Chemical composition and nutritive value of South African sorghum varieties as feed for broiler chickens

Sorghum (Sorghum bicolor (L.) Moench) is the fifth most important grain crop after wheat, rice, maize and barley. It is cultivated for food and feed in America, Asia, Australia and Africa. Newly developed sorghum varieties should be evaluated for their suitability as food and feed. The physical characteristics and proximate composition, total phenolic content, mineral content, amino acid profile and digestibility, and true metabolizable energy of four sorghum varieties were studied. The condensed tannin sorghum varieties PAN8625 and NS5511 had higher total phenolic content and antioxidant activity than the non-tannin varieties PAN8816 and PAN8906. Crude protein content diverged narrowly across the varieties, ranging from 81.2 to 95.4 g/kg DM. Starch and gross energy contents also differed, though varieties that were used had similar total and individual mineral contents. The threonine, leucine, phenylalanine, valine, proline and alanine contents of PAN8625 and PAN8906 were higher than those of NS5511 and PAN8816, which had similar contents. Amino acid digestibility and metabolizable energy of the tannin varieties were generally lower than those of the non-tannin ones. These results indicate that chemical and nutrient composition of sorghum varieties should be considered when selecting for broiler chicken feeding.