Seasonal variation in preovulatory events associated with synchronization of estrus in dwarf goats

This experiment was conducted to define the temporal relationships among estrus, the LH surge and ovulation after estrus synchronization in dwarf goats and to assess the effect of season on these parameters. In November (breeding season), March (transition period) and July (non-breeding season), estrus was synchronized in 12 dwarf goats by means of intravaginal sponges containing 60 mg medroxyprogesterone acetate (MAP) for 10 d, coupled with 125 microg cloprostenol i.m. 48 h before sponge removal and 300 IU eCG i.m. at sponge removal. A different group of animals was used during each time period. Onset of estrus was monitored using two males, and blood samples for the measurement of plasma LH were collected at 2-h intervals from 24 to 60 h after sponge removal. Ovulation was confirmed by laparoscopy at 54 and 72 h after sponge removal. A seasonal shift was detected in the intervals to onset of estrus, LH surge, and ovulation after sponge removal (P<0.05), with sponge removal to onset of estrus being shorter (P<0.05) in November (25.0 +/- 1.56 h) and July (28.9 +/- 2.43 h) than in March (40.9 +/- 3.27 h). The intervals between onset of estrus and the LH surge and between the LH surge and ovulation were found to be constant throughout the different seasons. An optimal time for breeding, artificial insemination, oocyte and embryo recovery, and embryo transfer may be predicted using information gained from these studies.     

Effects of different stimuli of service on estrus duration in dairy goats

The object of this experiment was to study the effects of different stimuli of service on estrus duration in dairy goats. Twenty Nubian goats were assigned randomly to 4 groups of 5 animals each: service (SER), mechanical stimulation of vagina (MES), accessory gland fluid insemination (AGF), and control (CON), Estrus was synchronized by using medroxyprogesterone acetate intravaginal pessaries (60 mg) over a 12-d period. Estrus was detected using 1 aproned vasectomized buck at 6-hour intervals during 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the SER group the male was permitted to service each female. In the MES group, stimulation was accomplished using a penis-like device maintained in the vagina 15 sec with light pressure on the fornix. In the AGF group, 1.0 ml of accessory gland fluid was deposited into the external cervical os. The CON group was only permitted to be mounted. All treatments were performed only once within the first 12 h of estrus. Estrus duration for the SER, MES, AGF and CON groups was (mean +/- SD) 22.8 +/- 5.0, 27.6 +/- 6.8, 37.2 +/- 2.7 and 42.0 +/- 9.5 h, respectively. The SER group was different from the AGF and CON groups (P<0.01), but not from the MES group (P>0.05). The MES group was different from the AGF (P<0.05) and CON groups (P<0.01). The AGF and CON groups did not differ from each other (P>0.05). It is concluded that service shortened estrus duration due to the mechanical effect of stimulation of the penis-like device against the vaginal fornix.     

Effect of ram exposure at the end of progestagen treatment on estrus synchronisation and fertility during the breeding season in ewes

Two experiments were conducted to examine the effects of ram exposure during the breeding season, in combination with progestagen treatment on estrus synchronization, fertility the LH surge and ovulation in ewes. Experiment 1 was subdivided into experiments 1a and 1b. In all experiments cross-bred ewes were treated with an intravaginal sponge for 12-14 days and three days before sponge withdrawal ewes were divided into control (no further treatment; n=191, 103 and 50 for experiments 1a, 1b and 2, respectively) or ram exposed (three mature rams per 50 ewes were introduced; +Ram; n=187, 99 and 49 for experiments 1a, 1b and 2, respectively). At sponge withdrawal ewes in Experiments 1a and 2 received 500 IU eCG and rams were removed from all the +Ram groups. In Experiments 1a and 1b, raddled, entire rams were introduced to ewes 48 h after sponge withdrawal. The timing of mating was recorded and ewes were maintained until lambing. In Experiment 2, estrus behavior was determined every 4 h and the time of the LH surge and ovulation were determined from a subset of 10 ewes per group. In Experiment 1a, less +Ram ewes were bred by 48 h after ram introduction (control 98% versus +Ram 89%, P<0.001) and in Experiments 1a and 1b 14% fewer (P<0.05) of the ewes bred in the first 3 h after ram introduction lambed to that service. In Experiment 1a, ram exposed ewes had a lower litter size than control ewes (1.93+/-0.06 versus 1.70+/-0.06 lambs per ewe; P<0.05). In Experiment 2, rams advanced (P<0.05) estrus, the LH surge and ovulation by 2-6 h compared with control ewes. We speculate that exposure of ewes to rams increased LH secretion and that this in turn increased follicle development and the production of oestradiol that led to a more rapid onset of estrus, the LH surge and ovulation compared to control ewes. Unexpectedly, ewes that were bred had lower fertility in the +Ram groups than control groups.     

