Effects of Small Peptide Supplementation on Growth Performance, Intestinal Barrier of Laying Hens During the Brooding and Growing Periods

Abstract

The growing period is a critical period for growth and development in laying hens. During this period, chicks grow rapidly, but are accompanied by unstable digestive function, incomplete organ development, and high mortality. Small peptide, a feed additive, which has been proved to promote intestinal development and immunity in poultry. In order to elucidate the effects of small peptides on growth performance, immunity, antioxidant capacity, and intestinal health of growing laying hens, a total of 900 Tianfu green shell laying hens (1-day-old) were randomly divided into 5 treatments with 6 replicates of 30 birds each in this 18-week trial. Dietary treatments included a corn-soybean meal-based diet supplemented with 0 g/kg, 1.5 g/kg, 3.0 g/kg, 4.5 g/kg and 6.0 g/kg small peptide, respectively. The results showed that the supplementation of small peptides significantly increased growth rate (P<0.05) in laying hens, as well as elevated the serum immunoglobulins (P<0.05) and antioxidant indices (P<0.05), however, it decreased inflammation parameters (P<0.05). The supplementation of small peptides enhanced the intestinal function by promoting gut development (P<0.05) and improving gut integrity (P<0.05), barrier function (P<0.05) and the diversity of gut microbiota (P<0.05) in the growing hens. The best performance was recorded among the hens fed 4.5 g/kg level of small peptide. Taken together, these results showed that small peptide supplementation could improve the economic value of growing hens by promoting growth rate, disease resistance, and the optimal amount of addition for Tianfu green shell laying hens was 4.5 g/kg.

Keywords: anti-oxidation; growth performance; immune; intestinal health; laying hen; small peptide.

Figure 1

Effects of small peptide supplementation on Serum Immune Levels of laying hens at 18 weeks of age. (A) Effects of different concentrations of small peptides on the serum IgA levels. (B) Effects of different concentrations of small peptides on the serum IgG levels. (C) Effects of different concentrations of small peptides on serum IgM levels. Data represent the mean ± SEM (n=6 independent samples). Bars having different superscript letters differed significantly (P<0.05).

Figure 2

Effects of small peptide supplementation on serum inflammatory levels of laying hens at 18 weeks of age. (A) Effects of different concentrations of small peptides on the level of IL-1β in the serum. (B) Effects of different concentrations of small peptides on the level of IL-6 in the serum. (C) Effects of different concentrations of small peptides on the level of IL-8 in the serum. (D) Effects of different concentrations of small peptides on the level of IL-12 in the serum. Data represent the mean ± SEM (n=6 independent samples). Bars having different superscript letters differed significantly (P<0.05).

Figure 3

Effects of small peptide supplementation on serum antioxidant index levels of laying hens at 18 weeks of age. (A) Effects of different concentrations of small peptides on the level of T-AOC in serum. (B) Effects of different concentrations of small peptides on the level of SOD in serum. (C) Effects of different concentrations of small peptides on the level of GSH-Px in serum. (D) Effects of different concentrations of small peptides on the level of MDA in the serum. Data represent the mean ± SEM (n=6 independent samples). Bars having different superscript letters differed significantly (P<0.05).

Figure 4

Effects of small peptide supplementation on the small intestinal morphology of laying hens at 18 weeks of age. The villus length and crypt depth were observed in sections of different intestinal segments (40×).

Figure 5

Effects of small peptide supplementation on the expression of intestinal tight junction protein of laying hens at 18 weeks of age. (A) Effects of different concentrations of small peptides on the expression of ZO-1 mRNA of the small intestinal segments (duodenum, jejunum, and ileum). (B) Effects of different concentrations of small peptides on the expression of Claudin-3 mRNA of the small intestinal segments (duodenum, jejunum and ileum). (C) Effects of different concentrations of small peptides on the expression of Occludin mRNA of the small intestinal segments (duodenum, jejunum and ileum). Data represent the mean ± SEM (n=3 independent samples). Bars having different superscript letters differed significantly (P<0.05).

Figure 6

Effects of small peptide supplementation on the intestinal immune factors expression of laying hens at 18 weeks of age. (A) Effects of different concentrations of small peptides on the expression of IFN-α mRNA in each intestinal segment (duodenum, jejunum and ileum). (B) Effects of different concentrations of small peptides on the expression of IFN-γ mRNA in each intestine (duodenum, jejunum and ileum). (C) Effects of different concentrations of small peptides on the expression of TGF-β1 mRNA in each intestine (duodenum, jejunum and ileum). Data represent the mean ± SEM (n=3 independent samples). Bars having different superscript letters differed significantly (P<0.05).

Figure 7

Effects of small peptide supplementation on the intestinal Antioxidant capacity of laying hens at 18 weeks of age. (A) Effects of different concentrations of small peptides on the expression of SOD mRNA in each intestinal segment (duodenum, jejunum, and ileum). (B) Effects of different concentrations of small peptides on the expression of GST mRNA in each intestinal (duodenum, jejunum, and ileum). (C) Effects of different concentrations of small peptides on the expression of GSR mRNA in each intestinal segment (duodenum, jejunum, and ileum). (D) Effects of different concentrations of small peptides on the expression of GPx mRNA in each intestine (duodenum, jejunum, and ileum). Data represent the mean ± SEM (n=3 independent samples). Bars having different superscript letters differed significantly (P<0.05).

Figure 8

Effects of small peptide supplementation on cecal microbial diversity of laying Hens at 18 weeks of age. (A) Histogram of relative abundance top10 of species at phylum level. (B) The petal map representing common and unique ASVs among each group. (C) Alpha diversity indexes (chao1, simpson, pielou-e and shannon) for each group. (D) The heat map of Beta diversity index Unweighted unifrac distance matrix: The larger the circle is, the darker the corresponding color is, indicating the greater the difference between the two samples. On the contrary, the smaller the circle, the lighter the corresponding color, indicating that the difference between the two samples is smaller. (E) Function annotation petal diagram: The common and specific gene information among different groups was analyzed, and the results of KO database function prediction were displayed.