Synthetic microspheres transferred to the rat oviduct on day 1 of pregnancy mimic the transport of native ova

Microspheres of various materials and diameters were transferred microsurgically to the rat oviduct on Day 1 of pregnancy and autopsies were done at various times thereafter up to Day 10 to assess the recovery and segmental distribution of microspheres and eggs in the genital tract or the viability of embryos. The number and distribution of eggs in the treated and control sides after unilateral transfers were not different on Day 4 and 5 and the number of embryos implanted on Day 10 was not significantly affected after bilateral transfers. The segmental distribution of eggs and starch microspheres within the oviduct on Days 2, 3 or 4 showed that both are transported partly intermingled from ampulla to uterus. When microspheres of poly(DL-lactide-co-glycolide), starch, dextran or dextran blue were transferred, their distribution in the genital tract in the morning of Day 5 showed that poly(DL-lactide-co-glycolide) and dextran microspheres stayed longer in the oviduct while starch and dextran blue microspheres were transported to the uterus at the same time as the eggs. Transfer of starch microspheres of 40-60 microns to one oviduct and 180-200 microns in diameter to the opposite oviduct showed that distribution on one side was nearly identical to that of the other side from Days 2 to 5. We conclude that the behaviour of synthetic surrogate ova in rats differs from that in rabbits. The rat oviduct does not change the rate of transport of native eggs following transfer of synthetic surrogate ova.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of nitric oxide synthase inhibitors on ovum transport and oviductal smooth muscle activity in the rat oviduct

The effect of the inhibition of nitric oxide synthase (NOS) on ovum transport and oviductal motility in rats was investigated. Three different NOS inhibitors were injected into the ovarian bursa at oestrus or day 3 of pregnancy. Oviducts and uteri were flushed 24 h later and the presence of ova was recorded. In oestrous and pregnant rats, treatment resulted in accelerated egg transport, as shown by a decrease in the number of ova present in the oviducts. In cyclic rats, intrabursal injection of 1 mg kg-1 of either N-monomethyl-L-arginine (L-NMMA) or N omega nitro-L-arginine methyl ester (L-NAME) elicited a 30% reduction in the number of ova present in the oviducts, whereas in pregnant animals, the same dose of L-NMMA produced a reduction of 40%. Simultaneous administration of the NO donor spermine NONOate (5 mg kg-1) completely reversed the effect of L-NMMA. Tubal motility was assessed by microsphere displacement analysis within the oviduct. Surrogate ova were transferred to the oviductal lumen at oestrus and 24 h later the effect of intraoviductal injection of 1 microgram L-NMMA or vehicle was assessed. The microspheres in the isthmus showed an oscillating motion, and periods in which movement was not detectable. However, L-NMMA treatment produced a 3.6-fold increase in the maximum instant velocities and a significant reduction in the resting periods of the microspheres compared with the control group (P < 0.001). These results provide evidence that NO inhibition increases tubal motility that results in accelerated ovum transport, and indicate that NO could act as a paracrine signal between different layers of the oviductal wall, providing a role for endogenous NO in regulation of tubal function.     

Cell-specific variations and hormonal regulation of immunoreactive cytochrome P-450scc in the rat ovary

Specific rabbit antibodies to the bovine cholesterol side-chain cleavage cytochrome P-450 (P-450scc) were used to cross-react with the enzyme in the rat ovary. The luteal cells of cyclic, pregnant, and pseudopregnant rats were immunostained. P-450scc was also expressed in the interstitial cells of prepubertal and cyclic adult rats, and in the thecal cells lining the preovulatory follicles. In cyclic females, RU 486 and oestradiol increased the intensity of P-450scc immunostaining. The granulosa cells of ovarian follicles whatever their stage of development, including preovulatory follicles, were not labelled, except after ovulation. The intensity of immunostaining of thecal and interstitial cells decreased during early pregnancy or pseudopregnancy, and disappeared after Day 9, whereas these cells were intensely labelled 24 h after parturition. The immunostaining of thecal and interstitial cells was again detected in 18-day pregnant rats, treated with the antiprogesterone RU 486. It is therefore concluded that both oestradiol and progesterone are involved in P-450scc regulation.     

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.     

