A tool for standardising Adult Equivalent calculations

Summary

This report details the methodology used to apply the Nutrient Requirements of Domesticated Ruminants in the calculation of Animal Equivalents, proving an accurate, consistent measure of the cattle grazing load for production systems across northern Australia.  The methodology is based on energy demand of animals as a result of animal specific factors.  Is not based on animal/environment interactions, although these are explored in depth in order to derive and apply the methodology. 
The Animal Equivalent standard unit is a 450 kg Bos taurus steer at maintenance, 2.25 years of age, grazing on pasture with diet quality of 7.75 MJ ME/kg DM and walking 7 kilometres each day.  Subsequent calculations express the energy demand of various animals relative to this standard unit. 
The variability of diet quality across northern Australia and its influence on energy demand is problematic in developing a consistent methodology based on animal specific factors.  This project has shown that the range of diet quality across northern Australia is reasonably consistent and that fixing diet quality has no material effect on the relative Animal Equivalent ratings of animals.  This model uses a fixed diet quality of 7.75 MJ ME/kg DM. 
Exercise, particularly distance walked each day by cattle, influences the energy demand of cattle.  A review of existing research on distance walked by cattle showed that cattle generally walk a similar distance each day, regardless of paddock size or configuration, allowing the distance walked each day to be fixed without limiting the application of this methodology across northern Australia.  This model uses a fixed distance walked of 7.0 km/day. It was determined that 1 AE = 72.6 MJ ME/day.​