulation rate (19.2 +/- 1.2 versus 15.5 +/- 1.1 and 12.2 +/- 1.3, and the number of haemorrhagic follicles (13.8+/-1.6 versus 3.8+ /- 1.4 and 3.8 +/- 1.7), but significantly decreased recovery rate (28.8 +/- 6.3 versus 47.7 +/- 5.7 and 48.7 +/- 6.7, 200 IU versus 50 IU and 0 IU eCG, respectively), the number of normal embryos recovered per doe with at least one embryo (5.8 +/- 0.9 versus 8.2 +/- 0.9, 200 IU versus 50 IU eCG doses) and the in vitro development of embryos post-vitrification (51.9% versus 66.1%, 200 IU versus 50 IU eCG doses, respectively). Inducing ovulation with hCG significantly increased ovulation rate when compared with GnRH (17.3 +/- 0.8 versus 13.8+/-1.4), but no significant differences in embryo recovery and embryo development post-vitrification were observed between the two treatments. No significant differences were observed between the two selected lines in ovulation and recovery rates, the number of haemorrhagic follicles and the number of recovered embryos per doe. However, the post-vitrification in vitro rate of development was 59.7% for line R and 51.9% for line V (p < 0.05). It was concluded that the use of 50 IU of eCG subcutaneous with hCG or GnRH prior to embryo cryopreservation programmes in rabbits achieves the best results for embryo recovery, with the best development of recovered embryos post-vitrification.     

Effect of an asynchrony between ovulation and insemination on the results obtained after insemination with fresh or frozen sperm in rabbits

The effects of the introduction of an 8-h asynchrony between ovulation and insemination on litter size components from rabbits were assessed. A total of 202 females belonging to a maternal line were used. Fresh and frozen sperm were used to perform the inseminations. Sperm was frozen with an extender composed of 1.75 M DMSO and 0.05 M sucrose. Four experimental groups were obtained depending on the type of sperm used (fresh or frozen) and on the moment that ovulation had been induced relative to the insemination (at the same time as insemination (t(0)) or 8 h before insemination (t(8))). Laparoscopy was performed on 12th day of pregnancy in pregnant females, and the ovulation rate, normal and total implanted embryos were noted. At kindling, total and live-born rabbits were noted. Results showed that better results were obtained after insemination with fresh semen than with frozen sperm (for females in the group t(0): 79% versus 61% fertility rate, 10.2 versus 6.4 normal implanted embryos and 8.1 versus 5.2 total number born, for fresh and frozen sperm, respectively). On the other hand, after the introduction of an 8-h asynchrony between ovulation and insemination, results were lower for both fresh (50% fertility rate, 7.5 normal implanted embryos and 5.7 total number born for the group of the asynchrony) and frozen sperm (31% fertility rate, 4.6 normal implanted embryos and 3.4 total number born for the group of the asynchrony). Although an approach between the moment of insemination and ovulation is justified when sperm survival could be compromised, results observed after the induction of an 8-h asynchrony were not those expected, perhaps due to the ageing of the oocytes before being fertilised, leading to both lack of fertilisation or early embryonic mortality.     

The effect of bovine pestivirus infection on the superovulatory response of Friesian heifers

The pathogenesis of reproductive loss associated with bovine pestivirus infection during the preovulatory period was investigated using superovulated heifers. Twenty-five Friesian heifers were selected and randomly assigned to either a control group (n = 12) which did not become infected or to a treatment group (n = 13) which became infected following intranasal instillation of 2 ml of serum inoculum containing 5.5 log(10) TCID(50)/ml non-cytopathic virus, 9 d prior to artificial insemination (AI). Transrectal ultrasonography was used to monitor follicular development and ovulation during the superovulatory period. Animals were superovulated using a standard protocol of twice-daily injections of FSH-P and then were inseminated twice commencing 12 h after the onset of estrus. The intensity of expression of estrus was higher in the control heifers than in the pestivirus-infected heifers. Of 13 pestivirus-infected heifers, only 3 heifers displayed standing estrus compared with that in the control group, in which 10 of 12 heifers exhibited standing estrus. The mean number of ova/embryos recovered from the control group heifers was 5.75 +/-2.31, of which 4.00 +/- 0.72 were evaluated as transferable quality embryos. In comparison, heifers in the pestivirus-infected group yielded only a mean of 0.60 +/-0.34 ova/embryos, of which 0.23 +/- 0.22 were transferable quality embryos. Based on ultrasonographic examination, 24 h after the first AI 82% of the presumptive ovulatory follicles had ovulated in the control group compared with an ovulation rate of only 17% in the treated group. The results of this experiment demonstrated that bovine pestivirus infection during the preovulatory period could adversely affect ovulation, thus leading to a significant reduction in the number of palpable corpora lutea and in the number and quality of embryos recovered.     

