Laboratory and in Vivo Evaluation of the Nutritive Value of NaOH-Treated Wheat Straw

Abstract

Three laboratory trials were conducted to determine the effects of type of chemical, concentration of chemical, and concentration and duration of sodium hydroxide (NaOH) treatment upon the nutritive value of ground wheat straw (WS). NaOH, potassium hydroxide and ammonium hydroxide improved in vitro dry matter digestibility (IVDMD) of the straw at either the 2 or 4% (W/W) levels. In vitro organic matter digestibility (IVOMD) of WS increased (P<.01) while levels of acid detergent fiber (ADF) (P<01), acid detergent lignin (P<.05), cell wall constituents (P<.01) and hemicellu-lose (P<.05) decreased with increasing concentrations of NaOH (0 to 16% W/W) per dry weight of WS. Concentrations of crude protein (P<05), ash (P<05) and ADF (P<01) increased while hemicellulose decreased (P<.01) as duration of chemical treatment increased (0–56 days). An interaction (P<.01) between NaOH concentration and duration of treatment was detected upon IVOMD. In a steer feeding trial, diets containing either 50% untreated or NaOH-treated WS were evaluated. In addition, three levels of dietary urea (0, 1 or 2%) were evaluated with the NaOH-treated WS. Average daily gain (ADG) and daily dry matter (DM) intake were increased (P<.05) by treating ground WS with NaOH. However, the addition of urea to the NaOH-treated WS diets decreased (P<05) ADG and DM intake and increased (P<.05) feed/gain ratio. Carcass parameters were generally not affected by treatment. In digestion and nitrogen balance trials evaluating the same diets, the apparent DM and crude fiber digestibilities were increased (P<05) by treatment of WS with NaOH. Percent urinary N excretion was increased (P<.05), and percent N retention tended to be lower with the yrea-containing diets.