The impact of soybean meal protein solubility and exogenous enzymes on the nutrient digestibility by broiler chickens

Resumen

Soybean meal (SBM) is a crucial component of broiler chicken feed, comprising up to 35 % of the total formulation. However, the nutritional value of SBM can be affected by various factors, including thermal processing, which can impact KOH protein solubility. Enzymes have been introduced in SBM maize-based diets for broiler chickens to enhance nutrient utilization. To evaluate the enzyme synergism and the effect of SBM protein quality on nutrient utilization, this study investigated amylase and protease supplementation on nutrient digestibility by broiler chickens fed with two SBM based on KOH protein solubility. 720 one-day-old male broiler were distributed in battery cages in a completely randomized design in 8 treatments, 9 replications of 10 birds each and in a 2 × 4 factorial arrangement, 2 different KOH protein solubilities of SBM (75 % and 85 %) and 4 enzyme doses (0; 80 KNU of amylase per kg of feed; 30,000 NFP of protease per kg of feed; and 80 KNU of amylase combined with 30,000 NFP of protease per kg of feed). All diets were mash form based on SBM-maize, with phytase (2,000 FYT per kg of feed). Samples of SBM were collected for quality protein analysis. Dry matter (DM), crude protein (CP) and KOH protein solubility were determined. From 19 to 21 d of age, excreta samples were collected to estimate apparent total retention (ATTR) and apparent metabolizable energy (AME). Ileal digesta was collected to determine ileal nutrient digestibility (AID) and ileal digestible energy (IDE) at day 26. For feed analysis, excreta, and ileal content, samples were prepared and grounded at 1 mm to determine gross energy, DM content, and CP. Data obtained were submitted to ANOVA and means were compared by Tukey test at 5 % probability using the GLM procedure. AME value was greater when broiler chickens were fed with high KOH protein solubility SBM (85 %), as reported by Ravindran et al. (2014). IDE was greater for birds fed with amylase and protease combined, regardless of SBM type (3458 kcal/kg), positive effects from enzyme supplementation were also reported (Liu et al., 2020; Saleh et al., 2020). No interactions were observed between SBM differing in KOH protein solubility and enzyme dosages combined or not. In conclusion, birds fed SBM with 85 % KOH protein solubility exhibited better energy utilization, regardless of enzyme supplementation. However, the use of a synergistic blend of amylase and protease enzymes further improved the ileal digestibility of energy.