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At least 19 recordsLinked to original sources
PubMed2004

Effect of addition of a progesterone intravaginal insert to a timed insemination protocol using estradiol cypionate on ovulation rate, pregnancy rate, and late embryonic loss in lactating dairy cows.

The objectives of this study were to determine the effects of incorporating a progesterone intravaginal insert (CIDR) between the day of GnRH and PGF2alpha treatments of a timed AI protocol using estradiol cypionate (ECP) to synchronize ovulation on display of estrus, ovulation rate, pregnancy rate, and late embryonic loss in lactating cows. Holstein cows, 227 from Site 1 and 458 from Site 2, were presynchronized with two injections of PGF2alpha on study d 0 and 14, and subjected to a timed AI protocol (100 mixrog of GnRH on study d 28, 25 mg of PGF2alpha on study d 35, 1 mg of ECP on study d 36, and timed AI on study d 38) with or without a CIDR insert. Blood was collected on study d 14 and 28 for progesterone measurements to determine cyclicity. Ovaries were scanned on d 35, 37, and 42, and pregnancy diagnosed on d 65 and 79, which corresponded to 27 and 41 d after AI. Cows receiving a CIDR had similar rates of detected estrus (77.2 vs. 73.8%), ovulation (85.6 vs. 86.6%), and pregnancy at 27 (35.8 vs. 38.8%) and 41 d (29.3 vs. 32.3%) after AI, and late embryonic loss between 27 and 41 d after AI (18.3 vs. 16.8%) compared with control cows. The CIDR eliminated cows in estrus before the last PGF2alpha injection and decreased (P < 0.001) the proportion of cows bearing a corpus luteum (CL) at the last PGF2alpha injection because of less ovulation in response to the GnRH and greater spontaneous CL regression. Cyclic cows had greater (P = 0.03) pregnancy rates than anovulatory cows at 41 d after AI (33.8 vs. 20.4%) because of decreased (P = 0.06) late embryonic loss (16.0 vs. 30.3%). The ovulatory follicle was larger (P < 0.001) in cows in estrus, and a greater proportion of cows with follicles > or = 15 mm displayed estrus (P < 0.001) and ovulated (P = 0.05) compared with cows with follicles <15 mm. Pregnancy rates were greater (P < 0.001) for cows displaying estrus, which were related to the greater (P < 0.001) ovulation rate and decreased (P = 0.08) late embryonic loss for cows in estrus at AI. Cows that were cyclic and responded to the presynchronization protocol (high progesterone at GnRH and CL at PGF2alpha) had the highest pregnancy rates. Incorporation of a CIDR insert into a presynchronized timed AI protocol using ECP to induce estrus and ovulation did not improve pregnancy rates in lactating dairy cows. Improvements in pregnancy rates in cows treated with ECP to induce ovulation in a timed AI protocol are expected when more cows display estrus, thereby increasing ovulation rate.

Abortion, Veterinary↗
PubMed1998

Effect of time of artificial insemination on pregnancy rates, calving rates, pregnancy loss, and gender ratio after synchronization of ovulation in lactating dairy cows.

In order to assess the optimal time of artificial insemination (AI) in relation to ovulation, lactating dairy cows (n = 732) from herds with rolling herd averages of 9980 to 11,800 kg from three milkings per day were randomly assigned to five groups by stage of lactation and parity. Ovulation was synchronized by administration of GnRH followed 7 d later with PGF2 alpha followed 2 d later with a second treatment with GnRH. Cows were inseminated at 0, 8, 16, 24, or 32 h after the second injection of GnRH (ovulation occurs between 24 and 32 h after GnRH). Pregnancy diagnoses were performed by ultrasound at 25 to 35 d post-AI. Pregnancy rates per AI were similar for the groups inseminated at 0, 8, 16, and 24 h and lower for the group inseminated at 32 h. A significant quadratic effect of treatment suggests that the middle time periods (8, 16, and 24 h) may produce the greatest pregnancy rate per AI. However, the group inseminated at 0 h had lowest pregnancy loss, and the group inseminated at 32 h tended to have the greatest pregnancy loss compared with that of the other groups. The calving rate was similar between the groups inseminated at 0, 8, 16, and 24 h and lower in the group inseminated at 32 h. The time of AI also appeared to affect gender of calf: cows bred at 0 and 32 h having a higher percentage of female offspring. In conclusion, there appears to be substantial flexibility in the time of AI after the second injection of GnRH, and lower reproductive rates were observed only when AI was after the time of ovulation.

