Effects of monoclonal antibody against PMSG administered shortly after the preovulatory LH surge on time and number of ovulations in PMSG/PG-treated cows

Normally cyclic heifers received 2500 i.u. PMSG i.m. at Day 10 of the oestrous cycle and 15 mg prostaglandin (PG) i.m. 48 h later. From 30 h after PG the LH concentration in the peripheral blood was estimated every hour using a rapid RIA method which allowed the LH concentration to be known within 4 h. Monoclonal antibody against PMSG was injected in the jugular vein of 29 heifers at 4.8 h after the maximum of the preovulatory LH peak; 28 heifers were not treated with anti-PMSG (controls). Peripheral blood concentrations of PMSG, LH, progesterone and oestradiol were compared. Ovaries were collected by ovariectomy at fixed times, 22-30 h after the LH peak, and numbers were counted of small (2-10 mm), large (greater than 10 mm) and ovulated follicles, and of follicles with a stigma. In anti-PMSG-treated cows, the PMSG concentration fell sharply to non-detectable levels within 2 h of the treatment, indicating that PMSG was neutralized in these cows at the onset of final follicular maturation. In all cows, the concentration of oestradiol showed a significant decrease at about 8 h after the LH peak. After anti-PMSG treatment ovulations took place from 24 until 30 h after the LH peak, whereas in control cows follicles had already ovulated at or before 22 h and ovulations continued until 30 h. At 30 h 90% of the follicles had ovulated in anti-PMSG-treated cows vs 72% in the controls, resulting in 15 and 8 ovulations per cow respectively (P less than 0.05). Also, administration of monoclonal antibody against PMSG synchronized final follicular maturation and shortened the period of multiple ovulations. In conclusion, neutralization of PMSG shortly after the preovulatory LH peak suppresses adverse effects of PMSG on final follicular maturation, leading to an almost 2-fold increase of the ovulation rate.     

Superovulation and embryo quality in beef cows using PMSG and a monoclonal anti-PMSG

The long half-life of pregnant mare serum gonadotrophin (PMSG) reduces its application in the superovulation of cattle; thus, a monoclonal antibody to PMSG (anti-PMSG) was administered at the onset of estrus to increase the number of transferable embryos. Angus, Hereford and Angus x Hereford cows (n = 149) 3 to 9 yr old were assigned randomly to one of three dosages of PMSG (1500, 3000 or 6000 IU) with or without an equivalent dosage of anti-PMSG. Embryos were collected nonsurgically on Day 8 (estrus = Day 0), and all cows were ovariectomized on Day 9. The percentage of cows exhibiting estrus and ovulating decreased (P<0.05) with an increasing dosage of PMSG (82, 76 and 44% for 1500, 3000 and 6000 IU, respectively). Ovarian and total corpora lutea (CL) weight increased (P<0.001) linearly as PMSG dosage increased, but were reduced (P<0.001) curvilinearly by anti-PMSG, resulting in a PMSG by anti-PMSG interaction (P<0.001); the interaction was also significant (P<0.05) for ovulation rate (14.0 vs 14.3, 21.5 vs 24.4 and 29.2 vs 6.6 CL for 1500, 3000 and 6000 IU PMSG, without vs with anti-PMSG, respectively). Anti-PMSG increased (P<0.001) the number of small ovarian follicles (1 to 3 mm diameter) and decreased (P<0.001) the number of large follicles (>10 mm) at ovariectomy; the number of large follicles increased (P<0.001) with PMSG dosage. The number of total and transferable embryos recovered did not differ among PMSG and anti-PMSG dosages; however, the percentage of transferable embryos decreased (P<0.01) with increasing PMSG dosage. In general, neither PMSG dosage nor anti-PMSG influenced embryo quality.     

Changes in pulsatile secretion patterns of LH, FSH, progesterone, androstenedione and oestradiol in cows after superovulation with PMSG

