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PubMed2003

Ovulation rate after GnRH or PGF2alpha administration in early postpartum dairy cows.

The objectives of this study evaluating induction of ovulation in early postpartum dairy cows were to: compare two methods of GnRH (100 mcg) administration (i.m. route and s.c. implant), and determine if prostaglandin F(2alpha) (PGF) causes release of LH or ovulation similar to that reported for GnRH. In trial #1, serum LH peaked at 2h after i.m. administration of GnRH and was declining at 4h. The s.c. GnRH implant also caused an elevation in serum LH at 2 and 4h after treatment, with LH declining at 6h. Serum LH was unchanged in control cows. Experimental treatment caused ovulation in 4 of 14 GnRH i.m. treated cows, 4 of 12 GnRH implanted cows and 0 of 13 control cows. Parity had no effect on LH response but did affect resulting ovulation rate as multiparous cows were more likely to ovulate than were primiparous cows in response to either GnRH treatment. All cows that ovulated had a follicle larger than 12 mm at the time of treatment. In trial #2, serum LH increased as before after i.m. administration of GnRH, however, serum LH was unchanged in cows treated with PGF or saline. Gonadotropin releasing hormone caused more cows to ovulate than did PGF or saline treatments, and GnRH shortened the interval from treatment to the onset of CL function over the PGF treatment; 13.9+/-2.6, 28.2+/-4.1 and 22.3+/-4.1 days for GnRH, PGF and saline, respectively. In summary, there was no difference in the ability of s.c. implantation and i.m. administration of GnRH to cause ovulation. Prostaglandin F(2alpha) did not cause release of LH or ovulation. In 22 early postpartum dairy cows treated with 100 mcg GnRH i.m. in these two trials, nearly all cows (95%) responded with a release of LH but only 45% (10/22) responded with an ovulation and subsequent formation of a CL.

Animals↗
PubMed1999

Effects of follicular status at treatment on follicular development and ovulation in response to FSH in Spanish merino ewes.

Cyclic Spanish Merino ewes were treated on Day 13 of the estrous cycle with 12 mg, i.m., FSH-P in saline (n = 9) or propylene glycol (n = 24), currently with 100 micrograms, i.m., Cloprostenol (Day 0). From Day-6 to Day 0, the ewes were observed daily by transrectal ultrasonography, after Day 0, ultrasonography was performed every 12 h for 72 h. Sizes and locations of > or = 2 mm follicles were recorded at each observation. The ovulation rate was determined by laparoscopy on Day 7 after estrus. The number of ovulations ranged from 0 to 6 in ewes treated with FSH-P in saline and from 0 to 16 in ewes receiving FSH-P in propylene glycol (P < 0.05). In the latter group, the response was bimodally distributed; about half of the females had 1 ovulation, whereas the remainder had > 4 with a mean of 7 ovulations. The ovulation rate was associated with 2 characteristics of the largest follicle present at treatment (Day 0). First, if the largest follicle on Day 0 had not changed in diameter from Day-1 to Day 0, then 7 of 9 ewes had > 3 ovulations; if the largest follicle had either increased or decreased, only 8 of 24 ewes had > 3 ovulations (P < 0.05). Second, there was a linear trend (P < 0.07) for ovulation rate to decrease as the persistence of the largest follicle at treatment increased; no ewe in which the largest follicle on Day 0 remained present for more than 36 h ovulated more than 6 follicles. As with the ovulation rate, the numbers of large follicles on Days 1.5, 2 and 2.5 varied with the interaction of change in diameter of the largest follicle on Day 0 from Day-1 to Day 0 and with vehicle. In summary, the superovulatory response was affected by the change in diameter from Day-1 to Day 0 of the largest follicle on Day 0 and the period required for that follicle to regress after treatment with FSH-P and cloprostenol.

Animals↗
PubMed2000

Oviductal isthmic motility patterns as monitored by polyview in unrestrained sows around ovulation.

