Control of Ovarian Activity in Llamas (Lama glama) with Medroxyprogesterone Acetate

Contents Progesterone and progestogens have proved to be effective in controlling follicle development and synchronization of ovarian activity in different species. In this study, vaginal sponges containing 120 mg medroxyprogesterone acetate were used to synchronize ovarian activity in llamas and to predict the time when a mature follicle will be present. Plasma concentrations of oestradiol-17β and progesterone were measured to determine follicle and corpus luteum development. The sponges were kept in the vagina for 9 days. Six days after sponge withdrawal, ovulation was induced by either GnRH injection (n = 4), mating with a vasectomized male (n = 8) or mating with an intact male (n = 10). Plasma progesterone concentrations varied between animals until day 6 after insertion of the sponges. Thereafter, progesterone levels remained close to the detection limit of the assay until ovulation was induced. The mean oestradiol-17β plasma concentration reached its lowest value 3–4 days after insertion of the sponges. Thereafter, concentrations increased and reached peak levels at day 6 after withdrawal of the sponges. All animals ovulated and developed a corpus luteum with a normal life span after the ovulatory stimulus. Blood samples were collected frequently after mating to evaluate the endocrine response to copulation. Plasma concentrations of PGF_2α metabolite and cortisol increased in parallel after copulation. The metabolite concentrations returned to basal levels 3–4 h after mating whereas the cortisol concentrations remained elevated for about 12 h after copulation The luteinizing hormone secretory pattern resembled that reported when llamas with a mature ovulatory follicle were mated. In conclusion, the protocol evaluated in this study was shown to be useful for the synchronization of ovarian activity and for predicting the time when an ovulatory follicle will be present in llamas.     

Post-partum, ovarian function in dairy cows as revealed by concentrations of oestradiol-17 beta and progesterone in defatted milk

Concentrations of oestradiol-17 beta and progesterone in defatted milk have been used to study the post-partum restoration of ovarian function in 52 autumn-calved dairy cattle. In 32 cows the first preovulatory peaks in oestradiol-17 beta concentration (indicative of imminent ovulation) were less than or equal to 15 days and in 49 cows less than or equal to 49 days post partum. Delay to first ovulation was mainly due, not to failure of ovarian secretion of oestradiol-17 beta at preovulatory level, but to failure of oestradiol-17 beta at this level to exert its normal preovulatory function. Longer intervals to first ovulation were associated with longer intervals from calving to the clearance of placental oestradiol-17 beta, high peak milk yields and high body weight losses, suggesting that in high-yielding dairy cows these factors (themselves inter-related) may be associated with others, which are the immediate cause of the inhibition of the normal, preovulatory function of oestradiol-17 beta. Forty-eight per cent of cows had short, first ovulation cycles. Ovarian function, comprising oestradiol-17 beta secretion at preovulatory level, normal preovulatory function of oestradiol-17 beta and normal corpus luteum progesterone secretion were almost fully restored in this herd by the 49th day post partum.     

Preventive effects of CIDR-based protocols on premature ovulation before timed-AI in Ovsynch in cycling beef cows

Ovsynch is a program developed to synchronize ovulation for timed breeding. In this paper, the authors investigate whether controlled internal drug release (CIDR)-based protocols prevent premature ovulation before timed-artificial insemination (AI) when Ovsynch is started a few days before luteolysis in cycling beef cows. Nine beef cows at 16 days after oestrus were treated with (1) Ovsynch, i.e. gonadotropin releasing hormone (GnRH) analogue on day 0, prostaglandin (PG) F(2alpha) analogue on day 7 and GnRH analogue on day 9 with timed-AI on day 10, (n=3); (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from day 0, n=3), or (3) oestradiol benzoate (OB)+CIDR+GnRH (OB on day 0 in lieu of the first GnRH treatment, followed by the Ovsynch+CIDR protocol, n=3). In the Ovsynch group (1) plasma progesterone concentrations fell below 0.5 ng/mL earlier (day 5) than in both CIDR-treated groups (2) and (3), where this occurred on day 8. Plasma oestradiol-17beta concentrations peaked on day 8 in the Ovsynch group and on day 9 in both CIDR-treated groups. The dominant follicle ovulated on day 10 in the Ovsynch group and on day 11 in both CIDR-treated groups. Thus, both CIDR-based protocols prevented premature ovulation before timed-AI in Ovsynch when the protocol was started a few days before luteolysis. This reflects the fact that progesterone levels remained high until the beef cattle were treated with PGF(2alpha).     

