Effect of Forage Particle Size on In Situ Digestion Kinetics

Abstract

The effect of forage particle size on in situ DM digestion kinetics was evaluated. Six forages, "Florida-77" alfalfa, "Florigraze" rhizoma peanut, "Tifton-78" bermudagrass, "Mort" dwarf elephantgrass, "Pensacola" bahiagrass, and "Floralta" limpograss were ground through a 2-ram screen and separated into particle size fractions by dry sieving. Mean particle size of forages ranged from 256 to 341 /~m. Particle shape appeared different between legumes and grasses. Grasses had mostly rectangular and needle-shaped particles whereas legumes had square or triangular-shaped particles. Three particle sizes (710, 355, and 106 #m) of bermudagrass and rhizoma peanut were chosen for further evaluation. Percent NDF decreased while percent CP increased with decreasing particle size. Five-gram samples were incubated in situ for 0, 2, 4, 6, 12, 18, 24, 30, 36, and 72 h. Lag, rate, and extent of DM digestion were determined. Rate and extent of DM digestion of rhizoma peanut increased with decreasing particle size but was unchanged for bermudagrass. Different particle size fractions potentially can have different rates and extents of DM digestion.