Nutrient Requirements Tables for Nutrition EDGE Manuals

Summary

​This project derived estimates of metabolisable energy (ME) and protein requirements, and the relationship between intake and digestibility, for inclusion in a revised version of the northern beef training package, Nutrition EDGE. This was done to bring them into line with the Australian feeding standards (EDGE requirements currently derived from UK ARC standards based on Bos taurus data) and with associated changes to the adult equivalent (AE) calculations. The revised estimates of protein and ME requirements are higher, in most cases, then those currently used in the EDGE package. To some extent, this could be due to the Australian feeding standards tending to overestimate requirements for cattle grazing on tropical pastures but improved algorithms are not currently available. The revised tables are useful for the purpose of demonstrating to cattle producers the key principles of energy and protein requirements and how they change with the quality of the diet, the liveweight of the animal and its productivity either for growth or pregnancy/lactation.  However, they are not suitable for making judgements on the adequacy of a specific paddock scenario to meet production targets, or to determine the amount of additional nutritional inputs required to meet those targets.  For the latter case, nutritional advisors should consider using a tool such as 'QuikIntake' or the web-based spreadsheets associated with the GrazFeed site – their advantage is that they allow the user to work backwards from 'known' animal performance to calculate requirements without the need to predict diet quality other than a faecal NIRS assessment of digestibility. The constraints of current systems for estimating energy and intake requirements should be understood to avoid frustration and naïve application. For example, when the ME requirements (from either system) are translated into dry matter intake requirements, some of the required intakes are beyond what the animal would be expected to achieve even though the production rates may be achievable.  Care and intuition are therefore required in their use and interpretation.