Moderate Dietary Lactobacillus acidophilus Supplementation Enhances Mid-Growth Nutrient Utilization and Shifts Intestinal Lactobacillus and Escherichia coli Counts in Yellow-Feathered Broilers.

This study tested the hypothesis that dietary L. acidophilus would improve nutrient utilization in yellow-feathered broilers mainly through intestinal changes rather than a consistent increase in growth performance. A total of 195 one-day-old broilers were assigned to a control group (basal diet), a T1 group (basal diet with 10 g/kg L. acidophilus), or a T2 group (basal diet with 15 g/kg L. acidophilus), with five replicates of 13 birds per treatment over 63 days. The biological responses followed a clear pattern. First, supplementation did not significantly affect average daily feed intake, average daily gain, or feed-to-gain ratio at any growth stage or across the entire trial (days 1-63; p > 0.05), indicating limited direct effects on growth. Second, the main nutritional response occurred during days 22-42, when T1 increased the apparent nutrient digestibility of dry matter, organic matter, ether extract, crude protein, and gross energy compared to the control (p < 0.05). Third, intestinal responses aligned with localized gut modulation: both supplemented groups had higher culture-based Lactobacillus counts and lower E. coli counts in the cecum and ileum (p < 0.05), and T1 increased duodenal villus height (p < 0.05). In contrast, serum biochemical, immune, and antioxidant indices showed only isolated, phase-dependent changes and were not considered the primary response. Overall, moderate dietary supplementation with L. acidophilus enhanced nutrient utilization during mid-growth and was linked to targeted intestinal bacterial and morphological changes, but it did not consistently improve growth performance in yellow-feathered broilers.