Research note: using rapid adjustments of mitochondrial function to dietary changes as an indicator? an experimental test in slower growing broiler hybrid

This study investigated the effects of dietary energy and lysine levels on mitochondrial respiration and its association with growth performance in slower-growing broiler chickens. A 2 × 3 factorial arrangement of treatments varying in apparent metabolizable energy (AME; standard and -100 kcal/kg) and standardized ileal digestible lysine (SID Lys; 100 %, 90 %, and 80 %) was applied, resulting in 6 dietary treatments. Blood samples were collected on day 49 to assess mitochondrial respiration parameters, including routine respiration, LEAK respiration, oxidative phosphorylation (OXPHOS), combined Complex I and II (CI+CII) activity, OXPHOS coupling efficiency (OxCE), and the flux control ratio (FCR_Routine/CII). These parameters were further correlated with body weight and blood cell counts. Routine and OXPHOS respiration showed no statistically significant response to AME or Lys levels, although a numerical increase was observed with reduced Lys concentrations. LEAK respiration remained stable across all treatments, indicating preserved mitochondrial membrane integrity. Body weight, cell count and AME × Lys interaction had no significant effect on mitochondrial respiration parameters. While differences were not statistically significant, the trends suggest that nutrient availability may modulate mitochondrial activity, with potential implications for energy metabolism in slow-growing broilers.