Early development and location of embryos in the reproductive tract of Nili Ravi buffalo (Bubalus bubalis): a retrospective analysis

One year data on embryo recovery were analyzed to study the development and descent of preimplantation embryos in Nili Ravi water buffalo. Forty-five superovulatory attempts were performed on 23 buffalo. A total of 45 embryos were recovered either nonsurgically or after slaughtering the animals at various time intervals (85 to 176 h) post estrus. Embryos were located in the oviducts at 85 h after estrus. At 108 h post estrus, most of them (78%) were recovered from the uteri. The embryos had 8 to 16 cells at 85 h post estrus, grew to morulae at 108 h and to compact morulae at 125 h post estrus. Early blastocysts were observed at 141 h post estrus. Blastocysts were predominant (69%) at 156 to 176 h after estrus; no hatched blastocysts were recovered during this time interval. Based on our findings, embryo recovery at around 150 h post estrus (i.e., Day 6 of the cycle) is recommended for compact morulae or blastocysts in the water buffalo.     

Superovulatory response of river bufalo (Bubalus bubalis )

The ovarian response of 25 buffalo-cows was visually assessed, and their oviducts and uteri separately flushed 3 to 6 d post superovulatory estrus at slaughter. Ten buffalo-cows slaughtered on Days 5 and 6 were examined per rectum for corpora lutea (CL) and follicles > 8 mm prior to slaughter, and the estimate was compared later with the actual ovarian response. Five out of the ten buffalo-cows were nonsurgically flushed in vivo on Day 5 of the estrous cycle, a day before slaughtering, and as a result, six ova/embryos were recovered. After the flushing of the reproductive tract at slaughter, one more ovum was recovered from the uterus of each of the three buffalo-cows. As a result of treatment of three groups of five buffalo with 3000 IU pregnant mare serum gonadotrophin (PMSG) on Days 6, 10 or 14 of the estrous cycle, 3.8, 6.2 and 3.4 CL on the average were recovered, respectively (Experiment I). A mean number of 8.8 and 9.0 CL, respectively, was obtained in two groups of five buffalo each, after treatment with 40 mg of follicle stimulating hormone (FSH) on Day 10 of the stage of the estrous cycle (Experiment II) and 3000 IU PMSG regardless of the stage of cycle (Experiment III). The percentage of ova/embryos recovered in the three experiments was 32.8, 20.4 and 22.2, respectively.     

Blastocyst formation by pig embryos resulting from in-vitro fertilization of oocytes matured in vitro

Follicular oocytes collected from prepubertal gilts at a local slaughter house were matured (36 h), fertilized and developed in vitro. Of 785 embryos, 190 (24%) embryos cleaved to the 2-4 cell stages with blastomeres of regular size by 33 h after insemination. These cleaved embryos were surgically transferred into the oviducts of 4 synchronized recipient gilts and recovered from the uterine horns 4 or 7 days later: 13 morulae, 2 blastocysts and 1 expanded blastocyst were recovered after 4 days and 3 hatched blastocysts were recovered 7 days after transfer. Re-culture in vitro sustained further development of morulae recovered 4 days after transfer: 11 of 13 morulae had developed to the blastocyst/hatched blastocyst stages. Overall, 17 of 190 (9%) embryos developed to the blastocyst stage. The results indicate that pig oocytes can be matured and fertilized in vitro, and subsequently develop to the blastocyst stage.     

Endoscopic embryo collection and embryo transfer into the oviduct and the uterus of pigs

We describe the first complete embryo transfer program, including flushing of embryos from the oviducts via the uterine horns, transfer of embryos into the Fallopian tubes or the uterine horns and recording of the number of piglets born live. The described procedure is minimally invasive and allows the use of pigs simultaneously for embryo collection and production of normal pregnancies. A 30 degrees forward oblique endoscope provided optimal visualization of the reproductive organs and free access to the organs for embryo flushing and transfer. In contrast to surgical and nonsurgical methods, endoscopy allows to pre-examine the genital tract for reproductive abnormalities and successful ovulation. A total of 95 prepuberal gilts or cyclic sows were used in this trial. Embryos or oocytes were collected from hormonally treated pigs via endoscopy(n = 17) on Day 3 and via laparotomy or post mortem after slaughter (control group, n = 38) on Day 3 and 6 after insemination. One (unilateral collection, n = 7) or both oviducts (bilateral collection, n = 10) were flushed endoscopically. We recovered 114 (average 16/pig) and 279 (average 28/pig) oocytes or embryos with fertilization rates of 89% and 72%, respectively. In the control group 834 oocytes or embryos were collected at Day 3 and 6 after insemination (fertilization rate 64%, total 534 embryos, 33 at 2-, 367 at 4-, 2 at 8-cell stage, 24 morulae and 108 blastocysts). Of 836 embryos recovered by endoscopy, surgery or slaughter 528 Day 3 embryos at 2- to 4-cell stage were transferred into (one) oviducts (n = 27 pigs, about 20/pig) resulting in 9 pregnant pigs diagnosed at Day 28 by sonography. Of the 9, 8 carried a total of 49 piglets to term. A total of 195 Day 6 embryos were transferred into uterine horns (n = 12 pigs, about 16/pig), resulting in 5 pregnant pigs carrying a total of 38 offspring to term. The use of endoscopy in assisted reproduction of pigs has the advantages of allowing easy access to the ovary, oviduct and uterus, clear view of the organ manipulation without exposure and exteriorization of viscera during surgery.     