Six heifers were injected i.m. with 2500 i.u. PMSG followed by 15 mg prostaglandin 48 h later. Serial blood samples were collected through a catheter in the caudal vena cava every 10 min for 8 h on Day 10 (7 h after PMSG administration), during luteal regression (7 h after prostaglandin administration) and on the day thereafter. Four normally cyclic heifers served as a control group. Concentrations of progesterone, androstenedione, oestradiol, LH, FSH, and PMSG in the vena cava samples were measured and the frequency and amplitudes of episodic pulses of all hormones were estimated except for PMSG. Ovaries were collected by ovariectomy at 50 h after onset of luteal regression to determine the number of preovulatory follicles (non-atretic follicles greater than or equal to 10 mm). Stimulation of follicular growth by administration of PMSG resulted in the following effects on the secretion of steroids and endogenous gonadotrophins. (1) There were no alterations in progesterone concentration and the amplitude and frequency of episodic pulses. Mean (+/- s.e.m.) concentrations were 54.1 +/- 5.8, 19.1 +/- 3.1 and 3.4 +/- 0.9 nmol/l on Day 10 (L), during luteal regression (LR) and on the day thereafter (F) respectively. (2) There were no alterations in the episodic secretion patterns of androstenedione. Mean concentrations were 0.20 +/- 0.02, 0.15 +/- 0.02 and 0.11 +/- 0.02 nmol/l for the L, LR and F periods respectively. (3) There was an increase in oestradiol concentration from 17.1 +/- 3.0 pmol/l during the L period to 233.7 +/- 86.4 pmol/l during the F period. Pulse amplitude was enhanced compared to corresponding periods in control animals whereas pulse frequency remained the same. The oestradiol concentration was significantly correlated with the number of preovulatory follicles (r = 0.82, P less than 0.05). (4) There was a suppression of the frequency of episodic LH pulses (/8 h) during the LR (3.2 +/- 0.7) and F (4.3 +/- 0.4) periods compared to corresponding periods in control heifers (9.5 +/- 0.9 and 7.0 +/- 1.5 respectively). The preovulatory LH peak occurred earlier in 4 of 6 treated heifers. (5) There was a suppression of FSH concentrations, pulse amplitude and frequency during the LR and F (17.4 +/- 0.9 mg/l, 4.7 +/- 0.8 microgram/l and 7.5 +/- 0.4 pulses/8 h) periods compared to the corresponding F-period values (35.6 +/- 6.2 mg/l, 9.8 +/- 1.6 micrograms/l and 9.3 +/- 0.3 pulses/8 h) in control heifers.(ABSTRACT TRUNCATED AT 400 WORDS)     

Progesterone-synthesizing ability of preovulatory follicles of cows relative to the peak of LH

Preovulatory cow follicles (n = 34) were collected at different times after the onset of oestrus until shortly before ovulation. In-vitro conversion of tritiated pregnenolone in the presence of NAD+ by homogenates of the follicular wall was compared in phases relative to the LH peak. During phase 0 (before the LH surge) a moderate conversion into progesterone occurred, but it was subsidiary to that into 17 alpha-hydroxypregnenolone and other unidentified steroids. During phases 1 (0-6 h after the LH peak), 2A (6-14 h) and 2B (14-20 h) the production of progesterone and 17 alpha-hydroxypregnenolone remained constant; at phase 2B the percentage of remaining pregnenolone was higher than in the preceding phases. In phase 3 (20 h after the LH peak until ovulation) conversion into progesterone had increased about 4-fold to the highest levels observed (97% after 2 h incubation), and production of 17 alpha-hydroxypregnenolone and unidentified steroids was low. In an additional experiment, homogenates of the wall of 3 follicles at phase 3 were also incubated with tritated progesterone in the presence of NADPH. The percentage of remaining progesterone was high, and a moderate conversion into 17 alpha-hydroxyprogesterone occurred. In the main experiments, however, production of this steroid was not observed. The results indicate that steroid synthesis in the preovulatory follicle of the cow changes to the production of progesterone shortly before ovulation.     

Embryo production and endocrine response in ewes superovulated with PMSG, with or without monoclonal anti-PMSG administered at different times

