An investigation on the effect of maturity stage and variety on the quality of cereal forages

Two groups of cereal forage crops, including various cultivars of barley, oats, triticale and wheat, were planted at different sites and harvested at boot, anthesis and milk stages respectively. The effects of maturity stage and variety on nutritive values and predicted digestibility were measured by near-infrared reflectance spectrophotometry (NIR). The effects of stage, variety and their interaction were significant (P<0.001) for samples collected at one site (78 samples), but only the effect of stage was significant (P<0.001) for samples from the other site (125 samples). For samples from the first site, the mean concentration of neutral detergent fibre (NDF) and acid detergent fibre (ADF) increased from boot to anthesis stage and then decreased from anthesis to milk stage; the crude protein (CP) content decreased significantly from boot to milk stage; and the mean predicted digestibilities declined significantly from boot to anthesis and then to milk. For samples from the second site, the mean concentration of NDF and ADF did not differ between boot and anthesis stage but increased significantly from anthesis to milk stage; the CP content decreased significantly from anthesis to milk stage; and the mean predicted digestibilities did not change from boot to anthesis and then decreased to milk. The predicted digestibilities in NIR were calibrated by R-P (Rumen fluid Pepsin method) and P-C (Pepsin Cellulase method) respectively, but differences were noticed between them. Therefore, the experiment was carried out to measure the effect of method on the predicted digestibility by R-P and P-C method for each group respectively.