Temporal and vertical distribution of soluble carbohydrate, fiber, protein, and digestibility levels in orchardgrass swards

Herbage nonstructural carbohydrates (NC) contribute to livestock performance and silage fermentation. Knowledge of the distribution patterns of NC and other nutritional constituents in orchardgrass (Dactylic glomerata L.) swards could support harvest management decisions. Our objective was to determine diurnal and vertical patterns of total NC (TNC), crude protein (CP), and neutral detergent fiber (NDF) concentrations, and in vitro true dry matter digestibility (IVTDMD) and NDF digestibility (NDFD) in orchardgrass swards in October, June, and August. Herbage was sampled at 6-h intervals between 0100 and 1900 h from horizons positioned 40 to 27, 27 to 18, 18 to 12, and 12 to 8 cm above soil surface. Herbage composition varied among horizons in all months, and diurnally only in June and August. In June and August, only TNC with maxima of 109 to 123 g kg-1 at 1900 h exhibited consistent diurnal patterns. Swards harvested to residual heights of 18, 12, or 8 cm exhibited little spatial variation in TNC during June and August, but CP, NDF, and IVTDMD varied with harvest depth on all dates. As swards were harvested to successively greater depths, TNC increased in October, but not in June and August. In contrast, CP and IVTDMD decreased, and NDF increased, for harvests to successively greater depths in all months. For harvests in June and August, manipulation of depth would capture more variation in CP, NDF, and IVTDMD, but manipulation of time of day of harvest would capture more variation in TNC to meet animal performance and silage fermentation requirements

The diurnal cycling of sugars in grasses impact strip-graze management plans

Soluble sugar concentrations increase in forage plants during the day and decrease at night. The objective of this study was to quantify the sugar concentrations in the upper and lower parts of the grass canopy at the end of a light and subsequent dark period and relate these changes in animal grazing behavior and production responses. Tall fescue (Festuca arundinacea) grown in controlled-environment chambers was cut after a 15-h light and a subsequent 9-h dark period, and tillers were separated into leaves and stems. Leaves, but not stems, demonstrated diurnal fluctuation in sugars. Leaf sugars concentrations, after 15-h of light, were 1.6 times greater than those in leaves following the 9-h dark period. It is suggested that animal production may benefit from afternoon vs. morning turnout onto fresh pastures because of the extra sugars accumulating in the leaves during the day