Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “INSEMINATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1995

[Comparison of 2 artificial insemination technics. (Sperm tubal perfusion and intrauterine insemination)].

In 1991 Kahn et al, described a method of intrauterine Insemination called Fallopian Tube Sperm Perfusion (FSP) using 4.0 ml for the insemination volume, unlike the classic Intrauterine Insemination (IIU) in which insemination volume is 0.5 ml. The aim of this study is to compare pregnancy rate per cycle in both technics. Between August 1993 and January 1994, 60 couples with infertility were studied, 131 ovarian stimulation cycles were done, 95 with IIU and 36 with PTE. 18 clinical pregnancies occurred, 11 with IIU and 7 with PTE, for a pregnancy rate per cycle of 11.5% for IIU and 19.4% for PTE. This result confirms the reports by Kahn. PTE represents a new possibility for the treatment of different etiology infertility.

Adult↗
PubMed2004

Transcervical artificial insemination in sheep: effects of a new transcervical artificial insemination instrument and traversing the cervix on pregnancy and lambing rates.

Cervical anatomy limits the use of transcervical intrauterine artificial insemination (TC AI) in sheep. We have developed an instrument to cope atraumatically with the cervix; although this instrument has not affected fertilization rate or pregnancy rate through Day 3, the effects on sperm transport and pregnancy after Day 3 are not known. The objective of the present study was to determine whether our TC AI instrument affected sperm transport, pregnancy rates, or lambing rate. In Experiment 1, ewes were assigned to two treatments: TC AI using the new TC AI instrument (n=10) or AI via laparotomy using a laparoscopic AI instrument (n=10). Twenty hours after artificial insemination, the uterine horns and oviducts were recovered and flushed to collect spermatozoa. Sperm transport did not differ (P>0.05) between the two treatments. In Experiment 2, ewes were assigned to three treatments: TC AI using the new TC AI instrument+sham intrauterine AI via laparotomy (n=29); sham TC AI+intrauterine AI via laparotomy using a laparoscopic AI instrument (n=29); and sham TC AI+intrauterine AI via laparotomy using the new TC AI instrument (n=30). On Day 14 after AI, uteri were collected and flushed to recover blastocysts. Transcervical deposition of semen reduced (P<0.05) Day 14 pregnancy rate (17.2% versus 61%), but intrauterine deposition of semen using the TC AI instrument via midventral laparotomy increased (P<0.05) Day 14 pregnancy rate (76.6% versus 44.8%). In Experiment 3, ewes were assigned to two treatments: sham cervical manipulation (n=40) or cervical manipulation to mimic TC AI (n=40). Immediately after treatment, each ewe was mated with a ram and watched until the ram mounted and ejaculated into the ewe. Treatment did not affect Day 30 or 50 pregnancy rate (67.5 and 66.2%, respectively), determined ultrasonically, or lambing rate (62.5%). The differences between Days 30 and 50 pregnancy rates and lambing rate were not significant. In Experiment 4, ewes were assigned to two treatments: TC AI (n=99) or laparoscopic AI (n=99). Transcervical AI reduced (P<0.01) Day 30 (TC AI versus laparoscopic AI; 5.0% versus 46.0%) and Day 50 pregnancy rates (4.0% versus 41.0%), determined ultrasonically, and lambing rate (4.0% versus 41.0%). Although the TC AI procedure significantly reduced pregnancy and lambing rates, large numbers of spermatozoa deposited at natural insemination seemed to compensate. Because our TC AI procedure has all but eliminated any visual evidence of trauma, and because the procedure does not seem to affect sperm transport or embryonal survival until Day 3, we speculate that cervical manipulation associated with TC AI may activate pathways that interrupt pregnancy between Days 3 and 14.

Animals↗
PubMed1994

Intrauterine insemination in fertile women delivers larger number of sperm to the peritoneal fluid than intracervical insemination.

Randomized IUI or intracervical insemination of eight fertile women with 50 x 10(6) sperm was performed to determine whether IUI delivers more spermatozoa to the peritoneal cavity. After IUI (n = 4), 2,053 to 29,450 sperm were recovered in the PF at laparoscopy. No sperm were found in the PF after intracervical insemination (n = 4). After IUI, CM contained 1.0 x 10(6) to 57.0 x 10(6) sperm/mL; after intracervical insemination, 0 to 1.2 x 10(3) sperm/mL were seen. One therapeutic mechanism for IUI is delivery of larger sperm numbers to the fertilization site by rapid (4 hours) transport. In addition, there is greater retrograde colonization of CM that may result in sustained release of sperm.

