Breeding and Heat Detection

Everything in a breeding herd runs on one repeating clock. If you understand the clock, you stop guessing. If you do not, you will keep feeding non-pregnant sows for months without knowing it.

The cycle

A non-pregnant, mature sow or gilt comes into heat roughly every 21 days. The normal range is 18 to 24 days. Anything shorter than 17 days or longer than 25 days is a signal that something is wrong, and you should write it down and investigate rather than ignore it.

The cycle has four named stages, but for practical farm work you only need to think about two things: the short window when she will accept the boar, and the long stretch when she will not.

• Pro-oestrus (roughly 2 days): the vulva starts to swell and redden. She becomes restless and more vocal. She will not stand for the boar yet.
• Oestrus, or standing heat: she stands still and rigid when pressure is applied to her back, and she will accept the boar. This is your window. It lasts roughly 24 to 72 hours. Sows are generally in standing heat longer than gilts, and gilts can be as short as a day, which is exactly why gilts get missed.
• Met-oestrus (about 2 days): signs fade, she refuses the boar again.
• Di-oestrus (about 14 days): the quiet stretch. Nothing visible happens. If she is pregnant, this simply continues and she never returns to heat.

Ovulation and why timing matters

She does not release eggs at the start of standing heat. Ovulation happens towards the latter part of standing heat, and the eggs are only viable for a short period after release. Boar semen, by contrast, needs some hours inside her tract before it is fully capable of fertilising, and it survives well for a day or more. The practical conclusion is the one thing to memorise from this lesson: semen should be waiting for the eggs, not chasing them. Serving too early is far less damaging than serving too late.

She does not release one egg. She releases a batch, and every egg that is fertilised and survives becomes a piglet. This is why service timing directly changes litter size, not just whether she conceives.

After a successful service

If she conceives, the cycle stops. Gestation runs 114 days, which farmers everywhere remember as three months, three weeks and three days. She will not show heat again during pregnancy. After she farrows and while she is suckling, suckling itself suppresses the cycle. Once the piglets are weaned, the clock restarts quickly: a sow in good body condition normally comes back into heat 4 to 7 days after weaning. That interval is one of the most useful health signals you have. A sow that is too thin at weaning will take much longer, or skip entirely.

The two decision points

Out of the whole 21 day cycle, only two moments are under your control. The first is detection: did you notice she was in heat at all? The second is timing: given that you noticed, did you serve her in the right hours? A farm that fails at the first loses 21 days per miss. A farm that fails at the second gets small litters and blames the boar. The rest of this module is about getting both right.

Write this on the wall of your pen house: 21 days, 114 days, 4 to 7 days. Those three numbers run your whole breeding calendar.

Heat detection is a skill of the eye and the hand, and it is learned by looking at the same animals every day. There is no equipment to buy. What you need is a routine and the discipline to follow it.

Signs you can see from outside the pen

These appear before she will stand, and they are your early warning that a window is opening in the next day or two.

• Swelling and reddening of the vulva. This is usually the first change. In gilts it is often obvious. In older sows the vulva may swell less dramatically, so you must know what her normal looks like.
• Clear or slightly cloudy mucus discharge. A small amount is normal in heat. Thick, yellow, foul-smelling discharge is not heat, it is infection, and it is a reason to call a vet, not to breed her.
• Restlessness and pacing. She moves more, lies down less, and may be up when the others are sleeping.
• Vocalising. Grunting and calling more than usual, especially towards a boar.
• Off feed. Many sows eat noticeably less on the day or two around heat. A good feeder who suddenly leaves food is worth checking.
• Mounting or being mounted by penmates. In group pens this is a strong clue. A sow that stands still while another climbs on her is likely in standing heat.
• Ears pricked, rigid stance, tail held up or flicking. Seen best in the presence of a boar.

The one sign that decides everything

All of the above are supporting evidence. Only one sign confirms she is ready: the standing reflex. She locks her legs, stops moving, arches her back slightly, and will not be pushed off when weight is applied to her back. That is standing heat. If she does not stand, she is not ready to be served, no matter how red the vulva is.

This matters because vulva swelling often peaks a day before standing heat begins and may already be fading when she is at her most fertile. Farmers who breed on vulva colour alone breed too early and get poor conception. Breed on the standing reflex.

