COMPARISON OF IN-SITU DEGRADATION KINETICS OF LUCERNE GERMPLASM BY ANOVA OF NONLINEAR MODELS

The ANOVA of non-linear models was used to evaluate the in situ degrad ation of five lucerne germplasm grown in the Po Valley of Italy during the growing seasons of 1987-1989. The germplasm included one North Am erican synthetic cultivar, three Italian synthetic cultivars and one l ocal Italian ecotype. The degradation kinetics of dry matter (DM), neu tral detergent fibre (NDF), acid detergent fibre (ADF) and cellulose w ere measured using the nylon bag technique. Forage samples, cut at 10% bloom, were wilted, oven dried, ground (5-mm screen) and incubated fo r 0, 2, 4, 8, 12, 24, 48, 72, 120 and 168 h in the rumen of two dry Ho lstein cows fitted with ruminal cannula. The significance of two contr asts was tested: Contrast 1: ecotype versus synthetic cultivars and Co ntrast 2: North American versus Italian synthetic cultivars. Total DM yield of the ecotype showed no significant difference from the synthet ic cultivars, while in Contrast 2, the North American synthetic showed greater DM yield (83.5 vs. 72.5 metric tonnes (MT) ha(-1), P<0.05). C hemical composition data showed the ecotype having greater (P<0.10) ND F and cellulose content relative to the synthetic cultivars. The North American synthetic cultivar showed greater (P<0.10) crude protein con tent than the Italian synthetic cultivars. Effective DM degradability, at a ruminal turnover rate of 8% h(-1), was higher (P<0.05) for the s ynthetic cultivars (48.6%) compared with the ecotype (46.1%). This adv antage for the synthetic cultivars may have resulted from greater cont ent of non-cell-wall constituents and by the presence of cell wall con stituents available to ruminal microorganisms. ANOVA of non-linear mod els showed higher DM and NDF degradability for synthetic cultivars fro m 0 to 168 h and from 13 to 168 h at P<0.05, respectively. Therefore, cultivar selection significantly influenced the nutritive properties o f luceme forage. The application of ANOVA of non-linear models for Con trast 2 showed a generally greater (P<0.05) availability for the fibre fraction for the North American synthetic cultivar. These important n utritional differences could not have been detected using the traditio nal statistical analysis of single degradation parameters.