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** Artificially reducing the day length from May-August will decrease the interval from weaning to oestrus from 23.6 days  on average to 5.7 days.
 
** Artificially reducing the day length from May-August will decrease the interval from weaning to oestrus from 23.6 days  on average to 5.7 days.
 
* The oestrous cycle normally lasts 21 days, interrupted only by pregnancy and lactation.
 
* The oestrous cycle normally lasts 21 days, interrupted only by pregnancy and lactation.
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* Oestrus normally lasts ~53 hours.
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* Ovulation occurs 38-42 hours after the onset of oestrus.
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* During lactation, the physical stimuli of suckling will suppress cyclic activity.
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* Many sows show an anovulatory oestrus 2 days after farrowing.
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* When weaning occurs at 5-6 weeks, oestrus occurs within 4-6 days.
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* Earlier weaning results in a slightly longer interval before subsequent oestrus.
    
=== Cyclic Changes in the Ovaries ===
 
=== Cyclic Changes in the Ovaries ===
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