Comparison of pregnancy rates from transfer of fresh versus cooled, transported equine embryos

Donor mares of mixed, light-horse breeds, maintained at Colorado State University, provided 104 embryos for immediate transfer (fresh embryos). One hundred and thirty-six additional embryos were collected on various breeding farms in the United States and were shipped to Colorado State University via commercial airlines (cooled embryos). Embryos were harvested 7 d after ovulation, graded, and either transferred into a mare immediately (<1 h) or placed in Ham's F-10 medium plus 10% fetal calf serum in an atmosphere of 5% CO(2), 5% O(2), 90% N(2) and packaged in a passive cooling unit (Equitainer) for shipment to our laboratory. All embryos were measured and graded just prior to surgical transfer via flank incision into synchronized mares. Recipients had ovulated 1 or 2 d before (+1, +2), on the same day as (0), or 1, 2 or 3 d after (-1, -2, -3) the donor mare. Pregnancy of recipients was determined by ultrasonography on 12, 35, and 50 d after ovulation of the donor. Pregnancy rates at 12, 35, and 50 d were similar for fresh (74, 64, 61%) and cooled embryos (80, 67, 66%), respectively. Overall, embryo size affected (P<0.05) pregnancy rates at 12, 35 and 50 d. Embryos of Grade 1 (excellent) or 2 resulted in more pregnancies than those of Grade 3 or 4 (poor) embryos. Embryonic losses between 12 and 35 d or between 35 and 50 d were not altered (P>0.05) by treatment (fresh or cooled) nor by age of the donor mare (P>0.05), but embryonic losses between 12 and 35 d were greater (P<0.06) for embryos stored for >12 h (25%) versus those stored for <12 h (10%). The duration needed for shipment (<12 h or >12 h) of cooled embryos did not alter pregnancy rates at 12 d (P>0.05). Age of donor mare had no effect (P>0.05) upon pregnancy rates of cooled or fresh embryos transferred nor on embryo quality. In summary, equine embryos can be cooled to 5 degrees C and maintained in storage for up to 24 h without decreased fertility, compared with those of embryos transferred in <1 hour.     

The effect of estrus synchronization scheme, injection protocol and large ovarian follicle on response to superovulation in beef heifers

Two trials were conducted to examine the effects of estrus synchronization scheme, gonadotropin injection protocol and presence of a large ovarian follicle on response to superstimulation of follicular development and the ensuing superovulation. Estrus was synchronized with either a progestin compound (MGA) or by the use of a luteolytic agent (PGF). Superstimulation was induced with 280 mg equivalents of pFSH administered either by a single subcutaneous injection or by a series of 8 intramuscular injections over 4 d. Follicular development was followed for 5 d with real-time ultrasound, and the heifers were retrospectively classified as to the presence or absence of a large follicle (> or = 8 mm; morphologically dominant follicle) at the start of superstimulation. The 2 trials differed by season of the year and genetic origin of the heifers. In Trial I (20 heifers), the ovulation rate was influenced by the 3-way interaction of the synchronization scheme, injection protocol and morphologically dominant follicle (P = 0.05). The number of large follicles on Day 5 (Day 0 = day of start of superstimulation) and ovarian score (scale 1 to 5 based on extent of follicular development; 1 = least, 5 = most) on Day 5 were significantly correlated (P < 0.05) with ovulation rate. In Trial II (20 heifers), the ovulation rate, number of embryos recovered, number of transferable embryos and ovarian weights were all greater (P < 0.05 to P < 0.01) with the 8-injection protocol than the 1-injection protocol. The number of medium follicles (5 to 7 mm) on Days 2 and 3, number of large follicles (> or = 8 mm) on Days 3, 4 and 5 and ovarian scores on Days 4 and 5 were all significantly correlated (P < 0.05) with ovulation rate. In both trials, differences in follicle populations were not seen until Day 3 of the superstimulation procedure. Collectively, these trials do not provide strong support for a single injection of FSH, as used here, nor does it indicate a clear advantage for either MGA or PGF as a means of enhancing the ovulation rate or embryo quality.     

The relationship between ovulation rate and embryonic survival in gilts

Norwegian Landrace gilts were inseminated on the second day of their second oestrus and slaughtered 28 to 34 days after insemination. The number of corpora lutea (ovulation rate) and normal embryos was counted and the embryonic survival rate was calculated for the 306 pregnant gilts. Mean (+/-S.D.) ovulation rate, number of normal embryos and embryonic survival rate were 14.17+/-2.48, 10.55+/-3.30 and 74.8%+/-20.7%, respectively. The significant (P<0.001) curvilinear regression of embryonic survival rate on ovulation rate gives a maximum embryonic survival rate at 13.2 ovulations. Increased ovulation rate gives increased number of normal embryos up to 18.1 ovulations. Ovulation rate should be considered when assessing factors affecting embryonic survival in pigs.