Graded inclusions of sodium metabisulphite in sorghum-based diets: I. Reduction of disulphide cross-linkages in vitro and enhancement of energy utilisation and feed conversion efficiency in broiler chickens

Seven sorghum-based diets containing 0, 1.50, 2.25, 3.00, 3.75, 4.50 and 5.25 g/kg of the reducing agent sodium metabisulphite (SMBS) were prepared in which sodium levels were balanced with sodium bicarbonate. A red sorghum (766.4 g/kg starch, 78.6 g/kg protein) was hammer-milled through a 3.2 mm screen prior to being mixed into complete broiler diets containing 195 g/kg protein with an energy density12.97 MJ/kg, which were steam-pelleted at an 84 °C conditioning temperature. Each of the seven dietary treatments was offered to a total of 294 male Ross 308 chicks in seven replicate cages (6 birds per cage) from 10 to 24 days post-hatch to determine the effects of SMBS on growth performance, nutrient utilisation and nitrogen (N) digestibility coefficients in four small intestinal segments. SMBS did not linearly influence (P > 0.50) weight gains and feed intakes. However, SMBS quadratically improved (r = 0.416; P