Evaluation of Glycyrrhizic Acid Therapeutic Effect and Safety in Mycoplasma gallisepticum (HS Strain)-Infected Arbor Acres Broilers

SIMPLE SUMMARY: Mycoplasma gallisepticum (MG) can induce chronic respiratory disease (CRD) in chickens. Glycyrrhizic acid (GA) is the major ingredient of licorice and shows excellent anti-pathogenic microorganism and anti-inflammatory properties. Based on above, this study has evaluated the therapeutic effects and safety of GA in MG-infected broilers. Study results showed that GA could inhibit the proliferation of MG in vitro and expression of MG adhesion protein (pMGA1.2) in broiler lungs. GA restored production performances and attenuated MG-induced organ damage and abnormal biochemical indicator changes in MG-infected broilers. In conclusion, GA displayed significant therapeutic efficacy regarding MG infection and had no adverse effects on broilers (100 mg/kg/d). ABSTRACT: This study was conducted to evaluate the therapeutic effects and safety of GA in MG-infected broilers. Our results showed that the minimum inhibitory concentration of GA was 31.25 μg/mL. Moreover, GA inhibited the expression of MG adhesion protein (pMGA1.2) in the broilers’ lungs. GA treatment clearly decreased the morbidity of CRD and mortality in the MG-infected broilers. Compared with the model group, GA treatment significantly decreased gross air sac lesion scores and increased average weight gain and feed conversion rate in the MG-infected broilers. Histopathological examination showed GA treatment attenuated MG-induced trachea, immune organ and liver damage in the broilers. Moreover, GA treatment alone did not induce abnormal morphological changes in these organs in the healthy broilers. Compared with the model group, serum biochemical results showed GA treatment significantly decreased the content of total protein, albumin, globulin, alanine aminotransferase, aspartate aminotransferase, total bilirubin, creatinine, uric acid, total cholesterol, and increased the content of albumin/globulin, alkaline phosphatase, apolipoprotein B and apolipoprotein A-I. In conclusion, GA displayed a significant therapeutic efficacy regarding MG infection and had no adverse effects on the broilers (100 mg/kg/d).