How to Interpret Silage Analysis?

With silage still making up the bulk of most rations silage analysis results often overlooked as an important tool for ensuring that producers get the best from their silage.

Producing quality silage not only helps drives production, it helps producers take control of their on farm costs. Silage analysis can be used to help producers formulate the correct total mixed ration (TMR) diets for their particular on-farm need and there are various laboratory methods used to calculate the chemical composition of silage, such as Near-Infrared Reflectance Spectroscopy (NIR) or wet chemistry. But no matter which method used the results produced need interpreting to understand their significance.

Dry matter

Dry matter (DM) is the quantity of material left after the water has been removed from a silage sample. The dry matter is dependent on forage type and the time harvested. Grass silage is typically between 25-35%, Maize/Corn silage between 30-40% DM, Wholecrop silages between 35 and 45% DM

Wetter forages, especially grasses, can be low in sugar levels, making the ensiling process difficult. Also, wetter silage is the more prone to field contamination such as soil, which will negatively affect the ensiling process.

Higher DM forage are generally, more difficult to consolidate correctly. This can lead to heating of the silage, increase levels of mould and yeast spoilage and increased silage wasted.

pH

Is the measurement on a scale of 1-14 of acidity or alkalinity of silage. Lower values <4.5 indicate higher acidity levels which are required to preserve forages, helping retain as much of the original forage feed value as possible. With the exception of specialist silages such as corn cob mixes and crimped cereals, silage’s with higher pH values >5.0 may have undergone a poor fermentation and may be of lower quality or prone to spoiling.

Digestibility. D Value

The D value is the quantity of digestible organic matter in the DM, measured as a percentage. The values vary with forage type. It also tends to decrease over time as the forage matures, so harvesting the crop at the highest point of digestibility should be the aim of the producer if making high energy silage

Metabolisable Energy. ME

Is important as its a measure of the total energy content of silage available to an animal when fed. The calculation is based on the D value and is reported as MJ/Kg DM. The higher the value, the more energy the silage contains.

Neutral detergent fibre (NDF)

NDF value is a measurement in percentage of the fibre fractions found in silage, such as hemicellulose, cellulose and lignin. NDF measurement is important as it’s linked to potential intakes, and although some Fibre intake is essential to maintain rumen efficiency, but too much can cause problems. NDF like digestibility increases as a crop matures and intakes with higher NDF forages are decreased as the fibre content in the rumen increases.

Crude protein (CP) %

This is a measurement of the total protein content in silage.  As the name suggests though, crude protein does not differentiate between plant proteins and external sources such as nitrogen fertiliser residuals etc. The higher the crude protein the more a forage is buffered, making the ensiling fermentation more diffciult to achieve. Very high

Ammonia nitrogen (NH3)N

Is the measurement of the protein content in silage that has been broken down to ammonia, through the ensiling process. Silages with a lower value, indicate that the preservation of the silage was good and the protein protected. Higher values silages with ammonia contents >12% for grasses, >7% for maize/Corn silage and >15% for legumes,  indicate a poor fermentation has occurred and proteins have been degraded to ammonia, lowering the feed value of the silage.

Lactic acid

The amount of lactic acid gives some indication to the quality of the fermentation. The amount of lactic acid required  is dependent on forage type and the dry matter harvested. Typical well-fermented grass silages have lactic acid contents of between 3 and 12.

Ash

The total mineral content of the silage.  This represents the forage mineral content but also the ‘hygienic status’ of the silage (amount of soil ensiled). As the Ash content rises, fermentation challenge is increased, as well as associated feed losses. As a general rule the ash content in silage should be less than 10%

 Water Soluble Carbohydrate (WSC)

The amount of sugar available for the  fermentation if measuring freash forage or the amount left after the fermentation is completed (fermentation acids are produced from WSC).

Starch

The amount of carbohydrate that is present (generally) in the grain of maize, cereals or other starchy silage. Starch is an easily accessible energy source for the rumen.

 

Additional read:

What to do after you have your silage analysis results? 

How to do on-farm silage audit?

Lallemand Animal Nutrition does not purport, in this guide or in any other publication, to specify minimum safety or legal standards or to address all of the compliance requirements, risks, or safety problems associated with working on or around farms. This guide is intended to serve only as a beginning point for information and should not be construed as containing all the necessary compliance, safety, or warning information, nor should it be construed as representing the policy of Lallemand Animal Nutrition. No warranty, guarantee, or representation is made by Lallemand Animal Nutrition as to the accuracy or sufficiency of the information and guidelines contained herein, and Lallemand Animal Nutrition assumes no liability or responsibility in connection therewith. It is the responsibility of the users of this guide to consult and comply with pertinent local, state, and federal laws, regulations, and safety standards.

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