Mature nonlactating Altamurana ewes (n = 168) were synchronized in the seasonal anestrus period with FGA-impregnated intravaginal pessaries for 12 d. In Experiment 1, 48 ewes were divided into a 3 x 4 factorial design for anti-PMSG monoclonal antibody (AP) bioassay test. Concomitant injections of PMSG (1000, 1500, 2000 IU) and AP (0, 1, 2, 3 microl/IU PMSG) were given, and ovarian response was evaluated by laparoscopy. In Experiment 2, 120 ewes were divided into 8 experimental groups (n = 15 per group). The ewes treated with 1000 or 1500 IU PMSG at -24 h from sponge removal were given AP intravenously at 50 h after pessary withdrawal, 12 or 24 h after the onset of estrus, while the controls did not receive AP. Blood samples were collected from ewes (n = 6) treated with 1500 IU PMSG with or without anti-PMSG. Ovarian response and embryo production were evaluated on Day 7 after sponge removal upon laparotomy. It was found that 1 microl AP was effective in neutralizing 1 IU PMSG. No significant differences in serum concentrations of progesterone were observed among the groups of superovulated ewes. Estradiol-17 beta levels were reduced following AP treatment 12 h after the onset of estrus. At a lower dosage of superovulatory treatment (1000 IU PMSG), AP injected at 12 or 24 h after the onset of estrus significantly lowered large follicles (P < 0.01) and increased the rate of ovulation (P < 0.05). Moreover, embryo production showed a more than two-fold increase (P < 0.01) of viable embryos following AP injection at 12 or 24 h after the onset of estrus (3.2 to 3.3 vs 1.3, with vs without anti-PMSG). It is concluded that superovulatory treatment with 1000 IU PMSG plus AP administered at a fixed time after the onset of estrus may improve ovarian response and the yield of viable embryos in ewes.     

Pattern of sex steroids secretion and their relationship with embryo yield in Jersey cows superovulated with PMSG

The levels of progesterone and estrogen secretion were studied in relationship to the superovulatory response in Jersey cows. Progesterone and estrogen concentrations were measured in superovulated Jersey cows with the objective of correlating the patterns of steroid secretion with embryo yield and quality. Pregnant mare serum gonadotropin (PMSG) was used in combination with prostaglandin F(2) alpha analogue to induce superovulation in 18 multiparous, cyclic cows. Serum progesterone and estradiol levels from cows which exhibited estrus within 24 to 48 h after prostaglandin administration (n=13) were used to estimate the superovulatory response. Sex steroid concentrations at the day of estrus (Day 0) was a strong indicator of embryo yield. Progesterone was negatively (r=-0.56) and estrogen positively (r=0.80) correlated to the number of embryos collected. Dramatic increase in progesterone from Day 0 to Day 7 was a significant indicator of embryo yield. A higher rise of estrogen in the follicular phase was an indicator of a larger number of growing follicles and, consequently, better superovulatory response. Nonresponding animals did not show any significant change in the hormonal profile from the day of PMSG treatment to the day of embryo collection. The estimation of progesterone and estradiol concentrations, simultaneously, gave a more objective prediction of embryo yield.     

Recovery rate and quality of embryos collected from suckled cows and beef heifers after superovulation with PMSG

Recovery rate and embryo quality were investigated in beef heifers and suckled cows following superovulation induced by 2000 IU pregnant mare serum (PMSG) combined with different methods of estrus cycle synchronization (Norgestomet, Prid, Dinolytic, Norgestomet combined with Dinolytic). Genital tracts were flushed upon slaughter with Dulbecco's medium 6.5 to 7.5 days after insemination. Of the heifers, 42 out of 43 responded to treatment. The mean embryo recovery rate, based on the number of corpora lutea, was only 14.8%. Of the 83 embryos recovered, 54.2% had developed to the expected stage and only 40% appeared normal. Of the adult cows, 55 out 58 responded with an embryo recovery rate of 39.5%. Of the 149 embryos recovered, 48.9% had developed to the expected stage and 67.1% of these appeared normal. In both heifers and adult cows, the different methods of estrus synchronization produced no significant differences in recovery rate or embryo quality.     

Effects of progestagen treatments and PMSG on the induction of the preovulatory LH discharge in ewes

The characteristics of the induced preovulatory LH discharge were compared in ewes after treatment for 12 days with intravaginal sponge pessaries impregnated with 40 mg Fluorogestone Acetate or with subcutaneous ear implants containing varying quantities of Norgestomet. In Experiment 1, ewes were treated with intravaginal sponges or implants alone. In Experiment 2, ewes received similar treatments and 500 IU pregnant mares' serum gonadotropin (PMSG) i.m. at the time of sponge or implant removal. The duration of the LH discharge and an estimate of the total LH discharged were similar among treatment groups within the same experiment. Overall, the onset of LH release occurred approximately 8 h earlier in ewes treated with implants, whether or not PMSG was used. Use of PMSG, in conjunction with implant or sponge treatments, shortened the mean interval from sponge or implant removal to the onset of LH release from 41 to 28 h and doubled the estimated total LH discharged, compared with treatments using sponges or implants alone.     

