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The study compared the effect of dietary supplementation with an inorganic or organic source of zinc (Zn) on mucin 2 (MUC-2) and IgA gene expression, the cytokines IL-17 and TGF-β4 and the secretory IgA content (sIgA) in broiler jejunum. One-day-old chickens were fed an unsupplemented basal diet (BD) or the same BD supplemented with 30 or 70 mg/kg of added Zn from ZnSO 4 ·H 2 O or Zn chelate of glycine hydrate for 40 days. The highly expressed MUC-2 and IgA genes were observed in both groups supplemented with the low-dose Zn sources (30 mg/kg). A higher sIgA concentration was observed in both the ZnSO 4 groups and the glycine-zinc/30 mg group. Our data indicate that the organic Zn chelate has better availability than the inorganic Zn source, and the low-dose Zn diets proved to be more beneficial to the maintenance of intestinal immune homeostasis. ARTICLE HISTORY

The protective effect of Enterococcus faecium EFAL41 on chicken's caecum in relation to the TLR (TLR4 and TLR21) activation and production of luminal IgA challenged with Campylobacter jejuni CCM6191 was assessed. The activation of MIF, IFN-β, MD-2 and CD14 was followed-up after bacterial infection. Day-old chicks (40) were divided into four groups (n = 10): control (C), E. faecium AL41 (EFAL41), C. jejuni (CJ) and combined E. faecium AL41+C. jejuni (EFAL41+CJ). Relative mRNA expression of TLR4, TLR21 and CD14 was upregulated in the probiotic strain and infected (combined) group on day 4 and 7 post infection (p.i.). The caecal relative MD-2 mRNA expression was upregulated on day 4 p.i. in the EFAL41+CJ and CJ groups. MIF and IFN-β reached the highest levels in the combined groups on day 7 p.i. The concentration of the sIgA in intestinal flush was upregulated in EFAL41+CJ group on day 4 p.i. The results demonstrated that E. faecium EFAL41 probiotic strain can modulate the TLRs expression and modify the activation of MIF, IFN-β, MD-2 and CD14 molecules in the chickens caecum challenged with C. jejuni CCM 6191. The counts of EFAL41 were sufficient and high, similarly the counts of enterococci in both, caecum and faeces but without reduction of Campylobacter counts.

The concentration of secretory IgA (sIgA) in intestine flush and solid organs (spleen, bursa) in chickens pretreated with probiotic strain Enterococcus faecium AL41 (EF) and challenged with Salmonella Enteritidis PT4 (SE) was assessed. Forty 1-day-old chickens Cobb 500 were divided into four groups: control, EFAL41, SE and combined EFAL41+SE. The increased concentration of sIgA was determined on day 4 after salmonella infection in the intestine flush in EFAL41group. In combined EFAL41+SE group significant increase of sIgA in the intestine flush was found 7 days postinfection. Pre-treatment of chickens with E. faecium AL41 also showed beneficial effect in bursa in EFAL41 and EFAL41+SE groups. In spleen, total IgA was increased only in SE group. The results demonstrated positive effect of E. faecium AL41 on IgA production in chickens' intestine and solid organs after S. Enteritidis PT4 challenge. Validity of method using for IgA evaluation in solid organ was proved.

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