Assessing the impact of phage therapy on growth performance, microbiome and phage specific immune response in chickens.

Bacteriophages could be an effective alternative to antibiotics in preventing or controlling disease outbreaks in the poultry industry. This study evaluated the effects of Salmonella Gallinarum and Avian Pathogenic E. coli (APEC) phage treatments, previously shown to significantly reduce targeted bacteria in challenged chickens, on chicken growth performance, immune response, and gut microbiome. To measure the impact of phage treatment on growth and immune response, 7-day old (d) chickens were fed diets supplemented with Salmonella (1.0–2.0 × 108 PFU/mL) or APEC (107 PFU/mL) phages at 1mL/kg of feed. Growth parameters including average daily gain, average weight gain, average daily feed intake, and feed conversion ratio were calculated. Blood samples were collected at d21, d28, and d35 to detect antiphage antibodies (IgM, IgG, and IgA). Chickens receiving either Salmonella Gallinarum or APEC phages showed significantly higher ADG and AWG (p ≤ 0.05) compared to untreated controls, with no significant differences in detection of phage antibodies across groups. For microbiome analysis, chickens were challenged with either APEC or Salmonella Gallinarum and administered phages via gavage. Cecal contents were collected before and after phage treatments and microbial communities were characterized by 16 S rRNA sequencing. Differential abundance analysis (DESeq2, edgeR) revealed increased levels of beneficial taxa including Lachnospiraceae, Actualibacteriaceae, and Ruminococcaceae in birds treated with Salmonella phages, and Butyricoccaceae and Lachnospiraceae in APEC phage-treated birds (q ≤ 0.05). These results indicate phage treatment may enhance growth performance and promote a favorable gut microbial profile without inducing measurable B-cell mediated antibody responses, supporting their potential as antibiotic alternatives in poultry production.