Abstract
This study investigated the effects of dietary astaxanthin (AST) and artichoke leaf powder (ALP) on growth performance and intestinal morphology of broiler chickens reared under thermoneutral or chronic heat-stress conditions. A total of 2,160 mixed-sex one-day-old Ross 308 chicks were distributed into two independent experiments (1,080 birds per environment) using a 3 × 3 factorial arrangement with three AST levels (0, 60, and 120 mg/kg) and three ALP levels (0, 1, and 2 g/kg) from day 1 to 35. A significant AST × ALP interaction was observed for growth performance in both environments (p ≤ 0.05). Under thermoneutral conditions, supplementation with 60 mg/kg AST + 1 g/kg ALP resulted in the highest live body weight (LBW; 2106.79 g) and body weight gain (BWG; 2068.54 g), representing increases of approximately 120 g compared with the control. This treatment also improved feed conversion ratio (FCR; 1.35 vs. 1.42 in control), reduced mortality, and increased the European Production Index (EPI; 442.36 vs. 390.12 in control). Under chronic heat stress, 1 g/kg ALP without AST yielded the greatest LBW (2144.39 g) and BWG (2105.89 g), improving BW by approximately 112 g relative to the heat-stressed control, and achieved the lowest FCR (1.42 vs. 1.49 in control) and highest EPI (425.60 vs. 385.86 in control). Dietary supplementation also markedly improved intestinal morphology (p ≤ 0.05). Under thermoneutral conditions, villus height increased from 960.13 µm in the control to 1109.06 µm with 120 mg/kg AST, while the villus height-to-crypt depth ratio improved from 4.28 (control) to 7.12 with 60 mg/kg AST + 1 g/kg ALP. Under heat stress, villus height increased from 793.13 µm (control) to 1126.92 µm with 120 mg/kg AST + 2 g/kg ALP, accompanied by an increase in villus-to-crypt ratio from 4.23 to 6.31. Overall, AST and ALP supplementation enhanced growth performance and intestinal structural integrity, with moderate inclusion levels optimizing performance under thermoneutral conditions and higher or targeted supplementation conferring protection against heat stress-induced impairment.