Plasma concentrations of luteinizing hormone and progesterone during superovulation of dairy cows using follicle stimulating hormone or pregnant mare serum gonadotrophin

Plasma steroid profiles and ovarian response in llamas treated with eCG for superovulation combined with exogenous progesterone during early luteal phase

The objective of this study was to evaluate the effects of plasma progesterone (P₄) concentrations during eCG-ovarian follicular superstimulatory treatment performed in early luteal phase and estradiol concentrations during peri-ovulatory period on ovarian response, number and embryo quality. On Day -2, females (n = 75) having a follicle ≥7 mm were treated with GnRH to induce ovulation. On Day 0, females that had ovulations (n = 54) were treated with 1000 IU eCG and were assigned to one of two treatments: (1) intravaginal device (ID) containing 0.5 g P₄ (P₄ group) and (2) no ID (Control group). On Day 5, females were administered PGF_2α and the ID was removed. On Day 7 and 8, females were mated and embryo recovery was performed 7 or 8 days later. Blood samples were collected from Day 0 to 9. Number (± SD) of follicles ≥7 mm on day of mating was greater (P =  0.04) in the control (9.7 ± 4.2) than P₄-treated (6.7 ± 4.9) group; number of corpora lutea did not differ (5.5 ± 3.1 and 5.2 ± 3.4 respectively). Ovulation rate was greater (P <  0.01) in the P₄-group (77.4%; 130/168) than control group (53.3%; 135/253). Number of embryos with an excellent grade (grade 1) tended to be greater (P =  0.07) in the P₄-group (82.4%; 42/51) than control group (65.4%; 36/55). It was concluded that supplementation with exogenous P₄ during eCG treatment in early luteal phase inhibits excessive follicular growth, increases ovulation rate and improves embryo quality.

Decreased pulsatile LH secretion in heifers superovulated with eCG or FSH

This study was designed to test the hypothesis that treatment with super-ovulatory drugs suppresses endogenous pulsatile LH secretion. Heifers (n=5/group) were superovulated with eCG (2500 IU) or FSH (equivalent to 400 mg NIH-FSH-P1), starting on Day 10 of the estrous cycle, and were injected with prostaglandin F(2alpha) on Day 12 to induce luteolysis. Control cows were injected only with prostaglandin. Frequent blood samples were taken during luteolysis (6 to 14 h after PG administration) for assay of plasma LH, estradiol, progesterone, testosterone and androstenedione. The LH pulse frequency in eCG-treated cows was significantly lower than that in control cows (2.4 +/- 0.4 & 6.4 +/- 0.4 pulses/8 h, respectively; P<0.05), and plasma progesterone (3.4 +/- 0.4 vs 1.8 +/- 0.1 ng/ml, for treated and control heifers, respectively; P<0.05) and estradiol concentrations (25.9 +/- 4.3 & 4.3 +/- 0.4 pg/ml, for treated and control heifers, respectively; P<0.05) were higher compared with those of the controls. No LH pulses were detected in FSH-treated cows, and mean LH concentrations were significantly lower than those in the controls (0.3 +/- 0.1 & 0.8 +/- 0.1, respectively; P<0.05). This suppression of LH was associated with an increase in estradiol (9.5 +/- 1.4 pg/ml; P<0.05 compared with controls) but not in progesterone concentrations (2.1 +/- 0.2 ng/ml; P>0.05 compared to controls). Both superovulatory protocols increased the ovulation rate (21.6 +/- 3.9 and 23.0 +/- 4.2, for eCG and FSH groups, respectively; P>0.05). These data demonstrate that super-ovulatory treatments decrease LH pulse frequency during the follicular phase of the treatment cycle. This could be explained by increased steroid secretion in the eCG-treated heifers but not in FSH-treated animals.

