NUTRITIONAL-EVALUATION OF SPENT GRAINS FROM SORGHUM MALTS AND MAIZE GRIT

Potential use of the high protein by-product of beer production from 7 7% sorghum malt and 23% maize grit was investigated. Red sorghum spent grains (RSSG) and white sorghum spent grains (WSSG) contained 23.4 an d 19.3% crude protein (CP), 54 and 43% dietary fiber (NDF), 1.44 and 0 .78% ash, 4.5 and 3.2% hexane extract and tannin content of 7.5 and 1. 0 mg/g catechin equivalent respectively. Magnesium was the most abunda nt mineral in both RSSG and WSSG - 185 and 140 mg/kg, respectively. Ca lcium, zinc, iron and copper were generally low. Both samples containe d cadmium 1.12 (WSSG), 1.19 (RSSG) and lead at 1.38 mg/kg. Lysine was the limiting amino acid (chemical score 0.55) in both samples. Other e ssential amino acids were adequate or surplus. Stearic acid was the pr edominant fatty acid with varying levels of lauric, myristic, palmitic , and oleic acids in both samples. Feed intake and weight gain were hi ghest in rats fed 26.3% WSSG (contributing 50% of the diet protein) bu t protein efficiency ratio (PER) and net protein retention (NPR) were highest in diets where spent grains contributed just 25% of the diet p rotein. True digestibility of diets decreased as dietary fiber content increased such that animals on diets containing 100% spent grain prot ein (above 20% NDF) lost weight.