The Adult Equivalent (AE) is the standard measure of grazing loads used in extensive grazing areas across northern and pastoral Australia.
An Adult Equivalent is a 450kg Bos taurus steer at maintenance (not gaining weight). The energy (feed) requirements of different classes of animals (based on breed, sex, weight gain, pregnancy/lactation status etc.) determine their AE Rating relative to the equivalent animal. For example, a 500kg Bos indicus steer gaining 0.6kg/day has an AE rating of 1.6, which means it will require 1.6 times as much grass as a 450kg Bos taurus steer that is not gaining weight..
Bush AgriBusiness undertook a project in 2013 for Meat & Livestock Australia to develop a practical, defendable AE methodology which provides an accurate, consistent means of calculating cattle grazing loads for production systems across northern Australia.
Following this project, we saw the need to also apply the methodology to sheep. Whilst the DSE is an established methodology for measuring and comparing the grazing loads of sheep, the comparison between DSE and AE is not established, with estimates ranging from 6-12 DSE per AE. Therefore we applied the AE methodology to sheep, grazing under extensive rangeland conditions, allowing the grazing loads of sheep and cattle to be compared on a like for like basis.
From this we determined that a 45kg wether at maintenance (the DSE standard), has an AE rating of 0.12, which effectively means that 8.4 (1/0.1196) 45kg wethers at maintenance will consume the same amount of feed as one 450kg Bos Taurus steer at maintenance. The tables below provide the AE ratings for different classes of cattle and sheep, allowing the grazing loads of each to be totalled and compared.
Excel based tools were developed to calculate the grazing loads for a whole mob or individual class of cattle, the spreadsheet containing these tools can be downloaded here. These tools enable to you to analyse the grazing load of your herd, or compare the grazing load of different classes of cattle. This will help you manage and make best use of your carrying capacity. The equivalent tools for sheep are available for Bush AgriBusiness clients on request.
A series of tables were produced, for various breed types, to show the relative AE ratings of animals through different physiological states.
For any questions on the AE methodology or its application to cattle, sheep, or both, contact Ian. The final technical report on the cattle methodology is available here.