Effect of service and vaginal-cervical anesthesia on estrus duration in dairy goats

The object of this experiment was to study the effect of sterile service and vaginal and cervix anesthesia on estrus duration in dairy goats. During the fall season 21 Nubian goats (9 nulliparous and 12 multiparous) were randomly assigned to 1 of 3 treatment groups (n = 7 animals per group). The following groups were formed: service (SER), vaginal and cervix anesthesia (VCA) and control (CON). Estrus was synchronized using fluorgestone acetate intravaginal pessaries (FGA, 30 mg) over a 14-d period. Estrus was detected using a vasectomized buck at 6-h intervals over 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the SER group the male was permitted to service each female. In the VCA group the vagina and cervix of the does were anesthesied, after which the male was permitted to service the females. Both treatments were done once within the first 12-h initiation of estrus. Does were permitted to be mounted only in the control group (CON). Estrus duration for SER, VCA and CON groups was (mean +/- SD) 24.0 +/- 10.9, 42.0 +/- 15.9 and 40.3 +/- 10.8 h, respectively. The SER group was significantly different from the VCA and CON groups (P < 0.01); however, the VCA group was not different from the CON group (P > 0.05). It is concluded that service shortens the duration of estrus due to the mechanical effect of the penis against the vagina and cervix, and not to the accessory gland fluid.     

Effect of service on estrus duration in dairy goats

The objective of this research was to determine the effect of sterile service on estrus duration in multiparous and nulliparous dairy goats. Twenty Nubian goats (10 multiparous and 10 nulliparous) were randomly assigned to of 4 treatment groups (n = 5 animals per group). Group MNS, multiparous without service; Group MS, multiparous with service; Group NNS, nulliparous without service and Group NS, nulliparous with service. Estrus was synchronized by utilization of fluorogestone acetate intravaginal pessaries (40 mg.) over a 12-day period plus 250 IU, i.m. of pregnant mare serum gonadotropin (PMSG) at pessary removal. Estrus was detected with the aid of a vasectomized buck for 5 days after pessary removal for 6-hour intervals (0600, 1200, 1800 and 2400 hours). In the groups that were not serviced the teaser was equipped with an apron and was only allowed to mount. In the serviced groups, the teaser was permitted to mount and service each female on 2 occasions during the first 12 hours of estrus. Estrus initiation for Groups NNS, NS, MNS and MS were (mean +/- SD) 61.5 +/- 29.5, 61.2 +/- 35.4, 63.0 +/- 22.2 and 69.6 +/- 32.5 hours, respectively (P>0.05). Estrus duration for the same groups were (mean +/- SD) 42.0 +/- 12.0, 30.0 +/- 6.0, 42.0 +/- 7.3 and 28.8 +/- 10.7 hours, respectively. These results show that estrus duration was shortened by serving (P<0.01), and that there were no differences between multiparous and nulliparous goats with or without serving (P>0.05). It is concluded that estrus duration in goats is shortened by serving and that no differences in duration exist between multiparous and nulliparous.     

Effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats

The effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats during breeding season was studied. Nubian does (n=126) were divided into 2 equal groups: service and control. Estrus was synchronized with intravaginal sponges containing either fluorgestone acetate (FGA; 40 mg) or medroxiprogesterone acetate (MAP; 60 mg) for 12 or 14 d, respectively. Two vasectomized teaser bucks were used to detect estrus at 6-h intervals for 5 d after sponge removal (0600, 1200, 1800 and 2400 h). The teasers were fitted with aprons and permitted to mount all does in both groups, but to penetrate only the service does within the first 12 h of estrus. Does in both groups were inseminated twice at 12 and 24 h after estrus was first detected, using 1 straw per insemination containing 200 million of cooled spermatozoa from 1 buck. The semen was placed in mid-cervix. Estrus duration for the service and control does was (mean +/- SD) 29.4 +/- 6.5 and 41.8 +/- 9.6 h, respectively. Fertility for the service does was 73.7% (46/63); for control does it was 58.7% (37/63). Prolificacy was 2.1 (96/46) and 2.0 (74/37) for service and control does, respectively. Estrus duration (P<0.001) and fertility (P<0.05) differed between the service and control group, but prolificacy was similar (P>0.05). It is concluded that sterile service reduces the duration of estrus and increases fertility in artificially inseminated dairy goats.     

Effect of service number on estrus duration in dairy goats

The object of this research was to study the effect of sterile service number on estrus duration in dairy goats. Twenty-four Nubian goats (20 nulliparous and 4 multiparous) were randomly assigned to 1 of 4 treatment groups (n = 6 animals per group). The following Groups were formed: no service (GS-0); 1 service (GS-1); 2 services (GS-2); 3 services (GS-3). Estrus was synchronized by using fluorogestone acetate intravaginal pessaries (40 mg) over a 12-d period plus 400 IU im pregnant mare serum gonadotropin (PMSG) at pessary removal. Estrus was detected by using a vasectomized buck at 6-h intervals over 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the GS-0 group the teaser was outfitted with an apron and was permitted to mount. In the GS-1, GS-2 and GS-3 groups, the teaser was permitted to mount and service 1, 2 and 3 times, respectively, within the first 12 h after initiation of estrus. The duration of estrus for the 4 groups (GS-0, GS-1, GS-2 and GS-3) was (mean +/- SD) 41.0 +/- 5.9, 24.0 +/- 5.4, 22.0 +/- 4.9 and 22.0 +/- 7.2 h, respectively. These results show differences between the serviced groups and the nonserviced group (P<0.01), but they fail to show differences among the serviced groups (P>0.05). It is concluded that sterile service shortens estrus duration and that service number (1, 2 or 3) does not affect estrus duration.     

The effects of different PMSG doses on estrus behavior and pregnancy rate in Angora goats

Artificial insemination protocols depend on efficient behavioral estrus detection and insemination time in Angora goat. Therefore, we aim to determine the accuracy of an estrus scoring system in Angora goats with different PMSG doses during the breeding season. Does (n: 260) were randomly divided into three groups: group-1 (n: 93), group-2 (n: 85) and group-3 (n: 82). All animals received an intravaginal sponge on day 0 for 11 days, and on the day of sponge insertion 150 μg prostaglandin F2Α was administered. Pregnant mare’s serum gonadotropin was injected 300, 400 and 500 IU intramuscularly 24 h before sponge removal to groups 1, 2 and 3, respectively. Estrus signs were detected with a teaser buck, 24 h after sponge removal according to a visual scoring system. Artificial insemination was performed with 0.25 ml fresh diluted semen at 43 to 45 h after sponge removal. Differences were observed within PMSG groups in terms of standing, tail wagging, courtship behavior, vaginal discharge and vaginal hyperemia (P<0.001). Nevertheless, the most accurate indicators of estrus that result in pregnancy were tail wagging and courtship behavior followed by standing estrus (P<0.05). According to the results obtained, 300 IU PMSG dose is sufficient, both to inseminate at a fixed time (43 to 45 h after sponge removal) and to record the estrus behavior by teaser male 24 h after sponge removal. Higher PMSG doses (400 to 500 IU) altered the timing of ovulation; specifically, 500 IU dose shortened the duration of estrus behaviors. In conclusion, even though the different doses of PMSG displayed similar effects on estrus synchronization and pregnancy rates, we concluded that tail wagging, courtship behavior and standing heat are the most reliable estrus signs for artificial insemination in Angora goat.     

