Locally produced, expeller soybean meal (SBM) may be an important constituent of European broiler diets in the future. In the present trial 4 SBMs were produced from European grown soybeans, using different processing methods; this is the first time that the combination of these methods has been applied. Starter (d0–14) and grower (d15–28) diets were offered to 288 Ross 308 male broilers in a 2 × 2 design: 2 processing methods ((Extrusion-pressing (E) vs Flaking-pressing-cooking (F)) × 2 hulling methods ((with hulls (H) vs no hulls (NH)). Variables measured consisted of average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio, apparent ileal dry matter (DM) and crude protein (CP) digestibility, jejunal histomorphometry at d14 and d28 and ileal digesta viscosity at d28 of age. In addition, carcass and carcass part yield, organ weight, and empty gastrointestinal tract weight and length per small intestinal segment were assessed at d28. Processing method did not affect any of the variables tested. On the other hand, hull presence increased (P < 0.05) ADFI over the starter period, but not over the grower period. Presence of hulls increased proventriculus, gizzard and jejunum weight, and reduced carcass yield at d28 of age, likely due to the higher fibre content. Method of processing and hulling significantly interacted (P < 0.05) for ADFI and ADG at the end of the starter period, being highest for the E/H treatment, but overall broiler performance was similar between dietary treatments. Similarly, small intestinal architecture and DM and CP digestibility were not affected by dietary treatments at either d14 or d28 post hatch. Although there was some variation in soybean protein solubility and trypsin inhibitors amongst SBM products these factors did not appear to affect any of the measured variables.
In conclusion, all 4 methods of production resulted in comparable results in relation to performance variables. Hull removal did not confer a significant advantage, aside from increased carcass yield, possibly due to the adaptive growth of the gizzard and proventriculus.