Effects of Lactobacillus farciminis and Lactobacillus rhamnosus on the duodenal development of specific-pathogen-free broiler chickens

Background and Aim: The positive effects of Lactobacillus farciminis and Lactobacillus rhamnosus on growth and feed consumption indicators have been described; however, the underlying mechanisms remain unclear. This study aimed to determine whether the addition of L. farciminis CNCM-I-3699 (2.10¹⁰ GU/g) and L. rhamnosus CNCM-I-3698 (2.10¹⁰ GU/g) to the feed of Ross 308 specific-pathogen-free (SPF) broiler chickens (at a dose of 4 g/10 kg feed) affects live weight gain, the feed conversion ratio (FCR), and duodenal development in SPF broiler chickens. Materials and Methods: In total, 780 SPF broiler chicks were randomly divided into two groups (three replicates per group) immediately after hatching: The control group (n = 390) and the probiotic group (n = 390). Live body weight (g) and FCR were measured on days 1, 7, 14, 21, 28, and 35 of the study. Histological examinations (hematoxylin and eosin staining) of the duodenum were performed, and the villus height (VH), villus width, crypt depth (CD), muscle layer thickness, and VH: CD ratio were measured. In addition, immunohistochemical examinations were performed to determine the number of proliferating cell nuclear antigen (PCNA)-positive cells. Results: Feeding a probiotic mixture containing L. farciminis and L. rhamnosus to SPF broiler chickens for 35 days increased the duodenal absorption area and muscle layer thickness. In addition, it accelerated the histological development of the duodenum, as evidenced by the significantly higher number of PCNA-positive cells within the crypts. Although SPF broiler chickens in the ProL group exhibited greater live weight gain and lower FCR throughout the study, these differences were not statistically significant. Conclusion: These results suggest that L. farciminis and L. rhamnosus can serve as additives to SPF broiler chicken feed to promote growth and development.