Effects of Hiroshimana old pickle containing lactic acid bacteria as a potential probiotic source for broiler chicks

Fermented vegetable waste is rich in lactic acid bacteria; however, no studies have investigated the probiotic effects of fermented vegetable waste on the gastrointestinal tract of poultry. This study aimed to evaluate effects of the fermented vegetable waste, Hiroshimana old pickle (HOP), on the growth performance, intestinal morphology, immune-related gene expression, and gut microbiota composition of broiler chicks. The group supplemented with 1% HOP (H1 group) showed no significant change in body weight (BW) and had a numerically lower feed conversion ratio (FCR) compared with the control group. This response was accompanied by an increase in jejunal villus height, resulting in a higher villus height-to-crypt depth ratio and suggesting enhanced absorptive capacity. In contrast, although the group supplemented with 3% HOP (H3 group) showed the lowest FCR among the dietary groups, this was accompanied by reduced feed intake and a slight decrease in BW, without improvements in jejunal morphology. Therefore, the lower FCR in the H3 group was interpreted as reflecting a feed intake-restricted condition rather than improved feed utilization. In the cecum, the H1 group showed a slight but insignificant reduction in IL-1β and TGF-β4 expressions, whereas the H3 group had significantly reduced IL-1β and TGF-β4 expressions. Together with the reduced IL-10 expression observed in the HOP-supplemented groups, these changes indicate altered expression of both pro-inflammatory and regulatory cytokine genes, potentially reflecting reduced mucosal immune stimulation. Microbiota analysis revealed that the HOP-supplemented groups had increased abundances of bacterial families associated with short-chain fatty acid production, including Lachnospiraceae and Butyricicoccaceae. These changes may be attributed to the combined effects of lactic acid bacteria and fermented plant-derived substrates. Overall, the findings indicate that 1% HOP supplementation promoted favorable intestinal adaptation and showed potential in improving feed utilization, whereas the inclusion of HOP at a higher concentration (3%) may impair performance owing to reduced feed intake. HOP therefore shows potential as a sustainable functional eco-feed ingredient, with its efficacy dependent on the appropriate concentration.