Effects of nonantibiotic alternative growth promoter combinations on nutrient utilization, digestive enzyme activity, intestinal morphology, and cecal microflora of broilers

Given the ban on antibiotic growth promoters, six nonantibiotic alternative growth promoter combinations (NAGPCs) for broilers were evaluated. All birds were fed pellets of two basal diets--starter (0-21 d) and grower (22-42 d)--with either enramycin (ENR) or NAGPC supplemented. 1) control + 100 mg/kg ENR; 2) control diet (CON, basal diet); 3) control + 2,000 mg/kg mannose oligosaccharide (MOS) + 300 mg/kg mannanase (MAN) + 1,500 mg/kg sodium butyrate (SB) (MMS); 4) control + 2,000 mg/kg MOS + 300 mg/kg MAN + 500 mg/kg Bacillus subtilis (BS) (MMB); 5) control + 2,000 mg/kg MOS + 9,000 mg/kg fruit oligosaccharide (FOS) + 1,500 mg/kg SB (MFS); 6) control + 9,000 mg/kg FOS + 500 mg/kg BS (MFS) (MBP). The experiment used a completely random block design with six replicates per group: 50 Ross 308 broilers in the starter phase and 16 in the grower phase. All the NAGPCs significantly improved (P < 0.01) utilization of dry matter (DM), organic matter (OM), crude protein (CP), and crude fat (CF) on d 21, significantly increased DM, OM (P < 0.01), and CP (P < 0.05) on d 42, and significantly increased (P < 0.01) villus height, crypt depth, and the villus height to crypt depth ratio in the jejunum and ileum compared with CON and ENR. On d 21 and 42, trypsin, lipase, and amylase activity of the duodenum significantly increased in the MMS, MMB, MFB, and MFM groups. Compared with ENR and CON, MMS, MMB, and MBP increased the abundance of Firmicutes at d 21 and of Bacteroides at d 42 whereas MMB, MFB, and MBP decreased the abundance of Proteobacteria at d 21 and 42. Overall, the NAGPCs were found to have some beneficial effects and may be used as effective antibiotic replacements in broilers.