A method for transcervical embryo collection in the pig

Five cyclic primiparous sows were used to test a surgical procedure for in vivo transcervical collection of pig embryos. The procedure consisted of shortening the uterine horns. After surgery, all sows returned to estrus and embryos were recovered following artificial insemination. Transcervical uterine flushing was carried out in four sows. On average 3.6 +/- 1.5 (mean +/- SD) embryos were recovered from the five sows. The results indicate that it is possible to recover embryos transcervically from sows with a resectioned uterus.     

Effects of single deep insemination on transferable embryo recovery rates in superovulated dairy cows

Thirty superovulated Friesian lactating cows were randomly assigned to two groups. Group I donors were inseminated with one unit of semen deposited into the uterine body at 8, 20 and 32 h after the onset of estrus. Group II donors were inseminated with one unit of semen deposited deep into the uterine horns at 15 h after the onset of estrus. Neither the mean rates of fertilized ova nor the mean rates of transferable embryos were different between treatments (P > 0.05).     

Birth of normal kids after microinjection of pronuclear embryos in a transgenic goat (Capra hircus) production program in Brazil

This pilot project was designed to determine if normal kids could be produced after microinjection in pronuclear embryos and subsequent transfer to recipients in a transgenic goat program in Brazil. Twelve donors of the Saanen breed and 17 recipients of an undefined breed were used. The estrus of both donors and recipients was synchronized by a standard progestagen treatment and superovulation obtained by six pFSH injections. Donors in estrus were mated with fertile Saanen bucks. Zygotes were recovered surgically by flushing oviducts. The recovered zygotes with visible pronuclei were microinjected with 500 to 1000 copies of the human G-CSF gene. Two or four embryos were surgically transferred into the oviducts of recipients. One recipient became pregnant and two kids were born. No transgenic goat was identified after PCR analysis. Even though transgenic goats were not obtained, this experiment establishes the basis of a synchronization and superovulation regimen for use in goats raised in Brazil, for the purpose of collecting and manipulating the pronuclear embryos. This project also showed that microinjected one-cell goat embryos can survive to produce live young following surgical transfer.     

Inhibition of sperm transport and fertilization in superovulating ewes

In Experiment 1, all ewes were treated with follicle stimulating hormone (FSH-P) to induce superovulation. Ewes came into natural estrus or were treated with prostaglandin F(2)alpha (PGF(2)alpha) or 6-methyl-17-acetoxyprogesterone (MAP) to regulate the time of estrus. The ewes were mated during estrus and necropsied 3 h after mating. Regulation of estrus with either compound reduced the number of sperm recovered from the cervix, uterus, and oviducts and increased the proportions of sperm recovered from the cervix and uterine body that were immotile, dead, or had disrupted membranes. In Experiment 2, all ewes were in natural estrus. They either ovulated naturally or were superovulated, and ewes in each group were necropsied at 3 or 23 h after mating. Superovulation reduced the number of sperm in oviducts, uterus, and anterior segments of the cervix at both time intervals and increased the proportions of sperm that were immotile, dead, or had disrupted membranes. In Experiment 3, of 3x2 design, ewes were in either natural estrus or estrus regulated with PGF(2)alpha or with MAP; they ovulated naturally or were superovulated. Ewes were necropsied 3 d after mating and ova were examined. Both regulation of estrus and superovulation reduced the proportion of ova that were fertilized and reduced the number of accessory sperm attached to fertilized ova.     

