Effect of δ-aminolevulinic acid on growth performance, nutrient digestibility, blood parameters and the immune response of weanling pigs challenged with Escherichia coli lipopolysaccharide

Abstract

This study investigated the effects of dietary δ-aminolevulinic acid (ALA) on growth performance, nutrient digestibility, blood parameters and whether ALA improved the immune response of weanling pigs challenged with Escherichia coli lipopolysaccharide (LPS). Eighty pigs (body weight = 7.21 ± 0.51 kg) were allotted to four dietary treatments, with four pens per treatment and five pigs per pen. Basal diets were supplemented with 0, 5, 10, and 15 mg/kg ALA (as-fed basis) and fed for 35 days. At the end of the feeding period, 10 pigs were selected from both the 0- and 10-mg/kg ALA treatment groups; five were injected i.p. with LPS (50 μg/kg BW) and the other five pigs with an equivalent amount of sterile saline, resulting a 2 × 2 factorial arrangement. Blood sample and rectal temperature data were collected at 0, 2, 4 and 12 h after challenge. Growth performance was not affected by dietary treatments over the total experimental period. However, dry matter (DM) and nitrogen (N) digestibility was improved in the 15-mg/kg ALA treatment group at day 35 ( P < 0.05). Serum hemoglobin (Hb) and iron levels were also increased, with the 10-mg/kg ALA treatment showing the highest concentration ( P < 0.05). On day 35, red (RBC) and white blood cell (WBC) counts were elevated, with the 5- and 10-mg/kg ALA treatments having the highest counts ( P < 0.05). During challenge, LPS injection elevated rectal temperature at 2 and 4 h postchallenge ( P < 0.05). Plasma cortisol concentration was also increased by LPS injection at 2 and 4 h postchallenge and an ALA-alleviating effect was evident at 2 h postchallenge ( P < 0.01). Concentration of plasma insulin-like growth factor-I (IGF-I) was increased in the ALA-supplemented treatments at 2 h postchallenge ( P < 0.05). LPS injection increased plasma tumor necrosis factor-α (TNF-α) concentrations at 2, 4 and 12 h ( P < 0.01), while an ALA-alleviating effect was observed at 2 and 4 h postchallenge ( P < 0.05 and P < 0.10, respectively). Challenge with LPS decreased WBC counts at 2 and 4 h postchallenge ( P < 0.01). At 12 h postchallenge, RBC, WBC and lymphocyte counts were affected by LPS challenge, while an ALA effect was only observed on WBC count ( P < 0.05). In conclusion, dietary supplementation of ALA in weanling pigs can improve DM and N digestibilities, and iron status and have a beneficial effect on the immune response during inflammatory challenge.