Synchronizing estrus in mature cycling gilts can be a challenge. Now there’s a product called Matrix, which had been approved in Europe and Canada, available for use in the United States.  It can help minimize the number of days required for estrus detection, assist breeding-staff scheduling and align semen delivery and use. The product allows you to take a single female or a group of randomly cycling gilts and synchronize their estrus to occur ~22 days after the treatment starts.

The product is a liquid supplied in 1-liter bottles, with enough to treat 10 gilts. It contains a synthetic progestagen that’s given orally to the animal or applied to its feed for 14 days. The drug is stable when stored at room temperature but does have an expiration date. The active ingredient works by suppressing hormone release at the gilt’s brain, which prevents ovulatory follicle development and estrus. Following the 14-day treatment, most treated animals reach a similar stage of the reproductive cycle, and when the last dose is delivered, they are released from suppression of ovary activity.  

Before using, read all label instructions and safety precautions. There are safety issues, especially for women, and proper handling involves wearing gloves for dispensing or mixing the product in feed. Persons also should be trained in handling and administration, especially when considering the replacement gilt’s value, the treatment cost, and the feed and labor investments involved. There is a 21-day withdrawal period for treated animals that will not remain in the herd.

The critical step in achieving good synchrony is to select animals of mature weight (greater than 260 pounds) and age (180 days). The animals should be in good body condition, healthy and have positive weight gain and feed intake up to the point of selection. Gilts should have exhibited at least one estrus. Two or more regular estrous periods at 21-day intervals indicate that gilts are mature, cycling and fertile. These animals, regardless of maturity stage or the estrous cycle, are excellent candidates for treatment.

The product is designed to be top-dressed on feed; however, some administer it directly into the pig’s mouth using the oral-dosing gun. This can present some challenges in terms of ensuring full-dose ingestion, as some may flow from the animal’s mouth. When treatment is top-dressed, the feeding method is critical, as animals in group pens often eat each other’s feed. This can result in reduced treatment in some animals and excess treatment in others. Therefore, controlling individual feeding is best and may involve individual housing or moving animals to a designated feeding area. Often, a small amount of feed is given first, and then dosed with Matrix. This ensures the gilt gets the proper dose each day at the right time, since some animals will not eat large amounts of feed at one time. 

For producers that are unable to get estrus information due to labor, time or scheduling limitations, some decide to treat animals anyway. Without previous estrus information, it’s still possible to get some estrus synchrony, but it’s unlikely that all of the animals have cycled and are fertile. This results in investment in animals that cannot respond. If that has to be a routine practice, it’s important to evaluate the animals’ age and weight and how they responded.

The 14-day treatment schedule is essential; while there is little harm in being one day short or long in terms of scheduling practicality, there can be no interruption of treatment once the 14-day period begins. Also, there should not be large inconsistencies in daily timing of the dose, such as in the morning one day and the afternoon the next. This can cause problems in follicle development suppression and even lead to fertility and synchrony problems.

The last day of Matrix dosing ends the suppressive effects on ovarian follicles. The hormone is cleared within 24 hours, and the brain is released from suppression and initiates follicle development on the ovary. As a result, most gilts (more than 80 percent) come into estrus within five to eight days after the last dose. (See graph.) It’s important to use daily boar exposure to stimulate the females following treatment to advance estrus and improve synchrony.

Window of Opportunity

According to University of Illinois research, gilts treated with Matrix typically cycle between days 4 to 10 after the last dose. Estrus duration is about two days, and ovulation occurs 24 to 40 hours after estrus onset. Ovulation rates typically exceed 16, and some reports indicate that increased litter sizes result.