Manipulation of Follicle Development to Ensure Optimal Oocyte Quality and Conception Rates in Cattle PS Baruselli 1 , MF Sa´ Filho 1 , RM Ferreira 1 , JNS Sales 1,2 , LU Gimenes 1 , LM Vieira 1 , MF Mendanha 1 and GA Bo´ 3 1 Departamento de Reproduc ¸a ˜o Animal da Faculdade de Medicina Veterina ´ria e Zootecnia da Universidade de Sa ˜o Paulo, Sa ˜o Paulo, SP, 05508-000 Brazil; 2 Universidade Federal da Paraı´ba, Areia, Paraı´ba, Brazil; 3 Instituto de Reproduccio ´n Animal Cordoba (IRAC), Co ´rdoba, Argentina Contents Over the last several decades, a number of therapies have been developed that manipulate ovarian follicle growth to improve oocyte quality and conception rates in cattle. Various strate- gies have been proposed to improve the responses to repro- ductive biotechnologies following timed artificial insemination (TAI), superovulation (SOV) or ovum pickup (OPU) pro- grammes. During TAI protocols, final follicular growth and size of the ovulatory follicle are key factors that may significantly influence oocyte quality, ovulation, the uterine environment and consequently pregnancy outcomes. Proges- terone concentrations during SOV protocols influence follic- ular growth, oocyte quality and embryo quality; therefore, several adjustments to SOV protocols have been proposed depending on the animal category and breed. In addition, the success of in vitro embryo production is directly related to the number and quality of cumulus oocyte complexes harvested by OPU. Control of follicle development has a significant impact on the OPU outcome. This article discusses a number of key points related to the manipulation of ovarian follicular growth to maximize oocyte quality and improve conception rates following TAI and embryo transfer of in vivo- and in vitro- derived embryos in cattle. Introduction The success of several reproductive programmes is closely related to ovarian follicular development and oocyte quality. Over the past several decades, several therapies have been proposed for manipulating ovarian follicle growth in cattle. These hormonal manipulations have been successfully used to optimize the reproductive outcomes following the application of various biotech- nologies. Timed artificial insemination (TAI) programmes pro- vide an organized approach to enhance the use of artificial insemination (AI) and the progress of genetic gain and to improve reproductive efficiency in dairy and beef herds (Pursley et al. 1995; Baruselli et al. 2004). The success of biotechnologies, such as TAI, is depen- dent on the evolution of ovarian follicular manipulation techniques. The final follicular growth and the diameter of the dominant follicle at TAI are key factors that may significantly affect oocyte quality, ovulation, the uterine environment and consequently pregnancy outcomes. The use of superovulation (SOV) followed by AI is technique that generates greater numbers of embryos per donor. These techniques, which are associated with embryo transfer (ET) to recipients, are powerful tools that disseminate high genetic quality and improve reproductive performance mainly in heat-stressed dairy cattle and repeat breeders (Ambrose et al. 1999; Hansen et al. 2001; Baruselli et al. 2011). Ovum pickup (OPU) associated with in vitro embryo production (IVP) is another interesting technology that produces embryos from selected donors. This technol- ogy has the potential to enhance genetic progression through the female lineage in cattle (Merton et al. 2003; Pontes et al. 2010). Currently, 36.5% (307 845 ⁄ 843 862) of embryos produced worldwide are in vitro-derived embryos (Embryo Transfer Newsletter 2010). The suc- cess of OPU–IVP is directly related to the oocyte quantity and quality. This review discusses a number of key points relating to the manipulation of ovarian follicular growth to maximize oocyte quality and improve conception rates following TAI and ET of in vivo- and in vitro-derived embryos in cattle. The discussion focuses on (i) the effects of the final follicular growth and the diameter of the dominant follicle in protocols for the synchroniza- tion of ovulation for TAI, (ii) the importance of progesterone (P4) during the SOV treatment, and the timing of the induction of ovulation for TAI in SOV donors and (iii) factors related to donors that influence the competence of the oocyte to produce embryos in vitro following OPU programmes; these factors include breed, stage of ovarian follicular wave at OPU, nutrition and exposure to heat stress (HS). Ovarian Follicular Manipulation in TAI Programmes A variety of protocols for TAI have been developed to design specific treatments for various breeds, categories and types of management. The most common of these therapies uses GnRH or estradiol plus progester- one ⁄ progestin (P4)-releasing devices and prostaglandin F 2a . Beef cattle have a longer post-partum anoestrous period closely related to the presence of calves and poor nutrition (Montiel and Ahuja 2005). This condition limits the effectiveness of traditional TAI protocols (Baruselli et al. 2004). Post-partum anoestrous cows exhibit insufficient pulsatile release of LH to support the final stages of ovarian follicular development and ovulation. Treatment of cattle with equine chorionic gonadotrophin (eCG) has been suggested as an effective tool to increase follicular development and pregnancy rates in TAI programmes for suckled beef cows that exhibit a high prevalence of anoestrous or a low body condition score (Baruselli et al. 2004; Sa´ Filho et al. 2010a,b; Sales et al. 2011). The efficiency of this hormone is related to its FSH- and LH-like activities (Murphy and Martinuk 1991), which stimulate the Reprod Dom Anim 47 (Suppl. 4), 134–141 (2012); doi: 10.1111/j.1439-0531.2012.02067.x ISSN 0936-6768 Ó 2012 Blackwell Verlag GmbH