Impact of ACTH administration on the oviductal sperm reservoir in sows: the local endocrine environment and distribution of spermatozoa

The objective of the study was to investigate if short-term stress in sows (simulated by injections of synthetic adrenocorticotrophic hormone (ACTH)) during standing oestrus had a negative effect on the local environment in the utero-tubal junction (UTJ) and isthmus and the distribution of spermatozoa in these segments. Fourteen sows were monitored for ovulation using ultrasonography in two consecutive oestruses. The sows were fitted with jugular catheters and, from onset of the second oestrus, blood samples were collected every second hour. In the 2nd oestrus, seven sows were given ACTH every second hour, from the onset of standing oestrus until the sow ovulated (ACTH-group), whereas the other seven sows remained as controls (C-group) and were given NaCl solution. The sows were artificially inseminated 16-18 h before expected ovulation. Six hours after ovulation the sows were anaesthetised, and blood samples were repeatedly taken from veins draining the uterus and the UTJ-isthmus, respectively. This oviduct was thereafter removed and divided in four adjacent sections consisting of: (i) the UTJ, (ii) the first, and (iii) the second isthmus segment prior to (iv), the ampullary-isthmic junction (AIJ) and the ampulla. The three first-mentioned segments were flushed to retrieve spermatozoa, whereas the last one was flushed to collect oocytes/ova. The number of spermatozoa attached to the zona pellucida was counted. The concentrations of cortisol in jugular blood of the ACTH-group sows during the time of ACTH-injections were significantly higher than of the C-group sows (p<0.05), as were the levels of progesterone (p<0.001). Progesterone and cortisol concentrations measured in the blood samples draining the UTJ-isthmic region 6 h after ovulation did not significantly differ between the groups, but the C-group displayed significantly higher concentrations of progesterone in the UTJ-isthmic region compared with the levels measured in parallel samples taken of jugular blood (p<0.01). The C-group, but not the ACTH-group, also displayed a significant elevation in progesterone concentration 6h after ovulation compared with the basal levels before ovulation (p<0.01). Numbers of retrieved spermatozoa were not significantly different between the C-group and the ACTH-group. However, there was a tendency for a larger number of spermatozoa among sows in the ACTH-group, especially in the isthmic segment adjacent to the AIJ. In conclusion, simulated stress induced by injections of ACTH during standing oestrus results in elevated concentrations of progesterone before ovulation and may interfere with the rise of progesterone after ovulation. However, ACTH-injections appeared to augment transport of spermatozoa through the female genital tract of pigs.     

Accelerated ovum transport in rabbits induced by endotoxin II. Changes in oviductal smooth muscle activity

Oviductal motility, measured with open-ended perfused catheters in anesthetized animals injected with human Chorionic Gonadotropin (hCG), is depressed 2 h following endotoxin injection and returns to control levels by 3 h after endotoxin injection. This decrease in motility is prevented by indomethacin. Endotoxin did not affect spontaneous or phenylephrine (PE)-induced contractions of oviduct when it was added to the bathing medium of in vitro tissues. Oviductal segments removed 2 h after endotoxin (26 h after hCG) showed electrical activity confined to the ampullary-isthmic-junction (AIJ), where ova were located; the dose-response curve for PE was shifted to the right and the maximum contraction was depressed. Activity of tissues removed 4 h after endotoxin more closely resembled control tissues except that the maximum contraction to PE was depressed, ova had passed out of the oviduct and a proovarian bias in the isthmus was not present. The response of the oviduct to prostaglandins (PGs) in vivo is critically dependent on the previous exposure to PGs. In endotoxin-treated animals PGE then PGF levels increase and the decrease in motility coincides with increased PGE levels, but accelerated ovum transport with the return of motility and activation of the isthmus.     

Accelerated ovum transport in rabbits induced by endotoxin II. Changes in oviductal smooth muscle activity

Oviductal mortility, measured with open-ended perfused catheters in anesthetized animals injected with human Chorionic Gonadotropin (hCG), is depressed 2 h following endotoxin injection and returns to control levels by 3 h after endotoxin injection. This decrease in motility is prevented by indomethacin. Endotoxin did not affect spontaneous or phenylephrine (PE)-induced contractions of oviduct when it was added to the bathing medium of in vitro tissues. Oviductal segments removed 2 h after endotoxin (26 h after hCG) showed electrical activity confined to the ampullary-isthmic-junction (AIJ), where ova were located; the dose-response curve for PE was shifted to the right and the maximum contraction was depressed. Activity of tissues removed 4 h after endotoxin more closely resembled control tissues except that the maximum contraction to PE was depressed, ova had passed out of the oviduct and a proovarian bias in the isthmus was not present. The response of the oviduct to prostaglandins (PGs) in vivo is critically dependent on the previous exposure to PGs. In endotoxin-treated animals PGE then PGF levels increase and the decrease in motility coincides with increased PGE levels, but accelerated ovum transport with the return of motility and activation of the isthmus.     

