Effects of increasing the dietary level of vitamin E, without and with a low inclusion level of aspirin, on systemic responses of weaned pigs challenged with haemolytic E. coli

Abstract Text: This experiment was conducted to examine the main and interaction effects of aspirin as a non-steroidal anti-inflammatory drug, and vitamin E as an intracellular antioxidant, on systemic responses in weaned pigs challenged with an enterotoxigenic strain of E. coli. A total of 192 individually-housed male weaner pigs (Landrace x Large White) weighing 6.6 ± 0.04 kg (mean±SEM) were allocated to a 2 x 3 factorial experiment with the respective factors being without and with 125 ppm aspirin (acetylsalicylic acid; Bayer) and three levels of vitamin E supplementation (50, 100, and 200 IU, dl-a-tocopheryl acetate; DSM). All pigs were challenged with E. coli serotype O149:K91:K88 at 7, 8 and 9 d after weaning (6-9 ml of 1.54 x 10⁸ CFU/mL) and blood samples were collected on 0, 7, 10, 14 and 21 d after weaning. Plasma vitamin E content, haptoglobin and plasma urea content were measured on all measurement days, while blood cell count was measured from randomly selected pigs (n=8) on 10 d after weaning. Data were analysed using two-way analysis of variance. Plasma urea, haptoglobin and vitamin E contents measured at the start of experiment (0 d) were used as covariates for statistical analysis on subsequent measurement days. Increasing the dietary vitamin E content increased (P < 0.001) plasma vitamin E contents on all measured days. Increasing vitamin E supplementation significantly decreased plasma haptoglobin content after E. coli infection (2.51, 2.26, and 1.99 mg/mL, respectively, on d 10, P < 0.01; 2.36, 1.8, and 1.78 mg/L, respectively, on d 14, P < 0.001), while aspirin supplementation had no effect on plasma haptoglobin content. Increasing dietary vitamin E content increased the number of platelets without aspirin supplementation (447, 488, and 569 x 10⁹/L), but decreased the number of platelets with aspirin supplementation (549, 598, and 435 x 10⁹/L, respectively; interaction P = 0.058). Vitamin E supplementation increased (P = 0.017) white blood cell numbers (19.4 x 10⁹/L vs. 17.6 x 10⁹/L). Aspirin supplementation significantly decreased plasma urea content after oral E. coli infection (5.0 vs. 4.3 mmol/L on d 10, P < 0.001; 5.1 vs. 4.7 mmol/L on d 14, P = 0.072), while vitamin E supplementation had no effect on plasma urea content. Results indicate that vitamin E supplementation reduced immune responses, whereas aspirin supplementation minimised infection-associated nitrogen waste in E. coli-challenged weaned pigs.

Keywords: aspirin, vitamin E, weaner pigs