Estrus detection procedures are relatively straightforward. Yet, daily realities such as management of labor, facilities and the animals, can impact their success.

While estrus symptoms vary among females, the response to back pressure in a boar’s presence helps get an identifiable response. This is especially true for females that previously would not stand rigid in a boar’s presence, but now “lock” to these stimuli and remain quiet.

With gilts, the objectives are to eliminate fear of the detection procedures, maximize the daily routine, provide powerful stimuli and elicit estrus-related behaviors. Failure to detect estrus is common, but falsely identifying heat, from symptoms such as vulva swelling, may also occur.

Sows are calmer and less prone to fear humans, which makes it important to properly stimulate the female at the correct intensity. However, the fact that sows are commonly housed in stalls creates a challenge. Technicians must physically apply the stimuli even if it means getting in the stall with the sow.           

Labor scenarios differ between farms, and the number of people needed to control the boar and provide back pressure to the females will vary. In some farms, one person may suffice while others may need two to three. Labor shortages may reduce the personnel assigned to this task which may also reduce the success rate.

Technicians must know that the best way to detect estrus is to physically apply back pressure and note whether the animal will or won’t stand rigid. Other signs are not valid estrus indicators. For example, not all animals show the same rigidity response to a boar’s fence-line or physical presence without other stimuli such as rubbing or back pressure.

Technicians should place the boar near the sow’s or gilt’s head for two minutes or until the animal is rigid, whichever comes first. There must be time to react to the visual, olfactory, sound and tactile stimuli that the boar and worker are providing.

Animal housing conditions (stalls or pens), the number of animals per pen, boar-to-female ratio, sound, air speed, temperature, and the boar exposure method can improve or reduce detection effectiveness. Excessive riding in pen situations can alter the accuracy. Young gilts can be difficult to detect in stalls because they may require more intense boar stimulus. The number of females in a pen needs to allow for adequate contact time to the boar.

Since sight, sound and smell of the boar are powerful stimuli, factors such as low lighting, noisy barns, fast air speed or high gas levels may all limit exposure. Avoid heat detection during hot periods of the day.         

Physical or fence-line boar exposure can work well. Fence-line exposure should occur by moving the boar down a row, one stall or pen at a time. A minute or two later, a technician should rub the animal’s sides and apply back pressure. A more powerful method can be to move females to a pen or alleyway adjacent to, or within the boar’s pen. Another pen-housing option is to walk the female with a boar. But remember, the boar doesn’t detect females in heat as much as those in heat seek out the boar. Also, many estrus detection boars may not attempt to stimulate females with physical rubbing or mounting, which is why it’s important for technicians to provide stimuli.

Unintentional boar exposure, boars housed too close and the interval from last exposure can all influence a female’s ability to express estrus. A female in heat does not stand continuously but will stand for 15 to 30 minutes in a boar’s presence; then she will refuse to stand for a period of time.

So, by remembering the basic estrus detection techniques and recognizing some of the pitfalls, you can eliminate some basic errors and build on your success.