Nutrient composition of feeds
When planning a supplementary feeding program and choosing feeds it is important to know the nutrient composition of those feeds so that nutritional requirements for target animals can be met.
Energy requirements are expressed as megajoules (MJ) of metabolisable energy (ME). If a shortfall in daily requirements is known then from the table below it can be determined how much feed is required to correct the energy shortfall. For more information see Nutrient requirements of beef cattle.
Protein, calcium (Ca) and phosphorus (P) requirements are expressed as grams per day. From the table below it can be determined how much protein a feed is supplying. For example, 100 g of cottonseed meal (37% CP) supplies 37 g of crude protein (CP).
Bypass protein % is the percentage of crude protein which is not degraded in the rumen, and capable of passing through to the abomasum of cattle. The crude protein percentage (CP%) is calculated by multiplying the nitrogen (N) percent of feed by 6.25. This is because on average protein contains around 16% Nitrogen (1/0.16 = 6.25). Urea has 287% crude protein: 46% nitrogen multiplied by 6.25 which equals 287% protein. Gran-Am® contains 20% nitrogen or 126% crude protein. For more information on different types of protein see protein and urea supplementation.
The values in the table below are on an as fed basis. If values of feeds are given on a dry matter (DM) basis, multiply the dry matter value of the feed (as a fraction) by the corresponding measurement. For example, if a feed is 90% DM and has a value of 10 MJ ME/kg DM, then 0.9 x 10 = 9 MJ ME as fed, i.e. in every kilogram of the feed fed out in the paddock, it contains 9 MJ of metabolisable energy.
Nutrient composition of feeds used as supplements
|Product||Dry matter %||
As fed basis
|ME (MJ ME/kg)||CP %||Bypass protein %||Ca %||P %|
Additionally, knowing the nutrient composition of feed is important when comparing the cost of different feed sources. For example if you are comparing two feed sources for supplying additional phosphorus (P), they should be compared based on price per tonne of P, rather than price per tonne of product.
You can find more information on the nutritional composition of feeds and calculate and compare protein, energy and other components for different mixes of livestock feeds using the Feed cost calculator | NSW Department of Primary Industries.
Reviewed by Kieran Smith, Department of Agriculture and Fisheries.
This document was reviewed as part of the GrazingFutures Project. GrazingFutures is funded by the Queensland Government’s Drought and Climate Adaptation Program (DCAP) that aims to build drought and business resilience for Queensland livestock producers.