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.

Feed and fuel: the dual‐purpose advantage of an industrial sweetpotato

“…Other studies have demonstrated similar trends. Three of four cultivars compared in Swaziland decreased from an average CP of 190 g kg −1 DM at 70 DAP to 140 g kg −1 DM at 110 DAP . The CP of the C‐15 vines decreased from 175 g kg −1 DM at 60 DAP to 122 g kg −1 DM at 165 DAP .…”

“…Five cultivars grown in different regions of Ghana had fresh vine yields ranging from 8 to 28 t ha −1 , with an average of 12 t ha −1 in the coastal region and 22 t ha −1 in the forest region . Four cultivars grown in Swaziland had fresh yields ranging from 24 to 57 t ha −1 at 90 DAP, while the same four cultivars produced 52–144 t ha −1 at 110 DAP . Yields reported on a DM basis include two cultivars grown in the Turrialba Valley of Costa Rica, which produced 3–4 dry t ha −1 .…”

“…The nutritional value of the vines is recognized in some parts of the world as they are harvested for human food in many parts of Asia and the developing world . Several studies have also demonstrated their effective use as a protein‐rich supplement for livestock, including cows, pigs, goats and poultry . Unfortunately, sweetpotato vines are not currently utilized in the USA and most producers discard them at harvest .…”

Effects of Lactobacillus formosensis S215T and Lactobacillus buchneri on quality and in vitro ruminal biological activity of condensed tannins in sweet potato vines silage

“…We have demonstrated in our previous study that sweet potato vines have the potential to be an alternative feed resource for ruminants (Ali et al . ).…”

“…Sweet potato is known to contain antinutritional factors, such as condensed tannins (Phale and Madibela ), which have been reported to interfere with ruminal nitrogen (N) degradability (Ali et al . ). Preserving tannin‐containing forages may reduce the concentration as well as the biological activity of condensed tannins thereby improving the feed value of the silage.…”