Stochastic model to assess bioeconomic impact of PRRS on pig farms in Costa Rica

Abstract

Despite the economic importance of PRRS and its high prevalence in Costa Rica, there are no studies on the bioeconomic impact of the disease in the country or, even, in Central America. Such studies are essential in finding cost-effective preventive measures tailored for different production circumstances. Therefore, the

objective of this study was to evaluate economic and production parameters of a PRRSV-infection for a medium- sized farrow-to-finish pig farm system in Costa Rica with a farm-level stochastic Monte Carlo simulation model.

The effect of PRRS was assessed by scenario analysis, in which a baseline PRRS-free situation was compared against three alternative scenarios that assumed low, medium and high PRRS effects. The PRRS effects were based on data from local farms, scientific literature and expert opinion. Sensitivity analyses were performed to assess the impact of key input parameters on output variables. Results show that at the animal level, changes between the baseline and the PRRS-high scenario were estimated as: + 25 d in age to slaughter, − 9.9 pigs to slaughter (per breeding sow/yr), + 6% annual replacement rate, − 255 d in sow productive lifetime, - 6.9 mo in age at culling of sows, and + 24 non- productive days. For a medium size local farm (n = 588 sows), a reduction

of 5826 fat pigs to slaughter per farm/yr from baseline compared to PRRS-high scenario was observed. PRRS- induced loss per farm per year was estimated at -US $142,542, US $180,109 and -US $524,719 for PRRS-low,

medium and high scenarios, respectively. Revenues/costs ratio changed from 1.12 in the baseline to 0.89 in the PRRS-high scenario. The production cost per kg carcass weight increased from US $2.63 for the baseline to US $3.35 in the PRRS-high scenario. PRRS-induced loss was estimated at US $77.1 per slaughtered pig/yr and US $892 per breeding sow/yr for the PRRS-high scenario. Results from the model indicate that pig farms with medium to high prevalence of PRRS will require optimal market conditions in order to have positive economic outcomes. These results can be helpful in the design of better control strategies for PRRS.

A pesar de la importancia económica del PRRS y de su alta prevalencia en Costa Rica, no existen estudios sobre el impacto bioeconómico de la enfermedad en el país o, incluso, en Centroamérica. Dichos estudios son esenciales para encontrar medidas preventivas rentables y adaptadas a las diferentes circunstancias productivas. Por lo tanto, el objetivo de este estudio fue evaluar los parámetros económicos y de producción de una infección por PRRSV para un sistema de granja porcina de tamaño medio de cría a engorde en Costa Rica con un modelo estocástico de simulación Monte Carlo a nivel de granja. El efecto del PRRS se evaluó mediante un análisis de escenarios, en el que se comparó una situación de referencia libre de PRRS con tres escenarios alternativos que suponían efectos bajos, medios y altos del PRRS. Los efectos del PRRS se basaron en datos de granjas locales, literatura científica y opiniones de expertos. Se realizaron análisis de sensibilidad para evaluar el impacto de los principales parámetros de entrada sobre las variables de salida. Los resultados muestran que, a nivel animal, los cambios entre el escenario de referencia y el escenario de PRRS alto se estimaron en: + 25 días de edad hasta el sacrificio, - 9,9 cerdos hasta el sacrificio (por cerda reproductora/año), + 6% de tasa de reposición anual, - 255 días de vida productiva de la cerda, - 6,9 meses de edad hasta el sacrificio de las cerdas y + 24 días no productivos. For a medium size local farm (n = 588 sows), a reduction of 5826 fat pigs to slaughter per farm/yr from baseline compared to PRRS-high scenario was observed. PRRS- induced loss per farm per year was estimated at -US $142,542, US $180,109 and -US $524,719 for PRRS-low, medium and high scenarios, respectively. Revenues/costs ratio changed from 1.12 in the baseline to 0.89 in the PRRS-high scenario. The production cost per kg carcass weight increased from US $2.63 for the baseline to US $3.35 in the PRRS-high scenario. PRRS-induced loss was estimated at US $77.1 per slaughtered pig/yr and US $892 per breeding sow/yr for the PRRS-high scenario. Results from the model indicate that pig farms with medium to high prevalence of PRRS will require optimal market conditions in order to have positive economic outcomes. These results can be helpful in the design of better control strategies for PRRS