Biomasa y valor nutritivo de tres gramíneas forrajeras en diferentes períodos del a？o en la zona de bosque húmedo tropical, Barlovento, estado Miranda

in order to evaluate under cutting for four gramineous forage species, an experiment was set up at the experimental station of rio negro, belonging national experimental university simon rodriguez, located nearly the town of rio negro, municipality of acevedo, state of miranda. the ecosystem is considered as humid tropical forest with 2.450 mm precipitation mean and 26,5oc of mean annual temperature. the soil texture is a loam ph 6,0; containing low levels of n, p and k and high level of mg. the grass species evaluated were urochloa decumbens, urochloa humidicola cv. humidicola and urochloa arrecta harvested at 21, 28, 35, 42,49 and 56 days of age, during four different periods of the rainy regime of the area. a randomized block design with three replicates arranged as a split-split plot design was used. the variables studied were dry matter standing crop(dmc), height of the plants(h), leaf :stem ratio (l:s), crude protein content (cp), dry matter degradability (dmd), p and ca, d.m content. the rainy regime period and age of cutting had a significant statistical effects upon dmc, h and the l:s ratio. u. decumbens dmc out yielded (3.870 kg./ha) the other nown species. the l:s ratio and cp content diminished as the plant aged, staging the latter variable over the critical threshold value (7%) up to 42 days of age . similar trends occurred to p and ca content as plant aged, except u. humidicola with values under the cited level, during the minimum rainy period. the dmd varied from 62 to 69%, being significantly effected by age and grass species