Abstract
The advantages of using pregnant mares' serum gonadotrophin (PMSG) to stimulate increased preovulatory follicular development are that it is available in large quantities at low cost, and can be administered as a single dose because of its long half-life. The long half-life, however, can have disadvantages since it may cause over and/or prolonged stimulation, leading to a second wave of follicular development after ovulation and a secondary rise in oestradiol-17β. The latter may interfere with embryo quality.
PMSG antiserum
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The term PMSG antiserum as used throughout this paper includes antisera from cattle, goat or turkey and commercially produced monoclonal antibodies.
has been extensively tested in an effort to selectively remove PMSG from the peripheral blood of PMSG stimulated cattle after the initial phase of follicular stimulation but before the secondary post-ovulatory phase of stimulation. This neutralisation of PMSG with PMSG antiserum prevents the secondary development of ovarian follicles and the accompanying rise in oestradiol-17β; however, the evidence regarding the effect on the number of usable embryos recovered is conflicting. The best results, in this respect, have been obtained when PMSG antiserum was administered 5–6 h after the preovulatory LH peak but this event is difficult to assess in practice. Administration of PMSG antiserum at a fixed time in relation to the use of either PMSG or a synchronising injection of a prostaglandin analogue, or in relation to the onset of behavioural oestrus is unsatisfactory because of the variability of the timing of the LH peak in relation to these events. It may, however, be possible to use the preovulatory peak of oestradiol-17β as a marker for the administration of PMSG antiserum.