Abortion, Veterinary↗
PubMed1995

Cumulative pregnancy rates and pregnancy outcome after in-vitro fertilization: > 5000 cycles at one centre.

Cumulative pregnancy rates and pregnancy outcome analysis are useful methods for advising an infertile couple of the probability of in-vitro fertilization (IVF) success. All 5209 IVF cycles in 2391 couples at University Hospital, London, Ontario, Canada, over 10 years were studied. Cumulative pregnancy rates were estimated using life table analysis. The Cox proportional hazards model was used to estimate the influence of covariates. Oocyte retrieval and embryo transfer were achieved in 84 and 64% of cycles initiated respectively. There were 644 intra-uterine and 24 ectopic pregnancies (13%/cycle initiated, 15%/oocyte retrieval and 20%/embryo transfer). Cumulative pregnancy rates following six cycles were: tubal 55%, idiopathic 65%, endometriosis 60%, multifactorial 63% and male 40%. There were 68 spontaneous abortions (10.6%) and three induced abortions for congenital anomalies. The multiple gestation rate was 22%. Caesarean section and preterm delivery rates were 35 and 20% respectively, due in part to the high proportion of multiple gestations. Of 15 deliveries which resulted in stillbirths and/or neonatal deaths, 12 were multiple gestations; 18 pregnancies (3.3%) were complicated by congenital malformations. No increases in congenital malformations or spontaneous abortions were identified. Cumulative pregnancy rates were lower in cases of male infertility. Success rates did not decline with successive IVF cycles. IVF is an evolving infertility treatment.

Birth Rate↗
PubMed2006

The effects of a low dose of cabergoline on induction of estrus and pregnancy rates in anestrous bitches.

This is the first report of successful induction of normal estrus and ovulation in breeder bitches with as a low dose as 0.6 microg/kg/day of cabergoline formulation marketed for use in women. Sixty-one pure breed bitches from various breeds were used in the study at their already determined periods of anestrus. Twenty-four dogs formed the control group, while 37 bitches were administered with two different doses of cabergoline (recommended dose group, n=10, 5 microg/kg/day and low dose group, n=27, 0.6 microg/kg/day). Induced estrus rates and mean treatment and proestrus durations of dogs in these two dose groups were compared. At the second phase of the study, the effects of 500 IU human chorionic gonadotropin (hCG) administered on days 1 and 3 of estrus induced by the low dose of cabergoline, on the duration of behavioral estrus, ovulation rates, pregnancy rates and the number of offspring were investigated. For this purpose, the dogs with signs of proestrus (22/27) following the treatment in the low dose group were assigned into two subgroups. Five hundred IU of hCG (Pregnyl, Organon, Turkey) was intramuscularly administered to eight of these dogs [low dose (hCG+) group] on days 1 and 3 of estrus. The remaining 14 dogs were not treated with hCG [low dose (hCG-) group]. An aqueous solution of cabergoline (Dostinex, Pharmacia, Italy) was orally administered until 2 day after the onset of proestrus or for a maximum of 42 days. Blood samples were taken daily from all treatment and 11 control bitches during the first five days of behavioral estrus to measure progesterone concentrations. In the recommended dose and low dose groups, estrus was induced between days 8-45 and 4-48 (mean: 23.63+/-14.33 and 24.41+/-14.31 days), in the ratio of 80.0 and 81.5%, respectively (p>0.05). In both dose groups, post-treatment interestrous intervals were significantly shorter than both those of the control group and their own pre-treatment interestrous intervals (p<0.05). Ovulation rates, pregnancy rates and mean number of offspring delivered by the dogs in the recommended dose, low dose (hCG-), low dose (hCG+) and control groups were found to be similar (p>0.05). However, the mean duration of behavioral estrus of the dogs in the low dose (hCG+) group was found to be significantly longer compared to dogs in all other groups (p<0.05). In both dose groups, no correlation could be found between the anestrus stages and treatment durations (p>0.05). Shortly, it has been concluded from the study that (1) normal and fertile estrus can be induced more economically in bitches during different stages of anestrus using as a low dose of 0.6 microg/kg of cabergoline formulation marketed for use in women, and that (2) hCG injections on days 1 and 3 of the estrus induced by this method has no positive effects on the ovulation rates, pregnancy rates and the number of offspring per pregnancy.

