Nutritive Value of Tree Leaves in the Kansas Flint Hills

Abstract

Leaves from bur oak (Quercus macrocarpa Michx.), a bur oak hybrid (bur $\text{oak}_{{\rm H}}$), red elm (Ulmus rubra Muhl.), Osage orange (Maclura ponifera (Raf.) Schneid.), and cottonwood (Populus deltoides Marsh.) were analyzed for crude protein, in vitro dry matter digestibility (IVDMD), and tannic acid equivalents (TAE) from mid September through late October during 1979 and 1980. Samples were taken biweekly from the trees and from the ground after leaf fall. Cottonwood was significantly lower over the season in crude protein than all other species except bur oak. Crude protein content declined with advancing season in all species although not significantly. Leaves on the trees were considerably higher in crude protein than True Prairie understory vegetation or leaves on the ground although leaves on the ground had equal or greater crude protein levels than True Prairie understory vegetation. Sample date and species significantly affected digestiblity. Digestiblity generally increased during middle sample periods and returned to initial levels in late October. Averages over all dates showed digestibility of Osage orange > cottonwood > red elm > bur oak(H) > bur oak. Leaves on the tree were generally more highly digestible than those on the ground. Red elm, Osage orange and cottonwood leaves on the tree were more digestible than True Prairie understory vegetation. Osage orange and cottonwood leaves on the ground were more digestible than True Prairie understory vegetation. Tannic acid equivalents of bur oak(H) > oak > red elm and cottonwood > Osage orange. Tannic acid equivalents generally increased during the middle sample periods and returned to initial levels in late October. There were no TAE differences between leaves on the trees and those on the ground. Overall quality ranking based on the constituents measured showed Osage orange and red elm to be the highest quality leaves of the group, bur oak poorest, and cottonwood and bur oak(H) intermediate. On the basis of these limited tests, Osage orange and red elm would provide the best roughage source in times of severe drought or as a roughage substitute in cattle finishing rations.