Swine Gestation Calculator

About the Swine Gestation Calculator

Swine gestation averages 114 days — commonly remembered as "3 months, 3 weeks, and 3 days." The actual range is 112-120 days depending on breed, litter size, and whether the sow is a first-timer (gilt). Large meat breeds (Yorkshire, Landrace) average 114 days, while heritage breeds (Berkshire, Tamworth) may run 115-117 days, and miniature breeds (Juliana, KuneKune) 113-116 days.

Unlike sheep and cattle, sows are non-seasonal breeders and can be bred year-round. Commercial operations target 2.3-2.5 litters per year with 21-28 day weaning. The interval from weaning to estrus is typically 3-7 days. Litter size varies enormously by breed: commercial hybrids average 12-16 piglets born alive, heritage breeds 6-10, and miniature breeds 4-8.

Pre-farrowing preparation is critical for piglet survival — the first 72 hours are the highest-mortality period due to crushing, hypothermia, and starvation. Farrowing crates or well-designed farrowing pens with creep areas and supplemental heat reduce neonatal mortality from 20-30% to 5-10%. This calculator tracks all critical dates from confirmed breeding through weaning.

When This Page Helps

Accurate farrowing date prediction ensures timely crate setup, supplemental heat preparation, iron injection scheduling, and creep feeding — all critical for reducing the 15-25% neonatal mortality rate.

How to Use the Inputs

1. Enter the breeding date
2. Select the sow's breed type
3. Indicate if this is a gilt (first pregnancy)
4. Select your weaning target
5. View expected farrowing date and preparation milestones
6. Plan creep feeding and processing schedules

Example Calculation

Tips & Best Practices

• Move sow to farrowing area 5-7 days before the due date
• Maintain 85-95°F in the creep area for the first week of life
• Give iron dextran injection at day 1-3 to prevent anemia
• Start creep feed at 7-10 days to supplement dam's milk
• Don't breed gilts younger than 7 months or under 280 lbs
• Watch for MMA (mastitis-metritis-agalactia) in the first 48 hours postpartum

Neonatal Piglet Management

**Hour 0-6:** Ensure every piglet nurses colostrum — they must receive antibodies within the first 6 hours. Dry off piglets born wet to prevent hypothermia. Clip needle teeth if fighting at the udder causes teat damage. Weight each piglet. **Day 1-3:** Iron dextran injection (200 mg IM). Dock tails if needed. Castrate male piglets if intended for market. Identify runts for supplemental feeding. **Day 3-7:** Ensure creep area at 85-90°F. Monitor sow for MMA (fever, off-feed, swollen mammary glands). **Day 7-14:** Begin creep feed. Piglets begin exploring beyond the creep area. Growth should be 0.5-1 lb/day.

Breeding Calendar Math

Target: 2.4 litters/year per sow. **Gestation:** 114 days. **Lactation (weaning age):** 21-28 days. **Wean-to-breed interval:** 5-7 days. **Total cycle:** 140-149 days. **Annual capacity:** 365 / cycle = 2.4-2.6 litters. With 21-day weaning: 365 / 140 = 2.6 litters/year (commercial target). With 28-day weaning: 365 / 149 = 2.4 litters/year. With 42-day weaning (heritage/welfare): 365 / 163 = 2.2 litters/year.

Heritage vs. Commercial Breeds

**Commercial hybrids (Yorkshire × Landrace × Duroc):** 12-16 born alive, fast growth, lean carcass, require farrowing crates, 114-day gestation. **Heritage breeds (Berkshire, Tamworth, Gloucestershire Old Spots):** 6-10 born alive, slower growth, more marbling, can farrow outdoors, 115-118 day gestation, stronger maternal instincts. **Miniature pigs (KuneKune, Juliana, American Mini):** 4-8 piglets, 113-116 day gestation, can farrow indoors, popular for small farms.

Frequently Asked Questions

• How long is pig pregnancy?

  Average 114 days or "3 months, 3 weeks, and 3 days." Range is 112-120 days. Larger litters tend toward shorter gestation (each piglet is smaller). Small litters (1-4 piglets) may run 116-120 days.

• What's the difference between a gilt and a sow?

  A gilt is a female pig that hasn't farrowed yet (first pregnancy). A sow has farrowed at least once. Gilts typically have smaller litters (2-4 fewer piglets), longer gestation (1-2 days), and may need more farrowing assistance. First gilts should be bred at 7-8 months of age and 280+ lbs.

• When should I move the sow to the farrowing area?

  Move her 5-7 days before the expected farrowing date. This allows her to acclimate to the new environment, reduces stress, and gives you time to ensure supplemental heat and the creep area are ready. Sudden moves close to farrowing can delay or complicate the process.

• How do I know when farrowing is imminent?

  Signs include: restlessness and nest-building behavior, vulvar swelling and reddening, milk can be expressed from teats (within 24 hours), and a pink mucus discharge. Body temperature drops about 1°F 12-24 hours pre-farrowing.

• Why do piglets need supplemental heat?

  Piglets are born with almost no body fat and very little hair. They need an ambient temperature of 85-95°F (30-35°C) in the creep area for the first week, decreasing by 5°F per week. Without supplemental heat, hypothermia sets in quickly and is the #1 cause of neonatal death along with crushing.

• When can the sow be rebred after weaning?

  Sows typically return to estrus 3-7 days after weaning. Breeding on the first post-weaning heat usually produces the best conception rates and largest litters. This allows a 140-150 day cycle from farrowing to next farrowing, achieving 2.3-2.5 litters per year.