EVALUATION AND INTERPRETATION OF THE FORA GE ANALYSES IN THE FOODSTUFF LABORATORY AT ROSENAU OF THE AGRICULTURAL BOARD OF LOWER AUSTRIA

In the present investigation 7,556 forage analyses of the years 1989 t o 1993 of the foodstuff laboratory at Rosenau of the agricultural boar d of Lower Austria have been evaluated. There are analyses of nearly a ll forages used in daily feeding practice. The standard forages of the winter period, however, are best represented by numbers up to 1,500. The usual methods were used in analysing the crude nutrients (tecator system), the minerals (atomic absorption spectralphotometry) and the i n vitro-digestibility (Hohenheim gas production test). The energy eval uation was based on the digestibility coefficients of the DLG-tables ( 1991). On an average the legumes show high crude fibre contents of par tly more than 30 % and corresponding low energy concentration. The cru de fibre contents of grass silage and hay of the first cut were on ave rage 29 and 30 %, of the second cut 26 and 27 %, respectively. The res ults of maize silage (30 % DM, 23 % crude fibre, 6.4 MJ NEL) are satis fying. Of all types of forages regressions of protein and NEL content on crude fibre content have been computed. On the basis of these regre ssions the essential criteria for animal nutrition can be derived for the whole range of variation. The legumes are characterized by high Ca -contents (6 to 15 g), the contents of P were, however, similar to tho se of the grasses. The forage of the meadows shows on an average the f ollowing values (6 - 10 g Ca, 2.6 to 3.7 g P, 21 to 26 g K) . The trac e element contents of the grasses are a little higher than in the legu mes. The mineral content of silage maize is considerably lower than in the other forages (especially Ca and Mn). The relationships between c rude fibre and mineral content are not uniform with respect to both th e size and the sign. No general statement can therefore be given as to how and to what degree the mineral content changes depending on crude fibre content. The use of the individual linear regression equations, however, permits an estimate of the mineral content more exactly. The determination of the energy concentration using the Hohenheim gas pro duction test showed lower values than when deriving the energy concent ration using the DLG-digestibility coefficients, especially in the ran ge of lower energy concentration. In general both methods did not corr espond well in the determination of the energy concentration (R2 = 42 %, n = 608). Among the various types of forages the agreement between the two methods differed considerably. One possible explanation for th ese divergences could be that reduced digestibilities (e.g. by deficie nt conservation methods) are considered by in vitro-digestibility meth ods but not when using average data of foodstuff tables.