Variability and relationships among 12-hour IVDMD, starch, oil, protein, and physical characteristics of 16 sorghum conversion lines

Abstract

A factor frequently identified as a key to understanding sorghum [Sorghum bicolor (L.) Moench feed value to ruminant animals is rate of starch digestion. Recent research in corn (Zea mays L.) has established a strong ability to predict rumen starch degradation from grain physical and chemical parameters. It was therefore important to determine whether similar relationships could be established in sorghum. The objectives of this study were to determine: 1) range of variation for12-hour in vitro dry matter disappearance (IVDMD), chemical, and physical grain quality parameters among 16sorghum conversion lines; and 2) to establish the strength of the relationships of these characters. Entries were grown at Ithaca, Nebraska in 1991 and 1992 in a randomized complete block with four replications. Line effects were significant for 12-hour IVMVD, crude protein, oil, starch, individual seed weight, and hardness. The only traits significantly correlated with 12-hour IVDMD were crude protein and hardness, with r≤–0.32 for testa and non-testa-containing lines. Stepwise regression similarly revealed poor predictive ability for any of the traits on12-hour IVDMD. Unlike corn, prediction of digestibility from simply measured physical parameters was not possible in this set of16 sorghum lines. However, the lack of strong relationships provides opportunity to select lines with unique combinations of traits for individual targeted needs or markets.