Abstract：Two experiments were conducted to evaluate the effects of antimicrobial peptide Sublancin on growth performance, nutrient utilization and cecal microbiota of broilers. In experiment 1 (Exp.1), a total of 432 one-day-old Arbor Acres male broilers were allotted to 6 groups with 6 replicates per group and 18 broilers per replicate. The broilers in control group were fed a basal diet without antibiotic, and the broilers in antibiotic group, low-dose antimicrobial peptide group and high-dose antimicrobial peptide group were fed the basal diet supplemented with 20 mg/kg colistin sulfate, 150 mg/kg Sublancin and 300 mg/kg Sublancin, respectively. The Exp.1 lasted for 42 days. On the day 1, 21 and 42, the broilers were weighted and the feed intakes were counted to calculate the average daily feed intake (ADFI), average daily gain (ADG) and feed conversion ratio (FCR); on the day 21 and 42, one broiler was selected in each replicate, and the cecal digesta were collected to analyze the cecal bacterial populations. In experiment 2 (Exp.2), a total of 288 one-day-old Arbor Acres male broilers were assigned to 3 groups with 8 replicates per group and 12 broilers per replicate. The broilers in control group were fed the basal diet without antibiotic, and the broilers in antibiotic group and antimicrobial peptide group were fed the basal diet supplemented with 80 mg/kg chlortetracycline and 300 mg/kg Sublancin, respectively. The Exp.2 lasted for 28 days. On the day 1 and 21, the broilers were weighted and the feed intakes were counted to calculate the ADFI, ADG and FCR; on the day 19 to 21, feces and urine were collected to measured the nutrient apparent metabolic rate and nitrogen retention; on the day 22, each broiler administered orally 1 mL bacterial suspension of Escherichia coli (E. coli) K88 (109 CFU/mL), one broiler was selected in each replicate on day 28, and the cecal digesta were collected to analyze the cecal bacterial populations. The results showed as follows:compared with the control group, diet supplemented with 300 mg/kg antimicrobial peptide Sublancin or 20 mg/kg antibiotic colistin sulfate could significantly increase the ADG and FCR in starter phase (1 to 21 days), finisher phase (22 to 42 days) and overall phase (1 to 42 days) of Exp.1 (P<0.05), and could significantly decrease the populations of total aerobic bacteria and E. coli in cecum on day 21 and 42 (P<0.05). No significant difference was found in growth performance between 300 mg/kg Sublancin group and antibiotic group (P>0.05). Compared with the control group, diet supplemented with 300 mg/kg antimicrobial peptide Sublancin or 80 mg/kg antibiotic chlortetracycline could significantly increase the crude protein apparent metabolic rate and nitrogen retention rate (P<0.05). No significant differences were found in nutrient apparent metabolic rate and nitrogen retention rate between antimicrobial peptide group and antibiotic group (P>0.05). The nitrogen retention in antimicrobial peptide group was significantly higher than that in control group and antibiotic group (P<0.05). Compared with the control group, diet supplemented with 300 mg/kg antimicrobial peptide Sublancin or 80 mg/kg antibiotic chlortetracycline could significantly decrease the populations of cecal E. coli of broilers after challenge with E. coli K88 (P<0.05), but the populations of cecal E. coli in antimicrobial peptide group and antibiotic group had no significant difference (P>0.05). Results from this study suggest that antimicrobial peptide Sublancin could be used as a potential antibiotic alternative in broilers' diets. Diet supplemented with 300 mg/kg antimicrobial peptide Sublancin can enhance broilers' growth performance through increasing nutrient utilization and reducing the populations of intestinal pathogens.
