Prediction of the metabolizable energy value of whole-crop wheat from laboratory-based measurements

The accuracy with which several laboratory-based measurements predict the m etabolizable energy (ME) value of whole-crop wheat (WCW) was determined. Tw enty-six WCW forages differing in variety (cv. Slepjner, Hussar and Cadenza ), maturity at harvest (milk, cheese and dough stages) and treatment applie d (urea-treated, untreated or acid-based additive treated) were harvested i n 2 years and conserved anaerobically in 200-l barrels. The forages were th en scanned using near infrared reflectance spectroscopy (NIRS) and analysed for chemical composition, in vitro rumen fluid-pepsin digestibility, in vi tro neutral detergent-cellulase plus gamannase digestibility, in vitro ferm entation gas production and in situ rumen degradability ME was calculated u sing measured energy losses in faeces and urine and predicted energy losses as methane. The relationships between ME and the laboratory-based measurem ents were determined by regression. Guess energy was consistently the best predictor of ME (R-2 = 0.53 and 0.86 in years 1 and 2 respectively). Howeve r the autocorrelation involved, militates against the prediction of ME from gross energy. None of the chemical constituents or biological techniques g ave a good, robust prediction of ME. However, an NIRS calibration developed using the WCW samples was highly correlated (R-2 = 0.68) with ME. This wor k therefore suggests that traditional laboratory-based, food evaluation tec hniques are unsuitable far predicting the ME content of WCW but that NIRS h olds promise.