Impact of Postovulatory Food Deprivation on the Ova Transport, Hormonal Profiles and Metabolic Changes in Sows

The effect of food deprivation on ova transport, hormonal profiles and metabolic changes was studied in 20 crossbred multiparous sows during their second oestrus after weaning. To determine the time of ovulation, transrectal ultrasonographic examination was performed. The sows were divided into 2 groups, one control group (C-group), which was fed according to Swedish standards, and one experimental group (E-group). The E-group sows were deprived of food from the first morning meal after ovulation until slaughter. Blood samples were collected every second hour from about 12 h before expected ovulation in the second oestrus after weaning until slaughter and were analysed for progesterone, prostaglandin F_2α-metabolite, insulin, glucose, free fatty acids and triglycerides. All sows were slaughtered approximately 48 h after ovulation and the genital tract was recovered. The isthmic part of the oviduct was divided into 3 equally long segments and flushed separately with phosphate buffered saline (PBS). Uterine horns were also flushed with PBS. A significantly greater number of ova were found in the first and second part of the isthmus in the E-group (p = 0.05) while in the C-group most of the ova were found in the third part of the isthmus or the uterus (p = 0.01). The level of prostaglandin F_2α-metabolite was significantly higher in the E-group compared with the C-group. The concentration of progesterone increased in both groups after ovulation but there were no significant differences between the groups. The other blood parameters showed that the food-deprived sows were in a catabolic state. The 48 h period of fasting results, directly or indirectly in an delayed ova transport, which may be due to a delayed relaxation in the smooth circular muscle layer of the isthmus.     

Embryos of different ages transferred to the rat oviduct enter the uterus at different times

Indirect evidence of embryo signalling to the oviduct was sought in rats by examining the transport of embryos of different ages. One-cell or four-cell embryos were transferred to the oviducts of recipient rats on Day 1 of pregnancy, and the number, condition, and location of native and transferred embryos was assessed on Day 4. To control for the effect of the presence of foreign embryos and excess number of eggs and the transfer procedure upon the fate of native embryos, other groups of rats were sham-operated or left undisturbed. Recipients had a mean number of ova significantly higher than controls. In controls and recipients of 1-cell embryos, the majority of eggs reached the morula stage and all of them were located in the oviducts. In those animals receiving 4-cell embryos, half of the eggs had reached the blastocyst stage and 28% were in the uteri (p less than 0.005). These results support the idea that advanced embryos can influence the timing of their entrance to the uterus in rats.     

Conference lecture: influence of stress on estrus, gametes and early embryo development in the sow

Systems with loose-housed sows have become common. Regrouping, which is commonly done after weaning and may coincide with many important reproductive events, causes stressful situations with elevated blood cortisol concentrations. Depending on group size, approximately 2-7 d are required for a new group of sows to become relatively stable. In a series of studies, the social stress after regrouping was simulated with repeated adrenocorticotrophic hormone (ACTH) treatments for approximately 48h. Sows were allocated into control and experimental groups, fitted with jugular catheters, and blood samples were collected every 2 or 4h. Follicular development and ovulation were monitored by transrectal ultrasonography every 4h. Simulated stress during pro-estrus prolonged estrus and disturbed the follicular growth and ovulation. Giving ACTH during estrus elevated concentrations of cortisol and progesterone, and changed the intraluminal environment, including exaggerated amounts of mucus in the UTJ and isthmus. Although ACTH had no effect on the time of ovulation (relative to onset of standing estrus), or on embryo development, fewer oocytes/embryos were retrieved from the ACTH group than from the control group (51% vs. 81%, P<0.05), and there was a tendency towards faster embryo transportation to the uterus. Short-term fasting after ovulation had an unfavourable effect on sperm numbers in UTJ/isthmus, cleavage rate of fertilized ova, as well as ova transport through the isthmic part of the oviduct. Treatment with ACTH after ovulation reduced numbers of spermatozoa at the zona pellucida and retarded cleavage rate of fertilized ova. Therefore, the timing of stress seemed to be an important factor regarding effects on reproductive events.     

The effect of reserpine, oestradiol and in-vitro perfusion on oviduct calcium levels in the mouse during egg transport.

