title: Chemical composition, nitrogen degradability and in vitro ruminal biological activity of tannins in vines harvested from four tropical sweet potato (Ipomoea batatas L.) varieties.
abstract: This study investigated the potential of vines from four sweet potato varieties (Tia Nong 57, Tia Nong 66, Ligwalagwala and Kenya) as alternative feed resources for ruminant livestock. The chemical composition [neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP) and acid detergent insoluble nitrogen (ADIN)], in vitro ruminal nitrogen (N) degradability and in vitro ruminal biological activity of tannins in the vines, harvested at 70 and 110 days after planting (DAP), were determined. Variety and harvesting stage did not (p > 0.05) influence CP and NDF content of the vines. Concentration of CP ranged from 104.9 to 212.2 g/kg DM, while NDF ranged from 439.4 to 529.2 g/kg DM across harvesting stages and varieties. Nitrogen degradability (ND) at 70 and 110 DAP was highest (p < 0.05) in Ligwalagwala (743.1 and 985.0 g/kg DM, respectively). Treatment of vines with tannin-binding polyethylene glycol (PEG) increased (p < 0.05) in vitro ruminal cumulative gas production parameters (a, b and c). The in vitro ruminal biological activity of tannins, as measured by increment in gas production parameters upon PEG inclusion, had a maximum value of 18.2%, suggesting low to moderate antinutritional tannin activity. Ligwalagwala vines, with highly degradable N, would be the best protein supplement to use during the dry season when ruminant animals consume low N basal diets and maintenance is an acceptable production objective. Tia Nong 66 and Kenya varieties, with less degradable N, may be more suitable for use as supplements for high-producing animals such as dairy goats.
authors.affiliation: Department of Food Production, Faculty of Food and Agriculture, The University of the West Indies, St. Augustine, Trinidad & Tobago.
authors.forename: R
authors.initials: R
authors.lastname: Ali
authors.affiliation: Department of Animal Science, Faculty of Agriculture, Science and Technology, North-West University, Mmabatho, Mafikeng, South Africa.
authors.forename: V
authors.initials: V
authors.lastname: Mlambo
authors.affiliation: Department of Animal Science, Faculty of Agriculture, University of Swaziland, Luyengo, Swaziland.
authors.forename: M C
authors.initials: MC
authors.lastname: Mangwe
authors.affiliation: Department of Animal Science, Faculty of Agriculture, University of Swaziland, Luyengo, Swaziland.
authors.forename: B J
authors.initials: BJ
authors.lastname: Dlamini
mesh_terms: D000818:Animals; D019149:Bioreactors; D027723:Ipomoea batatas / Q000737:chemistry* / Q000145:classification; D009584:Nitrogen / Q000737:chemistry*; D012417:Rumen / Q000378:metabolism*; D013634:Tannins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D013634:Tannins; D009584:Nitrogen
keywords: antinutritional effects; foliage; harvesting stage; in vitro ruminal fermentation; nutritive value