Forage Dry Matter Yield and Nutritive Value of the Natural Pasture of Umbulo Wacho Watershed, Southern Ethiopia

The biomass production and nutritive value of the natural pasture of Umbulo Wacho watershed in Southern Ethiopia were studied. The upper and medium altitudinal zones had an open area and areas closed for 2, 3 and 4 years and the lower altitude had an open area and an area closed for 2 years. In each of the open and closed areas, three sites were selected (9 in open, 21 in closed) at each of which exclusion cages (30) were fixed. The re-growths of forage samples were cut at 30 days interval from May up to November from the exclusion cages. The overall dry matter (DM, %), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), ash, calcium (Ca) and phosphorus (P) contents of the forages were 30.8, 83.9, 12.7, 66.7, 32.6, 4.5, 16.2, 0.6 and 0.3%, of the DM, respectively; in vitro DM digestibility (IVDMD) was 72.1% and DM yield (DMY) was 71.34 g/1.21 m/30 d (0.59 tones/ha/30 d). The natural pasture (117.1 ha) produced 829.07 tones of DM/year (0.59 * 117.1*12) which can only meet 8.20% of the total DM requirement (10,107.11 tones/year) of the tropical livestock unit (4431) found in the watershed. Closing an area for long duration decreased (P < 0.01) CP, P, DMY and IVDMD, but increased ADF and ash. Advance from the rainy season towards the dry period reduced (P < 0.01) DM, DMY, CP, ADF, ash and P. With increasing altitude, DM increased (P < 0.01) but DMY, NDF and P decreased. The IVDMD was positively correlated with DMY and negatively correlated with NDF and ash (P < 0.05). The interactions among closed or open areas, sampling time and altitude were significant (P < 0.05) for most of the nutrient content and yield parameters. The forages could be cut twice (middle and end of the rainy season) when the nutrient contents are optimal. For integrated and sustainable use of forages in the watershed, further study in improvement of quality and utilization is suggested. Keywords: Forage; Dry Matter; Watershed; Natural Pasture