Boar contact and seven hours of interrupted suckling improved sow performance

In the majority of lactating sows, piglet sucking plus the metabolic demands of milk production prevent the post-partum resumption of oestrous cyclicity until after weaning. Therefore, lactation length ultimately determines farrowing frequency, with high suckled litter sizes and lactation body reserve loss also impairing subsequent reproductive performance. Sow-piglet separation (interrupted suckling; IS) for 12 h stimulated ovarian follicle growth and ovulation prior to weaning (Kemp and Soede 2012); however, the effect of a shorter period of IS on the timing of ovulation post-partum and subsequent reproductive output and efficiency is less clear. The current study tested the hypothesis that seven hours of IS would increase the incidence of lactation ovulation and improve the reproductive efficiency of sows remaining anoestrus until weaning.

From d 17 ± 0.2 post-partum (mean ± SEM), 32 Large White x Landrace sows (parity 4.1 ± 0.12) suckling 9.6 ± 0.24 piglets, experienced 3 days of zero (0IS) or 7 (7IS) hours of piglet separation (n = 16 sows/treatment). Average parity did not differ between treatments. In the 7IS treatment, separation was between 0800 and 1500 h, and was achieved through the use of a board placed between the sow and the creep area. From the start of IS until weaning (day 27 ± 0.2 post-partum), sows in both treatment groups received 5 min of nose-to-nose contact with a mature boar through the open door of their farrowing crate. During the night, a boar was housed in a farrowing crate within the farrowing shed. Sows were checked daily for oestrus in the presence of the boar, and inseminated at first detection of oestrus. The timing of oestrus, farrowing rates and the subsequent total litter size were recorded. An ANOVA model was used to determine treatment effects on the timing of oestrus and subsequent litter size (Genstat, 10th Edition; UK), with differences between proportions analysed by Chi-square.

Treatment (7IS versus 0IS) tended (P < 0.1) to increase the incidence of lactation oestrus and reduce the interval from parturition to first oestrus (Table 1). The parity of sows ovulating during lactation was higher (P < 0.05) than those which did not (4.4 ± 0.23 vs 3.9 ± 0.15). Subsequent litter size was unaffected by the timing of ovulation; however, the farrowing to farrowing interval was shorter (P < 0.05) for sows mated during, as opposed to after, lactation: 139.4 ± 0.39 vs 147.3 ± 0.29 days. The total number of piglets produced per 100 sows entering the 0IS and 7IS treatments was calculated to be 1125 and 1310.

Table 1.  Effect of seven (7IS) vs zero (0IS) hours of interrupted suckling (IS) between d 17 and 20 of lactation on the timing and incidence of oestrus and subsequent reproduction of sows weaned at 27 d

These data provide preliminary evidence that seven hours of sow-piglet separation for only three days during late lactation may increase reproductive efficiency. This management strategy could be used to improve reproductive output when environmental conditions are unfavourable (i.e. during summer) or body tissue mobilisation is high, particularly for high parity sows.