Factors affecting postweaning oestrus in the sow

Area of Science:

• Reproductive Biology
• Swine Husbandry
• Animal Science

Background:

• Postweaning oestrus is a critical factor for reproductive efficiency in sows.
• Understanding factors influencing the weaning-to-oestrus interval is crucial for optimizing breeding programs.
• Previous research has indicated various influences on sow reproductive cycles, but specific factors require further elucidation.

Purpose of the Study:

• To investigate factors affecting postweaning oestrus in Norwegian Landrace sows.
• To determine the influence of parity, season, feeding level, boar presence, and herd size on the weaning-to-oestrus interval.

Main Methods:

• Analysis of 3019 weanings across 75 herds in southeastern Norway (1977-1978).
• Examination of ovaries from sows exhibiting failure to return to oestrus postweaning.
• Statistical analysis to assess the impact of various factors on the time to first oestrus.

Main Results:

• Oestrus occurred in 52.3% of primiparous and 77.4% of pluriparous sows within 7 days postweaning.
• Silent heat (corpora lutea) and anoestrus were observed in 46.2% and 38.5% of primiparous sows, respectively.
• Delayed oestrus was significantly associated with later-year quarters (Q3/Q4 vs. Q1/Q2), lower feeding levels, and smaller herd sizes.

Conclusions:

• Seasonal variations and nutritional status significantly impact postweaning oestrus timing in sows.
• Herd size positively correlates with a shorter weaning-to-oestrus interval, suggesting potential social or management influences.
• Boar presence in close proximity did not affect the interval, indicating its limited role in stimulating oestrus postweaning in this context.