Facial Eczema Risk on Marlborough Farms

Implications for Sheep, Beef, and Dairy Systems

Facial eczema (FE) is a significant animal health and production risk for sheep, beef, and dairy farms in Marlborough, particularly during warm and humid late summer and autumn periods. While traditionally associated with the North Island, FE has become increasingly relevant in top-of-the-South regions, including Marlborough, with seasonal conditions now frequently supporting spore development.

FE often causes subclinical liver damage long before visible signs appear, resulting in production losses that are frequently underestimated. Understanding risk factors, guiding grazing practices, using tolerant genetics, and regular spore counting are all central to managing FE effectively.

What Is Facial Eczema?

Facial eczema is caused by ingestion of sporidesmin, a toxin produced by spores of the fungus Pseudopithomyces chartarum (formerly Pithomyces chartarum). The fungus grows on dead pasture litter at the base of the sward in warm, humid conditions, typically when ground temperatures exceed 12 °C for several consecutive nights.

Once ingested, sporidesmin damages the liver and bile ducts. This prevents normal excretion of chlorophyll breakdown products, leading to photosensitisation, skin damage, reduced growth, infertility, production loss, and occasionally death.

Why Marlborough Farms Are at Risk

Although Marlborough is generally considered drier than many North Island regions, FE risk increases when:

• Warm nights coincide with periods of humidity or rainfall

• Pastures contain significant dead litter

• Stock are forced to graze tightly or graze out pasture bases during feed shortages

Seasonal risk typically runs from January through May, but danger periods vary widely between years and locations.

Impact on Sheep, Beef, and Dairy Production

Sheep and Beef

• FE can reduce lamb growth rates, ewe fertility, and carcass performance

• In sheep, significant liver damage often occurs without visible facial skin lesions

• Young stock are particularly vulnerable, and growth checks can persist long after exposure

Dairy Cattle

• For every cow showing clinical FE, up to ten more may have subclinical liver damage

• Subclinical FE can reduce milk production by up to 50%

• Liver damage is permanent and can impact future performance and calving outcomes 

Grazing and Pasture Management Recommendations

Where and how animals graze greatly influences FE risk:

High-Risk Grazing Situations

• Hard grazing during FE risk periods

• Pastures with heavy ryegrass dominance and soft litter accumulation

• Grazing stressed paddocks after drought breaks or rapid regrowth following rain 

Risk-Reducing Strategies

• Avoid grazing animals down to the pasture base during risk periods

• Use lighter stocking rates and longer rotations

• Allocate safer pastures (e.g. higher residuals, lower litter) to young stock and high-value animals

• Prefer tall-fescue-based or diverse pasture systems where possible, as these generally produce lower spore counts than perennial ryegrass 

The Role of Genetics in Long-Term Control

Genetic tolerance does not prevent exposure to FE but reduces liver damage for the same spore challenge.

• Selecting FE-tolerant rams and bulls is one of the most effective long-term strategies for sheep and beef farms

• Genetic gains are cumulative, meaning consistent selection delivers measurable benefits within a few generations

• FE-tolerant stock cope better with unavoidable exposure when management controls are stretched

Why Spore Counting Is Essential

FE Risk Is Invisible

Pasture can look green and healthy while harbouring dangerous spore levels. Visual assessment alone is unreliable. 

What Spore Counting Provides

Spore counting:

• Measures the number of P. chartarum spores per gram of pasture

• Identifies when risk thresholds are exceeded

• Allows timely, evidence-based decisions about grazing, zinc protection, or pasture switching

Why Local and On-Farm Counts Matter

Spore counts vary:

• Between districts

• Between farms

• Between paddocks on the same farm

Regional monitoring is useful, but on-farm spore counts provide the most accurate risk assessment for individual properties. 

Counts are best taken just before grazing, as this reflects actual exposure risk to stock.

Integrating FE Management on Marlborough Farms

An effective FE strategy combines:

• Spore counting to understand current and emerging risk

• Grazing management to minimise spore intake

• Genetic selection to reduce long-term susceptibility

• Early planning before risk periods develop, as FE cannot be treated once liver damage has occurred

Conclusion

Facial eczema is a seasonal but highly variable threat for sheep, beef, and dairy farms in Marlborough. With climate variability increasing, reliance on historical expectations is risky.

Regular spore counting, informed grazing decisions, and long-term genetic improvement form the foundation of sustainable FE control. Farms that proactively manage FE protect animal welfare, productivity, and farm profitability, even in challenging seasons.