Development of an oxidative stress model in weaned pigs highlighting plasma biomarkers' specificity to stress inducers

To determine the effects of vaccination, heat stress, and dietary antioxidant concentration and investigate some blood parameters as an effective model of oxidative stress, 360 weaned piglets (8.7 +/- 1.6 kg) were randomly affected to eight groups in a 2 x 2 x 2 factorial design. Double vaccination at weaning against porcine circovirus type 2 (PCV2) and porcine influenza, heat stress at d 9, 10, 23, 24, 37, and 38 (37 degrees C over a 6 h period), or controls were applied to piglets that were given from weaning to d 14 NRC (2012) levels for vitamin E and selenium or extra supplementation in vitamin E, selenium, and superoxide dismutase-rich melon supplement. Blood samples were taken from 6 piglets per treatment at d 13 and 40, and serum haptoglobin, plasma glutathione peroxidase (GPx), and blood lipid peroxides were determined. Half-hemolysis time (HT50) of red blood cells (RBC) exposed to a controlled free radical attack were determined in whole blood and RBC concentrate. Both vaccination and heat stress decreased ADG (P < 0.05) during phase 2 period (d 14 to 41). Antioxidant supplementation increased HT50 of whole blood at d 13 (P = 0.01) and RBC at d 40 (P = 0.03) and GPx activity at d 13 and 40 (P < 0.01 and P = 0.02, respectively). Vaccination decreased GPx activity (P = 0.04, repeated measures analysis) and resulted in higher concentrations for haptoglobin at d 13 (P < 0.01) and 40 (P = 0.03) and lipid peroxides at d 13 and 40 (P = 0.02). Moreover, exposing vaccinated piglets to repetitive heat stress periods reduced their whole blood and RBC resistance (P < 0.01) at d 40 after weaning. In summary, oxidative stress biomarkers were associated with each specific stress inducer, and cumulative effects of heat and vaccination stressors associated with pig weaning produced responses for all selected biomarkers.