What to Do If a Sow Does Not Come into Heat? Practical Methods to Bring a Sow into Heat

The reasons why a sow does not come into heat are fairly complex. Just like with people, there must be a cause. Generally, the main cause is poor feeding and management, followed by diseases, and there may also be some other factors. Below, let us briefly summarize the reasons why sows do not come into heat and how we should respond during the breeding process.

What to Do If a Sow Does Not Come into Heat

1. Congenital factors: These are mainly physiological defects and genetic defects, such as underdeveloped reproductive organs, intersex pigs, abnormal hormone secretion, and so on. In addition, the presence of seasonal recessive breeding genes may also cause seasonal failure of sows to come into heat.

2. Caused by infectious diseases: Some diseases such as porcine eperythrozoonosis, porcine reproductive and respiratory syndrome, porcine pseudorabies, porcine brucellosis, Japanese encephalitis, parvovirus, chlamydia, and others can all lead to poor reproductive development in pigs, resulting in failure to come into heat or unclear estrus, thereby causing reproductive disorders.

3. Caused by poor feeding and management: This accounts for a very large proportion of sows failing to come into heat, mainly for the following reasons:

1) Nutrition: Due to malnutrition, sows become too thin and therefore do not come into heat; feeding a single type of feed causes malnutrition in sows, leading to failure to come into heat. Insufficient vitamins and trace elements in the feed of replacement gilts, or the presence of mycotoxins in the feed, can all cause sows not to come into heat. Excessive nutrition makes sows too fat, with fat infiltration in the ovaries and degeneration of follicular epithelial fat cells, causing follicular atrophy or ovarian cysts, which can also lead to failure to come into heat.

2) Weaning too late: If a sow loses more than 15kg of body weight during lactation, her physical condition becomes poor, causing delayed estrus or failure to come into heat after weaning.

4. Obstetric diseases of sows (such as endometritis) can also cause failure to come into heat.

How to Bring a Sow into Heat

The mechanism behind abnormal estrus in sows is mainly an imbalance in hormone secretion within the body. All methods are aimed at improving hormone secretion in the body, especially the secretion of sex hormones.

1. Control body condition: For sows that are too fat, restrict feeding to reduce body fat, and then induce estrus; for those that are too thin, increase feed intake to build up body condition.

2. Boar stimulation: Put sows that are not coming into heat in the same pen with a boar, letting the boar chase and mount them to promote estrus.

3. Relocation stimulation: When approaching the age of first estrus, move growing pigs within the barn to a different environment.

4. Group housing stimulation: Raise replacement gilts in small groups, with 10~20 per pen; group-house sows after weaning, with 6~8 per pen.

5. Exercise stimulation: Strengthen exercise for sows, practice grazing, and provide green forage, which helps promote estrus in sows.

6. Drug-induced estrus: Inject pregnant mare serum gonadotropin, human chorionic gonadotropin. Or inject a triple hormone combination, which can bring sows into heat and induce ovulation.

7. Udder massage: Massage the udder by hand, 1~2 times per day, about 10 minutes each time, for 5-6 consecutive days, and the sow will come into heat.

8. Brown sugar stimulation: Take 0.5—1 kg of brown sugar, pour it into an iron pot and scorch it, then add 1.5~2 kg of water and bring to a boil. After it cools, mix it into the feed and feed it to the pigs. After 3~5 days of feeding, sows that have not come into heat for a long time will begin to come into heat.

9. Careful observation: Some excellent breeds of pigs, especially purebred pigs, show unclear signs of estrus. If you do not pay attention, you may miss it.

How to Make a Sow Come into Heat Quickly

Estrus in sows varies depending on each pig's growth and development and physical condition, so what you call wanting a sow to come into heat quickly is unrealistic, because it takes a certain amount of time for all aspects of a replacement gilt's physical signs to mature. However, there are ways to help a sow come into heat smoothly (only for sows that have already farrowed). Within one week after giving birth and weaning, healthy sows without other diseases will generally come into heat naturally and smoothly; if they do not come into heat for more than one week, then oral medication or injection is needed (for example, if it is due to inflammation, first carry out anti-inflammatory treatment and then feed a estrus-inducing powder; if it is due to a lack of vitamin E, then give an extra injection of vitamin E -- commonly known as tocopherol). If there is no inflammation, you can also inject vitamin E: it increases litter size and can effectively prevent the occurrence of agalactia! Before breeding a sow, inject one dose of anti-inflammatory drug on that day, which can effectively prevent inflammation and increase the conception rate.

How to Promote Ovulation in Sows

1. Even if a sow comes into heat normally, sometimes mating may still fail, mainly because the sow does not ovulate. Promoting ovulation in sows often requires drugs. If a sow does not ovulate, you can generally choose to use ovulation-promoting drugs for intramuscular injection, which usually produces results.

2. However, note that unless absolutely necessary, it is best not to use drugs to promote ovulation in sows, especially for first-parity sows. Once drug dependence forms, it is very likely to affect future estrus and pregnancy. For first-parity sows, you can choose to provide supplemental lighting in the sow barn at night, because light can stimulate the ovarian function of sows to a certain extent, which can also play a role in promoting ovulation.

The above is what the editor has introduced to you. Many factors can cause sows not to come into heat; sows are the engine of a pig farm, so fellow pig farmers must be especially careful in daily management work, do a good job in disease prevention, and reduce some unnecessary losses.