Digestion Kinetics and Composition of Normal and Brown Midrib Sorghum Morphological Components

Publisher Website
Google Scholar
Abstract
The brown midrib (bmr) mutation has shown the potential to improve the nutritive quality of forage sorghum [Sorghum bicolor (L.) Moench]; however, no study has been conducted to directly compare the effect of the bmr gene in a sudangrass (sorghum × drummondii (Steudel) Millsp. & Chase) and its hybrid with a grain sorghum. Research was conducted to evaluate the relationship between cell wall composition and digestibility within the morphological components of normal and bmr sorghum cultivars. Cell wall constituents, structural carbohydrates, alkali‐labile phenolic monomers, and in vitro digestion kinetics were determined for ‘Piper’ (normal sudangrass), ‘S407’ (Piper. bmr‐6 sudangrass), and ‘F1006‐8 × S407’ (male sterile grain type bmr‐6 sorghum × Piper bmr‐6 sudangrass). Whole plants were harvested at the boot and hard dough growth stages and separated in to leaf blade, leaf sheath, inflorescence, and stem components. Significant differences were found between cultivars in concentrations of cell wall constituents. Neutral detergent fiber (NDF) concentration was lower (P < 0.05) in the bmr cultivars than in Piper due to lower concentrations of cellulose and acid detergent lignin (ADL). Concentrations of ADL averaged g kg−1 dry matter for Piper, 28 g kg−1 for S407, and 25 g kg−1 for F1006‐8 × S407. The bmr cultivars had lower (Pp‐coumaric acid and higher (P < 0.05) concentrations of vanillin than Piper. There were no differences (P > 0.05) among cultivars ferulic acid concentration. p‐Coumaric acid concentrations averaged 25 g kg−1 of NDF for Piper, 16 g kg−1 NDF for S407, and 14 g kg−1 NDF for F1006‐8 − S407. Rate constants for in vitro digestion of NDF were similar (P > 0.05) among cultivars. The bmr sudangrass (S407) had a greater (P < 0.05) extent of NDF digestion than either Piper of F1006‐8 × S407. Extent of NDF digestion averaged 0.596 for Piper, 0.623 for S407, and 0.597 for F1006‐8 × S407. Results of this study indicate that the bmr mutation can effectively be expressed in both sudangrass and sorghum × sudangrass hybrid backgrounds