A total of 53 sows were used to determine the effects of a lactational estrus stimulation
strategy on reproductive and litter growth performance. Treatment differences within
parity group, multiparous and primiparous, were also considered. Litter size was equalized
to 11.6 ± 1.2 pigs at d 2 postfarrowing. At d 18 of lactation, sows were allotted to
the control or an altered suckling method (ALT). The ALT sows were placed in adjacent
pairs within parity so pigs could be moved between litters by temporarily lifting
the divider between the two litters. On d 18, all but the 5 lightest weight pigs from
each ALT litter were weaned. The 5 lightweight pigs for each pair of litters formed a
combined litter that nursed each sow of the pair 12 h/d from d 18 to 25. Therefore, pigs
had nursing access 24 h/d, but each ALT sow was suckled only 12 h/d. Boar exposure
was provided to ALT sows for 15 min/d by removing sows to a pen outside the farrowing
room. Control and ALT sows were weaned at d 21 and d 25, respectively. Sow
weights and litter growth performance during lactation was similar between treatments,
although ALT sows had 16% greater total feed intake (P < 0.01) due to the extended
lactation length. Primiparous sows lost a greater percentage (7.4 vs. 3.4%) of BW and
consumed less feed (P < 0.01) than multiparous sows. A total of 26 ALT sows (93%)
were detected in estrus and mated in lactation. Although duration from initiating ALT
to estrus was greater (P < 0.001) than the wean-to-estrus interval for controls, ALT
sows were in estrus earlier (23.0 vs. 24.6 d; P < 0.001) than controls postfarrowing, with
primiparous sows responding more slowly (5.4 vs. 3.8 d; P < 0.01) than multiparous
sows for both treatments. Pregnancy rate and subsequent reproductive performance
were similar between treatments. In conclusion, ALT sows expressed lactational estrus
and performed reproductively similar to sows with conventionally weaned litters.
