Effect of moisture and temperature on the degradability of fiber and on nitrogen fractions in barley straw treated with urea V. Can Äeque a,* , S. Velasco a , J.L. Sancha b , C. Manzanares a , O. Souza a a Department of Food Technology, CIT-INIA, 28040 Madrid, Spain b Department of Animal Production, 3 Comunidad de Madrid, Servicio de Investigacio Ân, Aptdo 127, Alcala  de Henares, Madrid, Spain Received 28 February 1997; accepted 7 April 1998 Abstract The effect of the treatment of barley straw with urea (6% of the D.M.) on its chemical composition, digestibility, degradability and nitrogen fractions was studied varying the initial straw- treatment moisture level (20%, 30% and 40%) and storage temperature (258C and 358C). The urea treatment fundamentally affected the NDF content of the straw, which decreased as a result of hemicellulose solubilization. The decrease in NDF was greatest when the initial temperature and moisture content of the straw were both high, under which conditions the maximum solubilization of hemicellulose (25%) occurred. In vitro digestibility and degradability also improved with the urea treatment. In this regard, the greatest improvement (up to 20 points in the case of the digestibility results) was seen when hemicellulose solubilization was maximum. The amount of nitrogen retained by the straw (after deducting the residual urea) rose under conditions of increased moisture and temperature, reaching its highest values at moisture levels of 35% and 40%, when the best urea hydrolysis also took place. # 1998 Elsevier Science B.V. Keywords: Barley straw; Urea treatment; Digestibility; Fiber degradability; Nitrogen fractions 1. Introduction The treatment of straw with urea leads to the production of ammonia, which acts on the cell walls facilitating the access of bacteria to the polysaccharides within them (Horn Animal Feed Science and Technology 74 (1998) 241±258 * Corresponding author. Tel.: +34 91 3474023; fax: +34 91 5490956; e-mail: caneqe:inia.es 0377-8401/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S0377-8401(98)00169-2