Researchers Dr Marie-Ève Lambert of the University of Montreal in Canada and colleagues there and at the University of Guelph have described gilt replacement strategies in regard to PRRSV and assessed differences between high-density (HD) and moderate-density (MD) pig areas in Journal of Swine Health and Production.

They conducted a cross-sectional study in breeding sites located in an HD (n=68) and an MD area (n=52) in Quebec between May 2005 and August 2008. A questionnaire on strategies used to introduce replacement gilts was completed and PRRSV status was assessed by enzyme-linked immunosorbent assay or reverse-transcription polymerase chain reaction. Sites housing at least one pig positive by either test were classified as PRRSV-positive. Strategies were described according to herd characteristics, PRRSV status and area.

Self-replacement and purchase of mature or immature gilts were observed on 37 per cent, 35 per cent and 28 per cent of sites, respectively. In positive sites purchasing mature gilts, 18 per cent had a PRRSV-positive supplier, and gilts were introduced either directly into the sow herd (15 per cent) or after isolation (41 per cent) or acclimatisation (44 per cent).

Most positive sites purchasing immature gilts practiced acclimatization (93 per cent), either by commingling gilts with commercial pigs (93 per cent) or inoculating serum (seven7 per cent). Acclimatisation processes were rarely monitored through diagnostic procedures.

Lower sow inventory, higher prevalence of PRRSV infection and higher frequency of self-replacement were observed in the HD than the MD area. Negative and positive sites practising voluntary exposure to PRRSV both clustered spatially within the MD area.

Replacement strategies may have weaknesses that should be addressed to facilitate PRRSV management at the herd and regional levels, concluded Lambert and co-authors.

Reference

Lambert M-E., M. Denicourt, Z. Poljak and Sylvie D'Allaire. 2012, Gilt replacement strategies used in two swine production areas in Quebec in regard to porcine reproductive and respiratory syndrome virus. J. Swine Health Prod., 20(5):223–230.

Further Reading You can view the full report by clicking here. Find out more information on porcine reproductive and respiratory syndrome (PRRS) by clicking here.