Feed testing

Silage Testing

Silage materials can be tested for feed quality and mineral nutrients.

About this Testing

What is Silage

Surplus forage is conserved by ensiling and acid fermentation, providing feed for use during periods of deficit..Types of forage commonly conserved in this manner are pasture, annual ryegrass, cereal (wheat, barley, oats, triticale), maize and lucerne. Common methods of ensiling involve using a silage pit, stack, silo or as baled and wrapped silage (baleage). At Hill Laboratories we consider that a feed sample that has been ensiled for at least two weeks is a silage sample. 

During the ensiling process, plant sugars are converted to a range of acids and also a small quantity of ethanol. The lactic acid produced is largely responsible for preserving the silage until needed. Silage inoculant is often used to introduce desirable bacteria for silage fermentation and rapid pH drop.

Making high quality silage starts with harvesting the forage at the appropriate growth stage, with adequate moisture and soluble sugars for good fermentation. Maturity of the harvested crop, rate of wilting, chop-length, compaction and sealing of the stack or bales all impact on the resultant silage quality.

Silage Quality

The quality of silage is highly dependent on the quality of the forage harvested and the type of fermentation that has occurred. These factors will influence palatability to livestock, livestock productivity, dry matter losses and the risk of
toxins forming in the silage. Even under ideal conditions, loss of at least 8% of the forage dry matter is expected throughout the ensiling process.

Quality Indicators in the Silage Profile

  • pH
  • Dry Matter (%)
  • Crude Protein (%DM)
  • Acid Detergent Fibre (%DM)
  • Neutral Detergent Fibre (%DM)
  • Digestibility [DOMD] (%DM)
  • Metabolisable Energy [ME] (MJ ME/kg DM)
  • Soluble Sugars (%DM)
  • Starch (%DM)
  • NH4-N:Total N (%)
  • Lactic Acid (%DM)


There are some times when you need a complete picture of your silage, especially when metabolic disorders are an issue. Hill Laboratories provides an Extended Silage Profile with minerals which includes a full Silage Profile, Basic Plant Profile and Mo, Co and Se analysis.

Volatile Fatty Acid Testing of Silages

The determination of Volatile Fatty Acids (VFA) is a new test offered by Hill Laboratories and complements our existing silage tests. As a result of the complex reactions taking place during ensiling, and various factors affecting the eventual quality of the silage, the VFA profile sheds light on factors not measured appropriately by existing tests. The pH is an indication of the acidity of the silage, but does not give an indication of the organic acid composition that also affects the value of the silage. The VFA’s of concern are lactic acid, acetic acid, propionic acid, butyric acid and formic acid. Silage Analysis & Interpretation.

Example Pasture Silage and Volatile Fatty Acids Report

Silage and Feedstuff Test Options

Taking a Sample

Complimentary Feedstuff Test Kits (including sample bags, a courier bag, instructions and request form) are available from the laboratory.

Here are some tips when sampling for silage quality:

  • A silage auger can be purchased from the lab to take silage and baleage samples.
  • Be sure to fill the sample bag, especially if you are collecting silage for the Extended Silage Profile. We need at least 1kg of representative silage sample for a silage profile where dry matter, crude protein, digestibility, starch, energy and other tests are completed.
  • For any silage or feed tests use a clean airtight bag or Feed Test Bag.
  • Roll air out of the bag and seal the bag well (so that dry matter measurements are accurate and not affected by moisture lost in transit).
  • Send samples to the laboratory as soon as they're collected preferably by courier.
  • If you have to hold samples overnight, store them in a refrigerator.



How to Order a Test

Complimentary Feedstuff Test Kits are available from the laboratory. These sample kits contain instructions, an analysis request form, sampling bags and courier bag to send in the samples.

Guides and Supporting Information


Contact Us

Freephone 0508 HILL LAB (44 555 22) or email Ag.CSM@hill-labs.co.nz