One hundred and eighteen grass silage samples with known chemical composition and in vitro determined concentration of net energy for lactation (NEL) were scanned over the wavelength range from 1100 to 2500 nm at 8 nm intervals. Calibration equations for the prediction of crude protein (CP), crude fi bre (CF), crude fat (F), crude ash (A), dry matter of air-dried samples (DM) and NEL were developed by the use of principal component analysis (PCA) and modifi ed partial least squares regression technique (mPLS). NIRS demonstrated high predictive ability for CP (R2 = 0.97), CF (R2 = 0.96) and A (R2 = 0.94). Moderate accuracy was characteristic for F and DM (R2 = 0.81 and 0.79). Crude protein, F and DM deviations from reference methods were comparable to those which are expected by the use of the same reference methods in different laboratories. The determination coeffi cient for in vitro assessed NEL concentration was
0.76. Seventy-seven percent of samples lied within acceptable limits of ± 0.3 MJ NEL kg-1DM. Suboptimal sample distribution, i.e. small number of samples in classes below 4.6 and above 6.0 MJ NEL kg-1DM was observed. It seems that deviations of NIRS predicted values from the reference values were related to the concentration of NEL. It was concluded that NIRS shows the potential for reliable determination of chemical composition and energy value of grass
silage.Stoosemnajstim vzorcem travne silaže z znano kemično sestavo in in vitro določeno vsebnostjo neto energije za laktacijo (NEL) smo v valovnem območju med 1100 in 2500 nm na vsakih 8 nm izmerili spektre odbite bližnje infrardeče svetlobe. S pomočjo analize glavnih komponent (PCA) in regresijske metode modifi ciranih delnih
najmanjših kvadratov (mPLS) smo razvili umeritvene enačbe za napovedovanje vsebnosti surovih beljakovin (SB), surove vlaknine (SVl), surovih maščob (M), surovega pepela (P), suhe snovi zračno suhih vzorcev (DM) in NEL. Metoda NIRS je bila zelo dobra pri napovedovanju SB (R2 = 0,97), SVl (R2 = 0,96) in A (R2 = 0,94). Za M in DM je bila značilna zmerna točnost (R2 = 0,81 in 0,79). Pri SB, M in DM so bila odstopanja od referenčnih metod primerljiva
z odstopanji, ki jih lahko pričakujemo pri izvajanju istih referenčnih metod v različnih laboratorijih. Determinacijski koeficient za in vitro ocenjeno koncentracijo NEL je znašal 0,76. Sedeminsedemdeset odstotkov vzorcev je ležalo znotraj sprejemljivih meja ± 0,3 MJ NEL kg-1SS. Za vzorce travnih silaž je bila značilna ne-optimalna porazdelitev vzorcev, t.j. majhno število vzorcev v razredih pod 4,6 in nad 6,0 MJ NEL kg-1SS. Izgleda, da so odstopanja med NIRS
ocenjenimi vrednostmi in referenčnimi vrednostmi povezana z vsebnostjo NEL. Sklenili smo, da je z NIRS metodo mogoče zanesljivo oceniti kemično sestavo in energijsko vrednost travne silaže
