Roots & Vines as Animal Feed
Feed without buying feed
On a mixed farm, sweet potato is two crops in one: the roots feed people, and the vines — a third of the above-ground biomass — feed animals. Used well, the crop can supply pig, poultry and dairy rations without a single bag of purchased concentrate. This guide covers what to feed, how much, and how to turn crop "waste" into a feed budget.
At a glance
- Vine yield
- Roughly 10–20 t/ha fresh vines — often wasted
- Root dry matter
- 25–35% — an energy feed, not a protein feed
- Best fit
- Pigs, then poultry; dairy as a supplement
- Golden rule
- Feed fresh or ensile — never let vines rot
- Watch out
- Weevil-damaged roots carry bitter toxins (see Pests)
What the crop actually produces
Harvest leaves behind more than roots. A typical field produces 10–20 t/ha of fresh vines — about as much dry matter as the roots themselves, but most of it is left to wilt in the field. Vines are a genuine feed resource:
- Energy. Roots are a carbohydrate feed — high in digestible energy, low in protein. Think of them as the farm's own maize substitute.
- Protein from leaves. The leaves are the protein-rich part of the vine: 20–30% crude protein on a dry basis in young leaves, falling as vines age.
- Fibre. Mature stems add fibre, good for ruminants, less so for pigs and poultry.
Because the two parts balance differently, the classic smallholder strategy is roots for energy + vines for protein — a combination that replaces a surprising share of purchased concentrate.
| Part | Dry matter | Crude protein (DM) | Best suited to |
|---|---|---|---|
| Fresh roots | 25–35% | 3–7% | Energy for pigs, poultry, dairy |
| Young leaves | 15–20% | 20–30% | Protein for poultry, pigs |
| Mature vines + stems | 18–25% | 10–15% | Ruminants (dairy, goats, cattle) |
| Silage (chopped vines) | 25–30% | 12–16% | Dry-season dairy and pig feed |
Pigs: the classic sweet potato animal
Pigs and sweet potato are a traditional pairing across Asia, Africa and the Pacific — and for good reason. Pigs digest root starch efficiently, and they'll eat vines and culls that have no market value. A practical growing-pig ration:
- Boiled or raw roots as the energy base — up to half the ration for growers.
- Chopped fresh vines or leaves as the protein/roughage supplement.
- A protein top-up where vines are short — legumes, fishmeal, or a small concentrate ration.
Roots should be cooked or at least chopped for younger pigs; whole raw roots can pass through partly undigested. Cull and cracked roots — the ones no market will take — are the cheapest energy a pig farm can buy.
Field guide: a simple pig ration (per day, growing pig ~40 kg)
- 2–3 kg chopped fresh roots (or 1 kg boiled)
- 1–2 kg chopped fresh vines/leaves
- 0.2–0.3 kg protein supplement where available
- Fresh water always
Poultry: vines as the green feed
Chickens cannot handle the bulk of roots or mature stems, but they love finely chopped young leaves — a free source of vitamins and a little protein. Scattered daily, fresh leaves reduce bought-in vitamin premix and give birds something to scratch at. Boiled root can also be offered as an energy treat, but it must be fresh — poultry feed spoils fast.
Dairy: a dry-season silage lifeline
For ruminants, the real value of sweet potato vines is silage that bridges the dry season. Chopped vines wilted briefly and packed airtight ferment into a palatable silage that keeps for months — feed for the months when pasture is straw. Root silage (chopped roots packed with vines or dry forage) is a higher-energy version used widely in Asia.
Pro tip: wilt before ensiling
Wilt chopped vines for a few hours until they reach roughly 25–30% dry matter before packing. Too wet, and the silage turns butyric and smelly; too dry, and it won't ferment properly. Pack hard, seal airtight, and open only from one end.
Safety: what never to feed
- Weevil-damaged roots — the bitter, discolored tissue around weevil tunnels contains toxic terpenoids (ipomeamarone); trim it off before feeding (see Pest Management).
- Moldy roots or silage — never feed spoiled material; mold can carry mycotoxins.
- Raw, whole roots to young animals — chop or cook to avoid choking and poor digestion.
- Sprayed vines — respect pesticide withholding periods before feeding vines to animals.
The feed budget arithmetic
Feeding the crop's by-products changes the farm's economics in two ways: purchased feed falls, and waste falls. A hectare producing 15 t of roots and 15 t of fresh vines supplies a pig enterprise a large share of its energy and green feed for the season. Even where land is tight, an intercropped or edge-planted block of vines (see Permaculture) can feed a household flock. For the business case of processing and selling surplus instead, see Processing as a Micro-Enterprise.
Frequently asked questions
Can I feed raw sweet potato to pigs?
Yes — chopped or whole for mature pigs. Cooking improves digestibility for young pigs, but raw chopped roots are standard practice on many farms. Never feed weevil-damaged tissue raw.
Are the leaves poisonous?
No — sweet potato leaves are a normal livestock feed and a human vegetable across Asia. What is toxic is the bitter terpenoid tissue in weevil-damaged roots.
How do I make vine silage without equipment?
Chop, wilt to 25–30% dry matter, pack into a pit or heavy plastic bags/barrels, exclude air completely, weight it, and seal. Open from one end and use within days of opening.
Is feeding vines bad for the soil?
Removing vines exports some nutrients, so replace them with manure or compost (see Organic & Regenerative Practices). The manure from animals fed on vines returns most of it to the field.
Sources & further reading
This article distills field practice and science from the organizations below. Always confirm variety, chemical, and practice recommendations with your local extension service.