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Grass and Pasture in New Zealand – The What, Why, How of Grazing and Grass Related Issues for Horses


Maintaining Grazing Paddocks for Horses

New Zealand is the land of green pastures with many different grasses and plants growing in them. In the main, grass is the best fodder for a horse, it is natural and balanced with fibre, carbohydrates, fats and protein, some minerals and most vitamins. 

However, some grasses are better than others and only the best of equine dedicated properties can choose which grasses are grown. Many owners have horses on land where there they cannot have a say on the composition of the grazing. Many agistment properties are over grazed and not replenished so they become quite poor in the quality of the pasture, and weeds take over – some of them dangerous to horses. 

To get the best out of the property you are on, good maintenance will help maximise the quality in terms of nutritional value to the horse. A clear plan should be set up to ensure horses are rotated so paddocks are rested until they recover. As soon as the horse is moved, the area should be mown (that kills many weeds) and harrowed to aerate the soil and spread the poo. Ideally poo should be picked up from small paddocks but sometimes this is not always a possibility so harrowing will prevent it from clumping and souring the soil. Fertilising is a good option too, even just spreading lime can rebalance the pH of the soil and help improve growth. Spraying may be necessary for heavy infestation of persistent weeds, but regular mowing can reduce that need. Note that short grass has a much higher sugar level than long grass so allow the resting paddock to grow long before returning a horse that may be susceptible to high sugar intake which can create more energy, (for more information read the article ( or too much weight (for more, read the article ‘Laminitis from Dietary Intake’).

Poor Grasses and Weeds to Avoid for Horses

Firstly, nontoxic weeds (eg. blackberry, gorse,dock etc.) will move in on poorly maintained land and take up space, reducing the availability for nutritious grasses. Trampled paddocks can become weedy and poor, as the soil texture is altered and does nor support quality growth. In those conditions supplementing with Vitamin E is needed and a full mineral mix should always be a daily supplement. There are also some weeds and grasses to be avoided as they do have a toxic effect on a horse. 

Ragwort - (Jacobaea vulgaris)

Not normally eaten when growing and flowering  in the paddock but becomes palatable when dead and dry, especially when it is in hay. It is important to know if your hay has come from pastures that have ragwort. It create serious liver disease and can often be fatal. 

Catsear - (Hypochaeris radicata)

It looks like dandelion with a rosette of leaves but it has  multiple yellow flowers on a green hairy stem. Dandelion has one flower per smooth stem. Eating Catsear can cause neurological symptoms like staggers and/or stringhalt. 

Paspalum - (Paspalum spp)

A common pasture grass which grows well in a wet humid Spring or Summer in New Zealand. The sticky seed heads, if eaten, can cause stagger like symptoms, particularly when the seed heads have turned black. Not usually fatal unless the horse falls into a dangerous area and can’t recover. Removing from the pasture will resolve the condition.

Johnson Grass - (Sorghum halepense)

Originally eradicated, there is now a new infestation spreading in New Zealand. It is drought resistant and toxic when young and stressed by trampling, climate etc. The cyanide compound that develops in those conditions can be fatal.  

Tall fescue - (Festuca arundinacea)

This is an Australian species that has recently appeared in New Zealand. It causes equine fescue oedema, obvious signs are swelling of the head, neck, chest and abdomen. Depression and loss of appetite can occur. Some cases have proved fatal. 

Endophyte protected Ryegrass - (Lolium perenne)

Commonly used in dairy pastures, the grass is vulnerable to attack by a weevil and so a fungus was developed to protect the young grass. This fungus is called an endophyte. Ingesting this endophyte can cause staggers – a neurological state that makes the horse unrideable and sometime prone to falling over. 

Kikuyu – (Pennisetum clandestine)

A grass found in the upper part of the North Island on roadside verges and often in horse pasture as it spreads easily by long runners. It is not very good for horses as it does not provide good nutrition and squeezes out the grasses that do. In itself it is not toxic but it is an oxalate grass which does have a negative effect on the uptake of calcium in horses.

For more information read our article Calcium Supplementation- How this relates to oxalate grasses

What are Good Grasses for Horses?

