Control of ovarian function for assisted reproductive technologies in cattle

Ano: 2009 | Volume: 6 | Número: 1

Autores: R.J. Mapletoft, G.A. Bó, P.S. Baruselli

Palavras-chave: artificial insemination, cattle, embryo transfer, follicle wave emergence, synchronization

Resumo Inglês:

Although the discovery that follicles in bovine
ovaries grow in a wave-like fashion has presented
challenges for estrus synchronization and
superovulation, recent protocols, designed to control
follicular function have permitted fixed-time AI or
fixed-time embryo transfer with high pregnancy rates,
and the initiation of superstimulatory treatments at a
self-appointed time, all without the necessity of estrus
detection. The key is the synchronization of follicle
wave emergence. More recent studies have revealed that
it is not only possible to synchronize the timing of
ovulation for fixed-time AI in single ovulating animals,
but also in superstimulated donors. Ultrasound-guided
follicle ablation is very efficacious in synchronizing
follicle wave emergence but is difficult to apply in the
field. Similarly, the induction of ovulation with GnRH
or LH will effectively synchronize follicle wave
emergence, but ovulation occurs in only 60 to 70% of
cases. The administration of estradiol benzoate in
progestin-treated cattle effectively synchronizes follicle
wave emergence for both superovulation and estrus
synchronization, but estradiol benzoate is not available
in many countries. The challenge now is to use
knowledge of follicle wave dynamics to design
alternatives.