Comprehensive Evaluation of Probiotic Effects on Laying Hen Physiology: From Performance to Bone and Gut Morphology

This study investigated the effects of probiotic supplementation on performance, egg quality, antioxidant capacity, gut morphology, fecal microbiota, and bone morphology in Lohmann Brown laying hens aged 44 weeks over a 16-week period. Ninety-six hens were randomly divided into control and probiotic groups (n = 48 each). The probiotic group received probiotic supplement containing <i>Lactobacillus acidophilus</i> KUEN 1607 and <i>Pediococcus acidilactici</i> KUEN 1608 via drinking water at 0.5%. Probiotic supplementation significantly improved feed conversion ratio (FCR), eggshell strength and thickness, and albumen quality (<i>p</i> < 0.001) and reduced the incidence of cracked and shell-less eggs (<i>p</i> < 0.05). Yolk and serum cholesterol levels decreased (<i>p</i> < 0.001), and antioxidant parameters improved, along with elevated serum IgG (<i>p</i> < 0.001). Histological analysis showed an increased ratio of villus height to crypt depth (<i>p</i> < 0.001) in the jejunum, indicating enhanced intestinal health. Fecal samples revealed increased <i>Lactobacillus</i> spp. and reduced coliform counts (<i>p</i> < 0.001), suggesting improved gut microbiota balance. While bone volume and surface area showed no significant difference, 3D geometric morphometric analysis identified subtle shape changes in long bones, especially the femur and tibiotarsus. These findings demonstrate that the selected probiotic combination supports nutrient utilization, egg quality, gut integrity, immune status, and skeletal health, offering a sustainable strategy to enhance productivity and welfare in laying hens.