Validation of a ley-ruminant system model, 1: Growth and change in nutritive value of the forage
1991
Fagerberg, B. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Vaextodlingslaera)
Predictions for dry matter (DM) growth and nutritive value of pure grass and mixed grass-clover leys were made by means of a ley-ruminant system model. Predictions were based on field sampling and weather observations during four years in northern, western and central Sweden. Predictions of DM yield, crude protein (CP) and metabolizable energy (ME) contents were validated by field samples and the deviation was defined as prediction difference. Prediction differences of DM yield varied between 10% and 20%. The difference depended on the time that elapsed between sampling and prediction. Prediction times between one and three weeks were tested. Prediction differences for CP contents were 5-10%, whereas the predicted ME contents had lower differences (less than 5%). Two methods for analysing CP and ME contents were compared, the new and rapid Near Infrared Reflectance Spectroscopy (NIRS) method as well as the conventional VOS and Kjeldahl methods. The NIRS method is satisfactory for analysing CP contents, while the reliability of ME analysis needs to be improved.
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