Missing the heat cycle is one of the most expensive mistakes in backyard pig breeding. Every missed cycle means your sow eats feed for another 21 days without producing piglets. At ₱2,000-2,500 per bag of gestating feed (Suregrow, VIEPro Premium), that's roughly ₱1,400-2,000 wasted in feed alone, not counting the lost piglet revenue from delayed farrowing.
"Gipanglaway na ang anay." (The sow is drooling, she is in heat.)
But before breeding, make sure your gilt is physically ready. See when a gilt is ready to breed in the Philippines for age, weight, and body condition guidelines.
Filipino farmers have been reading sow behavior for generations. Here are the signs, and how to time the breeding right.
The Heat Cycle
A sow's heat cycle repeats every 21 days (range: 18-24 days). Heat itself lasts 24-72 hours depending on the sow's age. Gilts tend to have shorter heats than experienced sows, sometimes only 12-18 hours. That short window is why checking twice a day matters.
The cycle has stages, and only one stage is the right time to breed:
| Stage | Duration | Signs | Breed? |
|---|---|---|---|
| Pre-heat | 1-2 days | Vulva swells, reddens. Restlessness. Reduced appetite. | Not yet |
| Standing heat | 12-36 hours | Stands rigid when pressed on back. Ears erect. Receptive to boar. | Yes, this is the window |
| Post-heat | 1-2 days | Vulva returns to normal. Loses interest in boar. | Too late |
The Back Pressure Test (Standing Heat Test)
This is the most reliable method for backyard farmers:
The response is much stronger if a boar is nearby. Even the smell or sound of a boar will intensify the standing reflex. If you don't have a boar, a synthetic pheromone spray like Viddavet Boar Odorant (~₱1,400 for 100ml at viddavet.com.ph) can trigger the same reflex for AI timing.
- Stand behind or beside the sow
- Press firmly down on her lower back / loin area with both hands
- If she locks her legs, stands rigid, and does not move away, she is in standing heat
- Her ears will usually prick upward during standing heat
- If she walks away or squats, she is not ready yet
Some farmers bring a boar within sight (but not contact) while testing. That works well, but it also works fine without a boar for experienced sows. Gilts are trickier. They sometimes need boar presence or pheromone spray to show a clear standing reflex.
Other Signs to Watch For
Beyond the back pressure test, watch for these behavioral and physical cues:
- Vulva swelling and redness starts 1-2 days before standing heat
- Restlessness where the sow paces the pen, vocalizes more than usual
- Reduced appetite as she may eat less or refuse feed entirely during peak heat
- Mounting other pigs if housed with others
- Clear, sticky mucus from the vulva
- Seeking the boar by pressing against the pen wall closest to him, sniffing, calling
"Nagsulod na ang anay." (The sow has entered heat.) When farmers in the Visayas see these signs, they know it is time to call the boar owner or the AI technician.
Optimal Breeding Timing
Timing makes the difference between a large litter and a missed cycle:
- If standing heat detected in the morning: breed that evening
- If detected in the evening: breed the next morning
- Breed twice, 12-24 hours apart, for maximum conception rate
- The sow ovulates approximately 24-36 hours after the start of standing heat. Sperm need to be waiting
AI vs Natural Service Timing
If you're using artificial insemination, timing is even more important than with natural service. The boar provides repeated stimulation that extends the sow's receptivity, but with AI you get one shot per insemination.
| Method | First Service | Second Service | Typical Cost |
|---|---|---|---|
| Natural (boar service) | Evening if detected AM; next AM if detected PM | 12-24 hours after first | ₱500-1,500 per service, or one piglet from the litter |
| AI (DA/SWAIB subsidized) | Same timing rule | 12-24 hours after first | ~₱200 per service through AI sa Barangay centers |
| AI (private provider) | Same timing rule | 12-24 hours after first | ₱1,000-1,500 per service |
The DA's SWAIB (Swine AI sa Barangay) program under INSPIRE has expanded to over 16 centers in Region 6 alone, with new facilities in Isabela, Bataan, and Mountain Province. The processed semen comes from genetically superior boars, so you get better genetics for less money than a private boar service. Ask your municipal agriculturist if there's a SWAIB center near you.