LH and FSH profiles at superovulation and embryo production in the cow

The variability of the superovulation response in cattle is an important problem to the commercial embryo transfer industry. Plasma LH and FSH concentrations around the time of estrus and ovulation were studied in relation to embryo production, to try and elucidate this problem. Sixteen cows were superovulated with 38 mg FSH-P and estrus synchronized with prostaglandin F(2) alpha. On the third and fourth day of superovulation increases in plasma LH but not FSH were detected. The LH and FSH profiles appeared to be normal in the size of the surge but in many cases they were were abnormal in timing. Transferable embryo production appeared to be lower in cows in which the LH and FSH surges were not coincident, and in cows where the surges were early or late with reference to estrus. FSH appeared to be primarily responsible for the number of embryos produced and LH for their quality, i.e. the number transferable.     

Endocrine responses of goats after induction of superovulation with PMSG and FSH

Goats in Group A were pretreated for 9 days with a synthetic progestagen, administered via intravaginal sponge, and 1000 i.u. PMSG s.c. on Day 12 of the oestrous cycle. Goats in Group B had the same PMSG treatment, but not the progestagen pretreatment. Group C goats received a s.c. twice daily injection of a porcine FSH preparation (8 mg on Day 12, 4 mg Day 13, 2 mg Day 14 and 1 mg Day 15). Oestrus was synchronized in all animals by 50 micrograms cloprostenol, 2 days after the start of gonadotrophin treatment. The vaginal progestagen sponges were removed from Group A at the same time. Mean ovulation rate was slightly higher in FSH-treated than in the PMSG-treated animals, whereas the incidence of large follicles that failed to ovulate was significantly elevated in PMSG-treated animals in Group B. More goats in Groups A and B than in Group C exhibited premature luteal failure. Progestagen pretreatment appeared to suppress both follicular and luteal activity, as indicated by numbers of large non-ovulating follicles and by the magnitude and duration of elevated plasma oestradiol levels following PMSG stimulation, and by decreased plasma progesterone levels before and after PMSG treatment. Oestrogenic response to FSH was considerably less than that to PMSG, as indicated both by a considerably shorter duration of elevation of circulating oestradiol levels during the peri-ovulatory period, and by lower maximal oestradiol levels. Differences in the ovarian responses to PMSG and FSH may be attributed primarily to differences in the biological half-life of each preparation.     

Improved in vitro embryo development using in vivo matured oocytes from heifers superovulated with a controlled preovulatory LH surge

In bovine in vitro embryo production, the IVM step is rather successful with 80% of the oocytes reaching the MII stage. However, the extent to which the process limits the yield of viable embryos is still largely unknown. Therefore, we compared embryonic developmental capacity during IVC of IVF oocytes which had been matured in vitro with those matured in vivo. In vitro maturation was carried out for 22 h using oocytes (n = 417) obtained from 2- to 8-mm follicles of ovaries collected from a slaughterhouse in M199 with 10% fetal calf serum (FCS), 0.01 IU/mL LH, and 0.01 IU/mL FSH. In vivo matured oocytes (n = 219) were aspirated from preovulatory follicles in eCG/PG/anti-eCG-superovulated heifers 22 h after a fixed time GnRH-induced LH surge; endogenous release of the LH surge was suppressed by a Norgestomet ear implant. This system allowed for the synchronization of the in vitro and in vivo maturation processes and thus for simultaneous IVF of both groups of oocytes. The in vitro developmental potential of in vivo matured oocytes was twice as high (P < 0.01) as that of in vitro matured oocytes, with blastocyst formation and hatching rates 11 d after IVC of 49.3 +/- 6.1 (SEM; n = 10 heifers) vs 26.4 +/- 1.0% (n = 2 replicates), and 39.1 +/- 5.1% vs 20.6 +/- 1.4%, respectively. It is concluded that IVM is a major factor limiting in the in vitro production of viable embryos, although factors such as the lack of normal preovulatory development of IVM oocytes contributed to the observed differences.     