Progesterone and behavioral features when estrous is induced in Alpine goats

The objective of the present study was to evaluate the endocrine and behavioral features of estrous-induced Alpine goats. A total of 36 nulliparous, 40 non-lactating and 42 lactating does were treated with intravaginal 60 mg medroxyprogesterone acetate sponges for 9 d plus 200 IU eCG and 22.5 microg d-cloprostenol 24 h before sponge removal. Plasma progesterone concentration was analyzed from blood sampled on days 0 (sponge insertion), 5, 8 (cloprostenol administration) and 9 (sponge removal) in 11 nulliparous, 13 non-lactating and 11 lactating does. Estrous response did not differ (P>0.05) among nulliparous (97.2%), non-lactating (90.00%) and lactating does (85.7%). Interval to estrus and duration of estrus did not differ (P>0.05) among nulliparous (22.8+/-9.9 and 25.6+/-6.8h), non-lactating (23.7+/-15.8 and 25.0+/-6.0 h) and lactating does (22.2+/-10.4 and 24.9+/-4.2h). The accumulative percentage of does in estrus during the first 36 h after sponge removal was 88.1%. The correlation between interval to estrus and duration of estrus was r=-0.32 (P<0.001). Endogenous progesterone production is decreased until day 8 or suppressed by MAP on day 9. Conception rate was greater (P<0.01) in lactating (77.8%) than non-lactating (44.4%) but similar (P>0.05) to nulliparous (60.0%) goats. Estrus can be efficiently induced by means of hormonal treatment in goats and acceptable fertility can be obtained regardless of animal category.     

Effect of the method of estrus synchronization and PMSG dosage on estrus and twinning in Ethiopian Menze sheep

Mature, cyclic Ethiopian Menze ewes (n = 72) were used in this study. They were divided into 6 equal groups in a 2x3 factorial experimental design. Estrus and ovulation were synchronized in all ewes using either 2 dosages of prostaglandin F2 alpha 12 days apart (n = 36) or intravaginal progestogen sponges for an equal length of time (n = 36). At sponge removal or at the second prostaglandin injection, equal groups of ewes were injected with either 0, 200, or 300 IU of PMSG. Prostaglandin-synchronized ewes exhibit estrus significantly earlier (P = 0.025) than the progestogen-synchrcnized group. Although PMSG treatment increased twinning rates and therefore total number of lambs born, the differences between groups did not reach significant levels (P>0.10).     

Influence of GnRH administration on timing of the LH surge and ovulation in dwarf goats

This study was conducted to determine whether or not exogenous gonadotropin releasing hormone (GnRH) alters the timing or improves the synchrony of estrus, the LH surge, and ovulation following estrous synchronization in dwarf goats, and to assess the effects of season on these parameters. In January and June, estrus was synchronized in 12 Pygmy and Nigerian Dwarf goats with a 10-day progestagen sponge, 125 microg cloprostenol i.m. 48 h before sponge removal, and 300 IU equine chorionic gonadotrophin (eCG) i.m. at sponge removal. Six of the 12 goats were given 50 microg GnRH i.m. 24h after sponge removal. Onset of estrus was monitored using two males. Samples for plasma LH were collected at 2 h intervals beginning 22 h after sponge removal and ending at 48 h in January and at 58 h in June. Time of ovulation time was confirmed by laparoscopy at 36, 50, 60, and 74 h in January and at 50, 60, and 74 h in June. Administration of GnRH had no significant effect on the onset of estrus; however, it reduced the interval from sponge removal to the LH surge and improved the synchrony of the LH surge (P<0.05). Treatment with GnRH also reduced the interval from sponge removal to ovulation and improved the synchrony of ovulation (P<0.05). Season had a significant effect on the timing and the synchrony of estrus with and without GnRH treatment (P<0.05). A seasonal shift was also observed in the timing of the LH surge in the absence of GnRH treatment (P<0.05). Further research is required to determine the optimum time for GnRH administration and the minimum effective dose in dwarf goats.     

Timing of ovulation in relation to onset of estrus and LH peak in yak (Poephagus grunniens L.)

