Livestock equivalents for estimating stocking rates and grazing pressure in the rangelands of Western Australia

Livestock equivalents

This page provides the values for converting different stock and classes of stock to standard stock units, based on the estimated energy requirements of each stock type. For sheep and other small stock we use dry sheep equivalents (DSEs); for cattle and larger stock we use animal equivalents (AEs), and previously used cattle units (CUs).

The carrying capacity of a pasture – in standard livestock units – can be estimated by measuring the available energy of forage in a grazing system and dividing that by the energy needs of a standard livestock unit.

Recommended livestock units

• We recommend using DSEs for small livestock (sheep and goats) in the northern and southern rangelands.
• We recommend using AEs for large livestock in the northern and southern rangelands. AE is a nationally accepted standard and is based on the latest research.
  However, in the southern rangelands, DPIRD and pastoralists have used cattle units (CU) in the past, based on lighter steers. This has confused the conversion between CUs and DSEs and the calculation of carrying capacity. Table 3 shows cattle values in AE and CU.

How livestock equivalents are calculated

The livestock equivalents are based on the metabolisable energy of feed intake required to maintain an animal from one season to the next (McLennan et al 2020). Many older conversions were based on kg of feed intake, with or without feed quality being defined. Landgate commissioned a review of potential carrying capacity, and the report uses dry matter intake per cattle unit per year based on the AE standard (Petty et al 2018).

• One DSE is based on the feed energy required to maintain a 45 kilogram liveweight Merino wether with zero weight change, no wool growth additional to that included in maintenance, and walking 7 km/day. 1 DSE has an energy requirement of approximately 8.7 MJ ME/day.
• One AE is based on the feed energy to maintain a 450 kg Bos taurus steer 2.25 years of age, walking 7 kilometers each day (Petty et al 2018, McLennan et al 2020)).  1 AE has an energy requirement of  73 MJ ME/day.  Bos indicus (Zebu and Brahman crosses) cattle have about 10% lower energy maintenance requirements than Bos taurus (European breeds generally) cattle (Sainz et al 2013), but we have only used the values for Bos taurus in the tables below.
• CU was the standard used by DPIRD for cattle until 2021, but DPIRD is now moving to use the nationally accepted and scientifically supported AE livestock unit. In the past, CUs have referred to different 'standard' steer weights – 400 kg and 450 kg, and do not refer to energy requirements.  This variability in standard steer weights makes comparisons of carrying capacity using CU difficult.

Energy requirements of livestock

The energy requirements of standard livestock units (DSE and AE) are given below, but livestock energy requirements also vary with:

• growth rate (note that the standard units assume maintenance only)
• gender
• age
• pregnancy/lactation status
• condition and body weight
• distance walked
• topography
• quality of feed
• density and quantity of feed
• water supply and quality
• temperature
• seasonal conditions.

For sustainable pastoralism, stocking rate must be less than the seasonal carrying capacity of the pasture. In other words, livestock removal of forage must be less than the sustainable utilisable level.

We recommend using local and specialist advice to get accurate stocking rate and grazing pressure estimates.

Calculating livestock carrying capacity from feed on offer/pasture productivity

To estimate the carrying capacity of an area of land over a season, you need to know the metabolise energy requirements (ME) of the of the standard stock unit and the available metabolisable energy of the pasture type on offer.

For example:

One animal equivalent (AE) has a daily energy requirement of 73 MJ ME/day, which equates to the consumption of 9.37 kg of dry matter (DM) per day (assuming the feed has an energy quality of 7.75 MJ ME/kg DM).  this would require a yearly intake of about 3419 kg.

The sustainable utilisation rate (% of biomass that can be consumed) of rangeland pastures is usually 30% or less.

So a pasture with 200 kg DM/ha, and 30% utilisation would provide 60 kg of usable DM/ha ((0.3 x 2000). This means that one AE, needing 3419 kg of forage per year, needs a land area of (3419/60) 56.9 ha or a stocking rate of (100/56.9) 1.76 AE/km² per year. This estimated carrying capacity could be expected from a rangeland pasture with high pastoral potential when in good condition.

Potential stocking rate can be calculated from the number and type of grazing animals, including native and feral herbivores, using Tables 1–4.

Note: Carrying capacity using these values is for standard animal units at maintenance. Tables 1–4 show the equivalent values for different classes of stock, including growth for younger growing animals. Very young animals such as lambs or kids under 1 yr of age are not counted when estimating carrying capacity, as their feed requirements are included in their mother’s requirements.

Converting between AE, DSE or CU

In the northern rangelands, the carrying capacity of pastoral stations, land systems or pasture types is generally expressed in AEs. Based on energy requirements 1 AE is equivalent to 8.4 DSE (73/8.7).

In the southern rangelands, carrying capacity has generally been reported in DSE with values provided in Western Australian rangeland surveys.  To estimate the number of cattle that can be carried in the southern rangelands a conversion rate based on CUs has traditionally been used, where 7 DSE is equivalent to 1 CU.  DPIRD plans to progressively report carrying capacity in AEs for the southern rangelands, to provide uniformity of carrying capacity terms across the rangelands.

To convert CUs to AEs, multiply by 0.83; to convert AEs to CUs, multiply by 1.2). Note that reporting in AE when you are used to CU looks like a reduction in carrying capacity – this is NOT the case. AS explained above, an AE is based on a larger and therefore higher energy requirement animal than a CU.

Livestock equivalents used in the WA rangelands (Tables 1–4)

1 The values are for Merino sheep first, then meat-breed sheep (Merino/meat breeds).
2 Very young animals such as lambs or kids under 1 yr of age are not counted when estimating carrying capacity, as their feed requirements are included in their mother’s requirements..

Sources

• McLennan, S 2015, Nutrient requirement tables for Nutrition EDGE Manual, Meat and Livestock Australia, Sydney, Australia, viewed 26 July 2021.
• McLennan SR, McLean I and Paton C (2020) 'Re-defining the animal unit equivalence (AE) for grazing ruminants and its application for determining forage intake, with particular relevance to the northern Australian grazing industries', Meat and Livestock Australia, North Sydney, Australia, accessed 26 July 2021.
• Petty, S, Blood, D, Addison, J and Petty, E (2018) Potential carrying capacity review, Spektrum Consulting report for Landgate, Western Australia, accessed 26 July 2021.
• Sainz RD et al 2013, Performance, efficiency and estimated maintenance energy requirements of Bos taurus and Bos indicus cattle, In Oltjen J.W., Kebreab E., Lapierre H. (eds) 'Energy and protein metabolism and nutrition in sustainable animal production', Energy and protein metabolism and nutrition in sustainable animal production, vol 134. Wageningen Academic Publishers, Wageningen, accessed 26 July 2021.
• Terence J Dawson, Adam J Munn 2007, 'How much do kangaroos of differing age and size eat relative to domestic stock?: implications for the arid rangelands', Animals of Arid Australia: Out on their own?, eds. Chris Dickman, Daniel Lunney, Shelley Burgin, Royal Zoological Society of New South Wales, accessed 26 July 2021.
• van Gool, D, Angell, K & Stephens, L (2000) 'Stocking rate guidelines for rural small holdings, Swan Coastal Plain and Darling Scarp and surrounds, Western Australia', Miscellaneous publication 2/00, Department of Agriculture and Food, Western Australia, Perth, accessed 28 July 2022.