Cervix Uteri↗
PubMed1997

Effects of cryopreserved semen quality and timed intrauterine insemination on pregnancy rate and gender of offspring in a donor insemination program.

PURPOSE: Our purpose was to study the relationship among cryopreserved donor semen quality, pregnancy rates, and preconception sex selection after intrauterine insemination. METHODS: We reviewed the records of the 203 women in our donor insemination program from 1987 to 1994 who became pregnant after more than one insemination cycle and had no female-factor infertility. They were categorized according to the number of cycles required for pregnancy. Semen samples from 54 donors were analyzed before freezing and after thawing. Specimens resulting in pregnancy were compared to specimens from the same donor that did not. Semen characteristics were compared to gender of the child. RESULTS: Two hundred fifty two-women became pregnant of the 422 who were enrolled. The pregnancy rate per cycle was 13%. Semen quality was not related to pregnancy outcome or offspring gender. However, more male children (101 vs 83) were born. CONCLUSIONS: Semen characteristics in good-quality cryopreserved donor semen do not affect pregnancy rate or offspring gender.

Cryopreservation↗
PubMed2004

Influence of the number of motile spermatozoa inseminated and of their morphology on the success of intrauterine insemination.

BACKGROUND: Although intrauterine insemination (IUI) is one of the most common assisted reproductive technology methods in the world, the relative influence of various semen characteristics on the likelihood of a successful outcome is controversial. The aim of our study was to assess the results of IUI as a function of both the number of motile spermatozoa inseminated (NMSI) and the percentage of morphologically normal spermatozoa after preparation. METHODS: This was a retrospective study of 889 couples who underwent 2564 IUI cycles of ovarian stimulation with HMG or recombinant FSH in our centre between January 1991 and December 2000. RESULTS: A total of 331 clinical pregnancies were obtained, for a pregnancy rate/cycle of 12.91%. When the NMSI was < 1 x 10(6), the pregnancy rate/cycle was significantly lower (3.13%) than in any of the subgroups with NMSI > or = 2 x 10(6). Sperm morphology, assessed before or after preparation, was not in itself a significant factor that affected the likelihood of IUI success. Nonetheless, when the post-migration rate of normal sperm was < 30%, the pregnancy rate/cycle was 5.43% when NMSI was < 5 x 10(6) and 18.42% when NMSI was > or = 5 x 10(6) (P = 0.008). Pregnancy rates did not differ significantly according to NMSI when the percentage of normal sperm after preparation was > or = 30%, or according to percentage of normal sperm when the NMSI was > or = 5 x 10(6). CONCLUSIONS: Our results show that a minimum of 5 x 10(6) motile spermatozoa should be inseminated when the normal morphology of the sperm after preparation is < 30%; the quantity compensates at least in part for the defective quality. If this threshold of NMSI cannot be obtained, IVF should be recommended.

Adult↗
PubMed2005

Influence of sperm cell dose and post-insemination backflow on reproductive performance of intrauterine inseminated sows.

This study was carried out to evaluate the effects of the sperm cell dose and semen backflow on the pregnancy rate and number of embryos of sows inseminated once at 0-24 h before ovulation, using an intrauterine technique. The results were analysed from a total of 211 sows assigned to three groups inseminated with doses of 0.25 x 10(9) (T1), 0.5 x 10(9) (T2) and 1.0 x 10(9) (T3) spermatozoa. Semen backflow was observed in 95% of the females (143/151) evaluated for this purpose. The percentage of semen backflow is close to two-third of the volume and the percentage of sperm is around 15% of the infused sperm dose. Intrauterine insemination can be successfully performed provided that at least 0.5 billion of sperm cell dose is infused at an interval of 0-24 h before ovulation.

Animals↗
PubMed1999

[Effect of the administration of PGF2 alpha synchronously with insemination on the pregnancy rate in mares in an insemination program].

