RUMEN DEGRADATION OF THE MAIN FORAGE SPECIES HARVESTED FROM PERMANENT MOUNTAIN MEADOWS IN NORTH-WESTERN SPAIN

Herbage samples were collected in late June, and again in early September (1987) from permanent mountain meadows situated in North-western Spain (Leon). Botanical composition was determined by grouping the species into grasses, legumes and herbaceous 'weeds'. Rumen degradability of the dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF) of the botanical groups in each harvest season was determined by the nylon-bag technique. Grasses and legumes differed in their degradation characteristics, and the comparisons between forage species were different for the two harvest seasons. There were no significant differences between September grasses, June legumes and September legumes in the potential degradabilities of the DM (86.9, 87.1 and 88.4%) and CP (94.2, 92.4 and 93.8%). The NDF of grasses harvested in September was degraded to a greater extent (80.6%) than that of legumes from both harvests (70.9 and 73.6% in June and September respectively). However, June grasses showed significantly lower potential degradabilities for the DM (77.0%), CP (84.3%) and cell wall (65.9%). Legumes were degraded at a faster rate than grasses (mean DM degradation rates of 0.143 and 0.057 respectively), and lag times were longer for grasses (4.7 h) than for legumes (2.5 h). Rumen degradation characteristics of the herbaceous 'weeds' were estimated, but it should be remembered that many other factors may limit their utilization by ruminants. It was concluded that the major constraint to the nutritive value of these permanent swards would be the maturity of the grasses harvested in June, which markedly reduced the rumen degradability of the forages.