Effects of Dietary Supplementation Using Phytobiotics with Different Functional Properties on Expression of Immunity Genes, Intestinal Histology, Growth, and Meat Productivity of Broiler Chickens

The aim of this study was to investigate the expression of immunity-related genes and morpho-histological features of the intestines, and the growth and meat production of broiler chickens when fed plant extracts with different functional components. Chickens in the control group received a basic diet. The feed in the experimental groups contained plant extracts standardized to various biologically active components such as the extract of common chicory with inulin (INUL), St. John's wort with flavonoids (FLAV), maral root with ecdysterone (ECDS), and extracts of creeping thyme with flavonoids and tannins (FLAV-TANN). The results of this study showed that the application of the studied phytobiotics increased the expression of the pro-inflammatory gene <i>IL8</i>, with the 2^-ΔΔCT value ranging from 2.66 to 4.63. In the case of the antimicrobial peptide gene <i>AvBD9</i>, the 2^-ΔΔCT value ranged from 1.66 to 8.16, depending on the group. <i>AvBD10</i> gene expression increased (2^-ΔΔCT = 2.19) when the chickens were fed the chicory extract and decreased when thyme extract was used (2^-ΔΔCT = 0.33). The study also found that using biologically active components in the diets of broiler chickens was accompanied by a significant decrease in the height of epithelial cells in the cecum mucous membrane in the INUL group (61.3%, <i>p</i> ≤ 0.001), FLAV group (60.0%, <i>p</i> ≤ 0.001), ECDS group (48.2%, <i>p</i> ≤ 0.001), and FLAV + TANN group (67.6%, <i>p</i> ≤ 0.001). It also caused a reduction in the depth of crypts in the INUL (38.4%, <i>p</i> ≤ 0.001), FLAV (32.3%, <i>p</i> ≤ 0.001), ECDS (50.9%, <i>p</i> ≤ 0.001), and FLAV + TANN (53.4%, <i>p</i> ≤ 0.001) groups. The use of all extracts, except creeping thyme, caused changes in the size of muscular elements in the intestinal walls; thus, the thickness of the muscular layer increased 1.5-2.0 times under the influence of flavonoids in St. John's wort and of inulin in chicory, to 430.99 and 579.87 μm, respectively (<i>p</i> ≤ 0.001), and decreased 1.9 times under the influence of ecdysterone in maral root to 151.59 μm (<i>p</i> ≤ 0.001). The use of phytobiotics increased feed consumption and stock safety, leading to an increase of 4.1-7.5% in the live weights of broiler chickens at the end of the rearing period, thus contributing to the higher slaughter quality of poultry; in particular, the weights of breast muscles in cockerels in the INUL group increased by 16.9% (<i>p</i> ≤ 0.05), while the weights in the ECDS and FLAV + TANN groups increased by 18.1% (<i>p</i> ≤ 0.05) and 23.1% (<i>p</i> ≤ 0.01), respectively. Thus, the use of the studied phytobiotics in the broiler chicken diet increases meat production and activates immunity, which indicates the possibility of replacing antibacterial drugs with natural nutraceuticals.