Investigations in different species including the horse have demonstrated that prostaglandin F2 alpha (PGF2 alpha) is involved in initiating uterine contractions occurring during mating and artificial insemination (A.I.). Uterine contractions play an important role with respect to the sperm transport within the female genital tract. The objective of the present investigation was to evaluate whether the administration of PGF2 alpha (Dinoprost) synchronously to A.I. could have a positive effect on the pregnancy rate in mares. A field study including 346 warmblood-mares (age two to 20 years) belonging to a private studfarm was conducted during the breeding season 1996. The mares were assigned to two groups, group A: mares with spontaneous ovulation, group B: mares in which the ovulation was induced by a GnRH-analog-implant (Deslorelin). PGF2 alpha (Dinoprost) was administered either intramusculary (i.m., 5.0 mg) or intrauterine (i.ut., 0.5 mg diluted in 1.9 ml isotonic NaCl-solution and added to the semen dosis). The study was carried out in a double-blind fashion using isotonic NaCl-solution as a placebo. The mares of each group were randomly assigned to one of the two treatments (i.m. vs. i.ut.). The following first cycle pregnancy rates (day 18) were obtained in mares treated and inseminated once per oestrus: group A1 (PGF2 alpha, i.m.): 54.5% (n = 33); group A2 (placebo, i.m.): 69.7% (n = 33); group A3 (PGF2 alpha, i.ut.): 65.4% (n = 26); group A4 (placebo, i.ut.): 69.8% (n = 32); group B1 (PGF2 alpha, i.m.): 56.5% (n = 46); group B2 (placebo, i.m.): 29.6% (n = 27); group B3 (PGF2 alpha, i.ut.): 66.7% (n = 45); group B4 (placebo, i.ut.): 60.0% (n = 30). The pregnancy rates did not differ between the different groups with the exception of group B2 (p < 0.05). In mares treated repeatedly during the oestrus period (group A, n = 88; group B, n = 23), the pregnancy rates did not differ significantly between treatment and control groups. From the results obtained it is concluded that the PGF2 alpha-application did not show an effect on the pregnancy rate. Further factors influencing the results to a small degree were the stallions, semen age and quality and frequency of insemination per oestrus.

Animals↗
PubMed2003

A randomized comparison of three insemination methods in an artificial insemination program using husbands' semen.

OBJECTIVE: To compare pregnancy rates with single intrauterine insemination (SIUI), double intrauterine insemination (DIUI) and fallopian tube sperm perfusion (FSP). STUDY DESIGN: Ninety patients undergoing a standard ovarian stimulation regimen were randomized to receive SIUI, DIUI or FSP. The end point was either pregnancy or completion of 3 treatment cycles without pregnancy. RESULTS: There were no differences in demographic data or ovarian responses. The total number of motile spermatozoa inseminated in the FSP group was significantly lower than in the SIUI group. No significant differences were found in pregnancy rate per cycle or patient, multiple pregnancy rate and outcome of pregnancy between the 3 groups. CONCLUSION: Similar pregnancy rates were achieved after SIUI, DIUI and FSP during stimulated cycles.

Adult↗
PubMed1997

An open multicenter study to compare the efficacy of intraperitoneal insemination and intrauterine insemination following multiple follicular development as treatment for unexplained infertility.

PURPOSE: This multicenter study was carried out to compare the efficacy of intrauterine insemination (IUI) and intraperitoneal insemination (IPI) associated with multiple follicular development as treatment for unexplained infertility. METHOD: A total of 205 couples completed the trial. Sixty-seven couples underwent treatment with IPI (group A) and 138 couples underwent treatment with IUI (group B). RESULTS: Clinical pregnancy was obtained in 23 couples in group A (pregnancy rate: 34.3%) and in 36 couples in group B (pregnancy rate: 26.1%). No significant difference was observed between group A and group B. As for the evolution of pregnancies and the incidence of twin pregnancies, no significant difference was observed between the two groups. CONCLUSIONS: Because IUI and IPI allow us to obtain same results and IPI is more invasive than IUI, the latter technique can be considered the method of choice and IPI should be used when IUI is difficult to perform, as in the presence of a tight cervical canal.

Adult↗
PubMed2002

Development of a new transcervical artificial insemination method for sheep: effects of a new transcervical artificial insemination catheter and traversing the cervix on semen quality and fertility.