Comparison of plasma concentrations of estradiol-17β and progesterone, and conception in dairy cows with cystic ovarian diseases between Ovsynch and Ovsynch plus CIDR timed AI protocols

The objectives of this study were 1) to determine the effects of adding a CIDR to the Ovsynch protocol on plasma concentrations of estradiol-17β and progesterone and conception in dairy cows with cystic ovarian diseases and 2) to examine associations among the estradiol-17β and progesterone concentrations and conception. Cows were diagnosed as having cystic ovarian diseases if they were found to have a cystic follicle (diameter ≥25 mm) without a corpus luteum by two palpations per rectum with an interval for 7 to 14 days. They were treated with either the Ovsynch (GnRH on Day 0, PGF(2α) on Day 7 and GnRH on Day 9, with AI on Day 10; n=15) or Ovsynch+CIDR protocol (Ovsynch protocol plus a CIDR from Day 0 to Day 7; n=23). Plasma estradiol-17β concentrations were determined on Days 0, 7 and 9, and plasma progesterone concentrations were determined on Days 0, 7, 9 and 17. The plasma estradiol-17β and progesterone concentrations at all of the days examined and conception rates did not differ significantly between the two timed AI protocols. The progesterone concentrations on Day 17 and conception rates were lower (P<0.05) for cows with low concentrations of estradiol-17β (<2 pg/ml) on Day 9 than for cows with high concentrations of estradiol-17β (≥2 pg/ml). The present study suggests that, in dairy cows with cystic ovarian diseases, addition of a CIDR to the Ovsynch protocol had no remarkable effects on plasma estradiol-17β and progesterone concentrations during and after the treatments or on conception after timed AI. This study indicates that the low plasma estradiol-17β concentration at the second administration of GnRH in the protocols can be a predictor for impaired luteal formation and lower likelihood of pregnancy in dairy cows with cystic ovarian diseases.     

Effect of the dominant follicle aspiration before or after luteinizing hormone surge on the corpus luteum formation in the cow

Luteinizing hormone (LH) surge and follicle rupture act as trigger to start corpus luteum (CL) formation. Thus, we aimed to investigate whether a dominant follicle that has not been exposed to an LH surge can become a functional CL. For this purpose, follicular fluid from the dominant follicles (DF) of cows was aspirated before or after a GnRH-induced LH surge, and subsequent CL formation was observed. Holstein cows were divided into four groups as follows: Luteal phase, a DF was aspirated 7 days after GnRH injection; Pre-LH surge, a DF was aspirated 42 h after PGF(2alpha) injection during the mid luteal phase; Post-LH surge, a DF was aspirated 24 h after GnRH injection following PGF(2alpha); and Intact follicle, ovulation was induced by GnRH injection after PGF(2alpha). Observation of morphological changes in the aspirated follicle using color Doppler ultrasonography and blood sampling was performed on Days 0, 3, 6, and 9 (Day 0 = follicle aspiration). CL formation following DF aspiration was observed only in the Post-LH surge group. In both the Luteal phase and Pre-LH surge groups, however, none of the cows showed local blood flow at the aspirated site or CL formation. Luteal blood flow area, CL volume, and plasma progesterone concentration in the Post-LH surge group were no different from those in the Intact follicle group. The present results clearly demonstrate that rather than follicle rupture, it is the LH surge that is essential for CL formation in cows.     