A method for monitoring oviductal isthmic motility in sows incorporating a computer programme (Polyview) was developed. This method was found to be reliable and easy for recording and analysing data. Isthmic motility patterns were monitored from 11 h prior to and up to 36 h after ovulation in 13 unrestrained multiparous sows during their second oestrus after weaning. The amplitudes and frequencies of phasic pressure fluctuations in relation to the hormonal profiles were also calculated. The isthmic motility patterns were regular before ovulation changing to wave patterns during the peri-ovulatory period and eventually to irregular patterns after ovulation. The amplitudes and frequencies of phasic pressure fluctuations were significantly higher (p<0.05) prior to and soon after ovulation than afterwards. Plasma oestradiol-17beta levels significantly (p<0.05) decreased before ovulation while plasma progesterone levels increased significantly (p<0.05) after ovulation. Despite a significant decrease in the plasma levels of oestradiol-17beta prior to ovulation, the amplitudes and frequencies of phasic pressure fluctuations remained high until shortly after ovulation. This could have been due to the endogenous levels of oestradiol-17beta bound to the nuclear oestradiol-17beta receptors that might still have been present in the isthmus. Conversely, the irregular isthmic motility patterns, the decline in the frequencies of phasic pressure fluctuations and amplitudes seen after ovulation may have been due to the rising plasma levels of progesterone. The amplitudes and frequencies of phasic pressure fluctuations were highest at the time when oestradiol-17beta levels were highest and when progesterone levels were low. It can be concluded that the changes in the isthmic motility patterns, amplitudes and frequencies of phasic pressure fluctuations in relation to the changes in the plasma levels of oestradiol-17beta and progesterone seen in the present study prior to and after ovulation indicate a possible role of the oviduct in regulating gamete transport.

Animals↗
PubMed1998

Seminal plasma does not advance ovulation in hCG-treated sows.

In gilts, seminal plasma treatment before or during the LH-surge has been found to advance ovulation in all animals by as much as 8 to 14 h. Two experiments were performed to assess whether such an advancement occurs in multiparous sows in which ovulation is induced by 750 i.u. hCG at 68 h after weaning. In both experiments, seminal plasma was inseminated at 4, 5 and 6 h after hCG (7 and 6 sows, respectively) and control sows (6 and 6 sows, respectively) were not inseminated. In Experiment 1, using Meishan semen, all sows ovulated between 38 and 44 h after hCG; no advancement of ovulation was seen due to treatment. In Experiment 2, using GY seminal plasma, 3 and 4 sows, respectively had started ovulation at 44 h after hCG. Again, no advancement of ovulation was seen due to treatment. Therefore, in both experiments, seminal plasma treatment within 4-6 h after hCG failed to advance ovulation to a similar extent as found in spontaneously ovulating gilts. It is unclear what causes this lack of effect. Maybe seminal plasma treatment does not advance hCG-induced ovulation or batches of seminal plasma differ in their ovulation-advancing properties.

Animals↗
PubMed1981

Induction of ovulation in seasonally anovular ewes by the introduction of rams: effects of progesterone and active immunization against androstenedione.

The effects of progesterone priming and active immunization against androstenedione on ovulation, oestrus ad premature luteal regression were observed in seasonally anovular Merino ewes which had been induced to ovulate by the introduction of rams. Ovulation was induced in 27 out of 36 ewes, and the response was not affected by either immunization or progesterone priming. The ovulation rate (mean number of ovulations per ewe ovulating) was higher in ewes immune to androstenedione, but there was no significant effect of this treatment on oestrus or luteal maintenance. Priming with progesterone prior to the introduction of rams prevented premature regression of the corpora lutea but had no effect on the other measures of reproductive function. If active immunization were to be applied on a commercial scale, it would not interfere with the practice of mating ewes during the anoestrous season. The increase in ovulation rate in these ewes, with no increase in the proportion of ewes ovulating, indicates that the mechanism for the control of ovulation is separate from that controlling ovulation rate. The mechanism by which progesterone pretreatment prevents premature luteal regression awaits further investigation.

Androstenedione↗
PubMed1976

The effects of progesterone on oviposition and ovulation in the domestic fowl (Gallus domesticus).