The difficulty of traversing the cervix severely limits transcervical artificial insemination (TC AI) in sheep. Cervical trauma and poorly designed instruments can reduce fertility after AI. To overcome problems associated with TC AI, we developed a new TC AI catheter. Three bench experiments were conducted to determine the effects of the new TC AI catheter on semen quality independent of the effects of moving the catheter through the cervix. In each of the three bench experiments, the standard laparoscopic instrument for intrauterine AI in sheep was used as the control for the TC AI catheter. In Experiment 1, the total volume of semen extender expelled and void volumes for both types of AI instrument (TC versus laparoscopic) were determined. In Experiment 2, the effects of each type of AI instrument (TC versus laparoscopic) on semen quality, estimated as percentage motility and percentage forward progressive motility, of frozen-thawed semen was determined. In Experiment 3, the effects of both types of AI instrument (TC versus laparoscopic) on number of spermatozoa expelled was determined. The type of AI instrument affected neither semen quality nor the number of spermatozoa expelled. However, void volume differed (P < 0.01) between the two instruments. After differences in void volume were taken into account, an in vivo experiment was conducted to determine whether using our new TC AI catheter for TC or surgical intrauterine AI affected fertilization and pregnancy rates. For this, ewes were assigned to one of three treatments: (1) TC AI using the new TC AI catheter + sham AI via laparotomy (n = 9); (2) sham TC AI + AI via laparotomy using a laparoscopic AI instrument (n = 8); and (3) sham TC AI + AI via laparotomy using the new TC Al catheter (n = 10). To synchronize estrus, progestogenated pessaries were inserted and left in place for 12 days. On Day 5 after pessary insertion, PGF2alpha (15 mg) was given i.m. At pessary removal, 400 IU of eCG were administered i.m. Ewes were inseminated 48-52 h after pessary removal using fresh diluted semen (200 x 10(6) to 350 x 10(6) spermatozoa per 0.2 ml) pooled from the same four rams each day during the experiment. At 72 h after AI, uteri were collected postmortem and flushed. Oocytes and embryos were recovered and evaluated. Treatments did not affect (P > 0.01) ovum and embryo recovery rate (mean = 87.3%), fertilization rate (59.3%), or Day 3 pregnancy rate (mean = 66.6%). We conclude from these data that the use of our new TC AI catheter for TC AI or intrauterine AI should not impair the success of AI in sheep.

Animals↗
PubMed2003

Optimal treatment for poor responders to ovarian stimulation: does in vitro insemination offer any advantages to intrauterine insemination?

A retrospective study was performed of 1832 consecutive in vitro insemination (IVF)/intracytoplasmic sperm injection (ICSI) cycles over 18 months, to analyse the benefits or otherwise to the patient of continuing with in vitro treatment or converting the assisted conception cycle to intrauterine insemination (IUI). Two hundred and seventy cycles were identified in which three follicles or fewer were obtained after controlled ovarian hyperstimulation; in 143 of these cycles, the clinicians or patients elected to abandon all treatment, whereas treatment was continued in 127 patients. In 79 cycles, the patients proceeded with IVF/ICSI and in 48 patients, the cycles were converted to IUI. Data were analysed with regard to the clinical pregnancy rate. In addition, the data for IUI were compared with eight cycles of supraovulation IUI (S/IUI) performed over the same period. There were no significant differences in clinical pregnancy rates among any treatment modality 6/48 (12.5%), 6/79 (7.7%) and 1/8 (12.5%) for IUI, IVF and S/IUI, respectively (P = 0.64). The lowest total number of motile spermatozoa required to achieve pregnancy using IUI was 2.0 x 10(6). In conclusion, it appears that, if the treatment is suitable, patients who respond poorly to controlled hyperstimulation for IVF would not be disadvantaged in achieving a pregnancy by offering them conversion to the medically and financially less interventional IUI.

Adult↗
PubMed1997

Intrauterine insemination: effect of the temporal relationship between the luteinizing hormone surge, human chorionic gonadotrophin administration and insemination on pregnancy rates.

The optimal time period for intrauterine insemination (IUI) in relation to either luteinizing hormone (LH) surge or human chorionic gonadotrophin (HCG) administration leading to the best pregnancy rates has not been determined. In this study, 856 consecutive human menopausal gonadotrophin (HMG)-stimulated and 49 natural unstimulated IUI cycles carried out at a reproductive medicine unit affiliated with a tertiary centre were analysed in a retrospective fashion. There were three scenarios in the temporal relationship of the LH surge, HCG administration and artificial insemination. These were (group A) subjects who had an endogenous LH surge but were not given HCG; (group B) subjects who were given HCG after an observed LH surge, and (group C) subjects who were given HCG before the LH surge. The overall pregnancy rate (PR) was 16% per cycle. The PR was 9% in group A, 20% in group B and 14% in group C. The PR in group B was significantly better than group C (P = 0.04). In group B, the longer the time interval between the LH surge and HCG administration, the better the PR up to 20 h (P = 0.025); the timing of IUI based on the LH surge was not critical to the achievement of pregnancy within 3 days. In group C, PR improved with the increasing interval between HCG and IUI from <28 h up to 60 h. We conclude that a better PR is achieved if a spontaneous LH surge occurs before HCG administration, especially where the administration of HCG is delayed 8-20 h after an observed LH surge; the timing of IUI based on the LH surge is not critical to the achievement of pregnancy within 3 days.

