Infertility in Pigs: Causes, Symptoms & Prevention

Infertility in pigs can be a major setback for farmers relying on consistent breeding for pork production. Low conception rates, irregular heat cycles, or failed pregnancies can lead to financial losses and breeding delays. Understanding the root causes of infertility is essential for maintaining a productive herd. Below are the most common causes of infertility in pigs, explained in detail with tips for prevention and control.

Poor Nutrition

Nutrition plays a major role in the reproductive performance of both sows and boars. A diet lacking in energy, protein, or essential minerals like zinc, selenium, and phosphorus can lead to weak heat cycles, early embryonic death, or irregular ovulation.

Sows on inadequate diets may fail to return to estrus or may abort early. Boars on poor nutrition can suffer from reduced libido and low-quality semen. To prevent this, pigs should be fed a balanced diet that meets their age, weight, and reproductive stage requirements. Special focus should be given to flushing diets before breeding and transition diets for pregnant sows.

Heat Stress

High temperatures affect hormone production and sperm viability in pigs. Sows exposed to extreme heat may stop cycling or have silent heat, making detection difficult. Boars under heat stress produce less semen, and the semen they do produce often contains fewer viable sperm.

Proper ventilation, shade, and cool drinking water are essential in hot weather. In commercial setups, fans and sprinklers can help regulate body temperature. Farmers should also avoid breeding pigs during the hottest part of the day.

Infectious Diseases

Infectious diseases are a major cause of reproductive failure in pigs. These diseases can affect the uterus, ovaries, or developing embryos, leading to conception failure, abortion, or birth of weak piglets. Below are some of the most common infectious threats:

a). Leptospirosis

Leptospirosis is a bacterial disease that spreads through contaminated water, urine, or contact with infected animals. In pigs, it can cause embryonic death, stillbirths, and abortions, often late in pregnancy. The disease may go unnoticed until multiple sows fail to farrow or piglets are born dead. Controlling rodent populations, vaccinating breeding stock, and maintaining strict sanitation can significantly reduce infection risk.

b). Porcine Parvovirus (PPV)

PPV is one of the leading viral causes of reproductive failure in pigs. It usually does not make the sow visibly sick, but it can severely affect her litter. Infected sows often deliver mummified fetuses, small litters, or stillborn piglets. This virus is resistant in the environment, so good hygiene and timely vaccination before breeding are key to controlling it.

c). Brucellosis

Brucellosis is a contagious bacterial disease that affects pigs’ fertility and can be transmitted to humans. Infected animals often experience infertility, abortions, and inflammation of the reproductive organs. Boars may also develop swollen testicles or lose fertility altogether. There is no treatment for brucellosis in pigs, so prevention relies on sourcing animals from brucellosis-free farms and culling infected stock.

d). Erysipelas

Erysipelas is caused by Erysipelothrix rhusiopathiae and is more commonly known for its effects on skin and joints. However, it can also cause reproductive problems, especially in breeding animals. Infected sows may experience abortions, stillbirths, and decreased litter sizes. Routine vaccination and farm hygiene play important roles in managing this disease.

e). PRRS (Porcine Reproductive and Respiratory Syndrome)

PRRS is a viral disease that significantly impacts both the respiratory and reproductive systems. It is a major cause of infertility in pigs worldwide. Sows infected with PRRS may abort, deliver weak or stillborn piglets, or show prolonged weaning-to-estrus intervals.

The virus spreads rapidly in herds and can be difficult to control. Biosecurity, vaccination, and stable herd management are important for reducing its impact.

The above diseases can cause delayed heats, abortions, mummified fetuses, or the birth of weak piglets. Implementing a strict vaccination schedule, quarantine protocols for new animals, and regular vet checkups can help prevent outbreaks.

Poor Semen Quality

In artificial insemination or natural service, semen quality is critical for conception. Factors such as poor handling during semen collection, storage temperature errors, or using semen too late after collection can reduce success.

In boars, issues like testicular degeneration, infections, or mineral deficiencies can reduce sperm production. Always source semen from reputable providers and store it at correct temperatures (15–18°C). Use it within the recommended time frame, and handle it gently during insemination.

Hormonal Imbalances

Proper hormone function is necessary for ovulation, fertilization, and pregnancy maintenance. Disruption in hormones like estrogen, progesterone, or LH (Luteinizing Hormone) can cause irregular heats, failure to conceive, or early embryonic loss.