Improvement in embryo recovery using double uterine flushing

The objective of the present study was to evaluate the effects of double uterine flushing on the recovery of embryos/ova in cattle. Two hundred and ten embryo recovery procedures were conducted using a double uterine flushing method, and the results were compared with 432 conventional single-flushing procedures. Cyclic Limousin (n = 403) and Guzera (n = 239) donor cows received an intravaginal progesterone releasing device and 2 mg of estradiol benzoate on Day 0. Between Days 5 and 9, donors received decreasing doses of FSH, which ranged from 200 to 300 IU (Bos indicus) and 300 to 500 IU (Bos taurus). On the afternoon of Day 7, donors received an injection of 500 microg cloprostenol and progesterone implants were removed 12 h later (morning of Day 8). Artificial insemination was performed between 14 and 26 h after first detection of behavioral estrus. Cows were randomly assigned to have embryos recovered by a double-flushing method (n = 210) or the conventional single-flushing procedure (n = 432). For the double-flushing procedure, after first flushing the whole uterus with 1L of Dubelco's Phosphate Buffered Saline (DPBS), a Foley catheter was positioned in the uterine body to permit refilling of the uterus with fresh DPBS (80-150 mL). The catheter was closed with the plunger of a disposable 5 mL syringe, and the donors were allowed to rest in a holding area for 30 min. Thereafter, a second flush was performed to recover the solution remaining in the uterus. Animals from the control group were subjected to a single uterine flush. From 210 double-flushing procedures, 1409 viable embryos were recovered. In comparison, from 432 cows receiving the single-flushing procedure, 1993 embryos were recovered. Double flushing increased (P < 0.05) the number of embryos recovered per procedure compared to single flushing (6.7 +/- 0.4 versus 4.6 +/- 0.2, respectively; mean +/- S.E.M.). When double flushing was performed, average recovered embryos/ova increased (P < 0.05) from 8.3 +/- 0.4 to 12.7 +/- 0.7 in Limousin and from 7.9 to 11.5 in Guzera. Also, utilization of double flushing increased (P < 0.05) the number of viable embryos from 4.7 +/- 0.3 to 6.9 +/- 0.5 in Limousin and from 4.5 +/- 0.4 to 6.4 +/- 0.7 in Guzera. Mean total embryos/ova was similar (P > 0.05) between the control group and after the first uterine flushing in the double-flushing group; therefore, both flushings were conducted efficiently. In conclusion, double uterine flushing increased embryo recovery in cattle.     

Survival of DNA-injected cow embryos temporarily cultured in rabbit oviducts

Holstein or Angus cows were superovulated, inseminated with fresh bull semen, and necropsied about 12 h after estimated time of ovulation. Ova were centrifuged at 15,600 G for 3 to 8 min to reveal pronuclei. In Experiment 1, pronuclear bovine embryos were transferred to ligated or unligated oviducts of 1-d pseudopregnant rabbits for 7 d; 30 of 32 embryos were recovered from ligated oviducts but only 2 of 26 from oviducts and uterine horns of unligated oviducts. In Experiment 2, a Rous sarcoma virus-chloramphenicol acetyl transferase fusion gene was injected into one pronucleus of about half of 404 fertilized bovine ova, using a micromanipulator and interference contrast optics. Injected and noninjected embryos were then transferred to opposite ligated rabbit oviducts. Embryos were recovered after 7, 8 or 9 d. Of 120 centrifuged but ininjected embryos recovered from rabbit oviducts, 66 (55%) were in the morula to hatching blastocyst stage of development. Of 105 embryos centrifuged and injected with foreign DNA, 55 (52%) were in the morula to hatching blastocyst stage. In Experiment 3, centrifuged bovine embryos, noninjected or DNA-injected, were cultured in rabbit oviducts for 7 d then transferred nonsurgically to the uterus of recipient cows. Embryos were also flushed from superovulated cows 8 d after estrus and transferred directly to recipient cows. After 7 d, the uterus of recipient cows was flushed nonsurgically to recover embryos. The proportion of transferred embryos recovered with normally elongated trophoblastic membranes and the proportion of recipient cows with developing embryos were 14 of 25 DNA-injected embryos, 5 of 8 cows; 6 of 15 centrifuged but noninjected embryos, 4 of 6 cows; and 11 of 29 embryos transferred directly, 5 of 8 cows. Results indicate that bovine embryos can be cultured in rabbit oviducts and survive after transfer to cow uteri and that injection of foreign DNA may not increase embryonic loss within the first 2 wk after injection.     

