Grazing native vegetation on farms in the agricultural areas is not recommended
It is tempting to use native vegetation (remnan vegetation or bush) as a source of rouphage when paddock feed is limited — especially in very dry seasons — but the benefits are minimal and the damage is long term and cumulative.
The nutritional value of native vegetation is very low, unless there is significant invasion by pasture species. Grazing native vegetation will reduce its ability to regenerate, and increase the risk of weed invasion.
There are legal restrictions on the use or damage to some areas of native vegetation.
Native vegetation as a source of roughage may be marginally useful in periods of serious feed shortage, but any benefit gained are likely to be greatly overshadowed by the long-term degradation of the native species and loss of resource conservation values.
Covenants, biodiversity retention and obligations to funders, exclude some farmers from using native vegetation or revegetation sites for grazing.
Reasons why grazing native vegetation is not recommended
- The social and environmental value of bush on farms is generally higher than any commercial value.
- Grazing in bush remnants always increases weediness of the site, and this is very hard to reverse.
- Grazing prevents native plant regeneration.
- The total amount of accessible feed per hectare is likely to be very low.
- The digestibility of most native plants is low to very low, and fibre content is high.
- Several native plant species contain highly toxic compounds (flouroacetate, or '1080' being the best known) which can kill livestock.
Native vegetation that should never be considered for shelter or grazing
- where poison plants are known to be present or are likely to be present
- where rare or endangered plants are present
- where there is a covenant or other agreement excluding livestock
- where long-term bush protection is an objective.
Native vegetation can provide benefits while excluding livestock
Bush can provide shelter on the lee side in adjoining pasture paddocks. This shelter area can be used to reduce exposure to extreme events that could cause livestock deaths (usually of off-shears sheep and lambs), and provide a stable area not susceptible to wind erosion. This may be especially important for short term feedlotting.
Where grazing or sheltering in native vegetation is unavoidable
There are conditions when sheltering or feeding sheep in native vegetation could be a good management decision, if damage is minimised:
- post-lambing when other shelter is not available and cold, wet, windy conditions are forecast
- post-shearing (in the first 7–10 days) when other shelter is not available and cold, wet, windy conditions are forecast.
Minimising damage to native vegetation
Where using native vegetation for livestock is unavoidable, you can minimise damage using these guidelines:
- Use the area for as little time as possible.
- Use as small an area as possible.
- Leave plenty of time between uses to allow recovery.
- Use areas that are already degraded by pasture grasses and weeds.
- Feed cereal straw or hay in contained areas; do not leave long grain feeding trails.
- Do not put feedlots or confined feeding sytems in bush blocks.
Choosing the right native vegetation when grazing is unavoidable
Some native vegetation has higher feed value, and may also suffer less from livestock disturbance:
- dense areas of Acacia saligna — digestibility of the foliage of this species can be above 60%, but it is highly variable.
- young accessible growth of casuarinas and allocasuarinas — palatability is often high, though digestibility is very low.
- extensive areas of native grass — total digestible dry matter is likely to be low, except where extra nutrients are available, but digestibility of some species is good (greater than 55%)
- where weed invasion by pasture species is extensive.
Grazing in plantation and revegetation areas
Grazing in young, single species tree plantations can be valuable, but the animals must be removed before tree damage becomes significant. This option mainly applies to the high rainfall south west of Western Australia.
Grazing in mixed native-species revegetation areas will cause significant damage to small and palatable plants, and reduce the long term biodiversity and environmental value of those plantings.
Young plantations may provide significant grazing, because the soil nutritional levels are higher than in bush and there is usually plenty of pasture growing between the tree rows. However, the feed value reduces rapidly as the trees mature. Heavy grazing pressure can damage the trees, and this can reduce longer-term financial returns. Younger stock (lambs and weaners) usually cause less damage to young trees and livestock should be removed before the trees are seriously damaged.
In addition to feed value:
- Grazing can reduce fire risk by removing the fuel load.
- Grazing may reduce weed competition with the trees.
Damage to young trees is common, especially if grazing is heavy or over a long period. Young sheep cause fewer problems than older sheep, and rams and lactating ewes may be worst. Foliage loss causes temporary setback to plants, but damage to the trunk or main branches is more serious. Depending on the species and the objective of the plantation, this damage may cause serious commercial loss.
Soil disturbance and livestock droppings from heavy grazing may increase the weediness of the site, and increase competition with the plantation.
In plantations of mixed species (environmental and nature conservation plantings), livestock will often preferentially graze some of the trees and shrubs (eg acacias, casuarinas, allocasuarinas, quandongs and sandalwood). This will change the long-term mix of species.