Effect of dietary supplementation of bacteriophage on growth performance and cecal bacterial populations in broiler chickens raised in different housing systems

• Broiler chickens raised in battery cages had greater performance than those raised in floor pens.
• Dietary bacteriophage (BP) mixture improved growth performance of broiler chickens.
• Dietary BP mixture decreased Clostridium perfringens populations in the cecum.
• Positive effect of dietary BP mixture is independent of housing systems.

This experiment was conducted to investigate the effect of dietary bacteriophage (BP) on growth performance and cecal bacterial populations in broiler chickens raised in different housing systems. A total of 1170 1-d-old broiler chickens were housed in either battery cages (120 birds) or conventional floor pens (1050 birds). Within each housing system, birds were randomly allotted to 1 of 3 dietary treatments with 5 replicates. Dietary treatments included basal diets (negative control; NC), basal diets with 0.025 g/kg avilamycin (positive control; PC), and basal diets with 0.5 g/kg BP mixture (BP5). The mixture of the individual BP targeting at Salmonella gallinarum, Salmonella typhimurium, Salmonella enteritidis, Salmonella derby, Staphylococcus aureus, and Clostridium perfringens was used in this experiment. Diets were fed to birds for d 35. The effects of housing systems, dietary treatments, and their interactions were analyzed. No interactions for all measurements were observed, and thus, the main effects were presented. During overall experiment, birds raised in battery cages had greater (P<0.01) BW gain (BWG), feed intake, and less (P<0.01) feed conversion ratio (FCR) than those raised in floor pens. Greater BWG was observed (P<0.05) for PC treatment than for NC treatment, but those for BP5 treatment had intermediate values between other treatment groups. The FCR was less (P<0.05) for PC and BP5 treatment groups than for NC treatment, but there was no difference between PC treatment and BP5 treatment. For cecal bacterial populations, birds raised in battery cages had less (P<0.05) DNA copy numbers for C. perfringens, but greater (P<0.05) DNA copy numbers for Escherichia coli than those raised in floor pens. The BP5 treatment had less (P<0.05) DNA copy numbers for C. perfringens compared with NC treatment. In conclusion, dietary BP improves growth performance of broiler chickens and decreases targeted pathogenic bacteria populations, especially for C. perfringens in the gastrointestinal tract. This positive effect is likely independent of housing systems.