1. Following an injection of 0.5 or 0.1 mg progesterone/kg between 0 and 6 h after ovulation, oviposition of the resulting egg was delayed by 1 to 11 h and occurred 26 to 31 h after injection, depending on the dose. The injection terminated the laying of a sequence of eggs by causing the next ovulation to occur a day late. The delayed ovulation occurred at the time normally expected for the first ovulation a sequence and became the first of a new sequence. 2. Following an injection of 0.5 or 0.1 mg progesterone/kg between 6 and 15 h after ovulation, oviposition of the resulting egg was generally delayed by between 15 and 28 h and occurred at the same time of day as the next ovulation, which was delayed as in the first experimental situation. Subsequent ovulations were resynchronised and followed at intervals according to the normal sequence established before the injection. 3. Injection of 0.5, 0.1 or 0.05 mg progesterone/kg between 12 and 9 h before expected ovulation advanced the oviposition of the egg already in the uterus (shell gland) by about 3 h. The succeeding ovulation was either advanced or blocked. 4. These observations suggest that the pre-ovulatory surge of progesterone is directly or indirectly involved in the timing of oviposition and ovulation.

Animals↗
PubMed1994

Effect of progesterone on ovulation in the hypophysectomised hen.

1. One hundred and seven laying hens were hypophysectomised to clarify the relationship between hypophysectomy and the effect of progesterone (P4) on ovulation. 2. Hens were hypophysectomised at 6 intervals from 4.5 to 11.0 h before the expected time of ovulation. Ovulation occurred in the hens operated on from 4.5 to 7.3 h, but did not take place in birds operated on from 9.2 to 9.8 h before the expected time of ovulation. 3. When a single dose of P4 (2 mg/hen) was injected iv immediately after the removal of the anterior pituitary from 7.5 to 9.8 h before the expected time of ovulation, ovulation was induced. However, the percentage of hens responding decreased in proportion to the lapse of time between the hypophysectomy and the expected time of ovulation. No ovulation was induced in hens which were hypophysectomized and given P4 10.2 to 11.0 h before the expected time of ovulation. 4. It is suggested that ovulation is induced by P4 alone possibly in the absence of preovulatory gonadotrophins and that P4 acts directly on the ovary to induce follicle rupture.

Animals↗
PubMed2006

Ovulation detection methods for urinary hormones: precision, daily and intermittent sampling and a combined hierarchical method.

BACKGROUND: We evaluate the performance of ovulation detection methods and present new approaches, including evaluation of methods for precision, combining multiple markers into a hierarchical system and using ovulation markers in intermittent sampling designs. METHODS: With serum LH peak day as the 'gold standard' of ovulation, we estimated accuracy and precision of ovulation day algorithms using 30 ovulatory menstrual cycles with daily urinary and serum hormones and transvaginal ultrasound. Sensitivity and specificity for estimating the presence of ovulation were tested using visually assessed ovulatory (30) and anovulatory (22) cycles. RESULTS: Sensitivity and specificity ranged from 70 to 100% for estimating presence of ovulation with twice-per-cycle, weekly, twice weekly, every-other-day and daily specimens. A combined hierarchical method estimated ovulation day using daily specimens within +/-2 days of the gold standard in 93% of cases. Accuracy of estimating ovulation day within +/-2 days using intermittent sampling ranged from 40% (weekly sampling) to 97% (every-other-day). CONCLUSIONS: A combined hierarchical algorithm using precise and accurate markers allows maximal use of available data for efficient and objective identification of ovulation using daily specimens. In intermittent sampling designs, the presence and the timing of ovulation can be estimated with good sensitivity, specificity and accuracy.

Adult↗
PubMed2003

Role of arachidonic acid and protein kinase C during maturation-inducing hormone-dependent meiotic resumption and ovulation in ovarian follicles of Atlantic croaker.

