Reasons for unsatisfactory breeding
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Sows not showing signs of estrus can be a major concern in pig farming. It's important to evaluate the weaning-to-breeding interval, as this is a key indicator of reproductive performance. Ideally, this interval should be less than 7 days, with a maximum of 10 days. A longer interval can delay farrowing and reduce the number of litters per sow annually. Common causes include poor nutrition during lactation, especially in young sows, which leads to the "lean sow syndrome." It's crucial to check the parity distribution to identify if the issue is concentrated in younger sows. Don't automatically assume that poor breeding efficiency is due to infectious diseases—many cases are related to management practices rather than illness.
Observing estrus behavior is essential, but inexperienced staff may miss it. The vulva may appear red and swollen with mucus discharge, but some sows show no obvious signs. Morning and evening are the best times for observation, as this increases the chances of detecting estrus and improving fertility. High temperatures can also affect estrus timing, as heat stress reduces feed intake and nutrient absorption, worsening the lean sow syndrome. Keeping sows and boars together or ensuring proper feeding can help stimulate estrus.
Boar-related issues can also impact breeding success. Poor management during development can lead to low libido in young boars, who may initially show sexual impotence. This is often temporary, so they shouldn’t be discarded immediately. Heat, foot problems, or injuries can further reduce their mating ability. Boars with permanent mobility issues should be removed from the breeding program.
When sows show signs of estrus after mating, it usually indicates a failure in pregnancy. A replantation rate above 15% can extend the farrowing interval and lower annual productivity. Sows that return to estrus between 18-24 days post-mating may have had an early miscarriage. Timing of breeding is critical—sows should be bred 21-22 hours after the onset of estrus. In large farms, daily observation and single breeding sessions can lead to lower pregnancy rates. However, observing twice a day at 4–12 hour intervals improves both pregnancy rates and litter size.
Boar use also plays a role. Young boars may have low sperm count in their first ejaculations, but frequent use (up to four times a week) doesn’t harm fertility. Infectious diseases like Porcine Reproductive and Respiratory Syndrome (PRRS), Parvovirus, and Brucellosis can cause high return rates.
Empty sows are those that don’t give birth despite appearing pregnant. This can occur due to missed estrus detection, early ovulation, or premature death. An empty rate of up to 5% is normal, but higher rates may indicate either disease or poor management. Poor estrus detection can lead to inaccurate pregnancy diagnosis, inflating the perceived pregnancy rate while increasing the empty rate. Diseases like Brucellosis and PRRS can cause high return rates or low farrowing rates. Accurate detection and proper management are essential to maintaining a healthy and productive herd.