Anestrus↗
PubMed1999

Influence of advanced age on the blastocyst development rate and pregnancy rate in assisted reproductive technology.

OBJECTIVE: To evaluate the percentage of blastocysts developing, the pregnancy rate, the implantation rate, and the abortion rate in women >40 years of age using a cell-free culture system for the development of viable human blastocysts. DESIGN: Retrospective clinical study. SETTING: Private IVF units. PATIENT(S): Two hundred ninety-three cycles in patients undergoing IVF treatment for infertility. Sixty-two cycles were in patients > or =40 years of age, and 231 cycles were in patients <40 years of age. INTERVENTION(S): Pronucleate oocytes obtained from IVF were cultured in vitro for 5-6 days. One to four embryos were transferred. MAIN OUTCOME MEASURE(S): Blastocyst development rate, pregnancy rate, implantation rate, and abortion rate. RESULT(S): From 293 cycles, 3,115 pronucleate oocytes were cultured, producing 1,175 blastocysts. In the women >40 years of age, the blastocyst development rate was 22.2%, and in the younger group, the rate was 40.5%. The pregnancy rate and implantation rate in the > or =40-year age group were 21.1% and 8.9%, respectively; corresponding rates in the younger group were 44.6% and 19.9%. The abortion rate was increased for the > or =40-year age group (25% versus 13.3%). CONCLUSION(S): Success rates for the development of viable human blastocysts, pregnancy, and implantation decline significantly in women > or =40 years old.

Abortion, Spontaneous↗
PubMed1993

A modest increase in serum progesterone levels on the day of human chorionic gonadotropin (hCG) administration may influence pregnancy rate and pregnancy loss in in vitro fertilization-embryo transfer (IVF-ET) patients.

PURPOSE: Our purpose was to study the effect of a modest increase in preovulatory serum progesterone (P4) levels in hyperstimulated patients and its association with pregnancy rate and pregnancy loss following in vitro fertilization (IVF) and embryo transfer (ET). PATIENTS: Only patients with mechanical factor and three transferred embryos were included in the present study. They were divided into two groups according to two critical breakpoints for P4 serum levels on the day of hCG administration: serum P4 below 0.6 ng/ml in 28 cycles (group I) and > 0.6 ng/ml in 80 cycles (group II). SETTING: The setting was the IVF program at Carmel Medical Center, Haifa, Israel. RESULTS: The pregnancy rate per embryo transfer was 53% (15/28) in group I and 10% (8/80) in group II (P < 0.025). Of 15 pregnancies achieved in group I, 14 were ongoing pregnancies, compared to 4 of 8 ongoing pregnancies in group II (P < 0.03). CONCLUSIONS: Our findings suggest that a very modest increase in serum P4 levels on the day of hCG administration is associated with lower pregnancy and ongoing pregnancy rates in IVF-ET.

Adult↗
PubMed2003

Effect of resynchronization with GnRH on day 21 after artificial insemination on pregnancy rate and pregnancy loss in lactating dairy cows.

The objectives of the present study were to determine the effects of resynchronization with GnRH on Day 21 after artificial insemination (AI) on pregnancy rate and losses of pregnancy in lactating dairy cows. Holstein cows (n=585) on two dairy farms were assigned to one of two treatments in a randomized complete block design. On Day 21 after a pre-enrollment AI, animals assigned to the resynchronization (RES) group received 100 microg of GnRH i.m., whereas animals in the control (CON) group received no treatment. All animals were examined ultrasonographically on Days 21 and 28 after AI, and blood samples were taken for progesterone measurement on Day 21. Pregnancy was diagnosed on Day 28 and reconfirmed 14 days later. Nonpregnant cows on Day 28 were inseminated using timed AI after the completion of the Ovsynch protocol 10 and 17 days after enrollment in the study for RES and CON groups, respectively. Progesterone concentration > or =2.35 ng/ml was used as an indicator of pregnancy on Day 21. For RES and CON cows, pregnancy rate at Days 21 (70.9% versus 73.0%, P<0.56), 28 (33.1% versus 33.6%; P<0.80) and 42 (27.0% versus 26.8%; P<0.98) after the pre-enrollment AI did not differ. Administration of GnRH on Day 21 after AI had no effect on pregnancy loss in RES and CON groups from days 21 to 28 (53.2% versus 53.5%; P<0.94) and days 28 to 42 (17.9%; P<0.74) after AI. Pregnancy rate after the resynchronization period was similar for both treatment groups. Resynchronization with GnRH given on Day 21 after AI for initiation of a timed AI protocol prior to pregnancy diagnosis does not affect pregnancy rate and pregnancy loss in lactating dairy cows.