The effects of superovulation of donor sows on ovarian response and embryo development after nonsurgical deep-uterine embryo transfer

This study aimed to evaluate the effectiveness of superovulation protocols in improving the efficiency of embryo donors for porcine nonsurgical deep-uterine (NsDU) embryo transfer (ET) programs. After weaning (24 hours), purebred Duroc sows (2–6 parity) were treated with 1000 IU (n = 27) or 1500 IU (n = 27) of eCG. Only sows with clear signs of estrus 4 to 72 hours after eCG administration were treated with 750 IU hCG at the onset of estrus. Nonhormonally treated postweaning estrus sows (n = 36) were used as a control. Sows were inseminated and subjected to laparotomy on Days 5 to 6 (Day 0 = onset of estrus). Three sows (11.1%) treated with the highest dosage of eCG presented with polycystic ovaries without signs of ovulation. The remaining sows from nonsuperovulated and superovulated groups were all pregnant, with no differences in fertilization rates among groups. The number of CLs and viable embryos was higher (P < 0.05) in the superovulated groups compared with the controls and increased (P < 0.05) with increasing doses of eCG. There were no differences among groups in the number of oocytes and/or degenerated embryos. The number of transferable embryos (morulae and unhatched blastocysts) obtained in pregnant sows was higher (P < 0.05) in the superovulated groups than in the control group. In all groups, there was a significant correlation between the number of CLs and the number of viable and transferable embryos, but the number of CLs and the number of oocytes and/or degenerated embryos were not correlated. A total of 46 NsDU ETs were performed in nonhormonally treated recipient sows, with embryos (30 embryos per transfer) recovered from the 1000-IU eCG, 1500-IU eCG, and control groups. In total, pregnancy and farrowing rates were 75.1% and 73.2%, respectively, with a litter size of 9.4 ± 0.6 piglets born, of which 8.8 ± 0.5 were born alive. There were no differences for any of the reproductive parameters evaluated among groups. In conclusion, our results demonstrated the efficiency of eCG superovulation treatments in decreasing the donor-to-recipient ratio. Compared with nonsuperovulated sows, the number of transferable embryos was increased in superovulated sows without affecting their quality and in vivo capacity to develop to term after transfer. The results from this study also demonstrate the effectiveness of the NsDU ET procedure used, making possible the commercial use of ET technology by the pig industry.     

Changes in oestrogen-synthesizing ability of preovulatory bovine follicles relative to the peak of LH

Preovulatory bovine follicles (n = 28) were collected at different times after the onset of standing oestrus until shortly before ovulation. In-vitro conversion of tritiated androstenedione in the presence of NADPH by homogenates of the follicular wall was compared in phases relative to the LH peak. During phase 0 (before the LH surge) conversion into oestradiol-17 beta was high and production of oestrone was about 8-fold lower. During phases 1 (0-6 h after the LH peak) and 2A (6-14 h after the LH peak) the production of oestradiol and oestrone remained constant; the percentage of remaining androstenedione increased. In phase 2B (14-20 h after the LH peak) conversion into oestradiol and oestrone had decreased to about one third correlating with a higher percentage of remaining androstenedione. In phase 3 (20 h after the LH peak until ovulation) conversion into oestradiol and oestrone remained constant. The ratio between the production of oestrone and oestradiol remained constant throughout the phases of preovulatory development (0.13), indicating a concurrent inhibition of aromatase and 17 beta-hydroxysteroid dehydrogenase activities. Conversion into 19-hydroxyandrostenedione showed a pattern similar to that of oestradiol, and testosterone was produced in minute quantities. The results indicate that in preovulatory bovine follicles eventual inhibition of aromatization takes place at about 14 h after the preovulatory LH peak.     

Effects of superovulation on endogenous LH secretion in cattle, and consequences for embryo production

Stimulation of follicular growth during superovulation is achieved by the injection of FSH or compounds with high FSH-bioactivities. However, some LH-activity is required for follicle maturation. It is of relevance to evaluate, therefore, the effect of superovulatory treatments on endogenous LH secretion. Luteinizing hormone is secreted in discrete pulses, and the pattern of pulsatile LH secretion during superovulation is reviewed. Four of five published studies have shown that LH pulse frequency is significantly reduced by injection of eCG or FSH preparations. This suppression appears within 8 h of treatment Effects of superovulation on LH pulse amplitude are less consistent. The reasons for the decrease in pulse frequency have been investigated, and although the answer is not definitive, it would seem that increased follicular estradiol, acting perhaps in synergism with progesterone, may play a role. Changes in plasma progesterone concentrations are not related to changes in LH pulse frequency. What is the significance of decreased LH pulse frequency? We attempted to investigate this by inducing LH pulses during superovulation, but the result was a major reduction in ovulation rate. More research is required to determine if modification of endogenous LH secretion can improve superovulatory responses.