Exogenous dietary lysozyme improves the growth performance and gut microbiota in broiler chickens targeting the antioxidant and non-specific immunity mRNA expression

<div><p>Supplementation of exogenous enzymes in chickens has been widely practiced, yet mechanisms responsible are not fully delineated. To investigate the effects of the dietary lysozyme on the growth performance and immunity of broiler chickens, a total of 120 one-day-old Ross 308 chicks were randomly allocated into four groups, each having three replicates (30 birds/group). The chicks were fed the starter (1–21 d) and grower (22–35 d) diets supplemented with 0 (control), 70 (LYZ70), 90 (LYZ90) and 120 (LYZ120) g of lysozyme 10%^® per ton of basal diet for five weeks. The results revealed significant improvement in the growth performance and gut environment. There were significant decreases (<i>P</i> < 0.05 or 0.01) in the harmful fecal <i>Coliform</i> and <i>Clostridia</i> and an increase (<i>P</i> ˂ 0.05) in the beneficial <i>Lactobacillus</i> in the lysozyme-supplemented groups, especially in LYZ90. Moreover, the mRNA expressions of Cu, Zn-superoxide dismutase (<i>SOD1</i>), glutathione peroxidase (<i>GSH-Px</i>), interferon-gamma (<i>IFN-γ</i>), interleukin-10 (<i>IL-10</i>), and interleukin-18 (<i>IL-18</i>) were upregulated in response to lysozyme supplementation. In comparison to control, LYZ90 fed birds had a significant increase (<i>P <</i> 0.01) in the <i>GSH-Px</i> gene expression that enhances the antioxidant status of the gut. Expression of the biomarkers involved in the gut non-specific immunity indicated significant increases in the mRNA expression of <i>INF-γ</i> (<i>P <</i> 0.001), <i>IL-10</i> (<i>P <</i> 0.001), and <i>IL-18</i> (<i>P <</i> 0.05) in LYZ90 group. Also, serum globulin levels were significantly elevated (<i>P</i> ˂ 0.05) in lysozyme-supplemented groups. Histologically, the intestinal villi length and crypts depth were also enhanced (<i>P</i> ˂ 0.05) by dietary lysozyme supplementation. In conclusion, supplementation of broiler chickens with exogenous lysozyme, especially at 90 g of lysozyme per ton of basal diet dose rate, improved the growth performance, gut antioxidant status, and nonspecific immunity of broiler chickens.</p></div

Components of Rogosa agar.

<p>Components of Rogosa agar.</p

Primers sequences, target genes, amplicon sizes, and cycling conditions for SYBR green RT-PCR.

<p>Primers sequences, target genes, amplicon sizes, and cycling conditions for SYBR green RT-PCR.</p

Primers sequences, target genes, amplicon sizes and cycling conditions for Taqman RT-PCR.

<p>Primers sequences, target genes, amplicon sizes and cycling conditions for Taqman RT-PCR.</p

Composition of the experimental starter and finisher diets.

<p>Composition of the experimental starter and finisher diets.</p

Histological examination of jejunum samples stained with H&E.

<p>(A) control (×40), (B) LYZ70 (×40), (C) LYZ90 (×100), and (D) LYZ120 (×40). Large arrows point to intestinal villi. Small arrows point to intestinal crypts.</p

Reverse transcription polymerase chain reaction (RT-PCR) validation of selected genes differentially expressed due to lysozyme (LYZ).

<p>Selected genes were <i>SOD1</i> = Cu, Zn-superoxide dismutase and <i>GSH-Px</i> = glutathione peroxidase. **<i>P</i> < 0.01 vs. control, ⁺<i>P</i> < 0.05 and ⁺⁺⁺<i>P</i> < 0.001 vs. LYZ90, and ^#<i>P</i> < 0.05 vs. LYZ120. Statistical analysis was done by One-way ANOVA, Tukey’s <i>post hoc</i> test multiple comparisons. Error bars represent SE.</p

Effect of lysozyme dietary supplementation on growth performance of broiler chickens.

<p>Effect of lysozyme dietary supplementation on growth performance of broiler chickens.</p

Effect of lysozyme dietary supplementation on serum total protein (g/dl), albumin (g/dl), globulin (g/dl), ALT (U/L), AST (U/L), TAG (mg/dl), total cholesterol (mg/dl), creatinine (mg/dl), and uric acid (mg/dl) in broiler chickens.

<p>Effect of lysozyme dietary supplementation on serum total protein (g/dl), albumin (g/dl), globulin (g/dl), ALT (U/L), AST (U/L), TAG (mg/dl), total cholesterol (mg/dl), creatinine (mg/dl), and uric acid (mg/dl) in broiler chickens.</p

Effect of lysozyme dietary supplementation on villi length (μm) and crypt depth (μm) in broiler chickens (3 replicates per group).

<p>Effect of lysozyme dietary supplementation on villi length (μm) and crypt depth (μm) in broiler chickens (3 replicates per group).</p