Use of milk progesterone enzyme immunoassay for differential diagnosis of follicular cyst, luteal cyst, and cystic corpus luteum in cows

In 160 cows with ovarian cysts as determined by rectal palpation, differentiation was made of follicular cyst, luteal cyst, and cystic corpus luteum on the basis of milk progesterone concentrations estimated by an enzyme immunoassay before and at 10 days after cows were treated with gonadotropin-releasing hormone. Cows having a progesterone concentration in skim milk less than 1.0 ng/ml were considered to have follicular cysts and those with concentrations of 1.0 ng/ml or higher were regarded as the cases of luteal cyst or cystic corpus luteum. Luteal cyst was characterized by progesterone values remaining high in the cows for 10 days after treatment, and cystic corpus luteum was characterized by a decrease in progesterone concentration after cows were treated. By the rectal palpation procedure it was impossible to differentiate luteal cyst and cystic corpus luteum from follicular cyst. The frequencies of follicular cyst, luteal cyst, and cystic corpus luteum were 65%, 19%, and 16%, respectively. Of 104 cows with follicular cysts as defined by milk progesterone assay result, 73 (70%) responded to the treatment with gonadotropin-releasing hormone, the milk progesterone concentration increasing from 0.7 +/- 0.2 ng/ml (mean +/- SD) to 1.8 +/- 1.1 ng/ml. The accuracy of rectal palpation 10 days after treatment for judgment of luteinization of follicular cyst confirmed by milk progesterone analysis was only 30% (48 cows of 160).     

Hormonal and Metabolic Profiles of High-yielding Dairy Cows Prior to Ovarian Cyst formation or First Ovulation Post Partum

The present study aimed to investigate the pathogenesis of cystic ovarian disease (COD) in high-yielding dairy cows postpartum (pp). Hormonal and metabolic profiles during the first 3 weeks pp as well as during the final week prior to ovulation/cyst formation, were compared between dairy cows that developed either an ovulatory follicle (OV) or a cyst (CYST) < day 60 pp. Thirty-four lactations of 28 high-yielding (9500 kg/305 days) Holstein-Friesian dairy cows were studied. Ovaries of cows were scanned twice a week from day 10 pp on, until ovulation/cyst formation. Milk yield data, body condition scores and blood samples, for determination of oestradiol-17beta, insulin, beta-OH-butyrate and non-esterified fatty acids, were collected simultaneously. Milk samples for progesterone analysis were collected daily. Four lactations were excluded from further analysis because of irregular pp ovarian cyclicity, excluding COD. Eight lactations (26.7%) developed a cyst, while 22 lactations ovulated < days 60 pp. Ovulation and cyst formation occurred at similar times pp. Metabolic and hormonal profiles did not differ between CYST and OV lactations during the first 3 weeks pp. In the final week prior to cyst formation/ovulation, insulin concentrations were lower in CYST than in OV lactations while no differences were observed for any of the other parameters tested. In two lactations, cyst formation was preceded by suprabasal progesterone and increased oestradiol-17beta concentrations. These results suggest that cyst formation in high-yielding dairy cows pp is associated with lower insulin levels but not with other distinct hormonal and metabolic alterations. However from this study, we cannot exclude the involvement of subtle hormonal and metabolic changes in the pathogenesis of ovarian cysts. Suprabasal progesterone, and altered oestradiol-17beta concentrations, seem to play a minor role in cyst formation.     

GnRH treatment at CIDR insertion influences ovarian follicular dynamics in Japanese black cows