The roles of arachidonic acid (AA) and protein kinase C (PKC) during in vitro maturation-inducing hormone (MIH)-dependent meiotic resumption (maturation) and ovulation were studied in ovarian follicles of Atlantic croaker (Micropogonias undulatus). The requirement for cyclooxygenase (COX) metabolites of AA was examined using a nonspecific COX inhibitor, indomethacin (IM), as well as two COX products, prostaglandin (PG) F(2alpha) and PGE(2), whereas the role of lipoxygenase (LOX) was investigated using a specific LOX inhibitor, nordihydroguaiaretic acid (NDGA). The involvement of PKC was examined using phorbol 12-myristate 13-acetate (PMA), a PKC activator, as well as GF109203X (GF), a specific inhibitor of PKC and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), nonspecific inhibitor of protein kinases. Genomic mechanisms were examined with the transcription-inhibitor actinomycin D (ActD) and the functionality of heterologous (oocyte-granulosa) gap junctions (GJ) with a dye transfer assay. The AA (100 microM) and PGF(2alpha) (5 microM) did not induce maturation, and NDGA (10 microM) did not affect MIH-dependent maturation. However, IM (100 microM) partially inhibited MIH-dependent maturation. Conversely, AA and both PGs induced, and IM and NDGA inhibited, MIH-dependent ovulation in matured follicles. The PMA (1 microg/ml) did not induce maturation but caused ovulation in matured follicles, whereas PKC inhibitors (GF, 5 microM; H7, 50 microM) did not affect MIH-dependent maturation but inhibited MIH- and PMA-dependent ovulation. The PMA-dependent ovulation was inhibited by IM but not by NDGA. In addition, ActD (5 microM) blocked MIH-dependent, but not PMA-dependent, ovulation, and PGF(2alpha) restored MIH-dependent ovulation in ActD-blocked follicles. The AA and PGs did not induce, and GF did not inhibit, MIH-dependent heterologous GJ uncoupling. In conclusion, AA and PKC mediate MIH-dependent ovulation but not meiotic resumption or heterologous GJ uncoupling in croaker follicles, but a permissive role of COX products of AA during maturation is possible. A novel model of MIH-dependent ovulation is proposed in which 1). LOX and COX metabolites of AA are both required for ovulation, but at upstream and downstream sites of the pathway, respectively, relative to PKC, and 2). PKC is downstream of genomic activation.

Aging↗
PubMed1991

Synergistic induction of ovulation and prostaglandin synthesis in goldfish (Carassius auratus) follicles by sodium orthovanadate and hydrogen peroxide.

The effects of hydrogen peroxide (H2O2) and sodium orthovanadate (Na3VO4) on ovulation and prostaglandin (PG) production were investigated in goldfish (Carassius auratus) follicles. H2O2, at levels that did not stimulate ovulation, significantly increased the ability of Na3VO4 to induce ovulation. The enhancing effect of H2O2 on Na3VO4-induced (10 microM) ovulation was observed over a wide range of concentrations (0.3-19.2 ppm) but was maximal at 1.2-4.8 ppm. The H2O2 effect on ovulation diminished at concentrations greater than 4.8 ppm. Na3VO4 and H2O2 also stimulated prostaglandin E (PGE) and prostaglandin F (PGF) levels in incubates. An interactive effect of the two agents was significant only on PGE production. However, optimal H2O2/Na3VO4 concentrations for the stimulation of PG production were much higher than those for stimulating ovulation. In most incubations, Na3VO4-induced or Na3VO4/H2O2-induced ovulation was not inhibited by the cyclooxygenase inhibitor indomethacin (IM), but was blocked by the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA). Treatment of an Na3VO4/H2O2 mixture with catalase before the start of incubation totally abolished the enhancing effect of H2O2 on ovulation. This suggests that the enhancing effect of H2O2 on ovulation may not be a result of a chemical metabolite(s) produced by the two agents in mixture but rather is due to some direct effect of H2O2. This may have physiological significance in light of the published effects of H2O2 on various processes known to be involved in ovulation.

Animals↗
PubMed1998

The lipoxygenase inhibitor, nordihydroguaiaretic acid, inhibits ovulation and reduces leukotriene and prostaglandin levels in the rat ovary.

