Superovulation in beef heifers with PMSG: Effect of dose and monoclonal antibodies to PMSG

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.

Factors associated with variation in the superovulatory response of cattle

Kafi, M., McGowan, M.R., 1997. Factors associated with variation in the superovulatory response of cattle. Anim. Reprod. Sci. Variability in the superovulatory response of cattle is still one of the major limiting factors in extensive usage of embryo transfer technology. A variety of approaches including recent attempts to eliminate the suppressive effect of the dominant follicle have been used to reduce the unpredictability of the superovulatory response of cattle. The development of techniques such as transrectal ultrasonography, have enabled a re-evaluation of ovarian dynamics during superovulation of cattle. In addition, advances in reproductive hormone assays have increased knowledge of the mechanisms controlling follicular development, ovulation and corpus luteum function. This review focuses on the current understanding of factors affecting the superovulatory response of cattle. Also, abnormalities of ovulation and endocrine disorders that may occur during superovulation are reviewed.

Factors affecting superovulation in heifers treated with PMSG

In this study we determined 1) if the immunoneutralization of PMSG affected the ovulatory response, the number of large follicles and embryo yield compared with that of PMSG alone or pFSH, and 2) whether the stage of the estrous cycle at which PMSG was injected affected the ovulatory response and yield of embryos in superovulated heifers. Estrus was synchronized in 99 (Experiment 1) and 71 (Experiment 2) heifers using prostaglandin F2alpha (PG) analogue, cloprostenol, given 11 d apart in replicate experiments over 2 yr. In Experiments 1 and 2, heifers were randomly allocated to 1 of 3 treatments (initiated at mid-cycle): Treatment 1--24 mg of pFSH (Folltropin) given twice daily for 4 d; Treatment 2--a single injection of 2000 IU PMSG; Treatment 3--2000 IU PMSG followed by 2000 IU of Neutra-PMSG at the time of first insemination. In Experiment 3, 116 heifers were given 2000 IU PMSG on Day 2 (n = 28), Day 3 (n = 27), Day 10 (n = 41) or Day 16 (n = 20) of the estrous cycle. The PG was given at 48 h (500 microg cloprostenol) and 60 h (250 microg cloprostenol) after the first gonadotropin treatment. Heifers were inseminated twice during estrus, and embryos were recovered on Day 7, following slaughter and graded for quality. The numbers of ovulations and large follicles (> or =10 mm) were also counted. There was no effect of treatment on ovulation rate in Experiment 1, but in Experiment 2 it was greater (P < 0.002) in heifers given PMSG (14.7 +/- 1.5) than pFSH (7.5 +/- 1.4) or PMSG-neutra-PMSG (8.7 +/- 1.5). The number of large follicles was higher following PMSG than pFSH treatment in Experiment 1, and it was higher (P < 0.004) in heifers given PMSG (5.5 +/- 0.8) than pFSH (1.12 +/- 0.7) or PMSG-neutra-PMSG (2.7 +/- 0.8) in Experiment 2. The use of Neutra-PMSG did not affect the numbers of embryos recovered or numbers of Grade 1 or 2 embryos, but it did decrease the number of Grade 3 embryos in both experiments. In Experiment 3, the ovulation rate decreased (P < 0.004) when PMSG was given on Day 3 (5.7 +/- 1.46) of the cycle rather than on Day 2 (12.3 +/- 1.64), Day 10 (13.4 +/- 1.45) or Day 16 (12.5 +/- 1.87). There was no effect of day of treatment on the numbers of large follicles. The mean numbers of embryos recovered were lower (P < 0.01) in heifers treated on Day 3 (2.1 +/- 0.67) than on Day 2 (6.8 +/- 1.0), Day 10 (6.4 +/- 0.86) or Day 16 (7.8 +/- 1.87). It is concluded that Neutra-PMSG given to heifers treated with PMSG did not improve embryo yield or quality and that treatment with PMSG early in the cycle can result in acceptable embryo yields provided sufficient time elapses between treatment and luteolysis.

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.