Effect of drought stress on in vitro neutral detergent fiber digestibility of corn for silage

The objective of this study was to determine the effect of drought stress on neutral detergent fiber (NDF) and lignin (LIG) concentrations and on in vitro dry matter digestibility (IVDMD) and in vitro neutral detergent fiber digestibility (IVNDFD) of leaf blades and stem internodes of corn for silage. Eight plots were blocked (i.e., 4 blocks) and randomly subjected to a watered (W) or non watered (NW) treatment. Within each block, plots were split into 7 sub-plots, to which 1 of 7 corn hybrids were randomly assigned. Before planting, all plots were irrigated with 150 mm of water to ensure a consistent emergence of corn seedlings. After this pre-planting irrigation, NW plots were not irrigated ever again. After planting, W plots were irrigated with 225 and 360 mm of water pre-tasseling and post-tasseling, respectively. Stem internodes and leaf blades from the second phytomer below (LOWER) and the second phytomer above (UPPER) the ear insertion were collected to determine tissue composition and digestibility. Drought stress increased the concentration of NDF in both leaf blades (628 vs. 613 mg NDF/g DM) and stem internodes (625 vs. 572 mg NDF/g DM). Drought stress decreased IVDMD in stem internodes (0.575 vs. 0.525 IVDMD) but had no effect on IVDMD of leaf blades (0.561 IVDMD). Similarly, drought stress decreased IVNDFD in stem internodes (0.422 vs. 0.391 IVNDFD) but had no effect on IVNDFD of leaf blades (0.536 IVNDFD). Drought stress increased the concentration of lignin in the cell wall of leaf blades (161 vs. 141 mg/g CW) but had no effect on stem internodes (266 mg/g CW). Under the conditions of this study, water supply had a minimal effect on lignin concentration in the cell wall and did not increase the in vitro digestibility of fiber in corn for silage. The latter observation is contrary to the general industry belief that water stress increases fiber digestibility in forages.