Eicosanoids, the active metabolites of arachidonic acid, are grouped into cyclooxygenase products (prostaglandins [PGs] and thromboxanes) and lipoxygenase products (leukotrienes [LTs] and lipoxins). Numerous studies suggest a role for the lipoxygenase system in ovulation. The aim of this study was to further characterize the effects of lipoxygenase inhibition and the interactions of the lipoxygenase and cyclooxygenase systems in the rat ovary during ovulation. The lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), was administered in vivo and in the isolated perfused rat ovary to determine its effect on ovulation rate. The in vivo study confirmed the inhibitory effect of NDGA, and in the perfusion experiments, NDGA caused a dose-dependent reduction in the ovulation rate. To further define the interaction between the lipoxygenase and cyclooxygenase systems, a second set of perfusions was performed with NDGA (10 microM) and the combination of NDGA (10 microM) plus a nonselective cyclooxygenase inhibitor, indomethacin (10 microM). NDGA significantly reduced the number of ovulations compared to that in controls. The ovulation rate for the combination of NDGA+indomethacin was also significantly lower than in controls but not different from that in the NDGA-treated group. Steroidogenesis was decreased only in the NDGA+indomethacin perfusions. Ovarian tissue PGE2 and PGF2alpha levels in the NDGA-treated ovaries were significantly suppressed compared to those in controls. Almost a complete block of PGE2 and PGF2alpha was seen in the NDGA+indomethacin group. LTB4 levels in the 10-h-perfused ovarian tissues were significantly decreased by NDGA compared to those in control tissues. Furthermore, LTB4 (3 microg added twice) completely reversed the inhibitory effect of 0.1 microM NDGA on ovulation rate and partially reversed the effect of 10 microM NDGA in the perfusion model. These results demonstrate that the products of the lipoxygenase pathway, especially LTB4, are important in the process of ovulation in this cyclically ovulating species. The interconnected lipoxygenase and cyclooxygenase pathways may optimize ovulation and facilitate steroidogenesis.

Animals↗
PubMedDate not supplied

Effects of ovulation induction on ovarian morphology: an animal study.

OBJECTIVE: The aim of this study was to investigate whether the ovulation induction has relation with postneoplastic lesions. MATERIALS AND METHODS: Seventy-eight female, 90-day-old rats were enrolled for the trial. They were divided into three groups. In the first group, 13 rats received one cycle of ovulation induction with Follitropin Beta and human chorionic gonadotropin. The second group of 13 rats received three cycles of ovulation induction, and the third study group consisted of 13 rats which received six cycles of ovulation induction. Each group had a control group consisting of same number of rats that had not received ovulation induction. At the 12th month after the ovulation induction protocols ended, rat ovaries were extirpated for histopathological examination. In histopathological examination, malignant lesions, ovarian cyst and cyst diameter, epithelial stratification, epithelial tufting, mitotic index, polymorphism of epithelial cells and nucleus, epithelial cell nuclear diameter, chromatin density nuclear atypia, and mitotic activity in ovarian cyst epithelium were evaluated. RESULTS: No malignant ovarian lesion was found in the three groups. Ovarian cyst development was most frequent in the rats that underwent six cycles of ovulation induction. Epithelial stratification and tufting were most frequent in the rats which underwent ovulation induction six times. Significant difference was found between induction and control groups in second and third groups for cellular and nuclear polymorphism, presence of nucleolus, and nuclear chromatin density. CONCLUSIONS: Although development of malignant lesion were not found in any of the rat ovaries after ovulation induction, increase in the prevalence of epithelial dysplasia especially with increase in the number of induction cycles shows that some ovarian pathologies can occur subsequent to ovulation induction.

Animals↗
PubMed1999

Ovulation in plasminogen-deficient mice.

Many different studies suggest that plasmin generated from plasminogen plays a crucial role in the degradation of the follicular wall at the time of ovulation. We have assessed the physiological relevance of plasmin on ovulation by studying plasminogen-deficient mice. Ovulation efficiency (mean number of ova released per mouse) was determined both in a standardized ovulation model in which 25-day-old immature mice were injected with finite amounts of gonadotropins to induce ovulation and during physiological ovulation using adult normally cycling mice. Our results revealed that the temporal onset of follicular wall rupture (first ova observed in bursa or oviduct) was not delayed in plasminogen-deficient mice during gonadotropin-induced ovulation. However, there was a trend toward slightly reduced ovulation efficiency in the plasminogen-deficient mice. This reduction was only 13% and not statistically significant (P = 0.084) and may be connected to a delayed maturation of these mice manifested in reduced body and ovary weights. During physiological ovulation adult plasminogen-deficient mice had normal ovulation efficiency compared with plasminogen wild-type mice. Taken together our results indicate that under the conditions used in this study plasmin is not required for efficient follicular rupture or for activation of other proteases involved in this process. Alternatively, the role of plasmin may be effectively compensated for by other mechanisms in the absence of plasmin.

Animals↗
PubMed1990

Nursing does affect the duration of the post-partum to ovulation interval in cotton-top tamarins (Saguinus oedipus).