Abortion, Veterinary↗
PubMed1996

The effect of the gonadotrophin-releasing hormone analog, buserelin, administered in diestrus on pregnancy rates and pregnancy failure in mares.

Two trials involving 578 mares were performed to investigate the effect of a single intramuscular treatment of 40 microg buserelin, an analog of gonadotrophin releasing hormone, on pregnancy rate in mares. All mares were bred by natural mating and were allocated into pairs One mare in each pair was injected with buserelin either on Day 10 or 11 (Trial 1) or on Days 8 to 10 (Trial 2) after ovulation. Pregnancy status of mares was determined by transrectal ultrasonographic examination on Day 14 or 15 after the day of ovulation and was repeated between Days 28 and 30 of pregnancy. In Trial 1, buserelin treatment increased the pregnancy rate at Days 14 and 15 (72.5 vs 66.6%, P < 0.01). At the second pregnancy examination, pregnancy losses were lower in the treated group of mares (4.1 vs 7.4%; P < 0.05). In Trial 2, buserelin also improved the pregnancy rate (57.2 vs 53 5%; P < 0.05) at Days 14 and 15 Pregnancy losses between the first and second examinations were lower in the treated group of mares (6.5 vs 12.0%; P < 0.05). Buserelin increased pregnancy rates after breeding at the first estrus in both trials. In addition, buserelin treatment increased the pregnancy maintenance rate at Days 28 to 30.

Journal Article↗
PubMed2001

Metformin increases the ovulatory rate and pregnancy rate from clomiphene citrate in patients with polycystic ovary syndrome who are resistant to clomiphene citrate alone.

OBJECTIVE: To determine whether metformin treatment increases the ovulation and pregnancy rates in response to clomiphene citrate (CC) in women who are resistant to CC alone. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Multicenter environment. PATIENT(S): Anovulatory women with the polycystic ovary syndrome (PCOS) who were resistant to CC. INTERVENTION(S): Participants received placebo or metformin, 500 mg three times daily, for 7 weeks. Information on reproductive steroids, gonadotropins, and oral glucose tolerance testing was obtained at baseline and after treatment. Metformin or placebo was continued and CC treatment was begun at 50 mg daily for 5 days. Serum P level > or =4 ng/mL was considered to indicate ovulation. With ovulation, the daily CC dose was not changed, but with anovulation it was increased by 50 mg for the next cycle. Patients completed the study when they had had six ovulatory cycles, became pregnant, or experienced anovulation while receiving 150 mg of CC. MAIN OUTCOME MEASURE(S): Ovulation and pregnancy rates. RESULT(S): In the metformin and placebo groups, 9 of 12 participants (75%) and 4 of 15 participants (27%) ovulated, and 6 of 11 participants (55%) and 1 of 14 participants (7%) conceived, respectively. Comparisons between the groups were significant. CONCLUSION(S): In anovulatory women with PCOS who are resistant to CC, metformin use significantly increased the ovulation rate and pregnancy rate from CC treatment.

Adolescent↗
PubMed2005

Elective single blastocyst transfer reduces twin rates without compromising pregnancy rates.

OBJECTIVE: To compare IVF outcome in single versus two blastocyst transfer in good-prognosis patients. DESIGN: Retrospective data analysis. SETTING: University-based IVF practice. PATIENT(S): Assisted reproductive technology outcome was compared in 41 patients who underwent elective single blastocyst transfer and 66 patients who underwent two blastocyst transfer. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Implantation rates, clinical pregnancy rates, cumulative pregnancy rates, twin pregnancy rates. RESULT(S): Blastocyst cycles between January 2003 and August 2004 (n = 238) were reviewed. Criteria for elective single embryo transfer established by our clinic were applied retrospectively to blastocyst cycles. Patients who met the criteria were divided into two groups, those who underwent elective single embryo transfer (eSET) and those who underwent two embryo transfer (2ET). Patient and cycle characteristics were similar for both groups. There were no differences in implantation rate (76% vs. 66%) or pregnancy rate (76% vs. 79%) between the eSET and 2ET groups. There was a significant difference in the number of twin pregnancies (3.2% vs. 62%) in the eSET versus 2ET group. Cumulative pregnancy rates were found to be 83% for both groups. CONCLUSION(S): Single blastocyst transfer can be performed in good-prognosis patients without compromising pregnancy rates. Twin pregnancy rates can be significantly reduced with eSET.

