AUTHOR=Yang Shu-bao , Qin Yan-jun , Ma Xin , Luan Wei-min , Sun Peng , Ju An-qi , Duan Ao-yi , Zhang Ying-nan , Zhao Dong-hai 

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

JOURNAL=Frontiers in Veterinary Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2021.738816

DOI=10.3389/fvets.2021.738816

ISSN=2297-1769

ABSTRACT=<p>The purpose of this study was to examine the effects of <italic>in ovo</italic> injection of <italic>Astragalus</italic> polysaccharide (APS) on hatchability, body weight (BW), intestinal histomorphology, the number of IgA<sup>+</sup> 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 (APS<sub>L</sub>), 2 mg (APS<sub>M</sub>) and 4 mg (APS<sub>H</sub>). The solution was injected into the amnion of each egg. The results showed that <italic>in ovo</italic> 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 APS<sub>M</sub> group (<italic>P</italic> &lt; 0.05). At most time points, the villus height (VH) was increased (<italic>P</italic> &lt; 0.05) and the crypt depth (CD) was decreased (<italic>P</italic> &lt; 0.05) in the small intestine of the broilers, with higher VH/CD ratios in the APS<sub>L</sub> and APS<sub>M</sub> groups compared with the control group. The number of IgA<sup>+</sup> cells in the mucosa and the secretory immunoglobulin A (sIgA) levels in the intestinal washings were higher in the APS<sub>M</sub> and APS<sub>H</sub> groups than in the APS<sub>L</sub> 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 (<italic>P</italic> &lt; 0.05). These results indicated that <italic>in ovo</italic> injection of APS has the potential of promoting intestinal development and enhancing intestinal mucosal immunity of broiler chickens in the early stage after hatching.</p>