Supplementation of exogenous enzymes and a reducing agent in broilers fed red sorghum-wheat blended diets

Improving the feeding value of red sorghum is particularly relevant in some countries where sorghum grain is a drought-tolerant crop and a sustainable alternative to wheat and imported raw materials. The present study evaluated strategies to improve red sorghum utilisation by supplementing exogenous enzymes or a reducing agent. A total of 280 Ross 308 off-sex male broilers were allocated to seven dietary treatments for 35 d (8 replicates/treatment, 5 birds/cage). Two diets based on white sorghum (positive control) or red sorghum (negative control) were formulated to be nutritionally equivalent, each containing 100 g/kg wheat. The red sorghum diet was further supplemented with amylase, phytase (double dosing), protease (with or without nutrient matrix values) or sodium metabisulphite (SMBS). Overall, both white and red sorghum control diets supported growth performance well above breed standards, and nutrient digestibility and energy utilisation did not differ significantly between them. Among additives, replacing sodium bicarbonate with SMBS in the red sorghum-based diet led to the most pronounced growth response, yielding the heaviest final body weight (P = 0.014) and overall weight gain (P = 0.014), surpassing the red sorghum control diet. These improvements were not explained by AME or AMEn but coincided with a tendency for increased distal jejunal starch digestibility (P = 0.061). Birds fed the red sorghum-based diet supplemented with protease and phytase double-dosing presented growth performance to levels comparable to those fed the white sorghum control diet, whereas amylase had no effect. It is likely that the tight starch-protein matrix caused by kafirin protein bodies remains the major constraint in sorghum-based diets, and targeted disruption of disulphide bonds with SMBS indirectly improved starch digestion and weight gain. These findings highlight the potential of SMBS to enhance the feeding value of red sorghum in sustainable chicken meat production.