Prediction of the in vivo digestibility of whole crop wheat from in vitro digestibility, chemical composition, in situ rumen degradability, in vitro gas production and near infrared reflectance spectroscopy A.T. Adesogan a,b,* , E. Owen a , D.I. Givens b a Department of Agriculture, The University of Reading, Earley Gate, PO Box 236, Reading RG6 6AT, UK b Feed Evaluation and Nutritional Sciences, ADAS Drayton, Alcester Road, Stratford on Avon CV37 9RQ, UK Received 4 November 1997; accepted 6 April 1998 Abstract Twenty-six winter wheat forages (cultivars Slepjner, Hussar and Cadenza) harvested at three stages of maturity in each of two years, were conserved with or without Maxgrass additive or with urea (20 or 40 g kg 1 dry matter; DM) in 200 l barrels. The forages were analysed for in vivo digestibility in wethers, chemical composition, in vitro rumen fluid-pepsin digestibility, in vitro neutral detergent-cellulase plus gamannase digestibility (NCGD), in vitro fermentation gas production and in situ rumen degradability. Forages were also scanned using near-infrared reflectance spectroscopy (NIRS) and calibration equations developed for predicting in vivo digestibility. In vivo digestible organic matter content (DOMD) was poorly predicted by cell wall content (r 2 0.19), NCGD (r 2 0.41), rumen fluid DOMD (r 2 0.41), rumen degradability (r 2 0.44) and in vitro gas production (r 2 0.26). Although crude protein content was a better predictor (r 2 0.48), the relationship differed (P<0.05) with the year of harvest of the forages. In contrast, NIRS was a more accurate and consistent predictor of DOMD in vivo (r 2 0. 87). This study indicates that traditional laboratory-based feed evaluation techniques are unsuitable for predicting the DOMD of WCW, but that NIRS holds promise. However, as only 26 forages were used to derive the calibration equation, further research is required using large (150) data sets to validate the promise shown by NIRS and enable its adoption by the advisory services. # 1998 Elsevier Science B.V. Keywords: Nutritive value; Prediction; Whole crop; Digestibility; In vitro Animal Feed Science and Technology 74 (1998) 259±272 * Corresponding author. Tel.: +44 1970 624471; fax: +44 1970 611264; e-mail: ata@aber.ac.uk 0377-8401/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S0377-8401(98)00175-8