The objective of this experiment was to investigate the effect of varying extruder temperatures of full-fat soybean (FFSB) on apparent amino acid digestibility in broiler chickens. A batch of FFSB was same day processed in a commercial facility at extruder temperatures of 182, 199, and 154 °C to create three different soybean variants; control, overcooked and undercooked, respectively. The processed soybean batches were merged into three different diets at 35, 30, and 25% inclusion concentrations for the starter, grower, and finisher phases. All diets contained 0.5% titanium dioxide as an indigestible marker. A total of 1,860 male Cobb 500 broiler chicks were vaccinated with 1 x coccidia vaccine on d 1 via coarse spray and allocated to 3 treatment groups with 10 replicate floor pens (62 birds/pen) from 0 to 35 d of age. At d 14 and 28, birds were euthanized by carbon dioxide for the collection of ileal digesta. Both overcooked and undercooked processed soybean batches depressed the apparent ileal digestibility (AID) of all indispensable and dispensable amino acids at d 14 (P <0.05) by 3.8% and 3.2%, respectively. Lysine represented the lowest decreased of AID among all indispensable amino acids for both; d 14 and 28. The AID of Lys was 7% lower (P <0.05) in birds fed the overcooked soybean batch compared to the normal processed treatment at d14 and 28.
These results demonstrated how suboptimal processing conditions influence amino acid metabolism of birds. Moreover, these findings stress the importance of optimizing a safe extrusion temperature range without penalty of the soybean nutrient value, which it has a meaningful impact on processing and live production costs.