**Background:** Cassava is an important food crop rich in starch, but its utilization in animal feed is limited by anti-nutritional factors (hydrocyanic acid, tannin) and declining planting area. Processing methods such as mechanical crushing (MC), steam conditioning (SC), and puffing conditioning (PU) can alter starch structure and digestibility. This study hypothesized that combined application of processing methods and conditioning temperatures would increase cassava starch digestibility in vitro and improve broiler growth performance.
**Methods:** The study comprised both in vitro and in vivo components using a 3 × 3 factorial design with three processing methods (MC, SC, PU) and three conditioning temperatures (60, 75, 90 °C). For the in vitro study, cassava starch was extracted and subjected to simulated broiler digestive tract conditions. Starch digestion coefficients were measured at 0.25, 0.50, 0.75, 1, 2, 3, 4, 5, and 6 hours. Rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) were calculated using regression equations from Weurding et al. (2001b). For the in vivo study, 1008 one-day-old male Cobb broilers (47.5 ± 2 g) were randomly divided into 9 treatments with 8 replicates (14 broilers per replicate). Broilers were fed cassava–soybean basal diets with 0.4% titanium dioxide as an indigestible marker. Growth performance (ADG, ADFI, F/G) was measured over 42 days (starter period 1–21 d, grower period 22–42 d). Ileum digesta and excreta were collected to determine apparent digestibility of dry matter (DM), crude protein (CP), starch, and apparent metabolizable energy (AME). Data were analyzed by two-way ANOVA using SPSS.
**Key Results:** In vitro, starch digestibility at 90 °C was higher (p < 0.01) than at 60 or 75 °C, and PU demonstrated the highest digestibility (p < 0.01), followed by SC and MC (0.25–2 h). The starch digestion rate varied from 2.7% (60 °C + MC) to 5.8% (75 °C + PU). Amylose content and amylose/amylopectin at 60 °C were lower (p < 0.01) than at 75 or 90 °C. PU had lower amylose (24.8% vs. 26.7%), amylose/amylopectin (0.54 vs. 0.62), and SDS (2.4% vs. 6.5%) than SC (p < 0.01). RS content of SC or PU was lower (p < 0.01) than MC. In vivo, broilers fed diets conditioned at 90 °C had higher ADFI (p < 0.05) in the starter period. In the grower period, broilers fed diets at 60 °C had higher ADG (p < 0.05) than at 90 °C. Broilers fed PU diets had higher ADG and ADFI (p < 0.05) than MC and SC. F/G was higher (p < 0.05) for broilers fed diets at 90 °C or PU diets in both periods. Broilers fed SC diets had higher ileum apparent digestibility of starch (p < 0.05) than MC in both periods. The combination of 60 °C and PU generated the highest ileum CP digestibility (78.1%) in the starter period (p < 0.05). Broilers fed diets at 90 °C had lower AME (p < 0.05) than at 75 or 60 °C in both periods. SC diets had higher AME (p < 0.05) than MC in both periods.
**Clinical Implications:** This study demonstrates that processing methods and conditioning temperatures significantly affect cassava starch digestibility and broiler growth performance. Puffing conditioning at 60 °C optimizes starch digestion rate by reducing amylose content and amylose/amylopectin ratio. Steam conditioning improves ileum starch digestibility regardless of conditioning temperature, increases AME, and decreases F/G, thereby promoting growth performance. High conditioning temperatures (90 °C) are detrimental to broiler performance and nutrient utilization. These findings suggest that broiler diets can be effectively processed at lower temperatures (60 °C) when combined with puffing or steam conditioning, potentially reducing energy costs while improving feed efficiency.