# Combining Load–Close–Homogenize with Testing, Removal, and Rollover Strategies to Repopulate PRRSV Elimination Breeding Herds Using PRRSV-Positive Weaned Gilts

## TL;DR

This study shows how to eliminate PRRSV in breeding herds using a combination of strategies with PRRSV-positive gilts.

## Contribution

A novel integrated strategy combining LCH, T&R, and rollover methods for PRRSV elimination in breeding herds.

## Key findings

- The herd achieved PRRSV-positive stability within 8 months using LCH.
- Replacing PRRSV-positive sows with naive gilts led to PRRSV-negative status in 13 months.
- The first farrowing batch became PRRSV-negative after 8 months of herd closure.

## Abstract

In this study, two PRRSV elimination strategies, LCH and T&R, were integrated. Systematic, step-by-step PRRSV elimination protocols were also developed and executed. They encompassed pre-evaluation of the PRRSV elimination capacity of new repopulation farm, assessment of PRRSV status and strain diversity of the two supplier farms, analysis of the natural infection dynamics of PRRSV within the population, assessment of parameters for LVI material preparation and implementation, and detailed programs for monitoring changes from homogenized infection to whole herd elimination.

This study aimed to evaluate the effectiveness of combining load–close–homogenize (LCH), test and removal (T&R), and rollover strategies for PRRSV elimination in breeding herds using PRRSV-positive weaned gilts. Here, a novel strategy was explored for PRRSV elimination from more than 1500 weaned gilts, and we documented the process from PRRSV natural infection to elimination at the herd level. With LCH implementation, the herd achieved PRRSV-positive stability within 8 months. Consequently, by rolling in self-breeding PRRSV-naive gilts to replace PRRSV-positive weaned sows batch by batch, the time from being positive stable to negative was 13 months. A PRRSV-positive farm intending to retain its genes in its repopulate farrow to become a finished breeding farm can initiate PRRSV elimination from its weaned gilts; this will result in the first farrowing batch of piglets aged 8–10 weeks becoming PRRSV-negative after 8 months of herd closure. This approach offers a viable pathway for genetic retention and PRRSV elimination in breeding farms.