Ovarian follicular dynamics and estrous synchronization after Gonadotropin-releasing hormone (GnRH) treatment at Controlled Internal Drug Releasing device (CIDR) insertion were investigated in Japanese Black cows. CIDR was inserted for eight cows at 7 days after estrus. Cows were allocated to either Group A: 8-day CIDR insertion with GnRH treatment on d 0 (n=4, d 0=CIDR insertion) or Group B: 8-day CIDR insertion (n=4). Both groups were injected with prostaglandin F2alpha (PGF2alpha) on d 7. Ultrasonography and blood sampling were performed twice daily. Intensive sampling was performed every 15 min for 8 hr to determine the pulsatile release of LH on d -1, d 5 and d 10. Three of four cows showed intermediate ovulation within 2 days after GnRH treatment during CIDR insertion in Group A, whereas no ovulation was found in Group B. Three of four cows in Group A and all four cows in Group B ovulated after CIDR removal. Plasma progesterone concentrations from d 3 to d 7 in three intermediate ovulatory cows in Group A (8.4 +/- 1.6 ng/ml) was significantly higher than those in Group B (4.1 +/- 1.2 ng/ml; 4 cows) during CIDR insertion (P<0.01). Interval to estrus and ovulation after CIDR removal was observed at 60.0 +/- 12.0 hr and 76.0 +/- 6.9 hr in three cows in Group A, and 75.0 +/- 15.1 hr and 93.0 +/- 20.5 hr in Group B, respectively. There was a significant increase in LH pulse frequency on d 10 compared on d -1 or d 5 in both groups (P<0.05), in addition those on d 10 in Group A tended to be higher than in Group B. As a result, GnRH treatment at CIDR insertion at 7 days after estrus induced intermediate ovulation with formation of corpus luteum (CL) and rather synchronized emergence of ovulatory follicle during CIDR insertion. These induced CL increased plasma progesterone concentrations and contributed to precise synchronization.     

Effect of follicular aspiration at the onset of progesterone-based timed artificial insemination on the follicular dynamics and fertility of early postpartum Japanese black cows

The effect of gonadotropin-releasing hormone analogue (GnRH-A) or follicular aspiration at the onset of progesterone-based timed artificial insemination (TAI) on subsequent follicular growth and synchronization of ovulation was examined in early postpartum Japanese Black cows. A total of 40 (22 in Exp. 1 and 18 in Exp. 2) Japanese Black cows at 20-30 days postpartum were fitted with a progesterone releasing internal device (PRID) for 7 days, injected with a prostaglandin F2α analogue upon removal of the PRID and GnRH-A 48 h later, and inseminated 18 h after GnRH-A injection. In Exp. 1, the animals were divided into three groups (untreated control, GnRH-A injection or follicular aspiration) of different treatments on the first day of PRID insertion (day 0), and the synchronized ovulation rate in the follicular aspiration group (100%; 8/8) tended to be higher (P = 0.077) than that in the control group (42.9%; 3/7). In Exp. 2, follicular growth in the GnRH (n = 9) and follicular aspiration (n = 9) groups was monitored by ultrasonography. Four out of the nine animals in the GnRH group had a corpus luteum on either day 4 or day 7 (OV group), and the other five animals had no induced ovulation (NOV group). The diameter of the ovulatory follicle on day 9 in the OV group (1.44 ± 0.11 cm) tended to be greater (P = 0.078) than that in the NOV group (1.13 ± 0.07 cm). Follicular aspiration at the onset of PRID-based TAI of early postpartum Japanese Black cows, regardless of the resumption of ovarian cyclicity, tended to result in a higher rate of synchronization of ovulation than that of the untreated controls.     

Ovarian and endocrine responses associated with the treatment of cystic ovarian follicles in dairy cows with gonadotropin releasing hormone and prostaglandin F2alpha, with or without exogenous progesterone

