Evaluating the efficacy of compound probiotics as an antibiotic alternative: A comprehensive analysis of growth performance and intestinal health via feed and water routes

The present study investigated the impact of administering compound probiotics through distinct routes on the growth performance and intestinal health of broiler chickens. A cohort of 400 1-d-old male Arbor Acres (AA) broilers were distributed randomly into five treatment groups, each comprising eight replicate pens with ten broilers per pen. The treatments consisted of: 1) control (CON), a basal diet; 2) chlorotetracycline (CTC), the basal diet supplemented with 80 mg/kg of chlorotetracycline; 3) nosiheptide (NOS), the basal diet enriched with 5 mg/kg of nosiheptide; 4) compound probiotics in feed (CP-FE), the basal diet fortified with 1 g/kg of compound probiotics; 5) compound probiotics in solution (CP-SOL), the basal diet, with 20 g of probiotics per 1000 broilers daily added to the water from d 1 to 21. During the initial phase (d 1 to 21), the CP-FE regimen notably enhanced average daily gain (ADG) and diminished the feed conversion ratio (FCR), whereas the CP-SOL protocol significantly augmented body weight, ADG, and average daily feed intake (ADFI) (<i>P</i> < 0.05). Over the entire experimental period (d 1 to 42), the CTC treatment significantly improved FCR (<i>P</i> = 0.006). Broilers under the CP-FE and CP-SOL regimen exhibited a higher relative abundance of <i>Lactobacillus</i> in the cecal contents during the first phase (<i>P</i> < 0.001). In the subsequent phase (d 22 to 42), the CP-FE diet was associated with elevated levels of <i>Faecalibacterium</i>, <i>Alistipes</i>, and <i>Lactobacillus</i> (<i>P</i> < 0.05). Additionally, the CP-FE group experienced an increase in serum immunoglobulin (Ig) A concentration during the early phase (<i>P</i> = 0.009). In contrast, the CP-SOL group demonstrated no significant alterations in serum immune globulin levels on d 21 (<i>P</i> > 0.05), but displayed an increase in IgM on d 42 (<i>P</i> = 0.003). Irrespective of the administration route-feed or water-compound probiotics stimulated the expression of <i>IL-10</i> in the cecum (<i>P</i> = 0.006) and curbed the mRNA expression of <i>TNF-α</i> in the ileum (<i>P</i> = 0.011) in early phase. The supplementation also led to higher levels of acetic (<i>P</i> = 0.006) and total short-chain fatty acids (SCFAs; <i>P</i> = 0.005) level in the cecal contents in early phase. Furthermore, it upregulated the mRNA expression of claudin-1, <i>MUC-2</i>, occludin, and <i>ZO-1</i>, increased villus height, and the number of goblet cells, while reducing crypt depth (<i>P</i> < 0.05). The findings suggest that administering compound probiotics via water has a more pronounced effect on the growth performance and intestinal health of broilers.