A Novel, Non-Antimicrobial Protein Improves Growth Performance and Immune Responses of Pigs Experimentally Infected with Porcine Reproductive and Respiratory Syndrome Virus

Swine Awake® (SW) is a novel, bioactive, non-antimicrobial small protein that alters the immune system after consumption by animals. A study was conducted to evaluate supplementation of SW via oral gavage on growth performance and immune responses of weaning pigs experimentally infected with porcine reproductive and respiratory syndrome virus (PRRSV). Forty-eight commercial weanling barrows (5.5 ± 0.6 kg BW), free of PRRSV, were randomly allotted to either a Control treatment without supplementation of SW (CON) or oral gavage of SW at 5.0 mg/head/d (OGSW). Pigs were housed with two pigs per pen and 12 pens per treatment for 25 d [4 d before and 21 d after the inoculation of PRRSV (d 0)]. In addition, 32 weanling barrows (5.7 ± 0.7 kg BW) were housed in four pens with 8 pigs per pen at non-challenged barn to serve as a reference treatment (NegCON) during the same experimental period. White blood cells, viral load, PRRSV antibody titer, and porcine cytokines were measured in blood samples. All pigs were euthanized on d 21 to measure the percentage of fresh and microscopic lung lesions. Data were analyzed using PROC MIXED of SAS. Infection of PRRSV significantly reduced pig ADG by 45% (P < 0.001) and ADFI by 37% (P < 0.001) comparing CON with NegCON with no effect on pig mortality. Oral gavage of SW significantly improved pig ADG by 21% from d 0 to 21 (0.24 vs. 0.20 kg/day, P = 0.05) and tended to improve pig BW on d 21 (10.5 vs. 9.6 kg, P = 0.07) compared with CON. On d 21 OGSW significantly reduced microscopic lung lesions compared with CON (0.95 vs. 1.33, P = 0.05). Additionally, the number of neutrophils was decreased (P = 0.06) while the number of lymphocytes was increased (P = 0.05) in pigs receiving OGSW compared with pigs fed CON on d 21, resulting in lower neutrophils to lymphocytes ratio (P = 0.009). These white blood cells were similar between those in non-challenged pigs and challenged pigs supplemented with SW. Furthermore, OGSW tended to increase serum level of IL-12 on d 21 compared with CON (P = 0.10). No significant differences were observed on viral load, Ct values or percentage of fresh lung lesions. In conclusion, these results indicate that oral gavage of SW reduced the adverse effects of PRRSV by enhancing the immune system ahead of challenge which led to improved growth performance.