The objectives of this observational study were to document ovarian and endocrine responses associated with the treatment of cystic ovarian follicles (COFs) in dairy cows, using gonadotropin releasing hormone (GnRH) and prostaglandin F2alpha (PGF) with or without exogenous progesterone. A secondary objective was to determine pregnancy establishment following synchronization of ovulation and timed insemination in cows diagnosed with COFs. In trial I, 18 Holstein cows diagnosed with COFs received 2 injections of 100 microg GnRH, 9 d apart, with 25 mg PGF given 7 d after the 1st GnRH. A new follicle developed in all 18 cows after the 1st GnRH, and 83% of cows ovulated following the 2nd GnRH. Cows were inseminated 16 h after the 2nd GnRH. Of the 17 cows available for pregnancy diagnosis, 7 were confirmed pregnant. In trial II, 8 cows with COFs received GnRH and an intravaginal progesterone device (CIDR) concurrently, then PGF 7 d later. The CIDR was removed 2 d after PGF administration. Plasma estradiol concentrations declined following CIDR insertion. In all cows, a new follicle developed following GnRH treatment; estradiol-surge and estrus occurred spontaneously after CIDR-removal. Seven of 8 cows ovulated the new follicle. In dairy cows diagnosed with COFs, treatment with GnRH followed by PGF 7 d later, with or without exogenous progesterone, resulted in the recruitment of a healthy new follicle; synchronization of ovulation and timed insemination resulted in a 41% pregnancy rate.     

Factors Affecting Synchronization and Conception Rate after the Ovsynch Protocol in Lactating Holstein Cows

Objectives were to evaluate risk factors affecting ovulatory responses and conception rate to the Ovsynch protocol. Holstein cows, 466, were submitted to the Ovsynch protocol [day 0, GnRH‐1; day 7, prostaglandin (PG) F_2α; day 9, GnRH‐2] and 103 cows were inseminated 12 h after GnRH‐2. Information on parity, days in milk at GnRH‐1, body condition, milk yield, exposure to heat stress, pre‐synchronization with PGF_2α and the use of progesterone insert from GnRH‐1 to PGF_2α was collected. Ovaries were scanned to determine responses to treatments. Overall, 54.7%, 10.6%, 2.2%, 81.1%, 9.0%, 91.5% and 36.9% of the cows ovulated to GnRH‐1, multiple ovulated to GnRH‐1, ovulated before GnRH‐2, ovulated to GnRH‐2, multiple ovulated to GnRH‐2, experienced corpus luteum (CL) regression and conceived, respectively. Ovulation to GnRH‐1 was greater in cows without a CL at GnRH‐1, cows with follicles >19 mm and cows not pre‐synchronized with PGF_2α 14 days before GnRH‐1. Multiple ovulations to GnRH‐1 increased in cows without CL at GnRH‐1 and cows with follicles ≤19 mm at GnRH‐1. Ovulation before GnRH‐2 was greater in cows without CL at PGF_2α. Ovulation to GnRH‐2 increased in cows that received a progesterone insert, cows with a CL at GnRH‐1, cows with follicles not regressing from the PGF_2α to GnRH‐2, cows with larger follicles at GnRH‐2, cows that ovulated to GnRH‐1 and cows not pre‐synchronized. Multiple ovulations after GnRH‐2 increased in cows with no CL at GnRH‐1, multiparous cows and cows that multiple ovulated to GnRH‐1. Conception rate at 42 days after AI increased in cows with body condition score > 2.75 and cows that ovulated to GnRH‐2. Strategies that optimize ovulation to GnRH‐2, such as increased ovulation to GnRH‐1, should improve response to the Ovsynch protocol.     

Clinical response of ovarian cysts in dairy cows after PRID treatment

We investigated the therapeutic effects of a progesterone releasing intravaginal device (PRID) on cystic ovarian disease (COD) and reproduction performance of cows. The possible influence of PRID on metabolic and/or health status was also examined. A total of 40 Holstein-Friesian cattle, with ovarian cystic structures, > or =2.5 cm in diameter, persisting for more than 7-14 days, without a corpus luteum (CL) were used for the study. PRID or placebos were inserted into the vagina for 12 days. Five animals lost the intravaginal device before removal and one was culled. Based on plasma progesterone concentration on the day of treatment, 20 (17 PRID and 3 placebos) of the remaining 34 cows had follicular cysts (progesterone < or =1 ng/ml) and 14 (10 PRID and 4 placebos) had luteal cysts (progesterone >1 ng/m l). Fourteen (82%) of the PRID-treated follicular cystic cows responded with formation of a CL within 14 days after treatment, and an overall conception rate of 53.8%. Likewise, 70% of the treated luteal cystic cows responded with CL formation and 71.4% conception rate. No significant differences were observed in hematocrit (Ht), white blood cell count and serum levels of glucose, blood urea nitrogen, aspartate aminotransferase, and alanine aminotransferase, between the day of PRID insertion and removal, in animals with follicular and luteal cysts. PRID treatment resulted in ovulation 2-4 days later and formation of a CL in cows that recovered.     

