Abstract
This study investigated the effects of far-infrared ray (FIR) radiation on broiler performance, carcass traits, meat quality, intestinal morphology, and blood metabolites in birds fed different energy and amino acid (EAA) levels with or without β-mannanase from hatch to day 35. A total of 384 one-day-old Ross 308 broilers were assigned to a 2 × 2 × 2 factorial design: FIR radiation (yes or no), dietary EAA level (normal or low), and β-mannanase supplementation (yes or no). Data were analyzed using three-way ANOVA to evaluate the main and interactive effects of these factors, with Tukey's test applied for multiple comparisons. FIR exposure improved (p < 0.001) average daily gain (ADG) and average daily feed intake (ADFI) on days 1-35. Feed conversion ratio (FCR) was reduced (p < 0.05) on days 1-10, 11-21, and overall. FIR combined with β-mannanase enhanced (p < 0.001) ADG on days 1-10 and 11-21. Broilers fed a low EAA diet and exposed to FIR had higher (p < 0.01) ADFI on days 1-10. On day 35, FIR increased (p < 0.001) moisture, crude protein, and ash content in breast meat and improved (p < 0.05) relative breast meat weight. FIR also enhanced (p < 0.01) water-holding capacity and pH, while reducing (p < 0.05) cooking loss. FIR improved intestinal morphology by increasing (p < 0.001) villus height on days 21 and 35. A significant three-way interaction (p < 0.01) among FIR, EAA level, and β-mannanase was observed for villus height on day 21. Immunologically, FIR reduced (p < 0.01) blood levels of IL-1β and TNF-α on days 21 and 35, and IFN-γ on day 35. FIR also lowered (p < 0.05) blood glucose and lactate levels on both days. In conclusion, FIR radiation, particularly under nutrient-challenged conditions, enhanced broiler growth performance, carcass yield, meat quality, and immune status, with β-mannanase providing additional early growth benefits. FIR technology shows potential as a non-invasive, feed-independent strategy to improve commercial broiler productivity, warranting further field evaluation.