Adult↗
PubMed1997

Intrauterine insemination after ovarian stimulation with clomiphene citrate: predictive potential of inseminating motile count and sperm morphology.

This retrospective study aimed to evaluate the prognostic value of the inseminating motile count (IMC) and sperm morphology (using strict criteria) on success rates after homologous intrauterine insemination (IUI) combined with clomiphene citrate (CC) stimulation. A total of 373 couples underwent 792 IUI cycles in a predominantly (87.4%) male subfertility group. The overall cycle fecundity (CF) and baby take-home rate (BTH) was 14.6 and 9.9% respectively. The cumulative CF and BTH (per couple) after three cycles were 30.6 and 21.1% respectively. Overall, sperm morphology and IMC were of no prognostic value using receiver operating characteristic (ROC) curve analysis, but after classifying the study population into different subgroups according to IMC, sperm morphology turned out to be a valuable prognostic parameter in subgroup 1, i.e. IMC <1 x 10(6). In this subgroup, no pregnancies were seen when the morphology score was <4% and the mean value of sperm morphology was significantly different in the pregnant (8.3%) versus non-pregnant group (5.0%; P <0.05). The cumulative CF and BTH after three IUI cycles were comparable for all couples with the exception of those cases in which the IMC was <1 x 10(6) with a morphology score of <4% normal forms. We recorded only two twin pregnancies (2.5%) and no moderate or severe ovarian hyperstimulation syndrome. We conclude that in a selected group of patients without CC resistance and normal ovarian response following CC stimulation [maximum of three follicles with a diameter of >16 mm at the time of administration of human chorionic gonadotrophin (HCG)], IUI combined with CC-HCG can be offered as a very safe and non-expensive first-line treatment, at least with an IMC of >1 x 10(6) spermatozoa. In cases with <1 x 10(6) spermatozoa, CC-IUI remains important as a first-choice therapy provided the morphology score is > or =4%.

Adult↗
PubMed1996

Intrauterine insemination: evaluation of the results according to the woman's age, sperm quality, total sperm count per insemination and life table analysis.

We report on 332 infertile couples who underwent 1115 cycles of intrauterine insemination (IUI) with washed husband's semen. The indication for IUI was an abnormal post-coital test due to either a male or cervical infertility factor. The mean number of IUI cycles per patients was 3.4, the overall pregnancy rate 18.7%, and the pregnancy rate per cycle 5.6%. The cumulative pregnancy rate calculated by life table analysis showed that 16.0% of pregnancies occurred in the first three treatment cycles, while the cumulative pregnancy rate was 26.9% by the sixth cycle. The outcome of the therapy was adversely affected if the woman's age was > 39 years and/or total motile sperm count per insemination was < 1 x 10(6). No pregnancy occurred in women older than 44 years or in cases with a total motile sperm count before semen preparation of < 1 x 10(6).

Adult↗
PubMed1997

Direct intraperitoneal insemination compared to intrauterine insemination in superovulated cycles: a randomized cross-over study.

The aim of this randomized cross-over study was to determine whether direct intraperitoneal insemination (DIPI) is superior to intrauterine insemination (IUI) in hyperstimulated cycles. The treatment cycles were stimulated with either clomiphene citrate and human menopausal gonadotrophins, or buserelin and human menopausal gonadotrophins. 207 subfertile couples with a cervical factor, a male factor, a combined cervical and male factor, or an unexplained subfertility were randomly assigned to the first treatment cycle. IUI and DIPI were performed in alternate cycles to a maximum of 6 cycles per couple. Every treatment cycle was followed by a nontreatment cycle. The pregnancy rate per completed cycle was 24% for IUI and 16% for DIPI (p = 0.018), whereas the cumulative pregnancy rates for IUI and DIPI were 53 and 40%, respectively (p = 0.002). There were no significant differences between pregnancy rates for IUI and DIPI in the different categories of subfertility. We conclude that DIPI does not offer better pregnancy chances than IUI in superovulated cycles.

Adult↗
PubMed2006

Synchronization of estrus in suckled beef cows for detected estrus and artificial insemination and timed artificial insemination using gonadotropin-releasing hormone, prostaglandin F2alpha, and progesterone.