Fertilization following mixed insemination with 'cervix-selected' and 'unselected' spermatozoa in the rabbit

The possible selection of spermatozoa for fertilization by the female genital tract was investigated using genetically homogeneous, numerically adjusted 'cervix-selected' and 'unselected' rabbit spermatozoa. Samples of spermatozoa were marked by 15 min exposure to 1.3 mg TEPA/ml and then washed for 15 min. TEPA-treated and control samples were inseminated alternately into the vagina (= 'cervix-selected') or uterine horns (= 'unselected') of prospective donors. After 6 h spermatozoa were recovered from the uterine horns of the donors. Equal numbers of 'selected' and 'unselected' spermatozoa were inseminated either into the uterine horns (24 does) or oviducts (25 does) of recipients. The fertilization rates were 48 and 72%, respectively. Significantly more eggs were fertilized by untreated than by TEPA-treated spermatozoa. Almost identical fertilization rates, however, were observed between 'cervix-selected' and 'unselected' spermatozoa. It is concluded, therefore, that in the rabbit no selection of (preincubated) spermatozoa for fertilization takes place at the cervical level.     

Pregnancy resulting from cattle oocytes matured and fertilized in vitro

Follicular oocytes (n = 81) collected from cattle at a local slaughterhouse were matured and fertilized in vitro. Of 27 ova 19 (70%) were penetrated by spermatozoa and 40/54 (74%) inseminated ova transferred surgically to the oviducts of a synchronized heifer were recovered by non-surgical flushing of the uterine horns 6 days later. Of the 40 ova 15 (38%) were at the morula, early blastocyst or diminutive morula stages. Culture in vitro sustained further development of all embryos and 9 were expanding or expanded blastocysts. One pregnancy resulted from non-surgical transfer of 2 blastocysts. The results demonstrate that immature oocytes from cattle can be matured and fertilized in vitro, subsequently develop to the blastocyst stage, and develop into a normal pregnancy after non-surgical transfer.     

Transfer of vitrified blastocysts from one or two superovulated Large White Hyperprolific donors to Meishan recipients: reproductive parameters at Day 30 of pregnancy

The present study was designed to determine the effect of pooling embryos from two donors on the reproductive success of transfer of vitrified/warmed porcine blastocysts. Intact blastocysts were collected from superovulated Large White Hyperprolific gilts (n = 24) on Days 5-5.5 after artificial insemination. Embryos were recovered by flushing the uterine horns, and unhatched blastocysts were selected. Vitrification and warming were performed as described by Berthelot et al. [Cryobiology 41(2000) 116]. To evaluate in vitro development, 37 vitrified/warmed blastocysts were cultured, non-vitrified embryos (n = 48) were used as controls. Embryo transfers were conducted in asynchronous (-24 h) Meishan gilts (n = 20). Twenty vitrified/warmed blastocysts were surgically transferred into one uterine horn. Ten recipients received embryos from one donor (Group 1) and the other 10 transfers were performed with mixed embryos from two donors (Group 2). Pregnancy was assessed ultrasonographically at Day 25 after estrus and recipients were slaughtered at Day 30 after transfer. In vitro survival rate of the vitrified/warmed blastocysts was lower (P < 0.01) than that from control embryos (73.0% versus 93.7%). The pregnancy rate for Group 1 (70%) was not different (P > 0.05) than that from Group 2 (90%). No significant differences were detected between Groups 1 and 2 for in vivo embryo development (number fetuses/transferred embryos in pregnant recipients) or in vivo embryo survival (number viable fetuses/transferred embryos in pregnant recipients). However, the in vivo efficiency (number viable fetuses/total transferred embryos) was higher (P < 0.05) when transfers were performed with embryos from two donors (19.5% versus 30.5%). These results indicate that pooling embryos from two donors increases the in vivo efficiency after transfer of vitrified/warmed porcine blastocysts.     

Effect of the bovine viral diarrhea (BVD) virus on preimplantation bovine embryos: A preliminary study

