Pasture Guide for New Zealand Horse Owners

This guide is tailored to New Zealand pasture conditions and seasonal growth patterns. It highlights common pasture plants that can affect horse health, what to watch for, and when risk is highest.

Ryegrass (Perennial & Annual)

Common in NZ: Very high – dominant pasture species

Main risks: Endophyte toxins (perennial ryegrass), high potassium, excess sugars/energy

Highest risk seasons:

• Spring: Rapid lush growth, high sugars

• Autumn: Regrowth after rain, fertiliser use

• After drought-breaking rain at any time of year

Warning signs:

• Nervous or spooky behaviour

• Excessive sweating

• Muscle tightness or trembling

• Poor coordination or stumbling (ryegrass staggers)

Management tips:

• Remove affected horses from pasture immediately

• Feed low-rye, low-clover hay

• Be cautious with ryegrass hay (toxins can persist for months)

Kikuyu Grass

Common in NZ: North Island and warmer coastal regions

Main risks: High oxalates, calcium binding, potassium spikes

Highest risk seasons:

• Late spring through summer

• After rain following dry or drought conditions

Lower risk:

• Short, dormant, or winter kikuyu

Warning signs:

• Weakness or stiffness

• Poor growth or bone issues in young horses

• Behaviour changes

• Colic or diarrhoea

Management tips:

• Avoid grazing long or lush kikuyu

• Supplement with bioavailable calcium

• Take extra care with foals, young horses, and lactating mares

Clover (White & Red) and Lucerne

Common in NZ: Widespread in mixed pastures

Main risks: High protein and energy, photosensitivity in some horses, laminitis risk in susceptible horses

Highest risk seasons:

• Spring and early summer when growth is lush

• Dry periods when clover dominates over grass

Warning signs:

• Sunburn or scabs on white or pink skin

• Weight gain

• Increased laminitis risk

Management tips:

• Limit access when clover dominates pasture

• Avoid for horses with EMS, PPID, or laminitis history

• Provide adequate fibre from low-sugar hay

Catsear (Flatweed)

Common in NZ: Very common, especially in dry or overgrazed paddocks

Main risks: Linked to stringhalt with heavy, long-term intake

Highest risk seasons:

• Late summer and autumn

• During dry conditions and feed shortages

Warning signs:

• Jerky or exaggerated hind leg movement

• Difficulty backing up

Management tips:

• Avoid overgrazed paddocks

• Rotate grazing and improve pasture quality

• Seek veterinary advice if symptoms appear

Seasonal Risk Summary (NZ)

Spring:

• High sugar and rapid pasture growth

• Increased laminitis and ryegrass risk

Summer:

• Kikuyu oxalates and potassium spikes

• Catsear dominance in dry paddocks

Autumn:

• Regrowth after rain increases ryegrass toxicity risk

Winter:

• Generally lower pasture risk

• Be cautious with ryegrass hay and sudden pasture changes

General NZ Pasture Safety Tips

• Avoid overgrazing, especially in summer and autumn

• Introduce horses to new pasture gradually

• Provide supplementary low-sugar, low-rye hay when grass is limited

• Monitor behaviour and movement closely during seasonal changes

• When in doubt, remove the horse from the pasture first and investigate second

Key message: Many pasture-related health issues in NZ horses are seasonal and preventable with good grazing management and balanced mineral support.

 

 

 

Brown Top

 

 

Regarded by some as a weed grass, because of its low quality, but for horse owners it is a very useful addition to pasture. It is non-endophyte, high roughage, low sugar and horse-friendly. It persists well in low-fertility soil, dominating unimproved hill and upland pastures, or poorly managed lowland pastures. Its quality can be improved with fertilizer. Its fine, dull leaves densely cover the ground and tend to smother clover growth which is a good thing! Seed can be purchased from most pasture seed suppliers.

 

 

Kentucky Bluegrass - Poa pratensis

 

 

Is a perennial species of grass native to practically all of Europe, northern Asia and the mountains of Algeria and Morocco. . The Spanish brought the seeds of Kentucky bluegrass to the New World in mixtures with other grasses. This grass does very well in NZ. It is high roughage, low sugar, non-endophyte and horse-friendly. Its is a valuable pasture plant, and prefers well-drained, fertile soil. It is also used for making lawns in parks and gardens.  

 

Prairie Grass - One from the "Brome" family of grasses

 

 

Studies conducted in New Zealand by AgResearch in the mid 90’s concluded that this grass is the horse’s favourite. In many ways this is a good thing as it is non-endophyte but it is reasonably high in sugar and does lack persistence when sown in pasture. Grazing brome and Smooth brome have better persistence in pasture and so would be a better addition to a mix for resowing.

 

Cocksfoot

 

 

The grass pictured is non-endophyte Cocksfoot. This is a horse-friendly grass that comes in a number of different varieties which are usually classed as "clumping" or "non-clumping" The first picture shows somewhat how it grows in clumps. This growing habit tends to be the older varieties whereas the newer varieties grow more evenly throughout pasture. This is a generally persistent grass but can take a few years to become properly established. Seed is available from grass seed merchants and they can recommend the best variety for your pasture situation. 

 

 

Timothy grass – or meadow cat's-tail

 

Timothy is a perennial non-endophyte, horse-friendly grass that grows in late spring and early summer and has low drought tolerance. It generally grows well in the South Island but can be planted in cooler inland area of the North Island. It provides high quality pasture and hay and is also grown as a chaff crop. In the USA it is grown for use in hay cubes.

 

 

Yorkshire Fog - or Fog Grass

Yorkshire Fog is a common perennial non-endophyte, horse-friendly grass that thrives in wet, infertile, acid soils. It is a very dense, hairy grass that can become dominant and unpalatable if not kept under control.  Horses do not really like to eat it but it is ideal for planting as part of a mix for horses that tend to be overweight. When cut as hay it needs plenty of drying so it does not become musty. Seed can be purchased for resowing and is a good option where less nutritious pasture is needed.  

The following grasses are ok in your pasture but do not look to sew them - 

Sweet Vernal

This is quite a common grass in North Island pasture. Has a sweet smell which comes from the coumarin, a naturally occurring chemical found in many plants, but in excess has a bitter taste which most likely is to deter animals from grazing on it. It also is an appetite suppressant. It is very common in pasture and generally horses consume it without problems. There is a "But” though…if the plant becomes mouldy, certain fungi will convert the coumarin into dicoumarol, a substance that inhibits normal blood clotting. Dicoumarol substance was responsible for the bleeding disease known historically as "sweet clover disease" in cattle eating mouldy sweet clover silage.

Check if your hay has sweet vernal and do not feed if it has any sign of being mouldy.  

Plantain

The broadleaf weed or plant is considered safe for horses but they do not really like it. It survives in over-grazed situations and sometimes is the only plant in hard grazed areas of pastures. It can be high in problem sugars so is unsuitable for metabolic or laminitic horses.  

 

 

 

 

 

 

 

Paspalum