Mouse oviduct calcium content, determined by atomic absorbance after ashing of the tissue, showed a significant fall on Day 2 of pregnancy followed by a significant rise on Day 3. This pattern was altered by administration of reserpine and oestradiol in doses which were shown to alter the rate of egg transport. In-vitro perfusion of the oviduct, capable of maintaining muscular activity and back and forth movement of eggs for 24 h, was associated with lack of forward progressive motion of eggs and by a more rapid increase in tissue calcium levels during incubation than occurred in vivo.     

Optimization of embryo transfer protocols for mice

The efficiency of ova transfer and subsequent survivability were explored in this study. The goals of the experiment were to 1) determine the minimum number of ova necessary for pregnancy maintenance, 2) ascertain if the number of zygotes used in ova transfer approaches or exceeds uterine capacity, and 3) establish if location of deposition of ova influences embryo survival. A total of 1647 pronuclear zygotes were transferred in groups of 1, 2, 4, 6, 15 or 25 on Day 1 of gestation either via the oviducal ampulla or ostium to 156 nulliparous ICR pseudopregnant female mice. Pregnancy status was determined on Day 12 or Day 19 of gestation. Results indicated that pregnancy rates were not significantly increased by transferring larger numbers of zygotes (P < 0.1504) and that beyond transfer of 15 zygotes, the progressive increase in fetal numbers per litter declined. However, on Day 19 of gestation, no definitive evidence of limitation of uterine capacity was obtained with the numbers of zygotes transferred (P < 0.0531), and the estimates of numbers of viable and resorbed fetuses differed when determinations were made on Day 12 versus Day 19 of gestation. Mean numbers of developed fetuses per recipient declined (P < 0.0001), whereas the number of resorptions (partially resorbed fetuses or resorption sites) increased (P < 0.0001) over this period, reflecting fetal loss in mid- to late-gestation and possibly the transient nature of resorptions prior to Day 12. Additionally, there was no difference in pregnancy outcome when transferring ova into the oviducal ostium or isthmus (P < 0.5256). Finally, these results illustrated that when large numbers of zygotes were transferred into the oviducal ampulla, equivalent numbers of ova eventually implanted in the uterus; however, proportionally more of them began resorption.     

Effects of post-ovulatory food deprivation on the hormonal profiles, activity of the oviduct and ova transport in sows

The objective of the present study was to investigate the effect of post-ovulatory food deprivation on the hormonal profiles and consequently on the activity of the oviduct and ova transport in sows. Sows were randomly allocated to the control (C-group, n=6) or fasted (F-group, n=5) group. The F-group sows were fasted for four meals starting with the morning meal after detection of ovulation in the second oestrus after weaning. Ovulation was checked by transrectal ultrasonography. Blood was collected for the analyses of progesterone, oestradiol-17beta, prostaglandin F(2 approximately ) metabolite, insulin, free fatty acids and triglycerides. Oviductal isthmic motility was monitored on Polyview before and after ovulation until the time of slaughter. After slaughter, the isthmus opposite the side with transducer was divided into three equal segments and flushed separately and a third of the uterine horn part from the utero-tubal-junction (UTJ) was also flushed. A high proportion of ova in the F-group was found in the first and second parts of the isthmus. In the C-group, a high proportion of ova was found in the third part of the isthmus and the uterus. The mean isthmic pressure in the C-group decreased significantly (P<0.05) during the period immediately after ovulation while in the F-group mean pressure remained unchanged. The frequency of phasic pressure fluctuations were significantly (P<0.05) higher in the F- than in the C-group 13 to 24 h after ovulation. No significant differences in progesterone concentrations were seen between the two groups of sows. Prostaglandin metabolite levels were significantly (P<0.05) higher in the F-group than in the C-group. Oestradiol-17beta levels significantly (p<0.05) decreased earlier in the F- than in the C-group. Serum insulin levels were significantly (p=0.05) lower in the F- than in the C-group while free fatty acids were significantly (p<0.01) higher in the F- than in the C-group. There were no significant differences in the serum levels of triglycerides between the F- and the C-group. Therefore, it can be concluded in the present study that food deprivation is associated with changes in the hormonal profiles, activity of the oviduct and a delay of ova transport in sows.     

