Pastures for horses
Angela Avery, Rutherglen
Updated: September 2006
The pasture species selected should be based upon the environment and the needs of horses and managers. Good management involves sowing a range of pasture mixes to utilise the benefits of different species and different paddock conditions. The main factors to consider when selecting a pasture mixture include:
Rainfall distribution and reliability
Rainfall is the most important climatic factor. Both the total rainfall and the distribution of that rainfall throughout the year determines the growing season and therefore the species that will persist in an environment.
Soil nutrient level
Most pasture species require fertile soils to remain productive. Fertile soils are required to obtain the best results from species like short-lived ryegrasses. Species such as cocksfoot can tolerate poorer soils.
A large proportion of the soils in south eastern Australia are acid. The high levels of soil aluminium frequently associated with acid soils will restrict the suitability of soils to grow lucerne, which is highly sensitive to acid soils.
Soil physical characteristics
Heavy clay soils require more rainfall to wet-up and commence pasture growth in autumn than do light sandy soils. Heavy soils retain the moisture for longer periods into late spring and summer and may be able to support species that would not otherwise be normally grown in that rainfall zone. Phalaris prefers heavy soils whereas cocksfoot prefers light sandy soils. Lucerne and cocksfoot will not grow on poorly drained soils.
Perennial ryegrass has proved itself a premium feed because of its high digestibility. Rainfall and the severity of summer conditions govern where perennial ryegrass can be grown. In areas that experience hot dry summers, such as north east Victoria and southern NSW, perennial ryegrass is unlikely to persist with less than 700 mm annual rainfall. However, in regions with cooler and/or wet summer conditions perennial ryegrass will grow when the annual rainfall is above 600 mm.
Soils should be high in fertility and of medium to heavy texture. Perennial ryegrass is easy to establish and produces high quality forage. It is most productive in autumn and spring but given suitable conditions perennial ryegrass can grow through most of the year.
The selection of different varieties will also increase the ability of a perennial ryegrass pasture to grow throughout the year. Perennial ryegrass contains endophyte, a fungus that lives in the ryegrass plant. The levels of endophyte differ between varieties and between seed batches. Endophyte has been shown to cause "ryegrass staggers" in horses in New Zealand. Ryegrass staggers is a nerve and muscle disorder that causes horses to tremble. They are unable to move and can fall down. It is not usually fatal and affected horses normally recover when offered non-toxic feed.
Cocksfoot is more drought tolerant than perennial ryegrass but less tolerant than phalaris and requires a minimum of 450 mm annual rainfall. It is well suited to light textured soils with low moisture holding potential. Cocksfoot will not tolerate waterlogging, is slower to establish than perennial ryegrass, is less nutritious than perennial ryegrass and phalaris. The lower nutritive value and palatability of cocksfoot means that it is normally grown where perennial ryegrass and phalaris will not
persist well or in a mixture with one of the other perennial grasses.
European types of cocksfoot have the greatest potential for summer growth. Without adequate follow-up rainfall, intermittent bursts of growth can use up stored food reserves and kill out a large percentage of the plants. Cocksfoot does not contain animal toxins and it has few serious pests and diseases. Cocksfoot pastures tend to form tussocks through poor grazing management and can severely restrict clover development.
Tall fescue is a perennial grass suited to regions that receive above 600 mm of annual rainfall. Rainfall should summer dominant and represent approximately 60% of the total rainfall. Tall fescue is suited to medium to heavy textured soils and tolerates wet, acidic and moderately salted soils. Tall fescue is slow to establish, sensitive to grazing until properly established and is less productive than other perennial grasses in winter but will grow in spring, summer and autumn when there is adequate moisture. Tall fescue is highly nutritious and compares favourably with ryegrass. There are now also more winter-active cultivars of Tall fescue which have greater production in winter than the traditional Tall fescue cultivars.
Phalaris is a perennial grass that is grown in areas too hot and dry for perennial ryegrass, that is normally areas bellow 700 mm annual rainfall. Phalaris is suited to heavier soils and will tolerate waterlogging. It will however not tolerate high levels of aluminium commonly associated with acid soils. Phalaris seedlings are not vigorous and cannot withstand competition from weeds or more vigorous pasture species. It is productive over the autumn, winter and spring periods. Persistence problems experienced in some eastern states have been attributed to soil fertility, acidity and grazing management.
Phalaris stems need to be allowed to elongate in spring to form dormant buds at the base of the plant. These buds allow phalaris to survive over summer. This is particularly important with a newly sown phalaris pasture. Alkaloids in phalaris can cause sudden death and phalaris staggers in sheep during the autumn and winter when phalaris is the dominant species. It has not been shown to have these effects on horses.
Subterranean clover is an annual pasture legume that is grown in most pastures in southern Australia. To maintain clover in the pasture it is vital that plants are allowed to set seed each year. Varieties vary in the time they mature, those that mature early tend to be less productive. The variety selected must flower and complete seed development while there is sufficient soil moisture. The lower the annual rainfall the earlier the variety of clover sown. Clovers also have different levels of hard seed. These levels are important as they protect against the depletion of the seed stored in the soil by summer storms, false autumn breaks and dry springs. In districts with reliable autumn and spring conditions satisfactory production and persistence will be achieved from the late maturing varieties. Conversely, in districts with short and unreliable growing seasons, early to mid season varieties of sub clover should be sown. Some varieties of sub clover have special features for example, the sub species Trifolium yanninicum or white seeded clovers (Trikkala, Larisa and Gosse) will better tolerate wet winter soils than other groups of sub clover.
White clover is a perennial legume suited to regions that receive an annual rainfall above 750 mm or irrigation. It is easy to establish and has a prostrate growth habit, with the stems forming runners which spread across the soil surface and take root at the nodes. White clover grows most vigorously when conditions are mild. It will not grow well in cold winters and will die off during long, hot dry periods. Stolons can survive short dry spells even after the top growth has died off. When white clover plants die, regeneration is dependent on the seed reserves built up in the soil. In marginal regions white clover is often worthwhile in a pasture even when it may only persist for a few years. White clover will grow over a wide range of soil types and fertility levels and is capable of high production (mainly spring, summer and autumn) when fertility is high. Drought resistance is low. Persistence can be enhanced by maintaining vegetative cover and by reducing grazing pressure over dry periods. The smaller leafed varieties tend to be more persistent under drier conditions and harder grazing.
Lucerne is a high producing, highly nutritious perennial legume that is capable of growing in a wide range of environments. Lucerne will not grow on acid (soil test is essential to ensure the paddock suitability for lucerne) or wet soils (two-wheel drive car should be able to travel over the paddock all winter). Lucerne paddocks must be rotationally grazed and can cause cattle to bloat. On horse enterprises the best use of pure lucerne is for short grazings or for hay production. Lucerne has the ability to provide quality feed in summer as it has a deep tap root that makes use of summer rainfall. It can be grown with or without irrigation.