Five crossbred-Holstein cows, approximately three to seven years of age, were superovulated using pregnant mare's serum gonadotropin (PMSG) and prostaglandin F_2α (Prostin F_2α). At the induced estrus, each cow was artificially inseminated with frozen semen. Seven days after insemination, the lumen of the right uterine horn of each cow was inoculated with BVD virus in Eagle's minimum essential tissue culture medium, and the lumen of the left horn was infused with tissue culture medium only. Three days later, each cow was subjected to midventral laparotomy under general anesthesia and embryos were collected. A total of 22 embryos were recovered; 12 were from infected uterine horns and ten were from non-infected uterine horns. All embryos from the non-infected uterine horns were in the late blastocyst stage without the zona pellucida. Of the embryos collected from the infected uterine horns, eight of 12 (66.6%) still possessed zona pellucida and appeared in a degenerative state. The remaining four embryos were morphologically similar to those from the non-infected uterine horns. Electron microscopic examination of the degenerated embryos from the infected uterine horns demonstrated the presence of a structure which morphologically resembled the BVD virus. The results of this preliminary study indicate that the BVD virus within the uterine horns may interfere with normal development of preimplantation bovine embryos. Therefore, it is proposed that the BVD virus could adversely affect early stages of gestation in the cow, resulting in infertility.     

Effects of transferring in vitro-cultured rabbit embryos to recipient oviducts on mucin coat deposition, implantation and development

A mucin coat is deposited on rabbit embryos during passage through the oviduct; rabbit blastocysts cultured from the 1-cell stage in vitro have no mucin coat. When cultured blastocysts are transferred to recipients, the lack of mucin coat might account in part for subsequent failure of pregnancy. We have investigated the possibility that mucin coat deposition is induced following transfer of in vitro 72 h-cultured blastocysts to oviducts of asynchronous or synchronous recipients. One-cell embryos were collected by flushing oviducts 19-20 h post-coitus and were cultured in vitro for 72 h until they reached the blastocyst stage. The blastocysts were transferred to the oviducts of recipients that were synchronized either with the donors (synchronous) or 1 day later than the donors (asynchronous). They were recovered after 24-48 h and the mucin coat thickness and embryo degeneration rate were measured. The degeneration rate of blastocysts recovered from uteri of synchronous recipients was higher than that from asynchronous recipients (72.2% vs 40.0%). The mucin coats around embryos recovered from oviducts of asynchronous recipients after 48 h were thicker than those from synchronous recipients. More asynchronous recipients were pregnant and gave birth to more pups than synchronous recipients. These results indicate that the oviducts of asynchronous recipients secreted more mucin around the transferred embryos, causing higher rates of implantation of the in vitro-cultured blastocysts.     

Nonsurgical embryo collection from sows with surgically shortened uteri

To allow for the nonsurgical collection of swine embryos, the uteri of sows (n=7) were surgically shortened. A section of each uterine horn was resected to facilitate a transcervical flushing procedure. All sows with a shortened uterus exhibited natural estrus at least once after the operation. Four to six days after insemination, embryos were collected with a two-way Foley catheter. Embryos were collected (n=55, 6.3+/-6.0: x +/-SD ) from every treated sow. Although treated sows often did not exhibit estrus beyond 1 to 9 natural estruses, those sows (n=27) with persistent corpora lutea (CL) over a 4 to 5 wk period were given prostaglandin F(2alpha) (PGF(2alpha)) and they returned to estrus in 5.2+/-1.1 d: x +/-SD .     

Intrafallopian transfer of gametes and early stage embryos for in vivo culture in cattle

It may be possible to avoid inadequate in vitro culture conditions by incubating gametes or embryos in the oviducts for a short time. Ideally, an optimized procedure should be devised, combining in vitro and in vivo systems, in order to achieve synchronization in cattle. We transferred gametes as well as embryos in various stages of development and placed them into the oviducts. Embryos were recovered on Day 7 by flushing of oviducts and uterine horns. Blastocyst rates were determined on Day 7 and on Day 8. Experimental designs included transfer of in vitro matured cumulus oocyte complexes into previously inseminated heifers (COCs group), transfer of in vitro matured COCs simultaneously with capacitated spermatozoa (GIFTs group), transfer of four to eight cell stage embryos developed in vitro after IVM/IVF (Cleaved Stages group) and a group of solely in vitro produced embryos (IVP control group). Our results indicate that in vivo culture of IVM/IVF embryos in the homologous bovine oviduct has a positive influence on subsequent pre-implantation development. In addition, we have evidence that in vitro maturation and in vivo fertilization cannot be synchronized.     

