EFFECT OF MATURITY STAGE OF ITALIAN RYE GRASS AND LUCERNE ON RUMINAL NITROGEN DEGRADABILITY

Ruminal N degradability of Italian rye grass and lucerne was studied u sing the nylon bag technique: 5 samples of rye grass and 5 of lucerne were harvested during the lst cycle of growth at different stages of m aturity, between the leafy stage and the end of heading for rye grass and between the vegetative stage and the end of budding for lucerne. F or grass, degradability values were high at the beginning of growth, w ith a mean of 72.2% in the period from leafy stage to heading, but the y decreased rapidly after this stage to 64.6% (of 1. 1%/d). For lucern e, the decrease in N degradability was approximately linear between th e vegetative stage (79.0%) and the end of budding (70.0%), a decrease of 0.3%/d. After correction to take into account microbial contaminati on of bag residues, the reduction of N degradability with stage of mat urity appears smaller, ie 5% for rye grass and 4% for lucerne.