FAA Group

Forage Analytical Assurance (FAA) Group
Quality assurance for wet Near Infrared Reflectance Spectroscopy (NIRS) of silages

Grain processing and its effect on energy content of Whole Crop Cereal Silages

As part of its continuing research programme, the FAA group combined with other organisations in a Defra LINK project to create wet NIRS equations for Whole Crop Cereal (WCC) silages such as wheat and barley whole crop silages.

In this work, the energy value of 60 silages was measured by the standard UK method in sheep.

Research studies have shown high dry matter (DM) poorly processed WCC silages where the grain has not been chipped or broken are likely to have a lower energy values in high yielding dairy cows.

This is because the faster rumen outflow rates in dairy cows shorten the time food particles remain in the rumen before being washed out. In poorly processed high DM WCC silages rumen microbes cannot access the starch in the grain before it is washed out into the lower gut.

Whole grains cannot be digested in the lower gut and are excreted in the dung. Clearly grains that 'bypass' the gut cannot provide any energy to the animal.

The FAA energy equation is the prediction from sheep. It takes no account of level of WCC silage processing.

It is up to individual farm nutritionist to be aware of the importance of WCC silage processing on energy value. The LINK project suggested a method to correct energy levels in poorly processed WCC forages (original report).

Work by the FAA group has highlighted that it is essential to examine the condition of the grains very closely.
Looking at the grains without magnification is not good enough as it is almost impossible to judge the average level of processing of the grains.

Separate out a reasonable number of grains from a sample (collected using the FAA clamp sampling method) and place on a clean card. Then use either a magnification glass or better still take a digital picture and zoom in on the image.

Finally refer to the notes below to help you judge the level of processing (click on any image to magnify) and so the energy correction required.

FAA Group
email: info@faagroup.co.uk

Click to move directly to::-

Wet WCC silage

Dry WCC silage - well processed

Dry WCC silage - unprocessed

Dry WCC silage - poorly processed

Summary energy correction table

1. Wet WCC silage (below 55% DM)

Wet WCC silages need no energy adjustment.
So if the dry matter is below 550 g/kg (55 %DM) - use the ME value on the silage report.

Grains will tend to be:-

smaller - often longer and thiner.
moist, squashy and relatively soft.
whole and unbroken.

2. Dry WCC silage (above 55% DM) - well processed (approximately 90% broken grains)

Dry WCC silages with well processed grains need no energy adjustment.
Use the ME value on the silage report.

Grains will tend to be:-

large, rounded and well filled with starch.
dry and difficult to squash.

The vast majority of the grains should be chipped or broken.

3. Dry WCC silage (above 55% DM) - unprocessed (appromixately 10% broken grains)

Dry WCC silages with unprocessed grains need correction.
To correct use the equation -

Corrected ME = Silage report ME - (0.26 * Silage report starch * 0.0144)

So, if the reported ME = 11.2 MJ/ME kg DM and the starch = 250 g/kg DM then

Corrected ME = 11.2 - (0.26 * 250 * 0.0144)

Corrected ME = 11.2 - 0.94 = 10.3 MJ /kg DM

Grains will tend to be:-

large, rounded and well filled with starch.
dry and difficult to squash.

Only 10% of the grains are chipped or broken.

4. Dry WCC silage (above 55% DM) - poorly processed (approximately 50% broken grains)

Dry WCC silages with poorly processed grains need correction.
To correct use the equation -

Corrected ME = Silage report ME - (0.26 * Silage report starch * 0.0144 * 0.5)

So, if the reported ME = 11.2 MJ/ME kg DM and the starch = 250 g/kg DM then

Corrected ME = 11.2 - (0.26 * 250 * 0.0144 * 0.5)

Corrected ME = 11.2 - 0.47 = 10.7 MJ /kg DM

Grains will tend to be:-

large, rounded and well filled with starch.
dry and difficult to squash.

Only around 50% of the grains are chipped or broken.

Summary of energy corrections

Reduce silage report ME (MJ/ kg DM) by the following:-

	Starch level (%DM)
	15	20	25	30
Wet WCC silage (<55% DM)	Use reported ME	Use reported ME	Use reported ME	Use reported ME
Dry WCC silage (> 55% DM) well processed	Use reported ME	Use reported ME	Use reported ME	Use reported ME
Dry WCC silage (> 55% DM) unprocessed	0.6	0.8	0.9	1.1
Dry WCC silage (> 55% DM) poorly processed	0.3	0.4	0.5	0.6

FAA Group
email: info@faagroup.co.uk