Adult↗
PubMed2004

The effect of age on multiple ovulation rates, multiple pregnancy rates and embryonic vesicle diameter in the mare.

Numerous and conflicting reports exist regarding factors that may effect mare reproductive performance, in particular multiple ovulation (MO) and its consequences. Sequential ultrasonic examination was used to monitor 3075 ovulations in 1581 mainly Thoroughbred mares to ascertain: whether increasing age is associated with an increase in MO; whether this is counteracted by an increase in embryo mortality (EM) prior to Day 13; and whether this embryonic loss may be associated with small-for-age embryonic vesicles (Days 13/14). Overall ovulation rate was 1.31, MO occurring in 29.3% of cycles. MO incidence significantly (p<0.05) increased with age (20.7% in 2-4-year olds compared to 35.6% in 17-19-year olds). 25.2% of MO were apparent as multiple pregnancies (MP) (40.0% of all pregnancies arising from MO) and 37.8% as single pregnancies (SP) at Days 13/14. Older mares demonstrated significantly (p<0.001) lower pregnancy rates and of those pregnant, significantly (p<0.01) fewer were MP than younger mares. Observation of 1442 embryonic vesicles failed to demonstrate any consistent significant association between age and vesicle size in single ovulating (SO) or MO mares on Days 13/14. We conclude that: (i) increasing age was significantly (p<0.05) associated with increasing incidence of MO; (ii) increasing age was significantly associated with a decreasing incidence of pregnancy/ovulation (p<0.001), and MP (p<0.01), at Days 13/14; (iii) there was no consistent significant association between mare age and vesicle size.

Aging↗
PubMed2001

Transfer of two embryos instead of three will not compromise pregnancy rate but will reduce multiple pregnancy rate in an assisted reproduction unit.

OBJECTIVE: To compare the pregnancy rates and multiple pregnancy rates of cycles initiated in 1998 and in 1999, during which 3 and 2 embryos were advised to be replaced, respectively. STUDY DESIGN: A retrospective study RESULTS: There were no differences between 1998 and 1999 in the pregnancy rate per cycle started or per transfer, implantation rate and the multiple pregnancy rates, despite a significantly lower number of embryos replaced in 1999. A significantly higher implantation rate was found in cycles with frozen embryos than those without. Using logistic regression analysis, the chance of pregnancy was significantly improved only by the presence of frozen embryos in the fresh cycles with an odds ratio of 2.0 (95% confidence interval: 1.3-3.0) whereas the chance of multiple pregnancy was significantly increased by replacing 3 embryos instead of 2 (odds ratio: 2.1, 95% confidence interval: 1.1-4.2). CONCLUSION: Patients should be advised to have 2 embryos replaced without jeopardizing the pregnancy rates in the fresh cycles. The risk of multiple pregnancy is significantly increased when 3 embryos are transferred instead of 2.

Adult↗
PubMed2005

Strategic use of gonadotrophin-releasing hormone (GnRH) to increase pregnancy rate and reduce pregnancy loss in lactating dairy cows subjected to synchronization of ovulation and timed insemination.

The objective of this study was to determine the effect of GnRH (100 microg i.m.) treatment 5 and 15 days after timed insemination (TAI) on pregnancy rate and pregnancy loss in lactating dairy cows subjected to synchronization of ovulation. The study included 831 lactating dairy cows subjected to a Presynch-Ovsynch protocol for first service. On the day of TAI (Day 0), cows were randomly assigned to one of four experimental groups. Cows in Group 1 (n = 214) were treated with GnRH on Day 5; cows in Group 2 (n = 209) were treated with GnRH on Day 15; cows in Group 3 (n = 212) were treated with GnRH on both Day 5 and Day 15; cows in Group 4 (n = 196) were not treated. Pregnancy rate was evaluated at Day 27 and Day 45 after TAI. The interestrus interval and the proportion of cows diagnosed not pregnant based on expression of estrus and insemination before pregnancy diagnosis on Day 27 were determined. The results of this study are: (1) GnRH treatment on Day 5 or Day 15 did not increase pregnancy rate, or reduce pregnancy loss between Day 27 and Day 55 after TAI; (2) cows treated with GnRH on both Day 5 and Day 15 had a lower (P < 0.01) proportion of cows diagnosed not pregnant based on expression of estrus before ultrasonography on Day 27 (26.5%) compared to control cows (52.9%), and these cows had an extended (P = 0.05) interestrus interval (23.4 days vs. 21.5 days); and (3) GnRH treatment on both Day 5 and Day 15 after TAI reduced pregnancy rate on Day 27 (36.8% vs. 44.4% for control cows; P < 0.03) and Day 55 (28.3% vs. 36.2% for control cows; P < 0.01). Therefore, strategies to stimulate CL function using multiple doses of GnRH during the luteal phase need to consider potential negative effects.

