Hepatic transcriptomic analysis reveals potential mechanisms underlying improved growth performance in broiler chickens supplemented with guanidinoacetic acid under heat stress conditions

BACKGROUND: This study evaluated the effects of dietary guanidinoacetic acid (GAA) supplementation (0.06%) at different feeding phases on growth performance, carcass traits, plasma biochemistry, meat quality and hepatic transcriptomic responses in broiler chickens under heat stress exposure. METHODS: A total of 240 Ross 308 broilers (42 ± 1.2 g) were randomly assigned to four treatments: control (CON), GAA supplementation from pre-starter to finisher (day 1-35; GAA_P), starter (day 11-35; GAA_S) or finisher phase only (day 22-35; GAA_F). RESULTS: Inclusion of GAA from pre-starter to finisher (GAA_P) resulted in higher (P < 0.01) body weight and lower (P < 0.010) feed conversion ratio compared to CON. Broilers fed GAA_S also had lower final feed conversion ratio (P < 0.010). Carcass yield was higher in all GAA groups (P = 0.038), but breast meat and internal organ weights were unaffected (P = 0.301). Plasma alanine aminotransferase and aspartate aminotransferase were higher, whereas bilirubin was lower (P = 0.043) in GAA groups (P < 0.001). Tenderness was higher in GAA_P and GAA_F (P = 0.001). Transcriptome profiling identified 279 upregulated and 517 downregulated genes in response to GAA_P supplementation. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed upregulation of protein folding, endoplasmic reticulum processing and stress response pathways. By contrast, cell cycle, DNA replication and DNA repair pathways were strongly downregulated. Protein-protein interaction analysis demonstrated tightly connected networks of suppressed replication and repair genes (e.g. MCMs, CDKs, BRCA1 and RAD51). CONCLUSION: GAA inclusion throughout the whole rearing period (pre-starter to finisher) improved growth performance and production efficiency under heat stress exposure by inducing hepatic transcriptional reprogramming.