Progesterone profiles and oestrous cycle changes following superovulatory treatment of Holstein-Friesian dairy cows in a tropical environment

Changes of progesterone (P4) profiles and oestrous cycle were investigated up to 70 days in 20 superovulated Holstein-Friesian cows in a dry tropical environment (Brazil). Superovulated cows showed no significant differences in relation to P4 level at the time of embryo recovery (39.0 +/- 27.1 nmol/L, P = 0.536), first and second (12.0 +/- 6.0 and 10.7 +/- 2.2 nmol/L, P = 0.543) cycle. There was a close correlation between serum P4 concentration and the number of corpora lutea (CL; 13.3 +/- 9.5) at the recovery (P < 0.0001). After the embryo collection, cows returned to cycle in different ways: (i) group of donors returning to cycle after 2.2 +/- 0.8 days, (ii) group with a delay of 11.0 +/- 1.9 days; and (iii) animals having a long (28.8 +/- 2.2 days) acyclic period, which is significant (P < 0.001). The remaining animals (30%) showed cystic ovarian malformations. P4 level at the time of embryo recovery does not influence the oestrous cycle changes. The results suggest that Holstein-Friesian donor cows may suffer from cystic ovarian degeneration and may have a long acyclic period after superovulatory treatment in a tropical climate.

Influence of CIDR treatment during superovulation on embryo production and hormonal patterns in cattle

One of the major sources of success in embryo transfer is timing of AI relative to the LH surge and ovulation. The aim of this study was to compare the embryo production following superovulation during a PGF2alpha (control cycle) or a CIDR-B synchronized cycle (CIDR-B cycle). CIDR-B (CIDR-B ND, Virbac, Carros, France) was inserted on Day 11 of a previously synchronized cycle and left for 5 days. A total dose of 350 microg FSH was administered (eight injections i.m. for 4 days; first on Day 13, decreasing doses) and PGFalpha analog (750 microg i.m.: Uniandine ND, Schering-Plough, Levallois-Perret, France) injected at the time of third FSH injection. Artificial inseminations were performed 12 and 24 h after standing estrus (Day 0). Embryos were collected on Day 7. Luteinizing hormone was measured by EIA (Reprokit Sanofi, Libourne, France) from blood samples collected every 3 h for 36 h, starting 24 h after PGF2alpha (control cycle) or 12 h after CIDR-B removal (CIDR-B cycle). The effects of treatment group and interval between the LH peak and AI (two classes, < 10 and > or = 10 h) on embryo production and quality were analyzed by ANOVA. No effect of treatment was observed on embryo production variables. The intervals between the end of treatment and onset of estrus and between end of treatment and LH surge were greater in heifers treated during a control than a CIDR-B cycle, respectively (45.5 +/- 1.4 versus 31.9 +/- 0.7; 42.0 +/- 1.6 versus 31.0 +/- 1.5; P < 0.05), but maximal LH and estradiol concentrations, at the preovulatory surge were similar in control and CIDR-B synchronized heifers. The numbers of viable and Grade I embryos were significantly increased (P < 0.01) when animals had an interval from LH peak to first AI > or = 10 h (7.2 +/- 0.9 and 3.5 +/- 0.6) when compared to shorter intervals (4.2 +/- 1.1 and 2.0 +/- 0.7) whereas total number of embryos was unchanged (11.8 +/- 1.4 versus 10.3 +/- 1.8). It is concluded that late occurrence of LH peaks in relation to estrous behavior is associated with a lower embryo quality when first AIs are performed systematically 12 h after standing estrus. Further studies are needed to know if results may be improved when making AI at a later time after standing estrus or if LH assays are useful to better monitor AI time.

Embryo yield and plasma progesterone profiles in superovulated dairy cows and heifers