Comparative fertility of normal and repeat-breeding cows as embryo recipients

Morphologically normal embryos were transferred surgically into uteri of normal and repeat-breeder cows at seven days post-estrus to compare embryo survival rates in the two kinds of cows. All cows were less than ten years of age and had no abnormal genital discharges, cystic ovarian follicles, or anatomical abnormalities of the reproductive tract. Normal cows had not been inseminated after last calving. Repeat-breeders had at least four infertile services within the past six months (average of 6.2 services after calving). To test fertility of repeat-breeders at synchronized estrus, 22 anatomically-normal repeat-breeders were treated by intramuscular (i.m.) injection with prostaglandin F(2)alpha (PGF(2)alpha) on day 11 of an estrous cycle (estrus = day 0) and inseminated at induced estrus; 11 cows (50%) had a normal fetus at necropsy on day 60. Twenty-three repeat-breeders and 23 normal cows were assigned as embryo recipients and treated i.m. with PGF(2)alpha to synchronize estrus. All embryo donors were normal cows. Donors were treated with FSH and PGF(2)alpha and inseminated at estrus. On day 7 after estrus, embryos were recovered nonsurgically from donors and one embryo was transferred through a flank incision to the anterior end of the uterine horn adjacent to the corpus luteum of each recipient. Recipients that did not return to estrus were necropsied at day 60. Of 28 normal and 23 repeat-breeder recipients, 23 normal cows (82%) and 16 repeat breeders (70%) were pregnant at day 60 (P=0.235). Thus, at seven days post-estrus, the maternal environment of most of these repeat-breeders was satisfactory for maintaining pregnancy.     

Effects of GnRH on superovulated cattle

Gonadotropin releasing hormone (GnRH) was given to 109 cows and heifers during the course of 224 superovulations. Follicle stimulating hormone (FSH) was administered twice daily (5 or 6 mg) for 3.5 to 4 days beginning on any of Days 9 to 14 of the estrous cycle; prostaglandin (45 mg PGF(2)alpha or 750 ug cloprostenol) was given in a split dose on the fourth day. Donor cows and heifers were placed into four groups according to previous superovulation treatments, which consisted of one to three treatments or of no previous treatment. Every other cow or heifer within each of the four subgroups was treated with GnRH (200 mug i.m.) at standing estrus. Only donors that exhibited estrus within 32 to 72 h after the first prostaglandin treatment were used in the study. Animals were inseminated artificially 12 and 24 h after standing estrus was first observed. No differences were noted in the number of ovulations, total ova or transferable embryos recovered from the GnRH or control groups; however, two interactions were detected. Cows given GnRH had fewer palpable corpora lutea than control cows (P < 0.05), but this difference was not seen in heifers. The second interaction was that GnRH seemed to depress ovulation rate in donors not previously superovulated, but this effect was not observed with subsequent superovulations. Cows yielded more total ova than heifers (P < 0.01). There was no difference in return to estrus between GnRH and control groups after a second prostaglandin treatment at the time of embryo recovery. Most donors within each group resumed cycling between 5 and 12 d after embryo recovery.     

The influence of inhibited prostaglandin biosynthesis on post-ovulatory oviductal ova transport in sows

Changes in prostaglandin and progesterone concentrations after ovulation seem to affect reproductive functions in the sow. The influence of lowered prostaglandin levels on ova transport velocity through the isthmus part of the oviduct, and on progesterone concentrations, was studied during the second estrus after weaning in thirteen purebred Yorkshire multiparous sows. To determine the time of ovulation transrectal ultrasonographic examination was performed. In the second estrus, six sows were given intravenous injections of flunixin meglumine (2.2 mg/kg body weight) every sixth hour from 4 to 8 h after time of ovulation until about 48 h after ovulation, at which time the sows were slaughtered. Blood samples were collected every second hour from about 12 h before ovulation until slaughter. Progesterone and prostaglandin F2alpha (PGF2alpha) metabolite levels were determined. Immediately after slaughter the isthmus part of the oviducts were cut into 3 equally long segments and the number of ova in each segment, and in the upper part of the uterine horns, was determined. Before start of treatment, PGF2alpha metabolite levels were similar in the 2 groups (P=0.84). In the treatment group, PGF2alpha values dropped to below the detection limit immediately after start of treatment, whereas in the control group the concentrations were quite stable throughout the sampling period (P=0.005). Ova recovery rate was 94% in the treatment group and 95 % in the control group. At time of slaughter, in the treatment group ova had on average passed 2.1 segments whereas in the control group the ova had passed 2.5 segments (P=0.57). The progesterone levels increased continuously in both groups after ovulation but there was no difference in the mean progesterone concentrations between the two groups before (P=0.96) or after (P=0.58) ovulation. It can be concluded that the transport of ova through the isthmus part of the oviduct is unaffected by an inhibition of prostaglandin synthesis immediately after ovulation. Furthermore, the post-ovulatory progesterone profile seems unaffected by lowered PGF2alpha levels.