Copper Deficiency in Sheep: Recognition, Prevention and Treatment

Copper Deficiency (Swayback and Pine) in Sheep

Copper deficiency is a significant metabolic disease in sheep with serious welfare consequences. It occurs in two forms: primary copper deficiency (inadequate dietary copper) and secondary (conditioned) copper deficiency, where antagonists in the diet prevent copper absorption despite apparently adequate dietary levels. The UK has significant areas of pasture with naturally low copper availability, and certain soil types — particularly peaty soils and those high in iron, sulphur, or molybdenum — create high-risk environments.

Clinical Presentations

Swayback (Enzootic Ataxia)

The most dramatic presentation of copper deficiency, swayback affects lambs and occurs in two forms:

Congenital swayback: Lambs born with severe neurological deficits — inability to stand, trembling, blindness. Caused by copper deficiency in the ewe during early pregnancy preventing normal myelination of the central nervous system. Affected lambs cannot survive without intensive nursing care.
Delayed swayback: Appears at 3–6 weeks of age. Progressive hind limb ataxia (swaying, stumbling), often deteriorating to paralysis. Less severe neurological damage may respond partially to copper supplementation, but full recovery is unlikely once signs are present.

Pine (Ill-Thrift)

The more common and often overlooked presentation. Affected sheep show:

Poor growth rate and weight gain (particularly in lambs 3–6 months)
Dull, rough fleece lacking crimp (steely wool)
Pallor of mucous membranes (anaemia)
Depigmentation of black wool (fading to rusty brown)
Immunosuppression — increased susceptibility to infections
General lethargy and poor condition

Causes and Risk Factors

Dietary Antagonists

Secondary copper deficiency is more common than primary deficiency in the UK. Key antagonists that reduce copper absorption:

Molybdenum: Forms insoluble thiomolybdates in the rumen that bind copper. Pastures over limestone or "teart" (high-Mo) soils are particularly high-risk
Sulphur: Works synergistically with molybdenum; high-sulphur feeds and water sources increase risk
Iron: High dietary iron (from soil contamination of herbage) interferes with copper metabolism

Soil and Pasture Risk Factors

Peaty, acidic soils — naturally low copper
Limed heavy land — may increase molybdenum availability
Flooded or waterlogged pastures — sulphur accumulation
Brassica-rich diets (high in sulphur compounds)

Diagnosis

Diagnosis requires a combination of:

Clinical signs consistent with deficiency
Blood copper levels (plasma copper <9 μmol/L suggests deficiency; liver copper more sensitive)
Pasture and herbage copper analysis
Molybdenum and sulphur analysis to identify antagonism
Response to treatment (retrospective diagnosis)

Note: Sheep are also highly susceptible to copper toxicity — excess supplementation carries serious risk. Always diagnose before supplementing.

Prevention and Treatment

Supplementation Options

Boluses: Copper oxide wire particle (COWP) boluses provide slow-release copper over 4–6 months. Highly effective for individual animals in high-risk herds
Injections: Copper calcium EDTA injections (subcutaneous) — act rapidly but shorter duration. Use only under veterinary guidance
Dietary supplementation: Adding copper sulfate to mineral licks or compound feed. Requires accurate calculation to avoid toxicity
Top-dressing: Copper sulfate applied to pasture — lower efficacy, environmental concerns

Breeding and Genetic Considerations

Some sheep breeds (particularly Texel crosses, Romney Marsh, and Suffolk) are more susceptible to copper toxicity and require lower supplementation rates. Some breeds (Scottish Blackface, Welsh Mountain) cope better with low-copper environments. Breed selection appropriate to local soil conditions reduces metabolic disease risk.

Welfare Priorities

Ewes should be supplemented in mid-pregnancy (day 80–100) to prevent congenital swayback
Monitor lambs in high-risk flocks closely from birth — early signs of swayback require immediate veterinary assessment
Pine-affected lambs may suffer from chronic subclinical ill-thrift — subclinical deficiency is a welfare issue even without overt neurological signs