This study was conducted to compare the superovulatory (SOV) response of dairy cows (n=172) and heifers (n=172), with two SOV treatments started at the mid-luteal-phase of the estrus cycle. Donors were randomly treated either with equine chorionic gonadotrophin (eCG) plus neutra-eCG serum (eCG+N group, n=167) or follicle stimulating gonadotrophin (FSH-P group, n=177). No significant differences were observed among groups in the percentage of superovulatory responsive donors (SR donors; corpora lutea (CL) >/=2), the mean number of total ova, fertilized ova and viable embryos recovered. Cows yielded significantly less total ova and less fertilized ova (P<0.05) and tended to yield less viable embryos (P<0.06) than heifers. Plasma progesterone (P4) concentrations (n=135 donors) on the day of PGF(2alpha) (PGF) injection and on the day of SOV estrus were significantly higher (P<0.01) in eCG+N than in FSH-P donors and, the increase between those 2 days was also significantly higher (P<0.05) in group eCG+N than in group FSH-P, suggesting a higher luteotrophic effect of eCG than FSH-P. SR donors had P4 levels significantly higher (P<0.001) than non-SR donors only on day 5 after the SOV estrus and on the day of embryo recovery. Plasma P4 concentrations at 5 days after the SOV estrus and at embryo recovery correlated significantly (r=0.76, P<0.001).Heifers had significantly higher P4 levels than cows at gonadotrophin injection (P<0.01), PGF injection (P<0.001), 5 days (P<0.01) and 7 days (P<0.001) after the SOV estrus. At day 7 after the SOV estrus, P4 concentrations per ova recovered were significantly higher in heifers than in cows (P<0.01). The increase of plasma P4 per ova recovered, between days 5 and 7 after the SOV estrus, was significantly (P<0.01) higher in heifers than in cows. Also, the increase of plasma P4 between injections of gonadotrophin and PGF was significantly higher (P<0.05) in heifers than in cows.These results suggest that heifers have higher plasma P4 concentrations at diestrus (either before or after the SOV treatment) and this is associated with a higher embryo yield and quality, as compared to lactating cows. These higher plasma P4 concentrations reflect not only differences in ovulation rate as well as the competence of the corpus luteum, which is potentialized by gonadotrophin stimulation.

Decreased LH pulsatility during initiation of gonadotropin superovulation treatment in the cow: evidence for negative feedback other than estradiol and progesterone

LH pulse secretion is suppressed during superovulation of cattle. The objective of this study was to determine how soon after initiation of superovulation treatments this suppressive effect occurs, and to test the hypothesis that decreased LH pulsatility is not related to changes in circulating estradiol or progesterone. Heifers (n = 7/group) were injected with eCG (FOLLIGON: a single injection of 2,500 IU) or twice daily injections of decreasing doses of FOLLTROPIN-V (total equivalent of 280 mg of NIH-FSH-P1) or F.S.H.-P (total equivalent of 28 mg of Armour standard) or saline (time controls), starting on Day 10 (Day 0 = estrus). Blood samples were taken every 10 min for 12 h intervals on the day prior to first injection, at 8 to 20 h and 32 to 44 h after initiation of gonadotropin treatment, and also during prostaglandin (PG)-induced luteolysis. A simple method based on robust statistics and on graphical representations of time series was developed to characterize LH pulses. There was a significant interaction between time and treatment for mean LH, estradiol and progesterone when control and treated groups were analyzed together, and no interaction when only the gonadotropin groups were analyzed together. When compared to pretreatment values, pulse frequency of LH was significantly reduced (P<0.05) in each treatment group, 8 to 20 h and 32 to 44 h following initiation of gonadotropin treatment. Mean LH concentrations were also reduced 32 to 44 h following initiation of treatments (P<0.05). Mean estradiol concentrations increased two to threefold at 8 to 20 h following initiation of superovulation treatments (P<0.05). Progesterone concentrations also increased by 20 or 44 h. There was no significant correlation between estradiol or progesterone and LH pulse frequency, amplitude and mean concentrations at any time in control or superovulated animals. This study demonstrates that superovulation treatment in the cow causes a rapid decrease in pulsatile release of LH and suggests that this effect is not mediated through the negative feedback actions of estradiol and progesterone.

Changes in follicular populations following treatment of buffaloes with PMSG (eCG) and Neutra-PMSG for superovulation

