The role of livestock in the management of dryland salinity

Abstract

Management of dryland salinity in Australia will require changes in the design and utilisation of plant systems in agriculture. These changes will provide new opportunities for livestock agriculture. In areas already affected by salt, a range of plants can be grown from high feeding value legumes with moderate salt tolerance through to highly salt tolerant shrubs. A hectare of these plants may support between 500 and 2000 sheep grazing days per year. The type of plants that can be grown and the subsequent animal production potential depend on a range of factors that contribute to the ‘salinity stress index’ of a site, including soil and groundwater salinity, the extent and duration of waterlogging and inundation, the pattern and quantity of annual rainfall, soil texture and chemistry, site topography and other site parameters. Where the salinity stress index is high, plant options will usually include a halophytic shrub that accumulates salt. High salt intakes by grazing ruminants depress feed intake and production. Where high and low salt feeds are available together, ruminants will endeavour to select a diet that optimises the overall feeding value of the ingested diet. In areas that are not yet salt affected but contribute to groundwater recharge, perennial pasture species offer an opportunity for improved water and salt management both on-farm and at the catchments. If perennial pasture systems are to be adopted on a broad scale, they will need to be more profitable than current annual systems. In the high rainfall zones in Victoria and Western Australia, integrated bioeconomic and hydrological modelling indicates that selection of perennial pasture plants to match requirements of a highly productive livestock system significantly improves farm profit and reduces groundwater recharge. In the low to medium rainfall zones, fewer perennial plant options are available. However, studies aiming to use a palette of plant species that collectively provide resilience to the environment while maintaining profitable livestock production may also lead to new options for livestock in the traditional cropping zone.

Evolutionary process of Bos taurus cattle in favourable versus unfavourable environments and its implications for genetic selection

“…It is conceivable that the Mexican Criollo from the Chihuahuan Desert 3 possess alleles pertinent to plasticity for variations in water consumption, extreme fluctuations in ambient temperature, metabolism of a variety of herbaceous plants, and alternating between browsing and grazing. Existence of such alleles has implications for other semi‐arid regions such as the livestock component in the management of dryland salinity of southern Australia as described by Masters et al. (2006).…”

Stable carbon isotopes accurately predict diet selection by sheep fed mixtures of C3 annual pastures and saltbush or C4 perennial grasses

“…Perennial shrubs and grasses complement annual grazing systems in mediterreanean-type climates through the provision of a broader seasonal distribution of green feed for livestock (Masters et al, 2006). They may also provide environmental benefits such as maintenance of plant cover to reduce soil erosion and an improvement in the utilisation of rainfall, thus slowing recharge of water tables and dryland salinity (Cocks 2003;Lefroy et al, 2005).…”

Reproductive capacity of Merino ewes fed a high-salt diet

“…Some landholders in Australia are grazing sheep on saltbush to fill a summer/ autumn feed gap (Masters et al, 2006), a period that coincides with the greater demands of late pregnancy for autumn-or winter-lambing ewes. However, feeding saltbush may possibly have a negative impact on reproductive performance of the ewes as high salt intake may reduce intake and cause physiological changes associated with adaptation to the salt load.…”