Identification and Characterization of Limosilactobacillus reuteri Strain S3 Isolated from Chicken and Its Protective Efficacy Against Avian Coccidiosis.

Limosilactobacillus reuteri is one of the common lactic acid bacteria in the chicken gastrointestinal tract. Our previous study revealed that L. reuteri abundance declined in White Leghorn chickens following infection with Eimeria tenella, E. maxima, and E. necatrix, suggesting a potential role of this species in gut homeostasis during coccidiosis. In this study, eight L. reuteri strains were isolated from the intestinal tract of White Leghorn chickens. Strain S3 was selected as the most promising candidate after screening for acid and bile tolerance, adhesion ability, antagonism against pathogens. Oral administration of S3 strain at dose of 4 × 107 CFU/bird, 1.2 × 108 CFU/bird or 2 × 108 CFU/bird for 18 days improved average daily gain (ADG) in both White Leghorn chickens and Suqin laying hens. The ADG value in groups treated with 4 × 107 CFU/bird was significantly higher compared to that in the control group (p < 0.05). This treatment did not cause adverse effects on hepatic or renal function, but significantly increased the thymus index in both breeds and the levels of total protein and globulin in Suqin laying hens (p < 0.05). S3 strain also modulated gut microbiota composition in White Leghorn chickens, promoting beneficial lactobacilli colonization in the jejunum and achieving persistent colonization in the cecum. S3 strain selectively increased the proportion of CD3+CD4+ T lymphocytes in peripheral blood of Suqin laying hens. The anticoccidial efficacy of S3 strain was evaluated in Suqin laying hens challenged with E. tenella, E. maxima, and E. necatrix. The results showed that S3 strain alleviated clinical signs, reduced lesion scores, decreased oocyst output, and attenuated body weight loss. Anticoccidial index (ACI) values were 130.67, 148.06, and 163.40 for E. tenella, E. maxima, and E. necatrix infection, respectively. These results suggest that L. reuteri S3 is a safe chicken-derived probiotic with immunomodulatory and anticoccidial properties, and may serve as a feed additive for coccidiosis control in poultry production.