The objective of the study was to determine the timing of ovulation in relation to onset of estrus and the preovulatory LH peak in yaks. For this purpose, a sensitive LH enzymeimmunoassay previously established in buffaloes was successfully validated for measuring the hormone in yak plasma. Plasma LH and progesterone were estimated from blood samples collected from eight non-lactating cycling yaks at 2 h intervals after estrus onset until 6 h after ovulation (ovulation was confirmed by palpation of ovaries per rectum). The mean+/-S.E.M. preovulatory plasma LH peak was 10.11+/-0.35 ng/ml with the values ranging from 8.75 to 11.51 ng/ml in individual yaks. The mean+/-S.E.M. duration of the LH surge was 7.25+/-0.55 h with a range of 6-10 h. Onset of LH surge (mean+/-S.E.M.) occurred 3.0+/-0.65 h after the onset of estrus. Mean plasma progesterone stayed low (<0.25 ng/ml) during the entire duration of sampling. Ovulation occurred 30.5+/-0.82 h (range, 28-34 h) after the onset of estrus and 20.25+/-1.03 h after the end of LH surge. The occurrence of the LH peaks within a narrow time frame of 4-8h post estrus onset in yaks could have contributed to the animals ovulating within a narrow time interval.     

Use of Chronogest implants and Folltropin for estrus synchronization and superovulation in goats.

Six Barbari goats each were assigned randomly to treatments 1,2 or 3, comprising im injections of FSH (folltropin) at 12, 14 or 16 mg dose level respectively. Estrus was synchronized with intravaginal sponge impregnated with flugestone acetate (30 mg; chronogest) inserted for 12 days and cloprostenol (125 micrograms) im at the insertion as well as at removal of sponge. FSH treatment started 48 hr before the sponge removal as 4-day declining dose scheme. Estrus could be effectively synchronized in all goats under the study, with significant difference (P less than 0.05) in the onset of estrus between the treatment groups. All goats were administered with 750 IU hCG i.v. at estrus. Recording of ovarian response and embryo recovery was done 45 hr after the onset of estrus. The prime aim of superovulation was effectively achieved in Barbari goats with the use of chronogest implants and folltropin. There was no difference (P greater than 0.05) between the treatment groups in recovery of transferable embryos, however, 14 mg folltropin appeared to be near optimal dose. There was no adverse effect on the quality of recovered embryos with high doses of folltropin.     

The influence of the corpus luteum on ovarian follicular dynamics during estrous synchronization in goats

Ovarian follicular dynamics and fertility are unaffected by the presence or absence of a corpus luteum during synchronization of estrus with progestins in goats. On day 5 of the estrous cycle (estrus= day 0), a gestagen-containing sponge was inserted in the vagina for 11 days. To remove corpora lutea, one group of goats (CL-, n=41) received 7.5 mg of luprostiol on days 7 and 8 of the estrous cycle. The second group of goats retained the CL (CL+, n=38). Growth and development of follicles > or =4 mm in diameter were measured daily from onset of estrus to 2 days after subsequent ovulation in seven goats from each group, using rectal ultrasonography. Estrus was detected by the use of a reproductively sterilized buck and estrous does were subsequently mated. The number of waves of follicular development (CL- =3.57+/-0.2 versus CL+ =3.14+/-0.14; P>0.05) did not differ between groups. The second wave of follicular development was present at the time of progesterone decline in the CL- group and neither its duration (CL- =4.8+/-0.4 versus CL+=5.6+/-0.7 days; P>0.05) nor the day of commencement of the third wave of follicular development (CL -=11.6+/-0.7 versus CL+=11.8+/-0.6; P>0.05) were altered by the concentration of endogenous progesterone. The pregnancy rate was similar between the two groups. (CL-=68.29% versus CL+=65.79%; P>0.05). Thus, in goats, ovarian follicular dynamics and fertility were not altered by the presence or absence of a corpus luteum during estrous synchronization.     

