Chemical composition and degradability of Brachystegia spiciformis (musasa) leaves and stems harvested over 4 months from three sites in Zimbabwe

Brachystegia spiciformis terminal shoots (leaf and young stems) samples were harvested from September to December 1994 at Grasslands and Henderson Research Stations and Gwebi College of Agriculture. The samples were analyzed for crude protein (CP), ash, phosphorus, neutral detergent fibre (NDF) and acid detergent fibre (ADF) content. Four rumen cannulated steers were used to determine degradability profiles of dry matter and nitrogen using the nylon bag technique. Significant differences (P < 0.05) between sites and month of sampling for CP, ash and phosphorus, NDF and ADF were found. The CP content of the samples ranged from 82 to 120 g/kg DM. Lower CP levels were found in stems as compared to the leaf. Ash content ranged from 30 to 45 g/kg DM with samples from Grasslands significantly (P < 0.05) lower than those from the other two sites. The phosphorus levels were strongly affected (P < 0.05) by both the site and month of sampling and declined with time. The phosphorus values ranged from 1.23 to 2.67 g/kg DM. The stems were more fibrous than the leaves. From the exponential equation used in the degradability studies the soluble fraction (a) in the dry matter ranged from 17.6 to 29.9 and there were significant differences (P < 0.05) between both site and month of sampling. The potentially degradable fraction (b) in the DM was not affected by either site or month. The effective degradability at passage rates of 0.02, 0.05 and 0.08 passage rates were significantly affected (P < 0.05) by both the site and month of sampling. The degradability values at 0.02 passage rate were low, ranging from 33.5 to 56.2 and also showed a decline from October to December.