Why gilts get missed

Gilts are the most commonly missed animals on smallholder farms, for three reasons. Their signs are quieter, their standing heat can be short, and they are often kept in a group pen away from the boar where nobody watches them closely. A gilt that comes into heat on a Saturday afternoon and is only checked on Monday morning has cost you 21 days.

The fix is exposure and attention. Gilts need to be seen by a boar daily from around 5 to 6 months of age. Boar exposure does not only reveal heat, it helps bring gilts into puberty in the first place. Move the boar past their pen or walk them to him. Ten minutes of real nose-to-nose contact does more than an hour of looking over a wall.

What is not heat

Do not confuse these with heat: a sow that is simply hungry and pacing at feeding time; a sow that is hot and restless in the afternoon sun; discharge that is pus rather than mucus; a lame sow standing still because moving hurts. When you are unsure, mark her and check again in twelve hours. Heat has a direction to it, it builds and then it fades. Pain and hunger do not follow that pattern.

Keep a heat board. Every time you see a sign, mark the sow number and the date. Within one cycle you will start to see each animal's individual pattern, and after two cycles you will predict her.

Heat detection fails on most small farms not because farmers cannot recognise heat, but because checking happens whenever someone remembers. A short check done twice a day at fixed times beats a long check done randomly.

Why twice a day

Standing heat may last as little as around 24 hours in a gilt. If you check once a day, you can miss the whole window or catch it so late that you serve after ovulation. Checking morning and evening, roughly 12 hours apart, means you will catch the start of heat within about 12 hours and can time service properly. This single change is often the cheapest improvement a farm can make.

When to check

Check in the cool parts of the day: early morning before it heats up, and late afternoon or early evening. Pigs show heat signs poorly in the heat of the day. Also check before feeding, not after. A sow with her nose in a trough will not show you anything, and one who has just eaten is sleepy.

The routine, step by step

1. Walk the pens quietly first, with no boar. Look for the visual signs from the previous lesson: vulva, discharge, restlessness, mounting, appetite. Note every suspect animal's number.
2. Bring the boar. Either walk a mature boar slowly down the alley in front of the pens, or move suspect females into a pen next to him. Nose-to-nose contact matters. The boar's smell, his grunting and his physical presence together trigger the standing reflex; a female may not stand for you alone but will stand for him.
3. Give it time. Allow at least 2 to 3 minutes of contact per female or small group. Rushing past in ten seconds is not a heat check.
4. Watch her response. Ears pricked, body rigid, standing firm and pushing back towards the boar rather than moving away. That is your candidate.
5. Apply the back-pressure test while the boar is present, in front of her. The full method is in the next lesson.
6. Record immediately. Not later. Sow number, date, time of day, and the result: no signs, early signs, or standing.
7. Put the boar away. Do not leave him wandering. He tires, loses interest, and becomes less useful as a detector.

If you do not own a boar

Many smallholders share a boar or buy service. You can still do this. Options in order of usefulness: borrow or hire a boar for daily walk-past during your breeding week; keep a vasectomised or young teaser male; or run the check without a boar using the back-pressure test alone, accepting that your detection rate will be lower. If you rely on a neighbour's boar, arrange the visit in advance for the days you expect heat, based on your records. This is why records pay for themselves.

Managing the boar as a tool

Use a mature boar, ideally over 8 months and confidently working. Do not overuse him: a boar used for detection every hour of the day becomes bored. Keep detection sessions short and purposeful. Never let a detection session turn into an uncontrolled mating, because then you lose the ability to time service, and you will not know the service date, which means you will not know the farrowing date.

Who does the checking

Assign one named person, and a named backup. Heat detection done by whoever is around produces gaps exactly on the weekends and holidays when nobody is around. Train the backup by having them check alongside the main person for two full cycles.

Keep the results on a single sheet on the wall, one row per female, one column per day. Patterns jump out of a wall chart in a way they never do out of a notebook.

The back-pressure test is the confirmation step. It costs nothing, takes fifteen seconds per animal, and it is the difference between breeding on evidence and breeding on hope.

