Chemical and mineral composition, in-vitro gas production, in-sacco degradation of selected indigenous Kenyan browses.
The proximate and mineral composition, in sacco degradation and in-vitro gas production were determined in 15 indigenous Kenyan multipurpose tree and shrub (MPTS) leaf browse to assess their potential as goat feed. The species selected from a field survey were Maerua angolensis, Acacia brevispica, A. mellifera, A. tortilis, A. hockii, Zizyphus mucronata, Grewia bicolor, A. elatior, A. nilotica, Balanites aegyptiaca, A. senegal, A. abyssinica, Bridelia micrantha, Albizia amara and Albizia coriaria. The crude protein (CP) levels ranged from 112 g/kg DM for B. micrantha to 321 g/kg DM for M. angolensis;. The neutral detergent fibre (NDF) ranged from 218 to 601 g/kg DM for A. hockii and Albizia amara, respectively. The TEPH and TET were in the range of 1.52-26.4 and 0.301-24.4 g/kg DM, respectively. The major minerals Ca, P, Mg, Na and S were in the ranges of 6.51-28.1, 0.838-3.18, 0.442-8.51, 0.318-0.711 and 1.12-2.45 g/kg DM, respectively. The microelements varied widely (mg/kg DM) as follows: Fe (51.3-267); Mn (13.8-38.5); Cu (4.81-74.9); Mo (13.9-43.4); Co (1.76-17.4); Zn (12.2-93.2); and Se (19.5-124). The in sacco DM degradation at 48 h showed Z. mucronata as having the highest value, followed by M. angolensis with degradability of 93.3 and 88.6%, respectively. Gas production (volume (ml)/200 mg DM) levels (a + b) ranged from 19.2 to 52.2 in B. micrantha and M. angolensis, respectively. The overall levels of nutrients and degradation showed variations, but most of the forages were moderate to high in the nutrient composition and degradability parameters. The ranking of the forages in order of increasing nutritive value into 3 categories of 5 species was as follows: low (B. micrantha < Albizia amara < A. hockii< A. nilotica < Acacia tortilis); medium (A. abyssinica < G. bicolor < Albizia coriaria < A. elatior); and high (Balanites aegyptiaca < A. mellifera < A. senegal < Z. mucronata< M. angolensis). It was concluded that M. angolensis and Z. mucronata were outstanding and had potential for ruminant feed and as protein supplements to low quality tropical basal diets.