The effect of microbial-nutrient interaction on the immune system of young chicks after early probiotic and organic acid administration.

The combined effects of probiotics {Lactobacillus acidophilus, Lactobacillus casei, Streptococcus faecium, and Saccharomyces cerevi-siae) and organic acids (sorbic and citric acid) on intestinal morphology and expression of immune-related genes were investigated. One-day-old chicks were randomly assigned to 1 of 3 groups: birds not receiving probiotic or organic acids (control; T1), or birds receiving an oral combination (1 g/L in water) of 108 CFU/g of each of the aforementioned probiotics and organic acids (1% sorbic acid and 0.2% citric acid) for 7 (T2) or 14 d (T3). Each group was divided into 5 replicate pens of 20 birds each, and 5 birds from each group (1 from each pen) were killed on d 11 and 22. Intestinal sections were collected for histological assessment, and reverse transcriptase-PCR analysis was used to assess defensin and cathelicidins expression. Quantitative real-time PCR was used to assess toll-like receptors (T1R) and cytokine expression. Duodenal villus height was greater in T2 and T3 at d 11 (P≤ 0.036) and 22 (P ≤ 0.015) compared with T1. At d 11, duodenal goblet cell/unit area was less in T3, whereas it was greater in T2 compared with T1 in the jejunum (P = 0.009). Ileal goblet cell/unit area was greater in T3 at d 22 compared with T1 (P < 0.001). Avian beta-defensin-3 was expressed in all tissues except the bursa of T3 birds at d 11, and T1R-2 was down regulated in the cecal tonsil of birds in T2 and T3 at d 11 compared with T1 (P = 0.020 and 0.003, respectively). Expression of IL-12p35 in the ileum at d 11 was down regulated in T2 and T3 compared with T1 (P = 0.030 and 0.012, respectively). Reduced expression of INF-y was observed in the ileum in T3 compared with T1 at d 11 (P = 0.047). Ileal IL-6 and IL-10 and cecal tonsil interferon-gamma INF-&ggr; expressions were greater T2 at d 22 (P < 0.047) than T1. In conclusion, supplementation of combined probiotics and organic acids resulted in inconsistent gut morphology associated responses, and avian beta-defensins and cathelicidins expression were not associated with combined probiotics and organic acids supplementation. Birds supplemented with combined probiotics and organic acids for 7 d showing similar responses in T1R-2, IL-12p35, and IFN-y compared with those supplemented for 14 d indicates that shorter periods of supplementation might be enough to elicit beneficial responses. [ABSTRACT FROM AUTHOR]