When gilts or sows enter oestrus in their reproductive cycles (about 21 days long) they are ready to be bred.

小母猪和大母猪的发情期大概是21天，这是她们的生理循环周期，准备繁殖阶段。

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When gilts or sows enter oestrus in their reproductive cycles (about 21 days long) they are ready to be bred.

小母猪和大母猪的发情期大概是21天，这是她们的生理循环周期，准备繁殖阶段。

youdao