EFFECT OF HARVEST INTERVALS ON THE CHEMICAL COMPOSITION AND NUTRITIVE VALUE OF NAPIER GRASS (Pennisetum purpureum Schum.) SILAGES FOR GOATS

Chemical composition and nutritive values of napier grass (Pennisetum purpureum Schum.) silages subjected to two cutting intervals were studies; 1st harvest in July (A), and 2nd (B) and 1st (C) harvests in November. Each forage was ensiled with 4% molasses in plastic bags and stored for 5 or 9 months. A feeding experiment with castrated goats was conducted from April to June of the following year. Dry matter (DM) and crude protein (CP) content of the harvests varied from 9.5 to 22.8% and 6.6 to 13.6% of DM, respectively. The dry matter content of the silages fed to the goats were 13.0 to 24.4%, because some effluent was removed from each silage before the feeding trial. The pH values of the silages were between 4.03 and 4.29. Goats were given sufficient silage to meet maintenance nitrogen requirements from napier grass silage. Silage C was not completely consumed, and the silage had low digestibilities of DM, CP, hemicellulose and cellulose. Nitrogen balance was slightly positive for goats consuming silage B and was negative for goats consuming silages A and C. Nitrogen utilization was discussed in terms of ruminal $NH_3-N$ and volatile fatty acid concentration in the rumen fluids. It is concluded that goats could not maintain N-equilibrium not only when a younger forage was consumed at a level of N requirement by a restricted feeding, but also when an older forage could not be consumed enough for N requirement because of feed intake limitation.