South African Journal of Animal Science
On-line version ISSN 2221-4062
JANCIK, F.; KOUKOLOVA, V.; HOMOLKA, P. and HAMAN, J.. Comparison of analyses to predict ruminal fibre degradability and indigestible fibre in temperate grass silages. S. Afr. j. anim. sci. [online]. 2011, vol.41, n.3, pp. 297-308. ISSN 2221-4062.
ABSTRACT The objective of this study was to compare the ruminal degradability of neutral detergent fibre (NDF) and indigestible NDF (INDF) between silages (n = 24) that originated from three different temperate grass species, i.e. Dactylis glomerata L., Festuca arundinacea L. and hybrid, Felina - Lolium multiflorum L. × Festuca arundinacea S. The data is used to create prediction equations for the effective degradability of NDF (EDNDF), assuming ruminal solid outflow rates of 0.02 (low), 0.05 (medium) and 0.08/h (high), and INDF. The highest values for the potentially degradable fraction of NDF (b), EDNDF2, EDNDF5 and EDNDF8 (874, 560, 366 and 272 g/kg NDF, respectively) and the lowest for INDF (73.1 g/kg DM) were found for F. arundinacea. These parameters were significantly different from the hybrid Felina, which presented the lowest rate of NDF degradation (c), EDNDF5 and EDNDF8 (0.033/h, 341 and 250 g/kg NDF, respectively). The highest for c (0.038/h) and INDF (86.9 g/kg DM) and the lowest for b (847 g/kg NDF) were detected for D. glomerata. The combination of acid detergent fibre (ADF) and acid detergent lignin (ADL) (R2 = 0.844) were identified by a backward, stepwise, multiple regression analysis as the most accurate to predict INDF. Crude protein, ADF and NDF were found as the most suitable combination for predicting EDNDF2 (R2 = 0.715), EDNDF5 (R2 = 0.669) and EDNDF8 (R2 = 0.648). Calculated equations found practical application in laboratory analyses to evaluate the nutritional quality of feeds for ruminants.
Keywords : Grass silage; neutral detergent fibre; rumen degradation; prediction equations.