Economic impact of PRRSV in farrow to finish herds

Losses from PRRSV infection is due to decreased farrowing rates, increased pre-weaning mortalities and increased respiratory disease in finishing pigs.

Polson study

Based on a 250 sow farrow-to-finish herd in USA, Polson (38) calculated the financial impact of PRRS using following parameters:

1. (live) litter size,
2. pre-weaning mortality
3. farrowing rate.

The reduction in pre-tax profits due to the outbreak was US$236 per female, which can be translated into an 80% reduction in expected profit in the year of the outbreak.

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Brouwer study

In a study by Brouwer (7) the financial impact of PRRS was evaluated for 91 herds. In general the herd performance was severely affected over a period of 4-6 months. The average key parameters on the study farms can be found in Table 1.

Table 1: Comparison of herd performance

	Study farms
	1990	1991
Number of herds	91	91
Number of sows	189	192
Piglets born alive/litter (PBA)	10.7	10.1
Piglets born dead/litter (PBD)	0.6	1.1
Pre-weaning mortality (PWM)	11.3	15.2
Piglets reared/sow/year (PRSY)	21.4	18.9
Replacement rate (RR)	47.3	49.0
Farrowing Interval (FI)	155	156

The calculations in Table 2 use the impact of the reduction in piglets/sow/year, increased farrowing intervals and replacement rates to determine the financial impact.

The average loss was found to be DFl 215 per sow per year, corresponding to US$113 per female. Most of the economic loss was due the reduced number piglets/sow/year. See Table 2.

Table 2: Mean net economic loss (in DFl) per sow per year based on 91 herds

Mean	SD	Min.	Max.
Net loss due to PRSY	177	90	-46	453
Net loss due to FI	12	21	-45	60
Net loss due to RR	27	171	-390	480
Total	215	205	-307	780

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Acute PRRSV infection in a farrow to finish herd, Poland

The impact of an acute PRRS outbreak on a large Polish (2,330 sow) farrow-to-finish herd was evaluated by Pejsak and co-workers.

Farrowing herd

In the first 6 weeks of the outbreak 19.3% of the sows farrowed before day 110 of pregnancy and 2.2% of them died.

Before the outbreak the mean pre-weaning mortality rate was 6%, which gradually increased during the outbreak to a maximum of 75.6% over a 10 day period (see Figure 1). The main rise in mortality was due to an increased number of stillborn piglets.

The acute losses in the farrowing herd lasted for 14-16 weeks.

Finishing herd

Amongst the finishers an increased number of respiratory disease outbreaks were observed from about 2 weeks after the first sick animals were detected.

The mortality in this group rose significantly (see Figure 2) despite the fact that therapeutic measure were implemented immediately.

The production and health of pigs returned to normal levels about 5 months after onset.

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