Nutritive Characteristics of Different Varieties of Sorghum and Corn Grains

Abstract

Nine varieties of sorghum grain [Sorghum bicolor (L.) Moench], differing in endosperm type (waxy, normal or floury) and bird resistance, and four varieties of corn (Zea mays L.) were evaluated for chemical composition, in vitro dry matter disappearance (IVDMD) and in vitro gas production (IVGP). Sorghum varieties were grown in 3 consecutive yr; corn in 2 yr. Crude protein (CP) content of sorghum ranged from 11.1 to 16.5% and starch content from 61.9 to 83.0%. Corn varieties showed less variation in protein (8.8 to 10.7%) and starch (67.9 to 79.0%). Bird-resistant (BR) sorghum (brown testa) generally contained high tannin levels. The corn varieties showed slightly higher IVDMD than the sorghums, although IVDMD was very low for nonwaxy BR sorghum. IVDMD of waxy sorghums was similar to or slightly higher than that of normal sorghums in all 3 yr; however, IVDMD of both varieties was more similar to that of corn than to that of BR sorghum. Floury-BR Soft Endo sorghum was analytically comparable to the waxy types in yr 1 and 2 but had depressed (P<.05) IVDMD in yr 3. The waxy-BR 1133 was similar to the less digestible Darset (BR) in yr 2, but intermediate to the waxy and normal types in yr 3. Increased IVDMD was generally associated with increased enzymatic starch availability (IVGP). This was true for all types, except the floury-BR Soft Endo sorghum, for which increased IVGP may be attributed to the soft endosperm characteristic. Certain varieties or types of grain sorghum appear to be more similar to corn in composition, IVDMD and IVGP than do other types. Furthermore, the wide range in IVDMD and IVGP observed among these sorghums suggests that the wide variation in feeding value among grain sorghums may be due, in part, to variety or type.