Abstract
This study investigated the effects of early post-hatch supplementation with Limosilactobacillus fermentum on growth performance and intestinal health in broilers. A total of 480 one-day-old birds were allotted to four dietary treatments: a control (basal diet) and three groups receiving the probiotic either as a single dose on day 1 (Group I), intermittently on days 1, 2, 4, 6, 8, 10, and 12 (Group II), or continuously for the first 7 days (Group III). Compared with the control group, Group I significantly increased the 7-day-old body weight (BW) and average daily feed intake (ADFI), and decreased the feed conversion ratio (FCR) during d 1-7, d 8-14, d 22-49, and d 1-49 (P < 0.05). Compared with the control group, Group II significantly decreased FCR during d 1-21 and d 1-49 (P < 0.05). Compared with the control group, Group III significantly increased the 7-day-old BW, ADFI, and average daily gain (ADG), as well as the 49-day-old BW and ADG, and decreased FCR at all stages (P < 0.05). In terms of intestinal health, all experimental groups enhanced small intestinal morphology (increased villus height-to-crypt depth ratio), up-regulated the expression of intestinal barrier-related genes (OCLN, CLDN, ZO-1, MUC2), increased digestive enzyme activity and volatile fatty acids (VFA) levels, and modulated cecal microbiota (reduced Clostridium and Campylobacter abundance, increased Hungatella abundance) (P < 0.05); Group III consistently outperformed Groups I and II in these indicators. Additionally, secretory immunoglobulin A (SIgA) levels were higher in experimental groups, especially in Groups I and III at d 21 and d 49 (P < 0.05). In conclusion, early Limosilactobacillus fermentum supplementation promotes broiler growth and intestinal development, with continuous supplementation during d 1-7 being the most effective regimen.