“We plan a quarantine time of a minimum eight weeks and if we use MLV PRRS virus vaccines, we prefer around 12 weeks” Gilt introduction procedures are discussed by Danish swine veterinarian Dr. Kristian Havn in the context of a herd averaging 1,000 sows with an annual replacement rate of 45-50%, meaning a need to bring in 500 replacement gilts per year. A target of introduction to the sow herd at 34 weeks old dictates that gilts must be no older than 22 weeks on arrival, to accommodate a 12-weeks quarantine period. How to expose them to herd pathogens is still an open question, he says, because we will want them to produce an adequate level of antibodies in their colostrum when they eventually enter the farrowing room.