الكاتب: Multiple References

Superovulatory response has been shown to be improved if gonadotrophin treatment commences on or 1 d before wave emergence and treatment with estradiol-17g in the presence of circulating progestagen has been shown to synchronise the emergence of a follicular wave in cattle. The superovulation protocol used in recent years at this centre, however, involves administering estradiol benxoate simultaneously with an intravaginal source of progestagen at Day 7 (estrus = Day 0) of a reference estrous cycle and commencing gonadotrophin treatment 9 d later, which may not be synchronous with the emergence of a follicular wave. These protocols were compared in two trials. Purebred Simmental nulliparous heifers, 17 to 22 mo old, were superstimulated using either a standard or treatment protocol. Each protocol was applied to 16 heifers in trial 1 and 9 heifers in trial 2. On Day 1 (Day 7 of a reference estrous cycle) of the standard protocol, an intravaginal progestagen device was applied (CIDR-B; SmithKline Beecham, UK) and 10 mg estradiol benxoate injected im (Intervet, UK); gonadotrophin treatment began on Day 10; 30 mg luprostiol was injected im on Day 12; the ClDR-B removed on Day 13; with fixed-time AI at 1500 and 0900h on Days 14 and 15, respectively; and embryo recovery on Day 21. In the treatment protocol, estradiol benzoate was not used but 1 d after CIDR-B application 5 mg estradiol -17g (Sigma, UK) was injected im. Gonadotrophin treatment commenced 4 d later. Subsequent events were as for the standard protocol at the same time intervals a&r gonadotrophin treatment. The gonadotrophin used was a total of 9.0 mg oFSH (NIADDK-oFSH-17 equivalent; Ovagen, ICP, NZ) administered in declining doses twice per day over 4 d except for the treatment group in trial 1. In this trial, 1500 IU eCG was administered to treatment animals as a single im injection. Data were analysed using Generalised Linear Model procedures within the Genstat statistical package and are presented in Table 1