Some 19 buffaloes were synchronized by administration of a prostaglandin (PG) salt Lutalyse, with a single intramuscular (i.m.) injection of 25 mg at day -13. Luteolysis was induced by administration of 50 mg PG, in divided doses of 30 and 20 mg i.m. 12 h apart on day 0 of experiment. The 30 mg PG injection was designated as 0 h of experiment. Group I animals (n = 6) received saline and served as controls while animals in Groups II (n = 7) and III (n = 6) received 2500 I.U. PMSG (eCG) i.m. at day -2. Group III animals were administered 5 ml Neutra-eCG intravenously at 60 h. The number of follicles, classified on the basis of diameter as small (2-5 mm), medium (6-9 mm) and large (> or = 10 mm) was assessed by ultrasonography on days -2, -1, 0, 1, 2, 5 and 7 of experiment. The number of corpora lutea (CL) was recorded by palpation per rectum on day 8. The number of small follicles which did not differ among the three groups on days 0, 1 and 2 was significantly lower (P < 0.05) in Group II animals compared to those in Groups I and III on days 5 and 7. The number of medium follicles increased after eCG treatment and was significantly higher (P < 0.05) in animals of Groups II and III on days 0 and 1, compared to control animals of Group I. It was, however, not different among the three groups on subsequent days of experiment. The number of large follicles which did not differ among the three groups on days -2, 0, 1 and 2 was significantly higher in Groups II (P < 0.01) and III (P < 0.05) animals compared to those of Group I on day 5. On day 7, the number of large follicles was in the order (P < 0.05) Group II > Group III > Group I. The number of CL in Group II animals was significantly higher (P < 0.05) than that in Group I animals but was not different from that of Group III animals. These results suggest that treatment of buffaloes with eCG for superovulation reduces the number of small follicles and increases the number of large follicles 5-7 days after PG treatment. Administration of Neutra-eCG 60 h after PG treatment can partly reverse this trend but has no effect on ovulation rate. The possibility that part of the variability in ovulation rates in this study may have resulted from Neutra-eCG been given prior to or at the LH surge, or from the absence or presence of a dominant follicle at the time of eCG treatment cannot be ruled out.

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.

Changes in peripheral inhibin levels and follicular development following treatment of buffalo with PMSG and Neutra-PMSG for superovulation

Fourteen buffalo were synchronized by administration of a prostaglandin (PG) salt Lutalyse in a double injection schedule, with a single intramuscular (im) injection of 25 mg at Day -13, followed by 30 mg and 20 mg im 12 h apart on Day 0 of the experiment. The 30-mg PG injection was designated as 0 h of the experiment. Group I animals (n = 4) received saline and served as the controls, while animals in Groups II and III (n = 5 each) received PMSG (2500 IU im at -48 h. Group III animals were administered 5 ml Neutra-PMSG intravenously at 60 h. Blood samples were collected every 48 h from Day -12 to Day -4, every 24 h from Day -4 to Day 0, every 3 h from Day 1 to Day 4 and every 24 h from Day 5 to Day 10 of experiment for the measurement of peripheral plasma inhibin concentrations by RIA. The number of large follicles (> 10 mm diameter) in animals of Groups II and III was assessed by ultrasonography on Days -2, -1, 0, 1, 2, 5 and 7 of the experiment. Treatment with PMSG of Group II animals resulted in a significant increase (P < 0.05) in plasma inhibin concentrations over that of control animals of Group I at 24 to 99 h, with a peak inhibin concentration of 1.01 +/- 0.31 ng/ml at 48 h. Treatment with Neutra-PMSG in Group III animals caused a significant reduction (P < 0.05) in the peripheral inhibin concentrations at 84 to 120 h and in the number of large unovulated follicles at 168 h compared with that in Group II animals. Peripheral inhibin levels in Group III animals came down to those of Group I after 21 h of Neutra-PMSG treatment. These results suggest that treatment of buffalo with PMSG for superovulation causes a marked rise in peripheral inhibin concentrations. Administration of Neutra-PMSG after PG treatment reduces the peripheral inhibin concentrations and the number of large unovulated follicles.

Ovarian response and endocrine changes in buffalo superovulated at midluteal and late luteal stage of the estrous cycle: A preliminary report

