Effect of porcine reproductive and respiratory syndrome virus infection and soy isoflavone supplementation on carcass cutability and meat quality of pigs.

The objective was to evaluate the effects of porcine respiratory and reproductive syndrome virus (PRRSV) infection and dietary soy isoflavone supplementation on carcass cutability and meat quality of commercial pigs. Barrows (21 d of age) were randomly allotted to experimental treatments that were maintained throughout the study: non-infected pigs received an isoflavone-devoid control diet (CON, n = 22), and infected pigs received either the control diet (PRRSV-CON, n = 20) or that supplemented with total ISF in excess of 1,500 mg/kg (PRRSV-ISF, n = 25). Pigs were penned by treatment, with 6 pigs within a pen. Following a 7-day adaptation, weanling pigs were inoculated once intranasally with either a sham-control (PBS) or live PRRSV (1x105 TCID50/mL, strain NADC20). Pigs were maintained on experimental diets for 166 d after inoculation and then slaughtered (192 or 194 d of age; approximately 120 kg BW). At 1 d post-mortem, left sides were separated between the 10th and 11th rib for determination of loin eye area (LEA), backfat thickness (BF), and loin quality (ultimate pH, instrumental color, drip loss, visual color, marbling, and firmness). Loin chops were aged 14 d post-mortem prior to Warner-Bratzler shear force (WBSF) determination. Belly width, length, thickness, and flop distance were determined. Data were analyzed as a one-way ANOVA with pig as the experimental unit. Carcass yield, LEA, BF, and estimated lean percentage did not differ (P > 0.26) among treatments. Loins from CON pigs had increased ultimate pH (P = 0.01), reduced L* scores (P = 0.005) coupled with darker visual color scores (P = 0.004), were firmer (P < 0.0001), and exhibited reduced drip loss (P = 0.01) compared with PRRSV-CON and PRRSV-ISF pigs. However, WBSF did not differ (P = 0.51) among treatments after 14 d of aging. Bellies from CON pigs were more firm compared with bellies from PRRSV-CON and ISF pigs (P < 0.01). These data suggest PRRSV infection did not alter carcass characteristics but may have marginally reduced loin and belly quality. Supplementation with dietary soy isoflavones did nothing to mitigate the detrimental effects of PRRSV infection.