Split suckling versus intermittent suckling with primiparous sows: skip-a-heat effects on oestrus during lactation and reproductive performance

The stimulation of lactational oestrus with subsequent viable mating outcomes opens up the possibility of increasing lactation lengths and thus the weaning age of piglets without significant losses in sow productivity. Results from previous work in multiparous (MP) sows have resulted in >80% of sows being mated in lactation through stimulation techniques such as piglet separation and boar exposure (McDonald et al. 2013). Compared to MP sows, primiparous (PP) sows face extra metabolic challenges during lactation that may compromise subsequent reproduction. It was hypothesised that mating PP sows at the subsequent oestrus following their first oestrus during lactation (skip-a-heat) would improve reproductive outcomes when combined with either an intermittent suckling or split suckling oestrus induction protocol.

Primiparous sows (Large White × Landrace, PrimeGro™ genetics; n = 138) were allocated to one of three treatments: Control (C28), where piglets were weaned at d 28 of lactation; Intermittent suckling (IS21), where all piglets were separated from the sow for 8 h each day from d 21 of lactation until weaning at d 28; and Split suckling (SS21), where only half of the litter suckled at any one time from d 21 of lactation until weaning at d 28. All sows in the IS21 and SS21 treatments received twice-daily boar exposure whilst in the farrowing crate throughout the entire separation period. The IS21 and SS21 sows were mated at either lactational oestrus, or at the subsequent oestrus following lactational oestrus (skip-a-heat). The C28 sows and any IS21 or SS21 sows that did not experience a lactational oestrus (non-responders) were mated at their first post-weaning oestrus. Data were analysed using univariate GLM analysis or a Chi-square test (for farrowing rate) (IBM SPSS, Version 21.0; USA).

Approximately 40% of PP sows in the IS21 and SS21 treatments displayed oestrus during lactation, which was lower than in previous studies (Chen et al. 2013). Farrowing rates and litter size did not differ (P > 0.05) between treatments or between sows mated at lactational oestrus and those mated at the subsequent oestrus following lactational oestrus (skip-a-heat) (Table 1). Reproductive performance of PP sows mated during lactation was comparable to sows mated after weaning. Furthermore, skip-a-heat mating compared to mating at the lactational oestrus did not significantly improve reproductive outcomes in PP sows. These data suggest PP sows have a lower response rate to the induction of lactational oestrus compared to MP sows, which needs to be taken into consideration when implementing lactational oestrus induction protocols. However, PP sows that do respond can be mated at their first induced lactational oestrus with no negative effect on subsequent reproductive outcomes.

Table 1.  Lactational oestrus, farrowing rates, and second litter size of primiparous sows mated at lactational oestrus (first heat), at the subsequent oestrus following lactational oestrus (skip-a-heat), or at normal post-weaning oestrus (non-responders). Values are mean ± SEM