Changes in the peripheral concentrations of inhibin, follicle-stimulating hormone, luteinizing hormone, progesterone and estradiol-17beta during turnover of cystic follicles in dairy cows with spontaneous follicular cysts

Several studies have clarified that the follicular cysts degenerate and are replaced by newly growing follicles that develop into new follicular cysts without ovulation, i.e., turnover of ovarian follicular cysts in cows. However, the relativity of endocrinological changes, including the inhibin profile during turnover of spontaneous follicular cysts in dairy cows, is still unclear. In the present study, the relationship between turnover of follicular cysts and changes in the peripheral blood concentrations of progesterone (P), estradiol-17beta (E(2)), luteinizing hormone (LH), follicle stimulating hormone (FSH) and inhibin were examined in lactating dairy cows. Five cows diagnosed with follicular cysts (follicles of more than 25 mm in diameter in the absence of a corpus luteum) were investigated. Their ovarian dynamics were monitored using ultrasonography, and blood samples were collected at 2- or 3- day intervals throughout the experiment. The day when a follicle fated to become a follicular cyst reached more than 8 mm in diameter was defined as the start of a cystic follicular wave. Four of the 5 cows exhibited a similar patterns of cystic follicular changes and hormone profiles. The data from the 4 cows was used for analysis of the relationships between turnover of cystic follicles and the hormone profiles. Two or three new cystic follicular waves occurred in each cow during the experimental period. The mean diameter of the cystic follicles was more than 25 mm 13 to 15 days after the start of the cystic follicular wave, and it began to decrease 1 to 6 days before the start of the subsequent cystic follicular wave. The levels of E(2) and inhibin tended to decrease for 7 to 9 days before the start of a new cystic follicular wave and to increase concomitantly with new follicular cyst growth. The levels of FSH rose for 1 to 3 days before the start of a new cystic follicular wave. The present study clarified the relationship between FSH and inhibin during turnover of spontaneous follicular cysts in dairy cows and found that it was very similar to previous results for cows. The present results suggest that an increase in FSH secretion following a reduction in inhibin secretion triggers turnover of cystic follicles in cows with spontaneous follicular cysts.     

Comparison of the effectiveness of ovulation synchronization protocol in anestrous and cycling beef cows

Applicability of ovulation synchronization protocol using GnRH and PGF(2alpha) (PGF) injection to anestrous beef cows remains controversial. We compared the effectiveness of the protocol in the anestrous stage of the beef cow with that in the cycling stage using the same animals. Ovaries of five Japanese Black and three Japanese Shorthorn cows were ultrasonographically examined, and blood samples were collected daily for hormonal analyses. Each animal received the protocol twice (Day -6 to -8: GnRH, Day 0: PGF, Day 2: GnRH). Additional blood samples were taken before and after GnRH injection for LH and FSH measurements to evaluate the pituitary function. For the ovarian status at the onset of the protocol cows were divided into anestrous (n=8) and cycling (n=8) stages. There was no significant difference in size of the dominant follicle at the first and second GnRH injections, and in the magnitude of the pituitary response to GnRH between the two stages. However, the size of the corpus luteum and progesterone concentrations at the PGF injection in the anestrous stage were significantly smaller and lower (P<0.01), respectively, and ovulation synchronization rate in the anestrous stage was significantly lower (P<0.05) than in the cycling stage. In conclusion, ovulation synchronization protocol in anestrous beef cows has limited effectiveness.     