A study was designed to determine whether superovulatory and endocrine responses in buffalo differ when gonadotropin treatment is initiated at midluteal and late luteal stages of the estrous cycle. Twenty-eight buffalo were randomized into 4 groups (A, B, C and D). Buffalo in Groups A and B (n = 8 each) were superovulated with Folltropin (total dose 25 mg) and Lutalyse. Treatments in Group A were initiated between Days 8 to 10 (midluteal group) and in Group B between Days 13 to 15 (late luteal group) of the estrous cycle. Buffalo in Groups C and D (n = 6 each) were not superovulated and served as controls. Blood samples from all groups of buffalo were collected daily for plasma progesterone and estradiol determinations. The number of corpora lutea (CL) and unovulated follicles was recorded (following per rectum palpations) 5 or 6 d post-estrus. Buffalo in Groups A and B exhibited estrus in larger proportions and earlier (49.33 +/- 3.82 h and 46.67 +/- 2.46 h, respectively) than the control Groups C and D (77.33 +/- 5.33 h and 78.0 +/- 3.83 h, respectively). Mean number of CL was higher in Group B (3.38 +/- 0.46) than in Group A (2.25 +/- 0.75), however,the difference was not significant (P > 0.05). Plasma progesterone concentrations on the day of treatment were higher in late luteal superovulated and control groups than in midluteal superovulated and control groups. In both Groups A and B progesterone levels were significantly related (r = 0.78,0.76; P < 0.05) to the number of CL palpated after the superovulatory estrus. Progesterone levels on the day of estimation of ovarian response were approximately 4 times higher in Groups A and B than in Groups C and D. Peak estradiol concentrations were approximately twice as high in superovulated groups as in control groups.

Ancillary follicle and secondary corpora lutea formation following exogenous gonadotropin treatment in the domestic cat and effect of passive transfer of gonadotropin-neutralizing antisera

A combination regimen of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) was used to stimulate ovarian follicular development in domestic cats. The rate of elimination of eCG from circulation was estimated, and, following follicular aspiration, the formation of ancillary follicles and secondary CL was characterized. The effect of gonadotropin-neutralizing antisera on the development of secondary ovarian structures, CL function and humoral immune responses also was evaluated. After intramuscular injection, initial serum eCG concentrations were variable, with the elimination half-life estimated at 39 to 55 h and eCG persisting in circulation for several days. Following follicular aspiration, queens formed CL equal to the number of aspirated follicles and exhibited a rapid increase in progesterone concentration but developed high numbers of ancillary follicles by 5 d post aspiration. By 15 d post aspiration, all ancillary follicles had luteinized to form secondary CL. Treatment with neutralizing antisera at the time of follicular aspiration slowed (P < 0.05) CL formation but did not decrease (P > 0.05) the number of ancillary follicles or secondary CL. Progesterone concentrations did not differ (P > 0.05) from control queens while secondary humoral immune responses to eCG were qualitatively similar between groups. In summary, eCG was eliminated slowly from cats following intramuscular injection and this persistence in circulation may have contributed to the development of ancillary follicles and secondary CL. However, the administration of neutralizing antisera at the time of follicular aspiration was ineffective in preventing the formation of these secondary ovarian structures.

Superovulatory treatments do not alter pulsatile LH secretion in ovariectomized cattle

Previous work has shown a suppressive effect of superovulatory treatments on pulsatile LH release in cattle. This study tested the hypothesis that this suppression may be caused, at least in part, by a direct effect of commercial gonadotropin preparations on the hypothalamus/pituitary gland. Crossbred Holstein heifers, ovariectomized 20 d before the start of the experiment, received 6 injections of FSH (50 mg Folltropin) at 12-h intervals (n = 6); a single injection of 2500 IU eCG followed by 5 injections of sterile saline at 12-h intervals (n = 6); or 6 injections of saline at 12-h intervals (controls; n = 5). Blood samples were taken every 10 min for 8 h the day before and 3 d after the beginning of treatment to assess LH pulsatility. At the end of these sampling periods, a bolus injection of GnRH (7 ng/kg) was given to assess pituitary responsiveness. There were no effects of the superovulatory drugs on mean LH concentrations, nor on LH pulse frequency or amplitude (P > 0.05). The pituitary response to GnRH was significantly elevated in eCG- but not FSH-treated animals (paired t test; P < 0.05). These data demonstrate that superovulatory preparations do not suppress pulsatile LH secretion independently of the ovaries in cattle.

