Intermittent suckling is a successful method to induce lactational oestrus in multiparous communally housed sows

Communal housing supports the natural behaviour of sows and piglets but may increase the incidence of lactational oestrus. Lactational ovarian activity can be controlled with intermittent suckling (IS) protocols that allow lactational conception and prolonged lactation. We hypothesised that a novel IS-protocol combining late-onset of IS (initiated after 30 days postfarrowing) with communal housing would result in a minimum lactational oestrus rate of 85%. Oestrus rate, follicular growth, conception, backfat thickness, hormonal balance (progesterone, prolactin) and piglet average daily gain (ADG) in communally housed sows (n = 31, parities 1-7) were monitored during an IS-protocol (onset at median 32 d postpartum, total separation 8 h/day for 7 days, D_IS1-D_IS7), and until weaning at 9 weeks. Standing oestrus rate within D_IS1-D_IS7 was 87.1%, with multiparous (95.8%) surpassing primiparous (57.1%) sows. Follicle growth by D_IS5 was linked with greater sow backfat on D_IS1 (P = 0.017) but hindered by larger nursing litters (P = 0.014). Insemination resulted in 81.5% conception rate and 15.6 total born, the latter correlating positively with sow backfat at D_IS1 (P = 0.026). Conception was related to longer lactation pre-IS (P = 0.013), greater piglet ADG pre- and post-IS (P < 0.01) and better sow backfat preservation post-IS (P = 0.011). Shorter lactation pre-IS resulted in a smaller increase in prolactin between D_IS1 - D_IS5 (P = 0.001). Our study hypothesis was met, indicating that the likelihood of inducing a fertile lactational oestrus in communally housed sows with IS-protocols is high, with benefits expected from multiparity and longer preceding lactation. Achieving to combine better sow backfat preservation in sows with higher piglet ADG during postconceptional lactation suggested a beneficial effect from the IS protocol and communal housing on piglet creep feed intake. IS-protocols can improve the synchronisation of oestrus in communally housed lactating sows, thereby facilitating conception during lactation and separation of oestrus from weaning. Postconceptional lactation and the related effects on pregnancy require further research.