The effect of GnRH or oestradiol injected at pro-oestrus on luteal function and follicular dynamics of the subsequent oestrous cycle in non-lactating cycling Holstein cows

Oestrous synchronization involves synchronization of ovarian follicular turnover, new wave emergence, and finally induction of ovulation. The final step can be synchronized by the parenteral administration of either GnRH or oestradiol benzoate. This study investigated corpus luteum and follicular emergence after ovulation had been induced by the administration of either GnRH or oestradiol benzoate. The injection of oestradiol benzoate may have delayed the emergence of the first follicular wave subsequent to the induced ovulation; administration of oestradiol benzoate or GnRH lowered the progesterone rise so that the maximum dioestrous concentration of progesterone on Day 9 was lower when cows were treated during pro-oestrus compared to the spontaneously ovulating controls. One implication of findings from the present study is that induction of ovulation with either oestradiol benzoate or GnRH, administered 24 or 36 h after withdrawal of the CIDR device, respectively, may lower fertility. Future studies must identify the timing of administration relative to the time of CIDR device withdrawal and the optimum concentration of oestradiol benzoate or GnRH that would not have untoward effects on the development of the corpus lutea, particularly within the first week of dioestrus.     

Administration of human chorionic gonadotropin to suckled beef cows before ovulation synchronization and fixed-time insemination: replacement of gonadotropin-releasing hormone with human chorionic gonadotropin

Two experiments were conducted to evaluate whether hCG administered 7 d before initiating the CO-Synch + controlled internal drug release (CIDR) ovulation synchronization protocol (Exp. 1 and 2), or replacing GnRH with hCG at the time of AI (Exp. 1), would improve fertility to a fixed-time AI (TAI) in suckled beef cows. In addition, the effects of hCG on follicle dynamics, corpus luteum development, and concentrations of progesterone (P4) were evaluated. In Exp. 1, cows were stratified by days postpartum, age, and parity and assigned randomly to a 2 × 2 factorial arrangement of 4 treatments: 1) cows received 100 μg of GnRH at CIDR insertion (d -7) and 25 mg of PGF(2α) at CIDR removal (d 0), followed in 64 to 68 h by a TAI plus a second injection of GnRH at TAI (CG; n = 29); 2) same as CG but the second injection of GnRH at the time of insemination was replaced by hCG (CH; n = 28); 3) same as CG, but cows received hCG 7 d (d -14) before CIDR insertion (HG; n = 28); and 4) same as HG, but cows received hCG 7 d (d -14) before CIDR insertion (HH; n = 29). Pregnancy rates were 52, 41, 59, and 38% for GG, GH, HG, and HH, respectively. Cows receiving hCG (39%) in place of GnRH at TAI tended (P = 0.06) to have poorer pregnancy rates than those receiving GnRH (56%). Pre-CO-Synch hCG treatment increased (P < 0.05) the percentage of cows with concentrations of P4 >1 ng/mL at d -7, increased (P < 0.02) concentration of P4 on d -7, and decreased (P < 0.001) the size of the dominant follicle on d 0 and 3, compared with cows not treated with hCG on d -14. In Exp. 2, cows were stratified based on days postpartum, BCS, breed type, and calf sex and then assigned to the CG (n = 102) or HG (n = 103) treatments. Overall pregnancy rates were 51%, but no differences in pregnancy rates were detected between treatments. Pre-CO-Synch hCG treatment increased (P < 0.05) the percentage of cows cycling on d -7 and increased (P < 0.05) concentrations of P4 on d -7 compared with pre-CO-Synch controls. Therefore, pretreatment induction of ovulation after hCG injection 7 d before initiation of CO-Synch + CIDR protocol failed to enhance pregnancy rates, but replacing GnRH with hCG at the time of AI may reduce pregnancy rates.     

Effects of Gn-RH on blood serum hormone concentrations, ovulation rates and embryo production in lactating cows treated with PMSG.

