Replacement gilts are arguably the most important input for a breeding herd
By Dr. Sam Holst The success of a breeding herd hinges on the performance of its replacement gilts. With sow mortality continuing to trend higher across the industry, annual replacement rates for many farms have exceeded 60%. Couple this with tight gilt supplies and developing replacement animals correctly is a highly critical event. Acclimation Acclimation is the process of building immunity against pathogens that exist in the sow herd. Ideally, acclimation includes both vaccination and natural exposure pathogens within the herd the gilts are entering. This should be completed prior to breeding to avoid first exposure during gestation which can increase the risk of pregnancy loss, fetal mummification, and abortion. Regardless of herd health status, all replacement gilts should be vaccinated against Parvovirus, Leptospira, Erysipelas, Circovirus Type 2, and Lawsonia intracellularis (Ileitis). Vaccination for additional pathogens may be warranted depending on herd health status. Natural exposure builds immunity to farm pathogens. This can be accomplished both through direct contact with animals from the herd and controlled pathogen exposure (feedback). Controlled pathogen exposure consists of oral inoculation of replacement gilts to feedback materials and typically occurs multiple times during gilt development. Boar exposure Daily exposure of replacements to mature boars is critical for maximizing the number of gilts that cycle. The boar is the most effective stimulus for inducing onset of puberty in gilts; however, all forms of boar exposure don’t provide equal outcomes. Strive for direct contact, which increases the number of gilts that cycle within a gilt pool compared to fence-line exposure. Direct contact can be accomplished using: 1. Boar exposure area (BEAR) a. Designated pen with multiple individual boar stalls with pens on either side b. Gilts are moved from their home pens to the BEAR pen c. Following 5 minutes of estrus detection with boars stalled, boars are released to allow for direct contact with gilts i. Rule of thumb for direct contact is 30 seconds per gilt per day d. Herdsperson monitors and observes for and records heats e. Gilts are returned to home pens
2. Direct contact in gilt pen a. Boars are moved into gilt pens b. Herdsperson monitors and observes for signs of estrus i. Rule of thumb for direct contact is 30 seconds per gilt per day c. Boars are removed from gilt pens It is recommended to begin boar exposure when gilts are approximately 170 days of age (can use average age of group). Herdsperson should mark and record gilts when they are observed to be in estrus. After 14 consecutive days of boar exposure, all non-cyclic gilts within the group should be remixed to provide added stimulation. Daily boar exposure is resumed. Heat-no-service It is crucial that herdspersons keep accurate records of when gilts are first identified in estrus. This will allow for a heat-no-service (HNS) protocol to be implemented where gilts are not bred on their first identified estrus cycle but are passed and mated on the second or third cycle. Research shows that ovulation rate in gilts increases after the first estrus, so mating on the second or third cycle increases litter size. Using this approach, gilts will average 215-235 days of age at mating. Weight at first service In addition to age, weight at the time of mating needs to be considered. Gilts should be between 300-330 pounds at mating. Lightweight gilts have smaller litters and are greater risk to be culled after weaning first litter. Gilts that are too heavy generate an added feeding cost to gilt development and have reduced longevity. Individual stall acclimation The timing of when gilts are transitioned from group pens to individual stalls prior to breeding also impacts performance. Gilts need time to become acclimated to stall to allow for ad-lib feed intake prior to breeding. It is recommended that gilts are acclimated to stalls for at least 2-weeks before expected to cycle next based on recorded HNS dates. Flush feeding Nutrition is one of the biggest drivers of total born. We know that the practice of flush-feeding, which is providing daily ad-lib feed to gilts prior to mating, increases ovulation and total born compared to limit-feeding. Make sure that gilt development program allows for ad-lib feeding for at least 2-weeks prior to gilt breeding. Multiple matings Gilts have a shorter period of standing estrus (approx. 24-36 hours) than sows which can lead to more single matings with a once per day heat checking schedule. Gilts that receive two or more matings will have a significantly higher farrowing rate than those that are mated once. A twice daily (AM/PM with at least a 6-hour interval) estrus detection and insemination schedule for gilts should be considered to reduce the number of single matings. Summary Replacement gilts are arguably the most important input for a breeding herd. A thorough review of the entire gilt development process should be conducted to identify areas for improvement. Dedicating capital resources and labor to ensure that optimal gilt performance is achieved is a worthwhile investment.
Dr. Sam Holst is with the Swine Vet Center in St. Peter, Minn.