Comparative Effects of Continuous and Intermittent Water Acidification on Growth Performance, Gastrointestinal pH, Intestinal Morphology, Cecal Microbiota and Feed Cost in Broilers

The transition to antibiotic-free production has increased interest in water-applied organic acids (OAs), yet the effects of continuous versus intermittent application remain unclear. This study evaluated intermittent and continuous water acidification using a synergistic blend of free and buffered short-chain OAs (SWA) on broiler performance, gastrointestinal pH, intestinal morphology, cecal microbiota, and feed cost per kilogram of live BW gain. A total of 969 straight-run Ross 308 chicks (48.26 ± 0.40 g) were assigned to 3 treatments for 35 days: negative control (NC), intermittent acidification (SWA-Partial; 6 h/d during weeks 1, 2, 4, and 5), and continuous acidification (SWA-Full; 24 h/d from d 1 to 35), with 17 replicate pens/treatment (19 birds/pen). SWA-Full significantly increased final body weight and average daily gain while improving feed conversion ratio compared with NC ( P < 0.05), without affecting feed or water intake (P > 0.05). Gastrointestinal pH in the crop, proventriculus, and duodenum was reduced by SWA-Full at d 14 and by both SWA treatments at d 35 (P < 0.05). SWA-Full increased duodenal and ileal villus height and the villus height-to-crypt depth ratio compared with NC (P < 0.05) and increased cecal microbiota richness (observed species and Chao1) compared with NC (P < 0.05). Both SWA treatments increased Lactobacillus and Blautia and decreased Ruminococcus g4 and Alistipes, with SWA-Partial also increasing Prevotella. Feed cost per kilogram of live BW gain was lowest in SWA-Full (0.69 EUR/kg), followed by SWA-Partial (0.70 EUR/kg) and NC (0.75 EUR/kg; P = 0.04). Overall, these findings indicate that continuous water acidification with SWA may serve as a practical, antibiotic-free strategy to improve broiler growth performance, while modifying gastrointestinal conditions, intestinal morphology, and cecal microbiota and reducing feed cost.