Swine Gestation Calculator

Frequently Asked Questions

How long is a pig's gestation period?

Sows (mature females) typically farrow after 114 days, remembered as 3 months + 3 weeks + 3 days (the 3-3-3 rule). Gilts (first-litter females) may carry slightly longer at 115 days. Actual farrowing can occur 1-3 days early or late.

When should I move a sow to the farrowing crate?

Move sows to clean, disinfected farrowing crates 5-7 days before the expected farrowing date to allow her to acclimate. Moving too early wastes crate space; moving too late risks unsupervised farrowing in a group pen.

How can I confirm pregnancy in a sow?

The earliest signs are failure to return to estrus at 18-24 days post-breeding. Ultrasound can confirm pregnancy from day 25-30. A-mode ultrasound detects fluid; B-mode (real-time) can visualize embryos from day 25 and fetuses from day 35 onward.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

This calculator takes a breeding or service date and adds the standard gestation length for swine to produce an expected farrowing date. It then projects key reproductive and management milestones relative to that breeding date so you can plan farrowing-room scheduling, crate moves, and rebreeding windows in advance.

The 3-3-3 Rule

Pig gestation is commonly remembered as "3 months, 3 weeks, 3 days," which equals exactly 114 days. This rule is so consistent across commercial breeds that it has become the industry standard for scheduling. First-litter gilts average 115 days, one day longer than mature sows, so the calculator accounts for that difference when you select Gilt.

Actual farrowing can occur 1-2 days before or after the predicted date. Monitoring the sow closely from day 112 onward is recommended.

Signs of Approaching Farrowing

Within 24-48 hours of farrowing, sows typically show several recognizable signs:

Restlessness and repeated lying down and rising

Nest-building behavior (rooting and gathering bedding)

Swelling and reddening of the vulva

Milk let-down when the teats are pressed (colostrum present)

Reduced appetite in the 12-24 hours before farrowing begins

Farrowing Management

Temperature is critical for newborn piglets, whose thermoregulatory systems are undeveloped. The farrowing room should be kept at 65-70 degrees F for the sow, while a heat lamp or heated mat in the piglet creep area should maintain 85-90 degrees F for the first week.

Colostrum intake within the first 6-12 hours of life is essential for passive immunity transfer. Ensure every piglet nurses at least once before any supplemental feeding. Supervision during farrowing significantly reduces overlying losses, which account for the largest share of pre-weaning mortality.

Tips and FAQ

When should I move the sow to the farrowing crate?

Industry practice is to move sows approximately 7-10 days before the expected farrowing date. Moving them too late raises stress; moving them at day 84 (30 days before) is common in operations that want sows adapted to the crate environment before parturition.

What is the typical litter size?

Commercial sows in modern operations average 13-15 total born per litter, with 12-14 born alive. Gilt litters average 1-2 piglets fewer than mature sow litters.

How long after weaning does the sow return to heat?

Most sows return to estrus 3-7 days after weaning, which is why the rebreeding window in this calculator is shown at farrowing plus 3-7 days. Producers targeting a 2.4+ litters-per-year cycle aim to breed within that window.

Swine Gestation Calculator

Frequently Asked Questions

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