Luteinizing and ovulatory action of oestradiol in the pregnant rat

Oestradiol injection on Day 10 of pregnancy in rats, resulted in either ovulation or luteinization in 50% of cases on Day 12. Cytological data showed that the number of pituitary LH cells decreased significantly on Day 11 in all oestradiol-treated animals whether responsive or not to oestrogen by ovarian modifications, while the number of pituitary FSH cells only decreased significantly in females with characteristic ovarian signs of preovulation. Bioassay of pituitary FSH confirmed the cytological data. It is concluded that ovulation and luteinization only occurred in the pregnant rat when oestradiol triggered off a synchronous release of LH and FSH.     

Elevated peripheral concentrations of LH block ovulation and increase thecal and serum progesterone in the hamster

Insertion of osmotic minipumps containing 1 mg ovine LH on Day 1 (oestrus) elevated circulating serum concentrations of LH, progesterone and androstenedione when compared with values at pro-oestrus. Ovulation was blocked for at least 2 days at which time there were twice the normal numbers of preovulatory follicles. Follicular and thecal progesterone production in vitro was elevated when compared with that in pro-oestrous controls. Follicular and thecal androstenedione production in vitro was lower than in controls even though serum concentrations of androstenedione were elevated; the higher androstenedione values may be due to the increase in number of preovulatory follicles when compared with pro-oestrous controls. Follicles from LH-treated hamsters aromatized androstenedione to oestradiol and follicular production of oestradiol was similar to that in pro-oestrous follicles despite low follicular androstenedione production in the LH-treated group. Treatment with 20 i.u. hCG on Days 4 or 6 after insertion of an LH osmotic minipump on Day 1 induced ovulation of approximately 30 ova, indicating that the blockade of ovulation was not due to atresia of the preovulatory follicles. Serum progesterone concentrations on Days 2, 4 and 6 in LH-treated hamsters were greater than 17 nmol/l, suggesting that the blockade of ovulation might have been due to prevention of the LH surge by high serum progesterone concentrations.     

Effect of ovulation on sperm transport in the hamster oviduct

When hamsters mate shortly after the onset of oestrus (4.5-6 h before the onset of ovulation), spermatozoa are stored in the caudal isthmus of the oviduct until near the time of ovulation. At this time, a few spermatozoa ascend to the ampulla to fertilize the eggs. Superovulation resulted in a significant increase in the number of spermatozoa in the caudal isthmus at 6 h post coitus (p.c.) and in the ampulla and bursal cavity at 12 h p.c. Precocious ovulation resulted in a highly significant reduction in the total number of spermatozoa in the oviduct at 3 and 6 h p.c. This effect was completely overcome by intrauterine artificial insemination, suggesting lack of cervical patency as the block to sperm transport in precociously ovulated animals. Ligation of the ampulla-infundibulum junction in naturally ovulating hamsters resulted in significantly fewer spermatozoa in the caudal isthmus and ampulla at 12 h p.c. Preclusion of ovulation also resulted in fewer spermatozoa in the caudal isthmus and ampulla at 12 h p.c., suggesting that the products of ovulation stimulate sperm transport in the oviduct.     

Effect of various agents on ovarian plasminogen activator activity during ovulation in pregnant mare's serum gonadotropin-primed immature rats

The plasminogen activator/plasmin synthetic substrate S-2251 was used to measure the effect of indomethacin, cycloheximide, colchicine, dexamethasone, tranexamic acid, and aprotinin on the elevation of ovarian plasminogen activator (PA) that normally occurs during ovulation in the rat. Young Wistar rats were weaned on the morning of Day 21, given 4.0 IU of pregnant mare's serum gonadotropin (PMSG) s.c. at 0800 h on Day 22, and given 10.0 IU of human chorionic gonadotropin (hCG) on Day 24. These animals normally began ovulating between 0000 and 0200 h on Day 25. The induced ovulation rate was 11.5 +/- 2.2 ova/rat, based on the number of ova in the oviducts of control animals at 0900 h on Day 25. In the controls, PA activity in extracts of homogenized ovaries increased 3-fold from 0.125 +/- 0.010 OD units just before the administration of hCG to 0.371 +/- 0.021 at 12 h after hCG, i.e., near the time of ovulation. Indomethacin, in doses of 0.1-1.0 mg/rat, inhibited ovulation but did not inhibit the normal increase in PA activity, whereas indomethacin at the high dose of 10.0 mg/rat inhibited both ovulation and PA activity. Cycloheximide, at a dose of 0.1 mg/rat, was given at 12 h before hCG, immediately after hCG, and at 9 h after hCG. This agent inhibited ovulation most effectively when given at 12 h before hCG, yet it inhibited PA activity most effectively when given immediately after or at 9 h after hCG. Colchicine, at a dose of 0.1 mg/rat, inhibited ovulation, but not PA activity, when it was given 1 h before hCG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diminished oestrogen sensitivity and increased ovulation rate in adult female rats after prepubertal treatment with oestrogen or pimozide

