Abstract
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) (P < 0.05). Over the entire experimental period (d 1 to 42), the CTC treatment significantly improved FCR (P = 0.006). Broilers under the CP-FE and CP-SOL regimen exhibited a higher relative abundance of Lactobacillus in the cecal contents during the first phase (P < 0.001). In the subsequent phase (d 22 to 42), the CP-FE diet was associated with elevated levels of Faecalibacterium, Alistipes, and Lactobacillus (P < 0.05). Additionally, the CP-FE group experienced an increase in serum immunoglobulin (Ig) A concentration during the early phase (P = 0.009). In contrast, the CP-SOL group demonstrated no significant alterations in serum immune globulin levels on d 21 (P > 0.05), but displayed an increase in IgM on d 42 (P = 0.003). Irrespective of the administration route-feed or water-compound probiotics stimulated the expression of IL-10 in the cecum (P = 0.006) and curbed the mRNA expression of TNF-α in the ileum (P = 0.011) in early phase. The supplementation also led to higher levels of acetic (P = 0.006) and total short-chain fatty acids (SCFAs; P = 0.005) level in the cecal contents in early phase. Furthermore, it upregulated the mRNA expression of claudin-1, MUC-2, occludin, and ZO-1, increased villus height, and the number of goblet cells, while reducing crypt depth (P < 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.