found that piglets of crated gilts without nesting materials spent longer in the udder, probably to avoid cold compared with gilts that were provided with straw. They suggested that the unintentional udder massage by piglets might stimulate OT release, and result in a shortened farrowing duration in crated sows with no nesting materials.In the present study, however, circulating OT concentrations during the birth of the first five piglets did not differin line with prepartum housing environment