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Nutrition, Feeding & Water

Forage Testing: What Dairy Farmers Should Measure

Forage is the base of most dairy rations, and it changes from field to field and cutting to cutting. Testing turns guesses into numbers you can balance a ration around.

Key points

  • Test forage at harvest and whenever it changes.
  • Check dry matter on a regular schedule.
  • Take samples from several places and keep them clean and sealed.
  • Share every result with your nutritionist.
  • Keep records by field and cutting.

Why test, and what to measure

Forage often makes up the largest share of a lactating cow's diet. Small differences in moisture, fiber or protein change what the cow gets, and without a test you are formulating blind.

Testing also protects your feed investment. A result can show whether a silage fermented well, whether hay was harvested late, and whether you need to adjust supplements up or down.

Most labs offer routine packages for forage. The names can differ, so talk with your nutritionist about the package that fits your feeds and the questions you need answered. Common categories include dry matter, crude protein, fiber fractions, digestibility measures, ash, and minerals. Starch is important for corn silage. Fermentation analysis, such as acids and pH, is important for silage and haylage.

Dry matter comes first

Dry matter is the simplest test and one of the most important. If the moisture in silage changes, the amount of dry feed in each scoop changes with it, and the ration drifts away from target.

Many farms check dry matter on a regular basis with a microwave or air fryer method and then send samples to the lab less often. Ask your nutritionist for a method and a schedule that suits your operation.

How to take a good sample

A test is only as good as the sample. A handful from the top of the pile is not the pile. Take several grabs from across the face of a bunker, pile or bag, or from several bales, and combine them into one clean sample.

Mix well, fill the container as directed, and seal it so moisture does not change. Keep samples cool and get them to the lab quickly. Label each sample clearly with feed type, field, cutting and date.

When to sample

Sample at harvest or at the start of feeding, and again when something changes: a new field, a new cutting, a new bag or bunker face, or a change in weather that affects moisture.

Fermented feeds can change after opening. If feed out is slow or the face heats up, retest and watch cow response.

Reading and using the results

Do not read a report alone if you are unsure what the numbers mean. Your nutritionist can compare results with the ration and the herd's performance and tell you whether to change a supplement or leave things alone.

Keep records by field and year. After a few seasons you can see which fields, cutting times and storage methods give the best feed.

Treat each report as part of a running file. Compare this season's results with earlier years, and keep notes on weather, harvest date and storage. Over time you will see which practices consistently give better feed. Share the file with whoever formulates the ration so they do not have to start from zero at each visit. Good records also help when you buy forage, since you can compare what you are offered with what you have grown.

Dry matter checks in more detail

A moisture check is quick enough to do on a routine schedule. Weigh a sample, dry it by the method your nutritionist recommends, weigh it again and work out what share of the feed was dry matter. Repeat for a few samples and use the average.

Do this more often after rain, during a change of silage face, and when feeding wet byproducts. A change in moisture shifts how much dry feed each cow gets, and cows feel it before the milk tank shows it. Keep results in a log by date and feed.

Common mistakes

Sampling from one spot, using dirty containers, sending samples that sat in a warm truck, and failing to retest after a change are the most common. Another is testing but not telling the nutritionist, so the ration never changes.

Do not rely on book values or last year's result when conditions have changed. Weather and harvest timing change forage quality noticeably.

When to get help: Ask your nutritionist or local extension office which lab packages suit your feeds. Call your veterinarian if you suspect moldy or spoiled feed is affecting cow health.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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