In Vitro Digestion Kinetics and Quality of Perennial Grasses as Influenced by Forage Maturity

Objectives were to characterize changes in digestion kinetics of ‘Venture’ reed canarygrass (Phalaris arundinacea L.), ‘Regar’ meadow bromegrass (Bromus biebersteinii Roem & Schult.), ‘Garrison’ creeping foxtail (Alopecurus arundinaceus Poir.), ‘Fawn’ tall fescue (Festuca arundinacea Schreb.), and ‘Common’ timothy (Phleum pratense L.) with increased maturity. In 1991, three replicates each were harvested on four dates from early May to mid-June at Canton, Chazy, and Valatie, NY. Averaged over species and locations, NDF increased from 40.0 to 62.7%, indigestible fiber increased from 6.0 to 25.5%, lignin increased from 1.7 to 5.3%. and digestibility of fiber decreased from 79.7 to 44.2%. Lignin was highly correlated with fiber digestibility at all locations (r=−80, −.80, and −.76 for Canton, Chazy, and Valatie, respectively). Timothy was higher than all other species in lignin concentration at the first three stages. Rate of fiber digestion declined across harvest dates for all species (.0605 to .0396h−1 at Canton, .0654 to .0277h−1 at Chazy, and .0667 to .0287h−1 at Valatie); no species × harvest date interaction occurred at any location. Magnitude and speed of quality decline with maturity were more important than species differences in determination of digestion kinetics of perennial grasses. To ensure high quality forage, less emphasis should be placed on differences among grass species, and much more emphasis should be placed on harvest management.