submitted to a double FTAI, after the use of P4 analogue and GnRH, compared to gilts inseminated according to the onset of oestrus (Martinat-Botte et al. 2010). The reproductive performance of gilts with double FTAI after synchronization with P4 analogue followed by eCG and pLH application was similar to that of a control group in which multiple inseminations were performed (Degenstein et al. 2008). In weaned sows, the use of pLH at oestrous onset followed by a single FTAI 24 h later resulted in similar reproductive performance to that obtained with multiple inseminations without pLH application (Zak et al. 2011; Fontana et al. 2014).
Usually, 5 mg of pLH by the intramuscular route is the recommended dose for swine, although there are
studies showing the possibility of using 2.5 mg by the intramuscular route (Viana et al. 2005; Bennett-Steward
et al. 2007). On a commercial scale, the intramuscular application could require more labour, considering the difficulty of accessing the animal’s neck. The vulvar submucosal route could be a practical alternative as it has been shown to be effective for farrowing induction using a single administration of prostaglandin, allowing reduction of the dose to a quarter of the usual recommendation (Kirkwood et al. 1996; Kaeoket 2006).The use of a single hormone application and reduction
in the number of hormones used in protocols for a single or double FTAI have been considered in some studies, showing effectiveness to synchronize ovulation and reduce the number of inseminations (Martinat-Botteet al. 2010; Knox et al. 2011; Driancourt et al. 2013).This tendency in recent studies will likely facilitate the use of FTAI in the routine of commercial farms due to reduction of costs and labour with hormonal protocols. Information about the possibility of using a single FTAI combined with induced ovulation in spontaneous oestrus is lacking for gilts. This study aimed to evaluate
the effect of different doses and routes of pLH administration at the onset of oestrus, combined with a single FTAI, on the interval between onset of oestrus and ovulation (IOEO) and reproductive performance of
gilts.