Heat Stress and Silent Heats
Here's something most online guides don't mention: Philippine temperatures regularly hit 30-36°C during summer months (March to June), and that directly suppresses heat expression in sows. Research from The Pig Site shows:
| Temperature | Conception Rate | Anestrus Rate | Impact |
|---|---|---|---|
| Below 27°C | ~90% | Minimal | Normal breeding performance |
| 30°C | ~85% | 2.5% | Mild suppression, watch gilts closely |
| 33°C | ~78% | 8.75% | Serious, expect silent heats and missed cycles |
This means Philippine sows, especially in Cebu, Davao, Iloilo, and lowland areas, are at risk of silent heats and reduced conception for 3-4 months of the year. If your sow is "not coming into heat" during summer, the heat cycle might be happening but the signs are too weak to detect. Try the back pressure test with boar pheromone spray, and check at cooler times (early morning, late afternoon).
Cooling helps. Even simple measures like shade, sprinklers during the hottest hours, or a wallow area can bring the sow's body temperature down enough to restore normal estrus expression.
How to Get Stronger, More Reliable Heats
Some sows, especially gilts, show "silent heats" that are hard to detect. Here is what helps:
- Boar exposure. House gilts or sows within sight and smell of a mature boar. His pheromones stimulate stronger and more regular heat cycles.
- Flushing. Increase feed by 50% for 10-14 days before the expected heat. This boosts ovulation rate and can increase litter size by 1-2 piglets. Most farmers I've talked to skip this step, and it shows in their litter sizes.
- Check twice daily. Mornings (6-7 AM) and late afternoon (4-5 PM). Short heats in gilts can be missed with once-daily checks.
- Wean piglets on a consistent schedule. Sows typically come into heat 4-7 days after weaning. A Thai study on tropical sows found the average weaning-to-estrus interval was 3.9 days in hot season vs 3.6 days in cool season. Mark the weaning date and start watching closely at day 4.
Common Mistakes
- Checking only once per day. You can miss an entire gilt heat that lasted only 12-18 hours. This alone probably costs more farmers more piglets than any other mistake on this list.
- No boar nearby. Sows without boar exposure have more silent and irregular heats. Even the smell is enough.
- Breeding at first heat on gilts. Skip the first heat and breed at the 2nd or 3rd cycle for a larger first litter. The first heat produces fewer eggs.
- Not recording heat dates. A simple calendar on the pen wall helps you predict the next cycle and catch it reliably. If she came into heat on the 5th, mark the 26th.
- Breeding too early or too late in the standing heat window. Too early means sperm die before ovulation. Too late means eggs have already degraded. Follow the morning/evening rule above.
And honestly, the most common one we hear: farmers who notice the signs but wait until "tomorrow" to arrange the boar. By tomorrow, standing heat is over. When you see it, act that day.
Bisaya / Cebuano
Para sa mga mag-uuma: Pagkahibalo sa init sa anay
Mga senyales:
- Hubag ug pula ang kinatawo (vulva)
- Dili makapahulay, maglikay-likay
- Mobarog ug dili molihok kung pisilon ang likod, kini ang "standing heat"
- Ang dalunggan mobarog pataas
Kanus-a ipasakop sa laki (boar):
- Kung nakita sa buntag ang standing heat, ipasakop sa hapon
- Kung nakita sa hapon, ipasakop sa sunod buntag
- Duha ka beses ang pagpasakop, 12-24 oras ang gintang
Tip: Butangi og laki (boar) sa duol. Bisan dili mag-uban, ang baho sa laki makapalig-on sa init sa anay.
Kantidad: Ang matag missed heat cycle nagkagasto nimo og ₱1,400-2,000 sa feeds lang. Pag-AI sa Barangay, mga ₱200 lang matag service.
"Magbalik og kalibutan" (mobalik og init) ang anay kada 21 ka adlaw kung wala mabdos.
Learn More
- When is a gilt ready to breed? for age, weight, and body condition guidelines
- How to tell if your pig is pregnant for signs after successful breeding
- How many piglets does a native pig have? on litter size expectations
- Best pig breeds for small farmers covers breed reproductive traits
- Native vs commercial pig systems for breeding system comparison
- Feed calculator to estimate your sow's daily feed cost
Sources: pig333.com: Heat Detection in Sows, The Pig Site: Improving Sow Fertility, The Pig Site: Hot-Humid Environment and Swine Reproduction, ATI Region 6: AI sa Barangay Facilities, ATI Ilocos: Agustin Integrated Farm AI Story, DA INSPIRE Program, PMC: Factors Affecting Estrus and Ovulation in Weaned Sows (Thailand), Viddavet: Boar Odorant Spray, BAI Swine Breeding Extension Materials.
