Dairy cattle need a balanced diet, especially before and after calving, and good pasture growth is important in spring to boost early milk production. Throughout summer it pays to prevent cows grazing pastures to low levels, so they avoid eating the base of the plants and dead matter that could harbour toxins.
Cattle farmed for beef often graze a wider range of pasture types, from high-quality perennial ryegrass and white clover on flat and fertile soils, to pastures dominated by browntop on hill country.
The large areas of brown colouration often seen on hill pastures in the summer and autumn are mainly browntop seed heads.
White clover is an essential nitrogen source for dairy pastures. Red clover can be used under drier conditions where the white clover content of pasture is lower.
The regular use of nitrogen fertiliser, which occurs on many dairy farms, is detrimental to clover and reduces the clover-content of pastures to low levels.
Pasture productivity can be damaged by the treading of cattle and, in wet conditions, can also seriously compact the surface soil and reduce subsequent pasture growth.
Sheep graze pastures much more closely than cattle and are more selective grazers. They prefer clover to grass and enjoy a diet containing up to two-thirds clover. After lambing, in spring, sheep are usually kept in one paddock for about three to four weeks. This avoids unnecessary movement of ewes and lambs in order to reduce the likelihood of ewes abandoning their lambs.
After lambs are weaned, rotational grazing – where a mob of sheep graze the pasture very closely over a few days – can be resumed. They are then rotated or moved on to the next paddock.
The best pastures for sheep are mainly ryegrass and white clover, though poorer grasses, such as browntop and Yorkshire fog, often dominate hill-country sheep pastures. Where lamb production is important, perennial grasses (tall fescue, cocksfoot, timothy) and grazing herbs like plantain and chicory may be grown in special-purpose pastures.
Deer are very selective grazers and prefer red clover and broad-leafed herbs, such as chicory and plantain, to grasses. A mix of grasses, legumes and herbs will provide a useful deer pasture, but this must be rotationally grazed to avoid over-grazing of their preferred species.
Pasture for deer should be about 10 centimetres or taller. Deer also like to browse on trees such as willows, poplars and natural scrub.
Deer are very sensitive to the wild ryegrass endophyte and avoid it wherever possible, but readily graze endophyte-free pasture.
Horses are very selective grazers and avoid any ryegrass containing endophyte. They also avoid areas of unpalatable weeds and old dung patches (for at least six months), leading to patchy ungrazed and closely grazed areas. A pasture with a large ungrazed area is called ‘horse-sick’, but grazing with cattle will minimise this effect.
Goats prefer to browse taller grasses, weeds and shrubs, and are not sensitive to wild endophyte toxins in ryegrass. Because they graze taller herbage, they often create clover-dominant pastures, so some farmers graze sheep with goats as a complementary system.
Acting the goat
As well as helping improve pasture quality, goats have other beneficial attributes – they don’t get fly-strike like sheep, they need less feed in a drought, angora goats are easier to shear than sheep, and in 2007 were much more profitable. Goat meat – which, despite its present lack of popularity in New Zealand, is eaten by more people in the world than sheep meat – is lean and low in cholesterol.
Llamas and alpacas are less selective but patchier grazers than sheep, and are sensitive to wild endophyte toxins in ryegrass. They deposit their dung in set areas, and this leads to a loss of fertility in the remainder of the paddock.
Ostriches and emus will selectively graze the best quality forage that is available. Their feed demand may increase during winter to compensate for cold stress. They prefer softer-leafed plants, such as clovers, herbs, lucerne and grasses, but will also eat brassicas.