What the test is

You apply firm downward pressure to the sow's back, over the loin, and see whether she stands rigid and immobile. A female in standing heat locks up and takes the weight. A female not in heat moves away, sits, or shifts under the pressure.

The method, step by step

1. Do it with the boar present and in front of her if at all possible. His presence dramatically increases the chance she shows the reflex. Without a boar you will get more false negatives.
2. Approach from the side or front, not silently from behind. Speak to her. A startled sow moves, and movement reads as a negative.
3. First, run your hand along her flank and back so she knows you are there.
4. Place both palms flat on her loin, just behind the last rib and in front of the hips.
5. Press down firmly with your body weight through your arms. Hold for about 10 to 15 seconds. Firm and steady, not a slap and not a poke.
6. If she does not move, increase the challenge: straddle her briefly or sit on her back if it is safe to do so and she is a mature sow. A female in strong standing heat will hold a person's weight without shifting.
7. Also try the flank press and the vulva touch: some females respond to pressure on the flank or a hand on the rump when back pressure alone is ambiguous.
8. Record the result as standing or not standing, with the date and whether it was the morning or evening check.

Reading the result

A positive result is unmistakable once you have seen it: she freezes, ears often prick forward, the back arches slightly, and she will not be pushed off. This is the animal you serve.

A negative result is not a diagnosis. It means she is not standing right now. She may be a day early, in which case she will be positive at your next check. She may be a day late, and the window has closed. She may be pregnant already. She may be anoestrus. Your records tell you which, which is why the record matters as much as the test.

Common mistakes

• Testing without a boar and concluding she is not in heat. Many females will not stand for a human alone. Treat a boarless negative as weak evidence.
• Pressing too gently or too briefly. Two seconds of light pressure proves nothing.
• Testing at feeding time or in the heat of the day. Both distort behaviour.
• Testing on slippery or muddy floors. A sow who cannot get footing may stand still out of fear, giving a false positive, or move away when she otherwise would not.
• Testing only once. One test tells you about one moment. The routine is what gives you the picture.

Safety

You are working around a boar and a hormonally active sow. Never put yourself between a boar and a female in heat with no escape route. Keep a boar board or a solid panel within reach in any pen with a mature boar. Do not sit on the back of a gilt you do not know or an animal on a wet floor. Never test alone in a boar pen with the gate shut behind you.

Do this test on every suspect female at every check, and write down every result including the negatives. The negatives are what let you predict the next heat 21 days later.

You have found her standing. Now the question is when to put the boar on her, and how many times. Get this wrong and you will still get pregnancies, but smaller litters.

The principle

Ovulation happens in the later part of standing heat. Semen needs some hours in her tract before it can fertilise, and it lives well for a day or more. Eggs, once released, do not last long. So the rule is: have semen already in place before ovulation. Slightly early is far safer than slightly late.

A practical timing plan

Because you cannot see ovulation, you time from the first time she stood. Using twice-daily checks:

• First detected standing in the morning: serve that same afternoon or evening, then serve again the following morning.
• First detected standing in the evening: serve the following morning, then again that evening or the next morning.

In short, first service within roughly 12 hours of finding her standing, and second service roughly 12 to 24 hours after the first, as long as she is still standing. If she has gone off heat and refuses, do not force a second service.

Gilts, whose standing heat is shorter, should be served earlier relative to detection than sows. If in doubt with a gilt, serve promptly. With a mature sow whose heat runs longer, you have a little more room.

Why two services

A single service is a single bet on your timing being right. Two services spaced 12 to 24 hours apart cover a much wider portion of the ovulation window, so more eggs get fertilised. In practice this shows up as both a better chance she holds pregnant and a larger litter. If your boar and labour allow it, two services is the standard. A third adds little and tires the boar.

Running the mating itself

1. Move the sow to the boar's pen, not the boar to hers. He performs better on familiar ground and is less likely to be attacked.
2. Use a non-slip floor. A boar that slips once may refuse to mount again for days. Bed the mating area with sand, straw or rough concrete.
3. Be present and supervise. Stand to the side with an escape route. Never leave a mating unattended if you can help it, because you need to confirm it actually happened.
4. Check for a genuine service. Look for correct entry and a settled period of several minutes with the boar quiet on her back. A boar mounting the wrong end, or sliding off repeatedly, has not served her. Mark that as a failed attempt and try again in a few hours.
5. Assist only by steadying. If a young boar needs guidance, wear a clean glove and guide gently. Never force.
6. Let them separate on their own, then return the sow to a quiet pen and leave her undisturbed. Do not mix her into a fighting group immediately after service.
7. Record the date and time of both services and the boar used. Without the boar identity you cannot cull a bad boar or trace a genetic problem.

