Effect of maturity on degradation kinetics of sod-seeded cereal grain forage grown in northern Arkansas

Wheat (Triticum aestivum L.), oat. (Avena sativa L.), and rye (Secale cerea le L.) were overseeded into a dormant bermudagrass (Cynodon dactylon (L.) P ers.) sod and harvested at 3-wk intervals throughout March, April, May, and early June. Plant growth stage was documented for each forage on each harv est date, and harvested forages were evaluated for forage quality character istics. Degradation kinetics of DM and NDF for these forages were evaluated by the in situ method. Fractional degradation rates for DM and NDF in all three species were relatively rapid for vegetative forage (greater than or equal to0.086 h(-1)) but declined rapidly by the heading stage of developme nt and stabilized thereafter. Forage quality declined and forages were more resistant to ruminal degradation as plants entered the reproductive stages of growth. Based on these findings, growth stage is an effective predictor of most characteristics of in situ DM and NDF disappearance. The relations hips between these degradation parameters and growth stage were typically e xplained with quadratic or cubic models. Clearly, forage quality characteri stics of overseeded rye deteriorated more rapidly with phenological develop ment and growth stage than quality characteristics of overseeded wheat and oat grown in the same environment. For rye, this problem is further complic ated by its accelerated phenological. development. These factors combine to permit a very narrow harvest window in early spring, relative to the other cereal grains evaluated. Acceptable forage quality may persist for an exte nded period in wheat and oat; this suggests that producers wishing to utili ze these forages may lengthen the harvest window by planting more than one species, either as a mixture or preferably in independent stands.