Effects of FSH commercial preparation and follicular status on follicular growth and superovulatory response in Spanish Merino ewes

Ovarian follicular development was characterized in 24 Spanish Merino ewes to study effects of the follicular status and the FSH commercial product used on follicular growth and subsequent superovulatory response. Estrus was synchronized using 40 mg fluorogestone acetate sponges. The superovulatory treatment consisted in 2 daily i.m. injections of FSH from 48 h before to 12 h after sponge removal. Sheep were assigned randomly to 2 groups treated with 6 decreasing doses (4, 4, 3, 3, 2, 2 mg) of FSH-P or with 6 doses of 1.25 mL of OVAGEN. Growth and regression of all follicles > or = 2 mm were observed by transrectal ultrasonography, and recorded daily from Day 6 before sponge insertion to the first FSH injection, and then twice daily until estrus was detected with vasectomized rams. Differences were detected in follicular development from the first FSH injection to detection of estrus (-48 to 36 h from sponge removal) between groups. Administration of FSH-P increased the appearance of new follicles with respect to OVAGEN (6.3 +/- 0.7 vs 4.8 +/- 0.4; P < 0.05), and the mean number of medium (4 to 5 mm) follicles (8.9 +/- 1.2 vs 6.6 +/- 0.9; P < 0.05). However, the mean number of follicles that regressed in size after sponge removal (5.9 +/- 0.4 vs 3.3 +/- 0.4) and the number of preovulatory sized follicles that did not ovulate (60 vs 42.4%) were also higher in FSH-P treated ewes (P < 0.05). So, finally, there were no differences in ovulation rate, as determined by laparoscopy on Day 7 after sponge removal, between ewes treated with FSH-P or OVAGEN (6.3 +/- 1.9 vs 7.0 +/- 1.7 CL). In all the ewes, the ovulatory response was related (P < 0.05) both to the number of small follicles (2 to 3 mm in diameter) present in the ovaries at the start of treatment with exogenous FSH and to the number of follicles that reached > or = 4 mm in size at estrus, despite differences in the pattern of follicular development when using different commercial products.     

Induction of estrus in non-lactating dairy goats with different estrous synchrony protocols

The objective of this study was to evaluate two protocols of estrous synchronization in non-lactating Toggenburg goats. Nineteen goats were allocated, according to body condition score and weight, into two groups (A and B) and evaluated utilizing two treatments (T1 and T2). Animals in the T1 and T2 groups received an intravaginal sponge (day 0) containing 60 mg medroxyprogesterone acetate for 6 and 9 days, respectively, plus 200 IU equine chorionic gonadotrophin (eCG) and 22.5 microg cloprostenol 24 h before sponge removal. Females were bred only at the second estrus and received 22.5 microg cloprostenol 7 days later to prevent pregnancy. Percentages of animals in estrus did not differ (P > 0.05) between T1 (89.5%) and T2 (84.2%). From 33 females in estrus (T1 + T2), 28 (84.8%), 2 (6.1%), and 3 (9.1%) were identified in estrus at 06:00, 12:00 and 18:00 h, respectively. Additionally, 6 (18.2%), 0 (0.0%) and 27 (81.8%) were no longer detected to be on estrus at 06:00, 12:00 and 18:00 h, respectively. Interval from sponge removal and the onset of estrus (IE) did not differ (P > 0.05) between T1 (46.1 +/- 15.0 h) and T2 (53.6 +/- 16.1 h). Duration of estrus did not differ (P > 0.05) between T1 (30.0 +/- 12.0 h) and T2 (27.2 +/- 11.2 h). Both protocols were effective in inducing estrus in non-lactating goats. The onset and end of the estrus relative to hour of the day should be considered in estrous detection, natural breeding, and artificial insemination in goats.     

