title: The effect of starch on forage fiber digestion kinetics in vitro.
abstract: Purified corn and wheat starch were added to alfalfa, Coastal bermudagrass, fescue, and orchardgrass hays at 0, 40, 60, and 80% of the total as-fed substrate, and fiber digestion kinetics were determined in vitro. Kinetics were estimated by the model R = Doe-k(t-L) + U where R is residue remaining at time t, Do is digestible fraction, k is digestion rate constant, L is discrete lag time, and U is indigestible fraction. Parameters of the model were estimated by logarithmic transformation and a direct nonlinear least squares procedure. Corn and wheat starch did not differ in their effect upon lag time of fiber digestion, digestion rate, or potential extent of digestion. Alfalfa had a shorter lag time of fiber digestion (.86 h) than Coastal bermudagrass (3.05 h), but not than orchardgrass or fescue (1.66 and 2.42 h). Orchardgrass differed in fiber digestion rate (.0542h-1) from Coastal bermudagrass (.0698h-1) but not from alfalfa or fescue (.0670 and .0658h-1). The potential extent of fiber digestion was similar for fescue (75.8%) and orchardgrass (76.0%). The potential extent of fibre digestion for alfalfa (50.9%) differed from Coastal bermudagrass (64.3%), and both of these forages differed from fescue or orchardgrass. Addition of starch resulted in a linear increase in lag time of fiber digestion, but digestion rate was not affected. Potential extent of digestion was decreased when starch was added.
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle; D002482:Cellulose / Q000378:metabolism*; D004043:Dietary Fiber / Q000378:metabolism*; D004063:Digestion / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D007700:Kinetics; D000455:Medicago sativa; D008954:Models, Biological; D006109:Poaceae; D013213:Starch / Q000494:pharmacology*; D014908:Triticum; D003313:Zea mays
chemical_list: D004043:Dietary Fiber; D002482:Cellulose; D013213:Starch