The use of a monoclonal antibody to pregnant mare serum gonadotrophin in superovulation of cattle
Embryo transfer plays a very important role in the cattle industry and its application requires a consistent supply of viable embryos for use in such programmes. One way of achieving this is the development of reliable superovulation regimens, yielding a large number of high quality embryos. Superovulation with pregnant mare serum gonadotrophin (PMSG) induces a second wave of follicles after ovulation because it is eliminated slowly from the peripheral blood, causing high concentrations of oestradiol. This oestradiol may have an adverse effect on fertilization and early embryonic development. Administering PMSG antiserum after ovulation may improve the quality by neutralizing PMSG activity. The object of this study was to examine the role of monoclonal anti- PMSG (Neutra-PMSG; Intervet UK) in a superovulatory regime for cattle based on PMSG with the objective of increasing the number of viable embryos produced. Two experiments were conducted in this study. In experiment 1, cows were superovulated with 2500 iu of PMSG (Folligon; Intervet UK) im on day 101 of their oestrous cycle, whereas in experiment 2, heifers were superovulated with 1000, 2000, 3000 or 4000 iu of PMSG (PMSG1, 2, 3 or 4, respectively) im on day 10 1 of their oestrous cycle. In experiments 1 and 2, animals were given 2 ml of PG (PG3) im 48 h after PMSG injection and oestrus was observed in the same manner as described above. When data were evaluated in respect of the PMSG/APMSG dose level, there were no significant differences (P>0.05) in the numbers of CL and usable number of embryos between APMSG treatment and the appropriate control. Treatment with APMSG in the 3000 iu PMSG dose group reduced (P 0.05) the numbers of LF compared to control (1.3 v 5.5). When data were analysed based on the dose levels of PMSG, the total number of ova/embryos and the number of usable embryos were higher in heifers which received 2000 iu of PMSG compared to those which received 1000, 3000 or 4000 iu (7.1 v 2.1, 6.6 or 5.6 and 6.3 v 2.1, 4.8 or 3.2, respectively) . In conclusion the results indicate that PMSG dose 2000 iu is the favoured dose for superovulating heifers. The administration of Neutra-PMSG 36, 48, 60, 72, 84 or 96 h after PG3 injection, despite reducing LF numbers and preventing the rise in 0E2 after ovulation, had no significant effect on the number of usable embryos recovered.