Reports on callitrichid monkeys have not revealed a significant effect of nursing on interbirth intervals or on post-partum to ovulation intervals. We examined 25 post-partum intervals in cotton-top tamarin females to determine whether nursing infants would affect the length of the post-partum to ovulation interval. Urinary LH/CG and oestrone conjugates were measured in urine samples collected in the 6 weeks after birth. The post-partum to ovulation interval is the number of days between parturition and the rise of urinary LH and oestrone conjugates associated with ovulation. There was an 84% conception rate post partum. Neither mother's parity nor sex of the infants influenced the length of the post-partum to ovulation interval. The post-partum to ovulation interval for females nursing 2 infants was twice as long as for those not nursing or nursing 1 infant (P less than 0.05). The range of post-partum to ovulation interval lengths was more variable in nursing than in non-nursing females (P less than 0.01). Females spent less than 50% of observed time in contact and less than 20% of observed time nursing their infants. Neither the number of tamarins within the family nor the amount of time the mother was in contact with infants correlated with the length of the post-partum to ovulation interval. However, there was a positive correlation between the percentage time that mothers nursed 1 infant at a time and the length of the post-partum to ovulation interval (r = 0.75, P less than 0.02). The underlying mechanisms of suckling-induced delay of ovulation are present in the cotton-top tamarin as in other primate species. However, these nursing effects do not cause the substantial delay in fertility post partum that is associated with non-callitrichid primates.

Animals↗
PubMed1995

Effects of a second insemination after ovulation on fertilization rate and accessory sperm count in sows.

Insemination immediately after ovulation causes low fertilization results owing to a low fertilization rate and possibly also owing to polyspermic fertilization. The present experiment was undertaken to study the effects of a second insemination after ovulation on fertilization rate and embryonic development. In multiparous crossbred sows, transrectal ultrasonography was used at intervals of 4 h to determine ovulation. All sows (n = 91) were artificially inseminated with 3 x 10(9) mixed spermatozoa and, in 31 sows, a second insemination took place at 3 +/- 1 (mean +/- SD) h after ovulation. At 119 +/- 5 h after ovulation, the percentage of normal embryos and the accessory sperm count were determined. In the sows that were inseminated once, the percentage of normal embryos decreased when insemination took place more than 24 h before ovulation, from 88 +/- 20% (16-24 h; n = 15) to 63 +/- 40% (24-32 h; n = 10) (P < 0.05). In the sows that were inseminated again after ovulation, the percentage of normal embryos was high, irrespective of the period between first insemination and ovulation. The difference in percentage of normal embryos between the sows that were inseminated once or twice was significant when the first insemination took place between 24 and 32 h before ovulation; 63 +/- 40% (inseminated once, n = 10) and 97 +/- 5% (inseminated twice, n = 8) (P < 0.05). The accessory sperm count of the normal embryos in a litter was positively related to the percentage of normal embryos in a litter, and this relation was not affected by the interval between first insemination and ovulation or by the number of inseminations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The role of neurotransmitters in mediating copulation-induced ovulation in the rat.

Pentobarbitone-blocked pro-oestrous rats were subjected to either limited mating (maximum of 30 mounts), all-night cohabitation with males or stimulation of the vagina and cervix with a glass rod (2 or 5 min) to determine which type of stimulus was most effective in inducing ovulation. All-night cohabitation was the most successful procedure and resulted in 100% ovulation in those rats which mated. Treatment with either phenoxybenzamine, propranolol or pimozide did not interfere with this copulation-induced ovulation whereas methysergide treatment completely blocked copulation-induced ovulation. Administration of atropine resulted in a loss of mating behaviour and these animals therefore did not ovulate. Further experiments provided evidence that administration of atropine also blocked ovulation in response to vaginal stimulation with a glass rod. Pretreatment with methysergide or atropine had no effect upon the percentage of pentobarbitone-blocked, pro-oestrous rats ovulating in response to administration of LH releasing hormone (LHRH). However, those rats given atropine shed significantly fewer ova per rat following LHRH or LH infusion when compared with controls. These results suggest that the synaptic mechanisms responsible for mediating copulation-induced ovulation are different from those mediating steroid-induced ovulation, and that ovarian cholinergic receptors may play a role in ovulation.

Animals↗
PubMed2000

Responsiveness to boar stimuli and change in vulvar reddening in relation to ovulation in weaned sows.

