The purpose of this study was to investigate the effects of vaccination with a commercial European porcine r reproductive and respiratory syndrome (PRRS) -inactivated vaccine after 18 month-use on health status, semen characteristics and fertilizing capacity in vivo of boars. In a farrow to finish farm of 1,100 sows, that suffered from chronic course of PRRS with several outbreaks during each year, seven semen donor healthy crossbred boars (1.1–2.2 years old) of the same genetic background were initially twice vaccinated with the PRRS inactivated PROGRESSIS® vaccine (Merial, France), with a 4 weeks interval. At the same time, all gilts and sows of the herd were also vaccinated with this vaccine. Boars were monitored for abnormal clinical signs from 24 hr prior to 15 days after each vaccination. The rectal temperature was determined 24 hr after each vaccination. Ejaculates were collected at 24 hr prior, 24 hr after, and 15 days after each vaccination and the semen characteristics (semen volume and density, sperm viability and motility) were evaluated. A total of 305 sows were inseminated twice with semen from ejaculates collected from 2 weeks prior up to 6 weeks after the first vaccination. The sows were classified into 4 groups according to the time at which insemination was performed with semen collected. Farrowing data, including litter size (total born piglets) and farrowing rate were recorded. No systemic clinical signs and no local reaction on the area of the injection were observed in all boars. Moreover, all boars had normal appetite, behaviour and libido after each vaccination. The average rectal temperature was always higher than normal mean (38.6°C) in all boars and no significant statistical difference was observed between the 7 boars for the average rectal temperature from 1st-4th vaccination. No significant differences in semen characteristics, except of sperm viability were noticed between each time of semen examination (24 hr prior, 24 hr after and 15 days after each vaccination) and between 7 boars from 1st-4th vaccination. After the 1st vaccination sperm viability increased, but this it is probably more to the increase of age of seven boars during the trial and less to the vaccination. All semen characteristics were decreased 24 hrs after each vaccination, but it did not influence the semen quality as their values remained in normal levels. The semen characteristics were improved during the following days and reached values similar to them 24hr prior to vaccination, except sperm viability that remained more >70%, that means it did not influenced negative the semen quality. According to the fertilizing capacity in vivo of boars no change in litter size and farrowing rate of groups of sows that inseminated with semen that collected after the vaccination. In conclusion, the vaccination of boars with a PRRSV inactivated vaccine is safe and has not negative effects on health status and their semen characteristics and fertilizing capacity in vivo.
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