Grain protein and energy levels

A difference in wheat protein of 1 per cent is worth approximately $4 per tonne of mixed feed. Therefore, collecting as much information about grain as possible before purchasing is very important. However, various testing laboratories report protein levels in different ways.

As a buyer, you need to have grain analysed for moisture and crude protein content as a minimum. Moisture allows you to assess how you can store the grain and use it to convert the nutrient analysis from a dry matter to an as-fed basis. The protein value will influence the grain's inclusion level in the diet and its value. In most cases, the protein value is a good guide to amino acid nutrient levels without the need for further testing.

Measuring wheat protein

Protein values are calculated after analysis of the sample's nitrogen. For pig nutrition purposes, we use the nitrogen value multiplied by 6.25.

The reported protein value of wheat tested by Graincorp will be lower than the value from private laboratories such as SGS Agritech and Symbio Alliance. For a sample of wheat, Graincorp multiplies the nitrogen value by 5.7 to arrive at a protein value for its purposes, while SGS Agritech and Symbio Alliance multiply the nitrogen value by 6.25 to arrive at a crude protein figure (see Table 1). Therefore, the Graincorp figure needs to be converted for pig nutrition purposes.

Ensure that you know what conversion factor has been used to calculate the protein figure, as this will affect the value of your grain. Table 2 shows the protein levels resulting from the use of different conversion factors. Table 2 can also be used to convert protein using 5.7-6.25 for pig diet formulations.

Table 1. Conversion factors used to convert grain nitrogen % to grain protein %
Testing Lab Grain Conversion factor
SGS Agritech Wheat (manufacturing, not stockfeed) 5.7
  All other grains (including wheat for stockfeed) 6.25
Graincorp Wheat (all)* 5.7
  All other cereal grains 6.25
Major feed millers All grains 6.25
Symbio Alliance All grains 6.25
FeedTest All grain 6.25

*Corrected to 11% moisture

Table 2. Wheat protein levels determined from nitrogen contents according to different laboratory conversion factors
Grain nitrogen (%) Conversion factor
5.7 6.25
1.75 10.0 11.0
1.93 11.0 12.1
2.10 12.0 13.2
2.28 13.0 14.3
2.46 14.0 15.4

Tables 1 and 2 show that a stockfeed wheat sample tested at Graincorp with a grain nitrogen concentration of 2.1 per cent would be multiplied by 5.7 to give a protein content of 12 per cent. The same sample tested at SGS Agritech and Symbio Alliance would have the nitrogen concentration multiplied by 6.25 to yield a protein content of 13.2 per cent.

This example shows the importance of knowing what conversion factor has been used to arrive at your crude protein figure, as a difference of 1 per cent protein is worth about $4 per tonne of finished feed at a wheat price of $130 per tonne.

Measuring barley protein

A sample of barley tested by Graincorp and any grain tested by FeedTest will also have a higher protein value than that of a nutrition laboratory, such as SGS Agritech and Symbio Alliance, because all Graincorp and FeedTest samples are reported on a dry matter (DM) basis (see Table 3).

For pig nutrition purposes, we use the protein value reported on an as-fed basis, so you will need to check how it is reported and, if necessary, convert the lab result.

Table 3: Basis used to determine barley protein (%)
Laboratory Protein value reported
SGS Agritech As-fed basis (all grain)
Graincorp DM basis (barley only)
Major feed millers As-fed basis (all grain)
FeedTest DM basis

Table 4 shows how considerable differences can occur in the protein value reported to you. Therefore, you must know the moisture content of your grain so you can convert the analysis from a dry matter to an as-fed basis or you will overestimate the protein value of your grain. Such an oversight may significantly affect pig performance.

Table 4: Comparison between barley protein levels tested on a dry matter basis (DM) compared with as-fed basis
Barley protein (%) on a DM basis Barley protein (%) on an as-fed basis (12% moisture)
10 8.8*
11 9.7
12 10.6
13 11.4
14 12.3

* 10% multiplied by [(100-12) divided by 100]

Measuring digestible energy of grain

Pig nutritionists and feed suppliers can now measure grain's digestible energy (DE) using rapid analysis near infra-red (NIR) technology. This provides a low cost and accurate method of determining the DE content of your grains. Make sure you access this latest technology and the feed cost savings it offers. If you are not regularly getting your grain analysed for DE, you may be wasting your money because, without knowing the DE content, your nutritionist is relying upon book values. As grain can vary by 3-4 MJ DE/kg, you do not know if the grain is high or low DE until you test it. You may be losing up to $20 for every tonne of grain your operation uses. This equates to $85 per sow per year.

This technology represents one of the biggest breakthroughs in animal nutrition in the last decade. The calibrations are unique to Australia, and offer a new era in the accuracy and cost effectiveness of diet formulation.

AusScan Licensed Service Laboratories

SGS Agritech
Bob Lascelles
PO Box 549
Toowoomba Qld 4350
Ph: +61 7 4633 0599

Symbio Alliance
Elizabeth Owens
PO Box 4312
Eight Mile Plains 4113
Ph: +61 7 3340 5702

Summary

  • Before you purchase grain, collect as much information about it as possible.
  • As a minimum quality assurance check, have your grain analysed for moisture and crude protein content.
  • Check with the testing laboratory for their grain protein calculation method. If they use 5.7, convert for pig purposes by multiplying their result by 1.1. You need to do this for any wheat tested by Graincorp in Queensland.
  • Ask the laboratory whether their results are on a DM or as-fed basis. If on a DM basis, convert it to as-fed. For example, if in Queensland your barley is tested by Graincorp, convert the protein percentage from a DM basis to an as-fed basis by using the equation [protein %(as-fed) = protein %(DM) x (100-moisture%)/100].
  • Analyse your grain using the AusScan NIR calibration technology, as it is a low cost way to find out what you are feeding and maximise the cost effectiveness of your diets.