Boar workload and hygiene

An adult boar can work regularly but not endlessly. Spread his services rather than doing four in one day and none for a week. Give him rest between services on the same day. A young boar under a year should be used lightly.

Hygiene protects both animals. Keep the mating pen clean and dry, wash heavy manure off the sow's hindquarters before service, and wash the boar's underline and sheath area regularly. Dirty mating areas are a route to uterine infection, which shows up later as a sow who returns to heat repeatedly or has a discharge.

The follow-up

Mark the calendar. Check her at 18 to 24 days after service for a return to heat. If she returns, she did not conceive, and you have lost only 21 days, not 114. Check again at around 39 to 45 days for a second return. A sow that passes both checks without heat is very likely pregnant.

Your future herd is the gilts you select this year. Choose badly or breed too early and you carry the cost through several litters.

When is a gilt ready

Do not breed on age alone, or weight alone, or heat number alone. Use all three together, and require all three to be satisfied:

• Age: generally around 7 to 8 months at first service for common improved and crossbred types. Very early breeding of an underdeveloped gilt gives small first litters and a sow who breaks down early.
• Weight and condition: she should be well grown and in good, firm condition, not fat and not thin. Weigh her if you have a scale, or use a weigh tape and your eye. A gilt still visibly growing thin over the ribs is not ready.
• Heat number: serve at her second or third observed heat, not her first. Ovulation rate rises with each cycle, so waiting one or two cycles gives a noticeably bigger first litter.

This is exactly why you record every heat on every gilt from about 5 to 6 months. Without those records you cannot know which heat she is on.

Selecting replacement gilts

Select at weaning or growing stage, then confirm before breeding. Look for:

• Teats: count them. You want at least 12 well-spaced, well-formed, functional teats, evenly placed on both sides. Reject blind, inverted or pin teats. She cannot feed more piglets than she has working teats.
• Feet and legs: strong pasterns, straight legs, good walking action on a hard floor. Leg failure is one of the commonest reasons sows are culled young.
• Underline and vulva: a well-developed vulva of normal size. A very small, infantile vulva in a gilt of breeding age is a warning sign.
• Growth and temperament: pick from fast-growing, healthy litters and from calm mothers. A savage or panicky sow is dangerous at farrowing.
• Dam performance: if you know the mother's litter size and mothering ability, use it.

The breeding record card

One card per female, kept dry, with these columns: sow number, date of birth, dates of all observed heats, service dates and times, boar used, expected farrowing date, actual farrowing date, born alive, born dead, mummified, weaned, weaning date, and any remarks. Add the expected farrowing date to the card the day you serve her, by counting 114 days forward.

The two numbers that tell you if breeding works

Farrowing rate is the percentage of females served in a period that actually farrow. Take the number served in one month, wait, count how many farrowed from those services, divide, multiply by 100. A falling farrowing rate points at detection failure, timing failure, boar problems, thin sows, heat stress or disease.

Return rate is the percentage of served females that come back into heat. A high rate of regular returns at 18 to 24 days usually points at timing or boar fertility. A high rate of irregular returns, at odd intervals, points more towards early embryo loss, infection or nutrition. That distinction, which costs nothing to record, tells you where to look.

Costing your breeding decisions

Never take a price figure from a course. Get your own. Before you decide between keeping a boar, hiring service, or buying in bred gilts, phone at least three local suppliers and ask each the same questions: price per service, boar purchase price, price of a bred gilt, delivery cost, and what health guarantee comes with it. Write the three answers side by side. Then compare the total cost of a boar over a year, including his feed, against the cost of the number of services you actually need per year. On a farm with only a handful of sows, hired service is frequently the cheaper answer. On a larger farm, a boar you control gives you the daily heat detection tool that hired service cannot.