In 117 weaned sows, changes in estrous behavior and vulvar reddening were related to timing of ovulation. Detection of estrus was performed every 8 h with four levels of boar stimuli to record the change in responsiveness to these stimuli. This resulted in four overlapping phases of estrus, during which a standing response could be evoked: 1) man estrus (standing response to a back pressure test, in the absence of a boar), 2) spontaneous estrus (standing response in the presence of a boar, no back pressure test), 3) boar estrus (standing response to boar + back pressure test), and 4) detection-mating-area estrus (back pressure test in the presence of four boars). In addition to the detection of estrus, the change in reddening of the inner vulvar mucosa was recorded. Manifestation of estrus in response to the four stimuli occurred in 46, 56, 90, and 97% of the sows, respectively. Onset of the four phases occurred 24 h (SD 13 h), 23 h (SD 15 h), 34 h (SD 13 h), and 41 h (SD 12 h) before ovulation. The duration of the intervals between the various phases of estrus explained 10 to 50% of the variation in the timing of ovulation relative to the onset of the phases. However, these intervals could not be calculated for all sows because estrus was not expressed at every stimulus level by each sow. The end of vulvar reddening occurred, on average, 21 h (SD 14 h) before ovulation. Except for five sows that ceased to show vulvar reddening within 5 h after ovulation, the end of vulvar reddening occurred before ovulation, within a 70-h range. Of the sows showing boar estrus, 90% also showed vulvar reddening. For sows that showed vulvar reddening until after the onset of boar estrus (two-thirds of the sows), the end of reddening occurred within a much smaller range: from 36 h before, until 2 h after, ovulation. Onset of estrus, regardless at which stimulus level it is detected, appears too variable relative to timing of ovulation to be used as a predictor for ovulation. Duration of the different stages of responsiveness explains only some of this variation and cannot be obtained on all sows. Combining information on vulvar reddening and boar estrus can predict ovulation within a reasonable range for two-thirds of the sows.

Animals↗
PubMed2001

Factors influencing estrus and ovulation in weaned sows as determined by transrectal ultrasound.

Characterization of factors influencing estrus and ovulation in sows may facilitate development of procedures for improving reproductive performance. The experiment was conducted in confinement during 1997 to 1999 using 174 Large White x Landrace sows. After weaning, sows were checked for estrus twice daily. In the 1st yr, transrectal ultrasound was performed once daily and in the 2nd yr twice daily at estrus and on every day until ovulation. The effects of lactation length (< or = 16 d, 17 to 24 d, 25 to 31 d or > or = 32 d), parity (1, 2, or > or = 3), season (winter, spring, summer, or fall) and weaning-to-estrus interval (3, 4, 5, or 6 to 8 d) and their interactions on estrual and ovulatory responses were studied. There was no effect of frequency of ultrasound on any response variable, so data across years were pooled. Percentage of sows expressing estrus within 8 d of weaning was influenced by lactation length (P < 0.001), with sows lactating < or = 16 d (35.2%) less likely to express estrus than sows lactating > or = 17 d (94%). A parity x season interaction was observed (P < 0.001) for estrus, with the lowest expression in parity 1 (73.0%) and parity 2 sows in fall (67.2%), compared with > or = parity 3 sows (98.1%). No explanatory variable had a significant effect on weaning-to-estrus interval (4.4 d) or on follicle size at estrus (8.1 mm). Ovulation hour after onset of estrus was affected by weaning-to-estrus interval (P < 0.01), with sows returning in 3 d ovulating at 46.2 h and between 6 and 8 d at 30.2 h. For sows that expressed estrus within 8 d of weaning, the percentage of sows ovulating was influenced by lactation length (P < 0.001) and weaning-to-estrus interval (P < 0.001). Sows that lactated < or = 16 d were less likely to ovulate (78.0%) than those lactating > or = 17 d (> 92%). Sows that returned to estrus in 3 d were also less likely to ovulate (79.5%) than sows returning > or = 4 d after weaning (> 92%). A parity x season interaction was also observed on ovulation (P < 0.001), with parity 1 and 2 sows less likely to ovulate after expressing estrus in fall and spring compared with parity 3 and greater sows. The data suggest lactation length, early return to estrus, and parity by season effects are associated with risk of failure to express estrus and ovulate.

Animals↗