Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/16/2006
Publication Date: 10/10/2006
Citation: Casler, M.D., Hatfield, R.D. 2006. Cell-wall composition of smooth bromegrass plants selected for divergent fiber concentration. Journal of Agriculture and Food Chemistry. 54:8206-8211. Interpretive Summary: Intake potential of forage crops may be improved by genetic selection for reduced fiber concentration, allowing livestock to consume and utilize more nutrients from a fixed amount of feed. We determined that low-fiber plants do not have altered composition of their cell walls, but rather have a larger soluble and a smaller insoluble portion of the cell wall. This may be the reason that low-fiber plants are lower yielding and more susceptible to pests and stresses. This work will impact other forage breeders who are attempting to develop new varieties with improved forage quality, and livestock producers who purchase seeds of improved varieties.
Technical Abstract: Neutral detergent fiber (NDF) is considered the single best laboratory predictor of voluntary intake by ruminant livestock, creating interest in using NDF as a selection criterion in forage breeding programs. Because genetic reductions in NDF lead to increases in dry matter digestibility, but not to changes in digestibility of the NDF fraction, we postulated that low-NDF plants do not have altered composition of their cell walls. We tested this hypothesis using clones of smooth bromegrass (Bromus inermis Leyss.) with divergent NDF concentration. High-NDF and low-NDF plants did not differ in cell-wall concentration or in the concentration of any cell-wall component (fucose, arabinose, rhamnose, galactose, glucose, xylose, mannose, total uronosyls, and lignin). Instead, low-NDF plants had a cell wall that was more susceptible to solubilization in neutral detergent solution, suggesting that their cell walls were less well developed compared to high-NDF plants. Neutral detergent fiber should not be used as a substitute for cell-wall concentration in forage plants.