Immature female rats were implanted with oestradiol benzoate or cholesterol in the medial preoptic area at different ages, and the inhibition of the ovariectomy-induced increase of LH secretion by s.c. injected oestradiol was investigated. Medial preoptic oestrogen implants reduced the inhibition of LH secretion in 4-week-old rats, but not in younger animals. Elevation of the circulating oestrogen concentration or suppression of the central nervous dopamine activity by daily injections of oestradiol and pimozide, respectively, from Day 26 to the day of vaginal opening, i.e. during the time when the mechanism of the oestrogen-induced desensitization of the negative oestrogen feedback matures, resulted in considerable diminution of the LH-inhibiting effect of oestradiol in ovariectomized adult females. In intact cyclic rats, both prepubertal treatments led to a significant increase of the average number of eggs per ovulation that was mainly caused by reduction of the number of animals with a low ovulation rate.     

Transport of fertilised and unfertilized ova in sows

Transport of fertilised and unfertilized ova was studied in 22 crossbred (Landrace x Yorkshire) multiparous sows. Sows in the inseminated group (I-group, n=11) were inseminated once with 100ml of BTS extended semen from two fertile boars with a total of 10 x 10 (9) spermatozoa during the second oestrus after weaning between 18 and 8h prior to estimated time of ovulation, as estimated from the first oestrus after weaning. All the sows were slaughtered between 36 and 48 h after ovulation in the second oestrus after weaning by stunning and bleeding. After slaughter, the reproductive tract was immediately recovered, the isthmus was divided into three equal segments, and the number of ova was determined in each segment and in the upper third of the uterine horn from the UTJ. There were no significant differences (P>0.05) either in the intervals from ovulation to slaughter (42.3+/-6.2h versus 43.2+/-5.4h) or in the numbers of corpora lutea (CL) (18.2+/-5.5 versus 15.9+/-3.5) between the non-inseminated (N-group) and the inseminated groups (I-group), respectively. Ova recovery rate was 92.5% in the N-group and 82.9% in the I-group (P>0.05). In the I-group, ova had passed 2.2+/-0.3 segments whereas in the N-group, ova had passed 2.6+/-0.3 segments (P=0.38). It can be concluded that there is no difference in the transportation of either fertilised or unfertilized ova in the reproductive tract of pigs.     

Postovulatory effect of repeated intravenous administration of ACTH on the contractile activity of the oviduct, ova transport and endocrine status of recently ovulated and unrestrained sows

The effect of repeated intravenous administration of ACTH (Synacthen depot) on the contractile activity of the oviduct, ova transport and endocrine status was studied in 11 Swedish crossbred (Landrace x Yorkshire) multiparous sows. In the second estrus after weaning, the ACTH group (Group A, n=6) sows were administered 0.01 mg/kg body weight of ACTH every 6 h commencing 4 to 8 h after ovulation, whereas the control group (Group C, n=5) sows were administered saline solution. Immediately after standing estrus, a Millar pressure transducer was placed about 3 cm into the isthmus via a laparotomy. Blood samples for hormonal analyses and pressure recordings of the oviduct were collected from all sows until slaughter. After slaughter, the genital tract opposite to the side with the transducer was retrieved, and 3 equal isthmic segments and the first third of the uterine horn portion adjacent to the UTJ were flushed separately for ova recovery. Cortisol levels were significantly (P<0.05) elevated after ACTH administration. Progesterone and PGF2alpha metabolite levels were significantly (P<0.05) elevated only after the first ACTH administration. No significant differences (P>0.05) were seen in the mean pressure and frequencies of phasic pressure fluctuations either before or after every ACTH administration between Groups A and C. No significant difference (P>0.05) was seen in the proportion of ova recovered in the different segments between Groups A and C. It can be concluded from the present study that the administration of ACTH (0.01 mg/kg body weight) to sows at 4 to 8 h after ovulation, and after each subsequent ACTH administration, elevates cortisol levels, whereas progesterone and PGF2alpha metabolite levels are elevated only after the first treatment, and that this has no effect on the mean isthmic pressure, the frequency of phasic pressure fluctuations or ova transport.