Tropentag, September 16 - 18, 2015, Berlin, Germany "Management of land use systems for enhanced food security – conflicts, controversies and resolutions"

Vines of the Sweet Potato (Ipomea batatas): A Valuable Feed Supplement for Ruminants in Small Holder Systems

¹International Livestock Research Institute (ILRI), Kenya
²Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Atmospheric Environmental Research, Germany

Abstract

Availability of suitable feed, and in particular sources of protein-rich food, is a major constraint to increasing the productivity of smallholders in sub-Saharan Africa it is difficult to justify diverting land from growing crops for human consumption. The roots of the sweet potato are a high energy cash crop, and the leaves and vines (SPV), usually treated as rubbish, are high in protein and have been identified as a valuable livestock feed. Additionally sweet potato has a prodigious dry matter yield (equivalent to 7.3 and 7.5 t/ha for vines and roots respectively) when fertilised and tilled and thus has the potential to make a major contribution to livestock feeding requirements, while providing a high yielding crop for human consumption or sale. Recently, SPV silage (SPVS) has been posited as a way to even out seasonal shortfalls in feed production for smallholders.
For the first time we conducted a feeding trial to assess simultaneous effects of SPVS on intake, live weight gain (LWG), daily methane production (DMP) and methane emissions intensity (MEI). We fed SPVS (DE: 12.8 MJ/kg; CP: 156 g/kg, DM) to growing Dorper wethers (n=20; LW:18 kg SEM:1.3kg) at 5 inclusion levels (0, 20, 40, 60, 80% as fed) while they consumed a basal diet of chopped maize stover (DE: 10.7 MJ/kg; CP: 46 g/kg, DM) for 70d.
Sheep consuming SPV silage included at 40% (20% DM basis) maintained LW, while those consuming diets at 60 and 80% inclusion levels had significantly higher voluntary intakes (P< 0.01), LW gain (P<0.05) and lower MEI (P<0.05) than those consuming maize stover alone or SPVS at the 20% inclusion rate.
We conclude that SPVS has the ability to significantly improve productivity and decrease MEI in animals fed low-quality basal diets, and should be offered optimally at 24-32 g/kg LW (as fed) to animals receiving only poor quality pasture or stovers.

Keywords: Enteric methane emissions, livestock, supplement, sweet potato

Contact Address: John Goopy, International Livestock Research Institute (ILRI), Nairobi, Kenya, e-mail: j.goopycgiar.org