Effects of Probiotic Lacticaseibacillus paracasei NSMJ27 on Laying Performance and Gut Health Indicators in Aged Laying Hens

This experiment was designed to determine the effect of the <i>Lacticaseibacillus paracasei</i> (<i>paracasei</i>) strain NSMJ27, isolated from Korean fermented vegetable food (home-made kimchi), on laying performance, egg quality, intestinal histology, cecal short-chain fatty acids, and ileal antioxidant/immunity indicators of laying hens. Ninety-six 55-week-old Hy-Line Brown hens were randomly assigned to two dietary treatments with each treatment comprising eight replicates of six hens each. Experimental diets were prepared by mixing corn and soybean meal basal diets without or with <i>L. paracasei</i> NSMJ27 at 2.5 × 10⁹ CFU/kg. The experiment lasted 4 weeks. Laying hens fed with the NSMJ27-supplemented diet were not affected (<i>p</i> > 0.05) in their laying performance or egg quality. With respect to ileal morphology, villus height: crypt depth ratio tended to be higher (<i>p</i> = 0.067) in laying hens fed with <i>L. paracasei</i> NSMJ27 vs. control diets. Dietary <i>L. paracasei</i> did not affect (<i>p</i> > 0.05) the activities of glutathione peroxidase and catalase, malondialdehyde contents, or secretory immunoglobulin A in ileal mucosa, but increased (<i>p</i> = 0.048) the activity of superoxide dismutase compared with the control diet-fed laying hens. Dietary <i>L. paracasei</i> elevated (<i>p</i> = 0.016) the relative percentage of butyrate but lowered (<i>p</i> = 0.057) that of isovalerate in cecal digesta. Dietary <i>L. paracasei</i> did not affect the percentages of cells expressing macrophages, B cells, CD4⁺ T cells, CD8⁺ T cells, or TCRγδ T cell surface markers (<i>p</i> > 0.05). Overall, these results suggest that dietary <i>L. paracasei</i> NSMJ27 could enhance gut health via increasing gut antioxidant capacity and butyrate production in the cecal digesta of laying hens.