Various behavioral signs of estrous and their relationship with time of ovulation in dairy cattle

The objective of this study was to investigate the relationship between various behavioral signs of estrous and time of ovulation and, determine which behavioral estrous sign(s) best predicted time of ovulation. In total, 94 ovulations were observed in 67 Holstein-Friesian dairy cows. Different behavioral estrous signs were observed at 3-h intervals and their relation with time of ovulation (ultrasound examinations at 3-h intervals) was investigated. In all estrous periods, sniffing and chin resting was displayed, while mounting was displayed in 90% and standing heat in 58% of estrous periods. Estrus was more intense in primiparous cows compared to multiparous cows and when more animals were in estrus at the same time. Although, these factors influenced intensity of estrous behavioral signs, they did not influence time of ovulation. Ovulation occurred 30.0 +/- 5.1 h after onset of estrus (ranging between 18.5 and 48.5 h) and 18.8 +/- 4.4 h after end of estrus (ranging between 9.5 and 33.5 h). Although informative, these predictors are highly variable between individuals and the method used to determine the onset and end of estrus is time consuming this, therefore limits in their use as a practical predictor of ovulation. Sniffing and chin resting were displayed during the non-estrous period and are therefore, not useful predictors of ovulation time. For animals that displayed standing heat, onset of standing heat was a good predictor for ovulation time (occurring 26.4 +/- 5.2 h before ovulation). However, standing heat was only displayed in a limited number of cows, especially when only one cow was in estrus at a time. Onset of mounting was the best predictor for time of ovulation (occurring 28.7 +/- 5.3 h before ovulation), and it was displayed in 90% of the estrous periods. However, mounting cannot yet be assessed automatically, which limits its practical use as ovulation predictor.     

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

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

Ovulation of aged follicles does not affect embryo quality or fertility after a 14-day progestagen estrus synchronization protocol in ewes

The aim was to examine the effect of ovulation of aged follicles on embryo quality and fertility in ewes. In Experiment 1, ewes (n = 39) received a prostaglandin analogue on Day 6 of the cycle and then received either a progestagen sponge from Day 6 to 20 after estrus (Single sponge) or a progestagen sponge on Day 6 that was replaced on Day 11 and 16 and removed on Day 20 (Multiple sponges). In a subgroup of ewes, the growth of ovarian follicles was characterised using ultrasonography. Fertile rams were introduced 48 hours after sponge withdrawal; we slaughtered the ewes on Day 5 of pregnancy and recovered the embryos. The mean age of the ovulatory follicles was greater in ewes that received a single sponge compared with multiple sponges (8.7+/-0.8 days, range 4 to 14, versus 4.5+/-0.7 days, range 3 to 6; P<0.05). However, the groups did not differ (P>0.05) in ovulation rate (2.4+/-0.3 corporal lutea per ewe) or the proportion of good quality embryos recovered (71 to 82%; developed to the early morula stage or further). In Experiment 2, ewes (570 in total) received treatments similar to those in Experiment 1 but were kept until lambing. Ewes that received a single sponge came into heat earlier (P<0.05) than those that received multiple sponges, but > or = 97% of ewes in all groups (P>0.05) were bred by 48 to 72 hours after ram introduction. There was no difference (P>0.05) between groups for the proportion of ewes that lambed to first service (80 to 86%) or the number of lambs per ewe (1.94+/-0.08 lambs). We conclude that when luteolysis occurs at the beginning of progestagen synchronisation, ewes will ovulate aged follicles, but that compared to shorter duration follicles, these follicles produce oocytes that are equally competent to be fertilised and develop into good quality embryos and full-term lambs.     

The time of ovulation in relation to estrus duration in gilts

The objective of this study was to determine time of ovulation, monitored by transcutaneous ultrasonography, relative to the duration of estrus in gilts. We exposed 92 cyclic gilts, Camborough x Canabrid terminal line, at Day 19 of their third estrous cycle to vasectomized boars every 6 h for the detection estrus. Transcutaneous ultrasonography was performed every 6 h, starting 24 h after the onset estrus, to determine time of ovulation. Estrus duration was, on average, 52.6 h (range: 30 to 72 h), and ovulation occurred between 30 and 60 h after the onset of estrus (mean: 44 h), about 85 % of the way through the estrus period. The time of ovulation during estrus was dependent on the duration of estrus (Time of ovulation = (duration of estrus) x 0.409 + 22.7; r = 0.57, P = 0.0001). Prediction of the time of ovulation in relation to duration of estrus is important for determining the optimal time for inseminating gilts. This knowledge would contribute to an improvement in the fertilization rate and in reproductive efficiency of the breeding herd.