Effects of an LHRH antagonist on the time of occurrence and amplitude of the preovulatory LH surge, progesterone and estradiol secretion, and ovulation in superovulated Holstein heifers

Beginning on Day 10 or 11 of the estrous cycle, mature Holstein heifers were given a superovulatory regimen of twice-daily injections of porcine FSH, together with injections of PG with the fifth and sixth FSH injections. Every 12 h from 24 to 60 h after PG administration, the animals received im injections of different doses of the LH releasing hormone antagonist [N-Ac-D-Nal(2)(1), D-pCl-Phe(2), D-Trp(3), D-Arg(6), D-Ala(10)]-LHRH or vehicle. Follicular development was monitored by transrectal ultrasonography every 12 h from 24 to 120 h after PG administration. All animals were given hCG at 72 h after PG injection, and were artificially inseminated. At Day 7 of gestation, the corpora lutea were counted by ultrasonography, and embryos were collected by nonsurgical flushing of the uterus. Treatment with the antagonist resulted in a dose-dependent decrease in the amplitude of the LH surge and in delays in the time of occurrence of the LH surge, ovulation and the shift from estradiol to progesterone production. These results indicate that LHRH antagonists can be used to delay the LH surge and ovulation in superovulated heifers. This finding may be beneficial to studies in the superovulation of cattle.

Superovulatory responses in dairy cows following ovulation of the dominant follicle of the first wave

In the present study we investigated the effect of hCG administration on Day 7 (Day 0 = day of standing estrus) to ovulate the dominant follicle of the first wave and the associated increase in progesterone concentration on subsequent superovulatory response in dairy cows. Twenty cyclic lactating cows were allocated at random to 2 groups: control (n = 10) and hCG-treated (n = 10). The ovaries of each cow were scanned using an ultrasound scanner on Day 7, to confirm the presence of the dominant follicle and thereafter every other day until embryo recovery. All cows received a total dose of 400 mg Folltropin-V in decreasing amounts for 5 days (Days 9 to 13) and 35 mg PGF(2alpha) on Day 12. In addition, the treated cows received 1000 IU hCG on Day 7. All cows were inseminated twice during estrus, and the embryos were collected 7 days later by a nonsurgical procedure. Blood smaples were taken at different times of the treatment period for progesterone determination. All cows possessed a dominant follicle at Day 7, and all but one of the hCG-treated cows ovulated the dominant follicle and formed an accessory corpus luteum. Plasma progesterone concentrations were significantly higher (P<0.01) in hCG-treated cows than control cows on the first day of Folltropin treatment and on the day of PGF(2alpha) injection. The mean number of follicles at estrus, the number of ovulations, the total number of embryos and the number of transferable embryos were not different (P>0.05) between control and hCG-treated cows.

Pharmacologic manipulation of fertility

The professional application of agents to the manipulation of fertility of cows requires basic and applied knowledge of the physiologic mechanisms that are affected and of the pharmacologic agents that are used. In all areas of the pharmacologic manipulation of fertility, the achievement is less than the ideal, and further research is required to improve the efficiency of treatments. The induction of estrus in acyclic animals can involve a reduction in the depth of anestrus, pretreatment with progestagen to ensure estrous behavior and the formation of a normal corpus luteum, and then treatment with exogenous gonadotropin. Responsiveness to treatment can be variable and reflects the depth of anestrus of the animals. Improved treatment regimens require a knowledge of the basic mechanisms involved with the depth of anestrus, a means of assessing the depth of anestrus, and an understanding of the hormonal requirements of ovarian follicles for development and maturation in animals at different depths of anestrus. The optimal precision in the synchronization of estrus (and ovulation) in cyclic animals requires the synchronization of both follicular waves and the end of progestational phase. The end of progestational phase can be synchronized effectively using prostaglandin F2a (or analogs), or by treatment with progestagens with or without luteolytic agents. Procedures to synchronize follicular waves need to be established. The induction of superovulation can be achieved readily using gonadotropins prior to estrus synchronization using prostaglandin F2a. The responses to standard treatments in terms of ovulation rates and yield of transferable embryos are highly variable. The development of procedures to reduce this variability requires an understanding of the intra-ovarian mechanisms involved in recruitment of follicles for a wave of follicular growth, in the selection of dominant follicles for further development, and in the mechanisms controlling follicular atresia. Cystic ovarian disease can be treated effectively using HCG or GnRH (follicular cysts) or prostaglandin F2a (luteal cysts). The basic mechanisms resulting in failure of estrogen positive feedback on LH secretion (that results in cystic follicles) remain to be determined. Small but significant increases in pregnancy rates can be achieved treating cows with prostaglandin during the post-partum period, with prostaglandin to induce estrus for insemination, with GnRH or HCG at estrus, and with GnRH or progestagen treatment during diestrus. Beneficial effects of treatment have been shown in some trials but not in others.(ABSTRACT TRUNCATED AT 400 WORDS)