We determined whether a fixed-time AI (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus, or estrous detection plus TAI, and whether adding a controlled internal device release (CIDR) to GnRH-based protocols would enhance fertility. Estrus was synchronized in 2,598 suckled beef cows at 14 locations, and AI was preceded by 1 of 5 treatments: 1) a CIDR for 7 d with 25 mg of PG F(2alpha) (PGF) at CIDR removal, followed by detection of estrus and AI during the 84 h after PGF; cows not detected in estrus by 84 h received 100 mug of GnRH and TAI at 84 h (control; n = 506); 2) GnRH administration, followed in 7 d with PGF, followed in 60 h by a second injection of GnRH and TAI (CO-Synch; n = 548); 3) CO-Synch plus a CIDR during the 7 d between the first injection of GnRH and PGF (CO-Synch + CIDR; n = 539); 4) GnRH administration, followed in 7 d with PGF, followed by detection of estrus and AI during the 84 h after PGF; cows not detected in estrus by 84 h received GnRH and TAI at 84 h (Select Synch & TAI; n = 507); and 5) Select Synch & TAI plus a CIDR during the 7 d between the first injection of GnRH and PGF (Select Synch + CIDR & TAI; n = 498). Blood samples were collected (d -17 and -7, relative to PGF) to determine estrous cycle status. For the control, Select Synch & TAI, and Select Synch + CIDR & TAI treatments, a minimum of twice daily observations for estrus began on d 0 and continued for at least 72 h. Inseminations were performed using the AM/PM rule. Pregnancy was diagnosed by transrectal ultrasonography. Percentage of cows cycling at the initiation of treatments was 66%. Pregnancy rates (proportion of cows pregnant to AI of all cows synchronized during the synchronization period) among locations across treatments ranged from 37% to 67%. Pregnancy rates were greater (P < 0.05) for the Select Synch + CIDR & TAI (58%), CO-Synch + CIDR (54%), Select Synch & TAI (53%), or control (53%) treatments than the CO-Synch (44%) treatment. Among the 3 protocols in which estrus was detected, conception rates (proportion of cows that became pregnant to AI of those exhibiting estrus during the synchronization period) were greater (P < 0.05) for Select Synch & TAI (70%; 217 of 309) and Select Synch + CIDR & TAI (67%; 230 of 345) cows than for control cows (61%; 197 of 325). We conclude that the CO-Synch + CIDR protocol yielded similar pregnancy rates to estrous detection protocols and is a reliable TAI protocol that eliminates detection of estrus when inseminating beef cows.

Animals↗
PubMed1997

Pregnancy rates per artificial insemination for cows and heifers inseminated at a synchronized ovulation or synchronized estrus.

Two synchronization protocols were tested for lactating dairy cows and heifers. Nulliparous dairy heifers (13 to 23 mo; n = 155) and primiparous and multiparous dairy cows (60 to 289 d postpartum; n = 310) were assigned randomly to two treatments. Controls received 25 mg of PGF2 alpha and were artificially inseminated according to the a.m.-p.m. rule following detected estrus. All controls that were not detected in estrus were injected with 25 mg of PGF2 alpha at 14-d intervals until artificial insemination (AI) at a detected estrus or until timed AI at 72 to 80 h after a third sequential injection of PGF2 alpha. Treated cows and heifers received a protocol that used GnRH and PGF2 alpha to synchronize ovulation (Ovsynch). Cows and heifers that were treated with Ovsynch were injected i.m. with 100 micrograms of GnRH at a random stage of the estrous cycle. Seven days later, cows and heifers in this group received 25 mg of PGF2 alpha followed by a second injection of 100 micrograms of GnRH 30 to 36 h later. Subsequently, the treated cows and heifers received AI 16 to 20 h after the second injection of GnRH. Pregnancy rates per AI were similar (38.9% vs. 37.8%) for control cows and cows treated with the Ovsynch protocol, respectively. However, pregnancy rate per AI was greater for control heifers (74.4%) than for heifers treated with Ovsynch (35.1%). Evaluation of serum progesterone concentrations at each hormonal injection indicated that the first injection of GnRH synchronized luteal function of lactating dairy cows but not of heifers. In summary, one fixed-time AI at a synchronized ovulation provided similar pregnancy rates per AI as did AI following the a.m-p.m. rule after estrus had been induced by PGF2 alpha in lactating cows, but the fixed-time AI was not effective for heifers because of the lack of synchronization.

Animals↗