A mix of grasses and legumes – leafy to stemmy, is better than one dominant species. A horse will vary what they eat through the seasons, for example they are likely to graze grasses in the winter and spring, and legumes in the summer and autumn. Also different grasses and legumes grow at different rates throughout the year. There is quite a variety of climate and soil types throughout New Zealand so if you do have the opportunity to sow a paddock then check out the available mixes for equine grazing with your local seed supplier – they will have the best options for a horse in your particular area with regard to soil type and climate. Some mixes don’t contain perennial ryegrass  but if it does not have the endophyte then it is a good addition to a mix for horse pastures. The core of the best grasses for quality nutrition for grazing horses are:

  • Non Endophyte Perennial Ryegrass

  • Timothy

  • Prairie grass

  • Non endophyte Tall fescue

  • Kentucky bluegrass

  • Cocksfoot


  • Alfalfa 

  • Some white clover (limit)

  • Some red clover (limit)

  • Chicory

Other grasses and legumes may be added which provide fibre and may suit certain areas prone to drought for example. The seed specialist will advise on these.


If the paddocks cannot be ploughed and reseeded, sometimes overseeding can assist to improve the quality of the pasture. Again the advice of a local seed specialist is very useful.

Hay and Haylage-Baylage- Is it Good for a Horse?

Hay is grass that has been naturally sun dried and baled in the Summer and usually stored for a season before being fed as a supplementary feed to horses that are on poor pasture or stabled. Hay is not as nutritious as fresh green fodder and the longer it is stored the lower the levels of vitamins and minerals. It makes no sense when owners withdraw their horses from green pasture for behaviour reasons and then feed hay, they are still feeding grass. Fresh pasture is high in sugars which still exist in hay. It is the digestion difficulty of the sugars that creates negative behaviour and can be solved so that the horse can stay on the nutritious pasture.


Hay should smell fresh, have a slight green colour, be totally dry but not dusty, and with no weeds or mould. It should be cut from quality grasses ideal for horses. 

Haylage and Baylage is grass that has been cut earlier (and wetter) than hay and wrapped in plastic to encourage fermentation by anaerobic bacteria. Good quality haylage from a reputable source is digestible and palatable to a horse. However it is vital that the wrapping has no holes (not even pinhole) and that in warm conditions is eaten within a few days of opening. This is because once the seal is broken and it is open to any air for too long, botulism will result and that is extremely toxic to horses. Severe colic and even death may result.

Grass Sickness or Grass Affected Horses – What is This?

Firstly, Grass Sickness is a very serious disease in horses and is mainly prevalent in horses in Great Britain. There have been no recorded instances in New Zealand. A lot of research has been undergone over many years and the causal agent is still unknown, but currently it is thought it may be a soil borne bacteria Clostridium botulinum. Symptoms may start with mild intermittent colic but can also be severe and gut paralysis can develop and is then fatal.

Grass Affected Horses is not a veterinary accepted condition or term, it is a uniquely peculiar New Zealand definition which seems to have arisen as a generalism to describe horses that have changed in attitude to be either full of beans or grumpy and touchy. Some will say it comes from “toxins in the grass”. It should be noted that ingestion of toxins makes animals (and people!) sick, they don’t make them full of beans and energy. Bucket loads of toxin binders are poured into horses in an attempt to remove these mythical toxins. 

The problem truly arises from the horses poor digestion of grass (and feed) sugars and starches, causing mild gut ache as partially digested and fermented feed moves into the hindgut and the lactic acid comes in to break it down. It is easily fixed by feeding a supplement with digestive enzymes which enhance the process in the foregut and relieve the discomfort. The toxin binders on the market are actually a Silicated clay and may help to slow the passage of the feed through the gut. They have been developed overseas primarily for pigs and poultry to remove fusarium moulds from poorly stored and mouldy grains, especially corn. They have never been developed for New Zealand pasture which does not have those moulds. Sadly there is an obsession with these products and a lot of unnecessary clay is being fed to horses, some of whom just feel good and are maybe too bright and energetic for their owners. Maybe Grass Affected Horses should instead be called “Overfed- Underworked Affected horses.”

Removing horses from pasture and locking them up and feeding hay is irrational (hay is grass) and unfair on an animal whose natural environment should allow him freedom to roam and graze. In New Zealand we have so much opportunity for horses to live as natural existence as possible. In other parts of the world horses have to be stabled and this is a complex management issue and carried out by experienced professionals. If your horse is difficult to manage talk to a qualified professional – a veterinarian, an experienced trainer, about their symptoms. It may have nothing to do with the grass. 

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