Rapid milk progesterone assay as a tool for the selection of potential donor cows prior to superovulation

This study investigated the accuracy of a commercially available rapid milk progesterone (P(4)) assay (RMPA) and its usefulness for the screening of potential donor cows prior to superovulatory treatment. Superovulation was induced in 90 lactating Holstein-Friesian crossbred dairy cows with twice daily injections over a 4-day period for a total of 40 mg follicle stimulating hormone (FSH-P), starting 9 to 13 d post estrus. Prior to induction of superovulation, a milk sample was collected and assayed for a P(4) level using the RMPA. The test determines P(4) by a simple visual color inspection of the respective sample, which is compared to a standard containing 10.5 ng/ml of P(4). All animals were divided into six groups according to the color intensity of their sample; three groups had a lower level, one group had an equal level and two groups had a higher P(4) level than the standard. Results of the semiquantitative RMPA were verified by a quantitative enzymeimmunoassay (EIA). Samples evaluated as equivalent to the standard had a mean P(4) level of 10.7 +/- 1.3 ng/ml (x +/- SEM). In total, P(4) levels differed (P<0.05) among groups, except in those with lower P(4) concentrations (1.1 +/- 0.0; 1.0 +/- 0.0; 3.7 +/- 1.5; 10.7 +/- 1.3; 13.8 +/- 1.3; 19.0 +/- 1.5 ng/ml, respectively). The correlation between RMPA-groups and EIA P(4) levels was 0.69 (P<0.001). Donors classified as having less P(4) than the standard yielded fewer corpora lutea (CL) (P<0.005), ova and embryos (P<0.05), and transferable embryos (P<0.05) compared with donors having similar or higher P(4) levels (3.4 +/- 1.0 vs 10.8 +/- 0.7 CL; 1.7 +/- 0.8 vs 6.2 +/- 0.9 ova and embryos; 1.2 +/- 0.7 vs 2.8 +/- 0.4 transferable embryos). Our results indicate that RMPA determines milk P(4) levels with sufficient accuracy and is a simple and useful tool for the screening of potential donor cows.

Buserelin in a superovulatory regimen for Holstein cows. I. Pituitary and ovarian hormone response in an experimental herd

Two experiments were conducted with frequent blood sampling in standard superovulatory regimens using follicle stimulating hormone (FSH) and prostaglandin F(2) alpha (PGF) to study the effects of the gonadotropin releasing hormone analog, Buserelin, on changes in FSH, luteinizing hormone (LH), progesterone (P(4)) and estradiol (E(2)). In Experiment I, Buserelin (20 mug) was administered to a total of 28 dry Holsteins. One group was treated with Buserelin 36 and 60 h after PGF administration, a second group was treated 60 h after PGF, and a third group served as the controls. In Experiment II, 30 dry Holsteins received Buserelin (10 mug). One group was treated 48 h after PGF, a second group at 54 h after PGF, a third group 24 h after estrus was first observed and a fourth group was a control. The general pattern of a decrease in P(4) following PGF, an increase in E(2), the onset of estrus, an LH peak, and finally, an increase in P(4) in superovulated cows was observed. Buserelin consistently produced a sharp LH peak at 36 h when given 36 h after PGF. At later intervals, it produced either a major or minor peak depending upon whether a spontaneous LH peak had already occurred. There was too much individual cow variation in the interval from PGF to a spontaneous LH peak to consistently induce a uniform LH peak, except when Buserelin was given 36 h after PGF, which may be early for normal oocyte maturation. There was no treatment effect on FSH, and embryo recovery rate was unaffected by treatment (P>0.05).

