Effects of Vitamin A, Trp and Tre, and Omega-3 on Performance and Viral-Load in Growing Gilts Challenged with Porcine Reproductive and Respiratory Syndrome Virus

Gilts on rearing and quarantine often suffer immune stress that can modify metabolism, decrease ADFI and performance. The objective of this study was to assess the effect of different nutritional strategies on gilt performance and infection dynamics under porcine reproductive and respiratory syndrome virus (PRRSV) infection. One hundred gilts (46.5 ± 3.5 kg) were blocked as light (L) and heavy (H), and distributed into 10 pens (10 gilts/pen) and two replicates (L and H) randomly allotted to five groups: control (C-), high dose (40,000 UI/kg) of vitamin A (vitA), increased ratios Trp (1.4 g/kg) and Thr (2.3 g/kg) (AA), adding omega 3 (10 g/kg fish oil) (Ω3) groups; that were infected through intra muscular injection (IM); and, the positive control (C+) in a separate facility none-infected. Gilts were fed ad libitum to meet or exceed nutrient requirements for growth (10.2 g/kg Lys, 2.1 g/kg Trp and 6.8 g/kg Thr). Gilt BW (individually) and ADFI (by pen) were recorded weekly. The trial lasted 89 days (d) although for logistic issues C+ was only followed up to d 40. Viral load (VL) was quantified as the area under the curve for 0–40 d post infection (PI) of the log of PCR-based serum viremia. In the statistical analysis, the procedures ANOVA for performance traits, and Fisher Exact test for the proportions of PCR-positive gilts over time were used. Infection was at d 11 and by d 15 all IM inoculated gilts showed viremia. At d 20, C+ was 7.8 kg above infected groups (P < 0.001). An interaction showed that this difference was 12.6 kg at d 40 while L and H were equal in BW for C+, however L were smaller than H for the other groups (P = 0.032). Only comparing infected groups, gilts from AA group showed a trend to do not lose BW after 9 d PI while other groups lost at least 1 kg (P = 0.085). Moreover, AA group showed a higher ADG than group Ω3 (P = 0.081) until d 70. The VL of the infected gilts did not show differences among groups. Therefore, amino acids requirements may be higher under a PRRSV infection and show a potential to modulate infection dynamics and this can have an effect on gilt performance during the rearing period.