Stimulation of Oestrus and Ovulation in Lactating Sows

A Kansas State University study showed that sows could show oestrus when suckling just 12 hours per day and with boar access. These sows expressed lactational oestrus and their subsequent reproductive performance and litter weights were similar to sows weaned in a conventional way at 21 days, the researchers told delegates at the 2013 Kansas Swine Day.
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A total of 53 sows were used to determine the effects of a lactational estrus stimulation strategy on reproductive and litter growth performance, reported H.L. Frobose and colleagues.

Treatment differences within parity group, multiparous and primiparous, were also considered.

Litter size was equalised to 11.6 ± 1.2 pigs on day 2 post-farrowing. On day 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 day 18, all but the five lightest weight pigs from each ALT litter were weaned. The five lightweight pigs for each pair of litters formed a combined litter that nursed each sow of the pair 12 hours per day from day 18 to 25. Therefore, piglets had nursing access 24 hours per day but each ALT sow was suckled only 12 hours per day.

Boar exposure was provided to ALT sows for 15 minutes per day by removing sows to a pen outside the farrowing room. Control and ALT sows were weaned on day 21 and day 25, respectively.

Sow weights and litter growth performance during lactation was similar between treatments, although ALT sows had 16 per cent greater total feed intake (P<0.01) due to the extended lactation length.

Primiparous sows lost a greater percentage (7.4 versus 3.4 per cent) of bodyweight and consumed less feed (P<0.01) than multiparous sows.

A total of 26 ALT sows (93 per cent) were detected in oestrus and mated in lactation.

Although duration from initiating ALT to oestrus was greater (P<0.001) than the wean-to-oestrus interval for controls, ALT sows were in oestrus earlier (23.0 vs. 24.6 days; P<0.001) than controls post-farrowing, with primiparous sows responding more slowly (5.4 versus 3.8 days; P<0.01) than multiparous sows for both treatments.

Pregnancy rate and subsequent reproductive performance were similar for both treatments.

Frobose and colleagues concluded that ALT sows expressed lactational oestrus and performed reproductively similar to sows with conventionally weaned litters.


Frobose H.L., K.M. Gourley, M.D. Tokach, J.M. DeRouchey, S.S. Dritz, R.D. Goodband, J.L. Nelssen and D.L. Davis. 2013. Stimulation of estrus and ovulation in lactating sows.Proceedings of 2013 Kansas Swine Day, p16-26.

Further Reading

You can view the full paper by clicking here.
Read other papers presented at the 2013 Kansas Swine Day by clicking here.

January 2014

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