Abortion, Veterinary↗
PubMed1997

The optimal number of embryos to be transferred in shared oocyte donation: walking the thin line between low pregnancy rates and multiple pregnancies.

There has been growing concern about the number of multiple gestations resulting from assisted reproductive technologies. For in-vitro fertilization (IVF), there are guidelines concerning the number of embryos to be transferred. In oocyte donation, however, there is a paucity of studies addressing this issue and common practice is extrapolated from standard IVF procedures. This may not be correct since endometrial receptivity has been shown to be altered in oocyte donation. Thus the purpose of this study was to assess the optimal number of embryos to be transferred in oocyte donation. The study population included 254 patients with ovarian failure who underwent a total of 601 embryo transfers in a single shared oocyte donation programme. Pregnancy rates (PRs), multiple pregnancies, triplet pregnancy rates, and implantation rates were evaluated according to the number of embryos transferred. A significant linear increase in PRs was noted with the increasing number of embryos transferred up to five (11.1% for one embryo, 36.7% for five embryos). Multiple pregnancies increased significantly from 15.8% for two embryos transferred, to 44.4% for five embryos. The rate of triplet pregnancies also increased from 2.7% for three embryos transferred, to 8.3% for five embryos. Optimization of the number of embryos to be transferred is discussed.

Adult↗
PubMed2005

New Belgian legislation regarding the limitation of transferable embryos in in vitro fertilization cycles does not significantly influence the pregnancy rate but reduces the multiple pregnancy rate in a threefold way in the Leuven University Fertility Center.

After the introduction of new Belgian legislation limiting the number of transferable embryos to prevent multiple pregnancies after assisted reproductive technology, the implantation rate per embryo remained stable at 26% and the clinical pregnancy rate per embryo transfer did not change significantly (37.5% before and 32.5% after legislation), whereas the multiple pregnancy rate per clinical pregnancy decreased threefold from 25.9% to 8.0%) in the Leuven University Fertility Center.

Academic Medical Centers↗
PubMed1992

Serum testosterone concentration in response to exogenous GnRH does not predict service rates or pregnancy rates by yearling, performance tested, crossbred bulls.

Ten bulls with a scrotal circumference of less than 30 cm at the end of growth performance testing, and 10 cohorts of the same age, size and breed type with a scrotal circumference greater than 30 cm were used to evaluate if testosterone response following GnRH administration could be used to test for fertility, for semen quality, and for specific pathologic testicular parenchymal changes. Serum testosterone concentrations were determined immediately before and 2 to 3 hours following intramuscular injection of 250 ug GnRH. Bulls were examined for breeding soundness, then fertility was tested in a breeding trial; testicular histology was assessed by determining the percentage of cross-sections of seminiferous tubules with no spermatocytes. The mean (+/-SEM) post-GnRH serum testosterone concentration for all bulls was 11.71 (+/-0.64) ng/ml. In order to examine for an association, the GnRH response was classified as above or below the mean for resultant serum testosterone concentration. The GnRH response classification was not related to the scrotal circumference, percentage of tubules devoid of spermatocytes, or percentage of progressively motile spermatozoa (P>0.10). The percentage of morphologically normal spermatozoa was significantly higher (P<0.05) in the bulls with a higher than mean testosterone secretion in response to GnRH injection. In the breeding trial, the percentage of heifers bred and the percentage of heifers pregnant (60 days post breeding) were not significantly different (P>0.10) between the 2 classifications of GnRH response. The GnRH response test was related to the percentage of morphologically normal spermatozoa but did not predict fertility of yearling bulls in this study.

Journal Article↗