Tannin content, nutritive value and dry matter digestibility of Lonchocarpus capassa, Zizyphus mucronata, Sclerocarya birrea, Kirkia acuminata and Rhus lancea seeds

Tree seeds are a potentially valuable source of nutrients for livestock in Botswana but their use has been limited by scant research on their chemical and nutritional properties. Seeds of five browse trees from the hardveld region of Botswana were analysed for condensed tannins, proximate composition, in vitro dry matter digestibility and mineral elements. Content (% DM) of condensed tannins as determined by the butanol-HCl method were 2.62, 3.09, 3.10, 4.26 and 5.07 for Sclerocarya birrea, Zizyphus mucronata, Kirkia acuminata, Lonchocarpus capassa and Rhus lancea, respectively. The seeds contain low crude proteins (% DM) at 7.08, 6.17, 10.96 and 7.79 for, Z. mucronata, S. birrea, K. acuminata and R. lancea, respectively, except L. capassa with 54.2% crude protein. The dry matter digestibility (%) ranged from 7.95 for S. birrea to 72.34 for L. capassa. This coupled with low condensed tannin content suggests that some of them may be valuable protein supplements in ruminant diets. The NDF (%) and ADF (%) ranged from 24.53 and 8.70 in L. capassa to 80.33 and 67.10 in S. birrea, respectively. In general, the seeds had adequate quantities of phosphorus, calcium, magnesium, potassium, iron and copper to meet requirements for beef, sheep and goat production. The content of sodium, manganese and zinc (except in L. capassa) were below recommended levels required by ruminants for growth and productivity. The study suggested that these browse seeds serve as potential nutrient sources for free grazing animals on the ranges in Botswana. (C) 2001 Elsevier Science B.V. All rights reserved.