“…Several studies discuss the influence of additional factors such as climate (Mauch, 1937), stud farm where the mares are located during the gestation period (Aoki et al, 2013;Davies Morel et al, 2002;Langlois and Blouin, 2012;Van Rijssen et al, 2010), feeding management (Thorson et al, 2010;Uppenborn, 1933), type of insemination (Bene et al, 2014), inbreeding (Langlois and Blouin, 2012), length of last gestation period (Aoki et al, 2013), interval from ovulation to mating (Davies Morel et al, 2002), unspecified characteristics of the individual mare (Giger et al, 1996;Uppenborn, 1933;Valera et al, 2006;Van Rijssen et al, 2010), reproductive status of the mare (Van Rijssen et al, 2010), parity of the mare (Aoki et al, 2013;El-Wishy et al, 1990;Pool-Anderson et al, 1994;Sanchez, 1998;Staffe, 1935;Valente et al, 2006;Valera et al, 2006;Winter et al, 2007), age of the mare (Aoki et al, 2013;Bene et al, 2014;Bos and Van der Mey, 1980;Cilek, 2009;Davies Morel et al, 2002;Demirci, 1988;Guay et al, 2002;Heidler et al, 2004;Hintz et al, 1992;Kurtz Filho et al, 1997;Langlois and Blouin, 2012;Mauch, 1937;Sevinga et al, 2004;Valera et al, 2006;…”