Hormonal problems may arise from stress, poor nutrition, underlying infections, or genetic factors. In cases of repeat infertility, veterinarians may recommend hormone analysis or hormone treatments to correct the imbalance.

Improper Heat Detection

Missed heats or mistimed breeding are frequent causes of infertility on farms. If insemination or mating doesn’t align with ovulation, conception is unlikely. Some sows exhibit silent heat, making them harder to detect without careful observation.

Signs of heat include swollen vulva, mounting other sows, standing still during back pressure, restlessness, and increased vocalization. Daily heat checks using a teaser boar and recording estrus signs can improve timing accuracy.

Genetic Issues

Genetic defects can cause congenital infertility in both male and female pigs. In some cases, gilts are born with underdeveloped ovaries or malformed reproductive tracts. Boars may have poor sperm production due to inherited traits.

These animals often fail to breed despite appearing healthy. Genetic screening and culling of repeatedly infertile animals can help eliminate these problems from the herd.

Poor Management Practices

Housing conditions, hygiene, and stress levels have a direct impact on fertility. Overcrowded pens, lack of exercise, or exposure to continuous stress can suppress reproductive hormones. Stress may be due to poor handling, mixing unfamiliar animals, or loud noises.

Good stockmanship, calm handling, clean and spacious housing, and proper lighting schedules improve overall reproductive health. Always monitor the mating process and record all breeding attempts for future analysis.

Age and Parity of Sows

Older sows with multiple parities may experience declining fertility due to uterine fatigue or previous birthing injuries. Young gilts that are bred too early, before their reproductive systems are fully mature, may fail to conceive or carry pregnancies to term.

Aim to breed gilts at around 220–250 days of age and around 130–140 kg body weight. After 6–7 parities, evaluate sows for signs of reproductive decline and consider replacement.

How to Diagnose Infertility in Pigs on the Farm

Diagnosing infertility in pigs on the farm begins with close observation of the animals' breeding performance. The most obvious sign of infertility is repeated failure to conceive after multiple mating attempts.

Gilts or sows that do not exhibit signs of heat or fail to return to heat after service should be closely monitored. Keeping detailed breeding records is essential, as they help identify patterns such as irregular heat cycles, prolonged weaning-to-estrus intervals, or failed pregnancies.

Mistiming of insemination is a common cause of reproductive failure. A review of heat detection protocols ensures that sows are being bred at the right time. It’s important to check if signs like vulva swelling, standing reflex, and increased activity are being properly interpreted.

Veterinary examination plays a key role in diagnosis. A vet can conduct physical and reproductive exams to check for anatomical problems in the reproductive tract. In female pigs, ultrasound scanning can help confirm whether ovulation is occurring or if there are signs of pregnancy loss. It can also detect cysts, uterine infections, or other reproductive tract abnormalities.

Boars should also be evaluated during infertility investigations. Semen analysis helps determine sperm count, motility, and morphology. Poor semen quality may stem from infections, mineral deficiencies, or improper semen storage practices in the case of artificial insemination. Testicular palpation and scrotal measurements are also used to assess boar fertility.

Blood tests may be recommended to check for hormonal imbalances or to screen for infectious diseases like leptospirosis, PRRS, or brucellosis. These infections can suppress reproductive hormones or damage reproductive organs, leading to infertility.

Environmental and management factors should not be overlooked. Assessing the housing, temperature conditions, nutrition, and hygiene can reveal stressors that may be contributing to low fertility. Heat stress, overcrowding, and poor diet are often silent contributors to reproductive failure.

Using tools like My Piggery Manager can support infertility diagnosis by helping you track breeding records, heat cycles, and previous pregnancies in real-time. This digital recordkeeping helps pinpoint fertility issues faster and improves farm decision-making.

Conclusion

Infertility in pigs stems from a combination of physical, environmental, nutritional, and management factors. Identifying the root cause on your farm requires close observation, good records, and veterinary support. Start with the basics—nutrition, heat detection, and disease prevention.

Incorporate technology and farm management tools to track breeding performance and detect issues early. With proper care and consistent practices, fertility in your pig herd can be greatly improved, ensuring higher productivity and profitability.