To analyze the intervention mechanism of polysaccharides from charred Angelica sinensis (CASP) on the liver injury caused by Ceftiofur sodium (CS) and lipopolysaccharide (LPS) from the perspective of the intestine. Ninety-four one-day-old laying chickens underwent free feeding and drinking water for three days. Then, fourteen laying chickens were randomly selected as the control group, and sixteen laying chickens were selected as the model group. Sixteen laying chickens in the rest were randomly selected as the intervention group of CASP. Chickens in the intervention group were given CASP by the oral administration (0.25 g/kg/d) for 10 days, the control and model groups were given the same amount of physiological saline. During the 8th and 10th days, laying chickens in the model and CASP intervention group were subcutaneously injected with CS at the neck. In contrast, those in the control group were subcutaneously injected with the same amount of normal saline simultaneously. Except for the control group, the layer chickens in the model and CASP intervention groups were injected with LPS after CS injection on the 10th day of the experiment. In contrast, those in the control group were injected with the same amount of normal saline at the same time. 48 h after the experiment, the liver samples of each group were collected, and the liver injury was analyzed by hematoxylin-eosin (HE) staining and transmission electron microscopy. And the cecum contents of six-layer chickens in each group were collected, and the intervention mechanism of CASP on the liver injury from the perspective of the intestine was analyzed by the 16S rDNA amplicon sequencing technology and the short-chain fatty acids (SCFAs) detection of cecal contents based on Gas Chromatography-Mass Spectrometry (GC-MS), and their association analysis was carried out. The results showed that the structure of chicken liver in the normal control group was normal, while that in the model group was damaged. The structure of chicken liver in the CASP intervention group was similar to the normal control group. The intestinal floras in the model group were maladjusted compared to the normal control group. After the intervention of CASP, the diversity, and richness of chicken intestinal floras changed significantly. It was speculated that the intervention mechanism of CASP on the chicken liver injury might be related to the abundance and proportion of Bacteroidetes and Firmicutes. Compared with the model group, the indexes of ace, chao1, observed species, and PD whole tree of chicken cecum floras in the intervention group of CASP were significantly increased (p < 0.05). The contents of acetic acid, butyric acid, and total SCFAs in the intervention group of CASP were significantly lower than those in the model group (p < 0.05), and the contents of propionic acid and valeric acid in the intervention group of CASP were significantly lower than those in the model group (p < 0.05) and normal control group (p < 0.05). The correlation analysis showed that the changes in the intestinal floras were correlated with the changes in SCFAs in the cecum. It is confirmed that the liver-protecting effect of CASP is indeed related to the changes in the intestinal floras and SCFAs content in the cecum, which provides a basis for screening liver-protecting alternative antibiotics products for poultry.
Keywords: intestinal floras; layer chickens; liver injury; polysaccharides from charred Angelica sinensis; short-chain fatty acids.