The effects of gonadotrophin releasing hormone injection into pregnant mare serum gonadotrophin treated cows on serum levels of luteinizing hormone, estradiol-17 beta and progesterone and ovulation rates was evaluated in 20 cows. Pregnant mare serum gonadotrophin treatment does not always induce superovulation as was shown in this study. Luteinizing hormone levels reached peak concentrations at 1.0 h and remained significantly (P less than or equal to 0.05) elevated at 2.0 h, 3.0 h, 4.0 h, and 7.0 h after the first gonadotrophin releasing hormone injection. Progesterone levels in the gonadotrophin releasing hormone treated group were significantly (P less than or equal to 0.05) higher than in the controls on the third and fourth days following injection. A significant correlation (r = 0.58-0.72) was noted between the number of corpus luteum and progesterone levels on each day between day 2 and day 7. More embryos were recovered (46 vs 26) from the ten treated than from the ten control cows.     

Hypoxia-inducible factor-1alpha and nitric oxide synthases in bovine follicles close to ovulation and early luteal angiogenesis

The objective of the study was to characterize expression patterns of hypoxia-inducible factor-1alpha (HIF1A), inducible nitric oxide synthase (iNOS) and endothelial (eNOS) isoforms in time-defined follicle classes before and after GnRH application in the cow. Ovaries containing pre-ovulatory follicles or corpora lutea were collected by transvaginal ovariectomy (n = 5 cows/group) as follow: (I) before GnRH administration; (II) 4h after GnRH; (III) 10h after GnRH; (IV) 20h after GnRH; (V) 25h after GnRH; and (VI) 60h after GnRH (early corpus luteum). The mRNA abundance of HIF1A in the follicle group before GnRH was high, followed by a significant down regulation afterwards with a minimum level 25h after GnRH (close to ovulation) and significant increase only after ovulation. The mRNA abundance of iNOS before GnRH was high, decreased significantly during LH surge, with minimum levels afterwards. In contrast, the mRNA of eNOS decreased in the follicle group 20h after GnRH, followed by a rapid and significant upregulation just after ovulation. Immunohistochemically, the granulosa cells of antral follicles and the eosinophils of the theca tissue as well of the early corpus luteum showed a strong staining for HIF1A. The location of the eosinophils could be clearly demonstrated by immunostaining with an eosinophil-specific antibody (EMBP) and transmission electron microscopy. In conclusion, the parallel and acute regulated expression patterns of HIF1A and NOS isoforms, specifically during the interval between the LH surge and ovulation, indicate that these paracrine factors are involved in the local mechanisms, regulating final follicle maturation, ovulation and early luteal angiogenesis.     

Evaluation of the effect of a 3rd GnRH injection administered six days after the 2nd GnRH injection of Ovsynch on the reproductive performance of Japanese black cows

This study was designed to evaluate the reproductive performance of Japanese black cows following the 3rd injection of gonadotropin releasing hormone (GnRH) analogue administered concurrently with Ovsynch-based treatment on day 6 (day 1 = the day of ovulation). In Experiment 1, 12 cows were allocated into three groups: a control group that was subjected to Ovsynch treatment and then injected with a placebo on day 6; group 1 (Ovsynch + GnRH), which was subjected to Ovsynch treatment and was injected with GnRH analogue on day 6, and group 2 (Ovsynch + controlled internal drug-release (CIDR) + GnRH), which received Ovsynch-CIDR treatment and was injected with GnRH analogue on day 6. Blood collection and ultrasonographic observation of the ovaries were conducted daily. Both treatments induced the formation of an accessory corpus luteum and significantly increased the cross-sectional area of the luteal tissue when compared to the control. However, plasma progesterone (P₄) was significantly higher in the treatment groups than in the control group on days 11, 12, 17 and 18 in the group 1 and from day 10 to 21 in the group 2. In Experiment 2, 41 cows were assigned to the same three groups described above and then artificially inseminated on day 1. The pregnancy rates on day 45 did not differ among groups. In conclusion, administration of GnRH analogue on day 6 following Ovsynch-based treatment did not improve the reproductive performance of Japanese black cows, even though the P₄ concentration was higher in groups that received the GnRH.