A variety of strategies can be used to increase peripheral P4 concentrations. These can be broadly classified as strategies that stimulate increased endogenous P4 production or strategies that rely on administration of exogenous P4 and include (1) manipulation of follicular development to increase the size of the preovulatory follicle and hence the size of the subsequent CL (Baruselli et al., 2012; Mesquita et al., 2014; Ramos et al., 2015); (2) direct stimulation of CL development with luteotropic agents (Maillo et al., 2014; Sánchez et al., 2018); (3) induction of accessory CL using appropriately timed administration of GnRH or human chorionic gonadotropin (Santos et al., 2001; Stevenson et al., 2007; De Rensis et al., 2010; Torres et al., 2013).