This study assessed the efficacy of two phages, MHH6 and PR2, against Escherichia coli serotype O6 infected in chickens. A total of 420 broilers were randomly assigned to seven treatment groups. The negative control (NC) birds received no E. coli or phages, whereas the positive control (PC) birds were infected with E. coli only. The NC+MHH6 and NC+PR2 treatments received 109 pfu/ml of phages MHH6 or PR2, respectively; whereas the PC+MHH6, PC+PR2, and PC+MHH6PR2 groups were infected with 107.1 cfu/ml of E. coli strain O6 and treated with 109 pfu/ml of phages of MHH6, PR2, or both. E. coli infection was inoculated in two-day-old chicks, and phages were administered 24 hours later. The mortality rate of chickens in the PC+MHH6PR2 group was significantly lower (16.7%) than in the PC group (58.3%). The frequency of lesions and E. coli densities in the heart, liver, and spleen of chickens treated with MHH6 and PR2 phages were greatly decreased in infected chickens. After 98 days, the body weight of birds from the E. coli-infected groups treated with MHH6 and PR2 phages was lower than individuals in non-E. coli-infected groups (1,313-1,324 g/bird) but higher and significantly different from those in the PC group (1,172 g/bird). The majority of commercially important traits in chickens improved after phage treatment, proving that these phages are capable of controlling O6 E. coli infected in Noi chickens.

Keywords: Bacteriophage, Carcass characteristic, Chicken, E. coli, Growth performance