How many days does a sow's estrus generally last? Symptoms and ways to deal with failure to come into heat

A sow's estrus is the prerequisite for mating and farrowing, and whether the sow's estrus can be detected at the first opportunity is very important, so whether you are a beginner or a professional pig farmer, you need to make an accurate judgment about the sow's estrus and mating time, so how many days does a sow's estrus generally last? What symptoms are there? What should be done if the sow does not come into heat?

I. How many days does a sow's estrus generally last?

1. When does a sow start to come into heat?

In the early stage of sexual maturity, a sow's estrus time is irregular, and generally only after three estrus cycles does it become regular. Under normal circumstances, a sow comes into heat once every 18 to 23 days, with an average of once every 21 days. However, because breeds differ, the estrus time also differs; for example, crossbred sows come into heat once every 19 to 20 days on average. Local-breed sows come into heat once every 18 to 19 days. Foreign-breed sows come into heat once every 20 to 23 days.

2. How many days does a sow generally stay in heat?

When a sow is in heat, it generally lasts 2 to 5 days, with an average of one estrus lasting 2.5 days. During estrus, there will be certain changes depending on the season and breed. For example, in spring, the number of days a sow stays in heat is somewhat shorter. In autumn or winter, the number of days in heat is somewhat longer. Sows produced in China stay in heat longer, while introduced foreign breeds are relatively shorter.

3. After how many days does a sow generally begin her second estrus?

After farrowing, a sow will have a second estrus at weaning or when the litter is separated. Generally, 2 to 12 days after weaning is normal, and around 7 days after weaning is the best time for mating; if it exceeds 20 days, treatment methods should be adopted to assist her estrus and mating.

II. What symptoms does a sow show during estrus?

1. Changes in the vulva: When a sow is in heat, the vulva gradually changes from white-pink to pink, until it becomes purplish-red, and gradually swells.

2. Fluid inside the vulva: When a sow is in heat, some sticky fluid appears at the vulva, looking like a person's runny nose.

3. Appearance: When a sow is in heat, she is restless, often walking around or standing while other pigs sleep, and once a person comes near, she will approach the person.

4. Appetite: When a sow is in heat, her appetite decreases, and she often makes a distinctive grunting sound.

5. Reaction to boars: When a sow is in heat, she is relatively sensitive to boars; once a boar approaches, her body trembles, her gaze becomes blank, and she raises her large ears. If estrus is at its peak, she will directly mount other pigs, making them squeal.

However, because pig breeds differ, there will also be certain differences in estrus symptoms, but on the whole they all share common estrus symptoms, so they are still quite easy to identify.

III. What should be done if a sow does not come into heat?

1. What is the reason a sow does not come into heat?

(1) A sow not coming into heat may be due to a stress response: during the sow's growth period, if immunity is low or the temperature is too high, it will cause the sow to have a stress response and not come into heat.

(2) A sow not coming into heat may be due to disease: if a sow does not come into heat, it may be due to diseases such as endometritis or respiratory syndrome.

(3) A sow not coming into heat may be due to nutritional imbalance: during the sow's growth period, if the feed provided is nutritionally inadequate, it will also cause the sow not to come into heat.

(4) A sow not coming into heat may be due to improper management by the keeper: during the raising period, if the sow has too little exercise, it will cause her not to come into heat, so during the raising period, large pens should be used for breeding as much as possible.

2. Solutions for a sow not coming into heat:

(1) Change the pen to make the sow come into heat: When it is time for the sow to come into heat, move her to another pen as much as possible to make it easier for her to move around; at the same time, sows of similar body size can be placed together, and after a multiparous sow comes into heat and mounts a replacement gilt, this will prompt her to come into heat.

(2) Increase exercise to make the sow come into heat: Drive the sow to the hills or a wide, unoccupied area to exercise a bit, so as to promote estrus in the sow.

(3) Boar stimulation to make the sow come into heat: Let a boar approach a sow that is 180 days old, so as to induce estrus. Generally, contact can be made once every two days, and every three days a boar can be replaced to induce estrus.

(4) Inject hormones to make the sow come into heat: When a sow does not come into heat, an appropriate amount of human chorionic gonadotropin or pregnant mare serum gonadotropin can be injected to promote estrus in the sow. But if the effect is still not obvious after repeated use, then it should no longer be used.