Relationship between ruminal degradability and chemical composition of dehydrated lucerne

Abstract

The rumen degradation characteristics and effective degradability (ED) of dry matter (DM) and crude protein (CP) of 21 samples of dehydrated lucerne from 5 different processing plants were studied in three rumen fistulated wethers using the nylon bag technique. The animals were fed at an intake level of 40 g DM·kg-1 BW0.75 with a mixed diet of lucerne (40% dehydrated and 60% hay) and concentrate (2:1 on DM). The mean values of the ED of DM and CP, calculated for rumen outflow rates determined in each animal (2.28%·h-1, as average), presented a low variation (mean = 61.2%; CV = 5.31% for DM and mean = 73.5%; CV = 4.95% for CP). Degradation of DM was directly related to lucerne quality, with negative and positive correlations with the contents of fibre and CP, respectively. The best prediction of the ED of DM was derived from the contents of acid detergent fibre, which explained 73.3% of the total variation. The best prediction of the ED of CP (R2 = 0.592) was related negatively to the proportion of insoluble nitrogen in neutral detergent fibre and positively to the CP concentration as the first and second predictive variables. However, the first variable allowed a good estimation of the ED of CP for the dehydrated lucerne samples presented in a long form (R2 = 0.818). Degradation studies of DM and CP also indicated that most of the N available to animals was derived from rumen microbial synthesis.