Extension Notebook: Best practices and alternative methods for detection of estrus and breeding swine

The critical elements for success on all swine breeding farms include accurate detection of estrus and use of proven breeding methods that can establish pregnancy and birth of a large litter. The modern pig has been shown to have the potential to produce in excess of 30 live pigs each year. With the change from outdoor to intensive indoor production many years ago, farms adopted more controlled breeding practices to regulate the production of pigs for market. Farms transitioned from supervised natural matings using boars, to the nearly exclusive use of artificial insemination today.

Most breeding farms rely on labor for detection of estrus and timing inseminations. With sows housed in gestation crates, boars are moved in front of the sows for a minute or two each day while a technician applies the back-pressure test (BPT) to the female. A sow in estrus may show a rigid standing response to the mere presence of the boar, or in response to the person putting hand pressure and rubbing on the sow’s back. An estrus sow may show symptoms including movement toward the boar, ear twitch, erect ears, mucus discharge from the vulva, rigid standing, or vocalization.

Farms that are consistent in providing quality boar exposure once each day, good lighting and air quality, and adequate time for stimulation and applying the BPT, often show the best herd fertility. These farms have the greatest opportunity to accurately identify sows in estrus and also those not in heat. These actions allow farms to better time the inseminations for sows.

Many farms in the US average just over two inseminations per sow, with sows mated once on each day in standing estrus. In Brazil however, sows receive three services per estrus, with the timings somewhat closer together. While comparisons are not possible between the countries’ approaches, anecdotal evidence suggests higher fertility with more services.

There are other confounding issues, and modern swine reproduction provides options for the numbers of sperm used per insemination (1.5-3.0 billion live) and the choice of insemination deeper into the reproductive tract (cervical vs. intrauterine). All of the options have been proven to be successful on numerous farms while in others these same selections prove limiting to farm performance. This opposite effect may depend more upon the state of the herd itself, the management, and the approach used to implement the technology.

A look into the future for swine breeding suggests changes may be on the horizon. Global limitations to available labor on the breeding farms, animal welfare housing directives, and the development of new technologies have opened the way for alternative methods for estrus detection and timing inseminations. Cameras, sensors, electronic devices, and assays have been developed to help identify estrus and the time of ovulation. Camera systems can record animal movement, position, temperature, and behaviors, while measures of physiological fluids or states have been assessed for their predictive capability.

The accuracy and practicality of any of the systems are of prime interest and each has shown potential but also limitations. The identification of individual sows and their behaviors for estrus and non-estrus phases can each be quite variable. Remote sensing certainly has appeal from a labor standpoint but individual animal identification or marking when in groups would be required. Sow ear-tag sensors can identify sows and their visits to a boar. Various camera or sensor technology can monitor animal temperature at set locations. When sows are housed in individual stalls, sow movement can be assessed remotely for time standing or can be measured individually for physiological changes.

Regardless of the technology chosen, measures to diagnose true and false positives and negatives for estrus or ovulation would be critical for assessment. Even if the method is accurate, the practical aspects of costs, animal identification, time required, and labor or time savings, or improvement in productivity would need to be included.

All of the technologies are of interest and show potential, but demonstrating that the new approach solves a problem or provides an advantage or benefit to our existing methods will be the deciding factor.

Robert Knox is a swine Extension specialist, University of Illinois, Champaign-Urbana.