Buserelin in a superovulatory regimen for Holstein cows: II. Yield and quality of embryos in commercial herds

The gonadotropin releasing hormone analog, Buserelin, was tested in a superovulatory regimen in cows by administering 8 mug of it at the following times: Group I (12 cows), 48 h after the first prostaglandin F(2) alpha (PGF) injection: Group II (11 cows), 54 h after PGF: Group III (10 cows), 24 h after standing estrus was first observed; and Group IV (12 cows), served as superovulated controls. The cows were lactating Holsteins between 45 and 143 d post partum, with at least one estrus prior to superovulation. The number of embryos collected from Groups I, II, III and IV 7 d after estrus averaged 4.5, 8.1, 6.4 and 5.6, respectively (P>0.05). The fertilization rate in the three groups receiving Buserelin was 83 versus 76% for controls (P<0.10). Blood and milk samples taken just before starting follicle stimulating hormone treatment at the expected estrus and at the time of embryo recovery were tested for progesterone concentration, and results from a rapid ELISA test were useful in identifying cows that a) were unsuitable for superovulation, b) should have been in estrus but were not observed standing and c) produced few, if any, embryos.

Improved embryo yield and condition of donor ovaries in cows after PMSG superovulation with monoclonal anti-PMSG administered shortly after the preovulatory LH peak

Nonlactating Dutch-Friesian cows were selected from a local slaughterhouse and synchronized with Syncro-Mate B. Cows with a normal progesterone pattern were treated with PMSG (3,000 I.U. i.m.) on Day 10 followed by PG (Prosolvin 22.5 mg) 48 h later. Blood samples were collected daily and at hourly intervals from 30 h after PG. Monoclonal anti-PMSG (Neutra-PMSG) was administered i.v. at 5.8 h after the LH peak in 16 cows; controls (n = 16) did not receive Neutra-PMSG. For comparison, 16 additional cows were superovulated with FSH-P in decreasing doses, twice a day (total 32 mg), starting at Day 10. All cows were inseminated at 10 h after the LH peak. Embryos were evaluated on Days 6 and 7 after flushing upon slaughter (recovery 87%). The number of corpora lutea and follicles on the donor ovaries were counted. No significant differences in the concentrations of progesterone and LH were observed between the three superovulation groups. Upon Neutra-PMSG, PMSG in blood was completely neutralized, it was decreased to < 0.5 ug/l at AI from 7.0 ug/l at the LH peak. The number of transferable embryos was significantly higher after Neutra-PMSG (9.1 per cow) than without Neutra-PMSG (5.3). or upon FSH-superovulation (4.6). The number of cysts on the ovaries of Neutra-PMSG-treated cows was reduced similarly to that after FSH-superovulation. Treatment with Neutra-PMSG shortly after the LH peak positively affects final follicular maturation in PMSG-superovulated cows and results in a nearly two-fold increase of transferable embryos.

Preovulatory evaluation of the superovulatory response in donor cattle

Dairy cows and heifers (n = 134) were induced to superovulate with exogenous gonadotrophins. In 103 animals, peripheral plasma concentrations of progesterone (P4) and luteinizing hormone (LH) were measured during the preovulatory period. On the basis of these measurements, normal and deviating profiles of P4 and LH were defined. A high degree of correlation existed between the normality of the two profiles; when the P4 profile was normal, the probability for the LH profile also to be normal was greater than 10:1. This relationship was utilized to evaluate donors based on four preovulatory measurements of P4. When used on 31 animals used for collection of eggs, a superior superovulatory response was encountered in animals with normal vs deviating P4 profiles (eggs recovered: 7.2 +/- 1.1 vs 0.5 +/- 0.3, P < 0.001; transferable embryos: 4.4 +/- 0.9 vs 0.3 +/- 0.2, P < 0.01). It is concluded that evaluation of donors by measurements of progesterone in plasma at four preovulatory sampling points allows for the early exclusion of donors with inferior embryo yield.

Endocrine profiles and embryo quality in superovulated Japanese Black cattle

The relationships between plasma concentrations of progesterone (P4), estradiol-17beta (E2) and lutenizing hormone (LH) and embryo yield and quality were examined in 40 superovulated Japanese Black cattle. The results indicated that the ovarian function, especially the function of corpus luteum on the first treatment day, is an important factor for reliable superovulation in cattle. The levels of plasma E2 and LH at estrus were related to embryo yield and quality.