Effect of PRRS vaccination on average daily gain: A comparison of intranasal and intranasal-intramuscular administration

SAS: Iowa Select Farms, Iowa Falls, Iowa 50126, e-mail: [email protected]; JJZ: Iowa State University; DDP, MBR: NOBL Laboratories orcine reproductive and respiratory syndrome (PRRS) causes production and financial losses in swine herds worldwide.1–3 Several researchers have reported that PRRS virus (PRRSV) infection may have an adverse effect on nursery performance.4,5 Kerkaert, et al.,6 reported that chronic PRRSV infections in nurseries can reduce total profits up to 70%, with the losses due principally to decreased performance rather than increased mortality. Polson, et al.,5 observed that the financial losses that resulted from PRRSV infection varied according to mortality rates and duration of the disease episode. Nursery losses in the model ranged from $0.73–$18.21 per head. Mortality and the number of disadvantaged pigs can be increased twoor threefold, and average daily gain (ADG) may be decreased by as much as 25%–50% in the face of chronic PRRSV infections.1,5,7–9 Dee9 reported that ADG in PRRSV-infected nurseries was reduced by 0.22–0.33 lb (0.48–0.73 kg).8,10,11 Chronic PRRSV infections have been reported to reduce ADG of growing pigs by as much as 15%. These losses have prompted researchers and practitioners to search for methods to control the clinical effects of the disease.