Synchronisation of ovulation for management of reproduction in dairy cows

Abstract

Important developments have occurred in the last two decades, since the advent of the Ovsynch protocol, on the understanding and use of synchronisation programmes for management of reproduction in dairy herds. This better understanding of oestrus cycle control associated with suboptimal reproductive performance in dairy herds has led dairy producers to quickly adopt timed artificial insemination (AI) protocols. Recent surveys have documented that fixed-time AI has become an important component of management of reproduction in high-producing herds. Furthermore, timed AI protocols have also demonstrated benefits in pasture-based milk production systems because of the ability to increase insemination rate. In general, successful use of the Ovsynch protocol requires some fundamental physiological principles to be respected, including: induction of ovulation to synchronise follicle growth in the first 2 days of the programme such that a young antral follicle is recruited; maintenance of high concentrations of progesterone during the development of the ovulatory follicle, but also effectively lyse the corpus luteum to result in very low concentration of progesterone at AI; and having a healthy pre-ovulatory follicle of moderate diameter that is highly oestrogenic and responsive to gonadotropins to synchronously ovulate 12 to 18 h after insemination. Current methods oestrous and ovulation synchronisation are still not optimal and future improvements will likely require new technologies for hormone formulation and delivery such that additional interventions are minimised to maintain acceptance by producers.Keywords: dairy cow, reproduction, synchronisation, timed AI ImplicationsConsolidation of the dairy industry with constant increase in herd size has generated the need for systematic programmes to manage reproduction. The advent of synchronisation of ovulation protocols that secure artificial insemination at a pre-established time with adequate fertility has become an integral component of breeding management in multiple production systems. The better understanding of ovarian biology of dairy cows with improved control of follicle growth and luteal lifespan has resulted in refinement of these programmes in the last two decades, providing unique opportunities to manipulate follicle development, improve oocyte quality and enhance embryo survival. IntroductionReproductive management in dairy farms has markedly evolved in the past 20 years to a great extent because of the development of synchronisation programmes that allow for fixed-time artificial insemination (AI). Early research on control of follicle development and corpus luteum (CL) lifespan aimed to develop systems that synchronise follicle growth, luteolysis and finally ovulation at a predictable time such that timed AI could be performed to optimise fertility in cattle (Thatcher et al., 1996). Initial work studying the control of follicular wave with gonadotropin-releasing hormone (GnRH) by Macmillan and Thatcher (1991) paved the way for the development of the O...

Molecular determinants of a competent bovine corpus luteum: first- vs final-wave dominant follicles

“…Since the introduction of ovulation synchronisation into mainstream reproductive management of cattle (Pursley et al 1995), a plethora of studies have examined in detail the benefits of follicle synchrony in reproductive management programs (Bisinotto et al 2014, Wiltbank & Pursley, 2014. However, it has been shown that ovulation of follicles that have not undergone normal physiological maturation can lead to suboptimal luteal function compared with spontaneous ovulation.…”

Prostaglandin F2α or estradiol benzoate to induce ovulation in timed artificially inseminated dairy cows

“…The advent of protocols for ovulation synchronization, which enables artificial insemination at a pre-established time with adequate fertility, has become an important component of breeding management in multiple production systems (Bisinotto et al, 2014). By controlling both luteal and follicular function by exogenous treatments, it is possible to synchronize the time of ovulation and, therefore, perform artificial insemination (AI) without the need for estrus detection (Bó et al, 2002 The typical TAI protocol involves the use of an intravaginal progesterone insert to mimic the luteal phase, estradiol benzoate (EB) to synchronize follicular wave emergence, prostaglandin F2a analogues (PGF) to induce luteolysis, and an ovulation inducer that could be either an ester of estradiol (benzoate or cypionate) or a GnRH analogue, such as, gonadorelin and buserelin acetate (Kim et al, 2007;Souza et al, 2009;Bisinotto et al, 2014).…”

Effect of progesterone supplementation on fertility responses of lactating dairy cows with corpus luteum at the initiation of the Ovsynch protocol

“…Despite the improvement in reproductive performance associated with the use of timed AI over the past decade, individual fertility measured as pregnancy per AI (P/AI) has not changed [2]. This scenario highlights the importance of developing strategies applicable to large groups of cows that benefit the establishment and maintenance of pregnancy.…”