Effects of in ovo Injection of Astragalus Polysaccharide on the Intestinal Development and Mucosal Immunity in Broiler Chickens.

Shu-Bao Yang,Peng Sun,Ying-Nan Zhang,Dong-Hai Zhao,Ao-Yi Duan,Yan-Jun Qin,Xin Ma,An-Qi Ju,Wei-Min Luan

doi:10.3389/fvets.2021.738816

Abstract

The purpose of this study was to examine the effects of in ovo injection of Astragalus polysaccharide (APS) on hatchability, body weight (BW), intestinal histomorphology, the number of IgA+ cells and sIgA content in intestine, and the expression of intestinal immune-related genes in broiler chickens. On day 18 of the incubation, a total of 960 live embryo eggs were weighed and randomly divided into 4 treatment groups: a control group and three APS groups. The eggs in the control group were injected with 0.5 mL physiological saline. The eggs in the APS groups were injected with 3 different amounts of APS in 0.5 mL physiological saline: 1 mg (APSL), 2 mg (APSM) and 4 mg (APSH). The solution was injected into the amnion of each egg. The results showed that in ovo injection of APS did not affect the hatchability but increased the body weight of the 14 d and 21 d chickens, with a significant increase observed in the APSM group (P < 0.05). At most time points, the villus height (VH) was increased (P < 0.05) and the crypt depth (CD) was decreased (P < 0.05) in the small intestine of the broilers, with higher VH/CD ratios in the APSL and APSM groups compared with the control group. The number of IgA+ cells in the mucosa and the secretory immunoglobulin A (sIgA) levels in the intestinal washings were higher in the APSM and APSH groups than in the APSL and control groups. The gene expression levels of interleukin (IL)-2, interleukin (IL)-4, interferon gamma (IFN-γ), and Toll-like receptor (TLR)-4 were significantly enhanced by APS stimulation at most time points (P < 0.05). These results indicated that in ovo injection of APS has the potential of promoting intestinal development and enhancing intestinal mucosal immunity of broiler chickens in the early stage after hatching.

Highlights

In comparison to mammals, the growth and development of the avian embryo and hatchling are dependent on the nutrients in the fertile eggs
The control group was injected with 0.5 mL physiological saline, while the three experimental groups (APSL, APSM, and APSH group) were injected with 0.5 mL of 3 different concentrations of Astragalus polysaccharide (APS) solution (1, 2, and 4 mg APS in 0.5 mL physiological saline), respectively
This study aimed to explore the effects of intra-amniotic injection of APS on growth performance, intestinal development and intestinal mucosal immunity

Summary

Introduction

The growth and development of the avian embryo and hatchling are dependent on the nutrients in the fertile eggs. In ovo feeding during incubation is regarded as a way to correct this imbalance by providing additional nutrients to meet the developmental needs of embryos and post-hatch chickens during fasting [2, 3]. As studies indicated the fasting may lead to retardation in development of the gastrointestinal tract and even the entire body [7, 8]. Studies have shown that in ovo injection of various biologics into the amnion, such as prebiotics and synbiotics, may rapidly promote small intestinal growth and development by establishing a healthy and balanced gastrointestinal tract (GIT) microbiome in the early stage of its formation [9, 10]

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