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Test bad hay, too

As the summer draws to a close, farmers often find they have made some good hay and some not-so-good hay, because of rain delay, less legume than expected or other reasons. They often don’t test the lesser-quality hay and simply feed it to heifers or other animals. This can be a big mistake!

Knowing what is in the hay can make the difference between getting the expected animal performance or not. Often individuals do not test hay, assume certain needs, and buy and feed supplements without knowing if the supplements are really needed.

The table is an example of analysis of four alfalfa and grass hays.


First look at the crude protein. Animal needs range from about 7% for mid-gestation, mature dry cows to about 13% for beef cows nursing calves, and higher for milking dairy cows. You can see that all samples, except No. 3, are adequate for non-lactating, idle adult animals, and samples 1 and 4 are adequate for growing or lactating animals without additional protein supplement.

Acid detergent fiber, or ADF, is the old test to estimate energy. Now most forage-testing labs can analyze for digestible fiber, or NDFD, to better estimate energy of the forage.

Samples 2 and 4 have about the same ADF content, but Sample 2 has much higher digestible fiber and would result in better animal performance.

Neutral detergent fiber, or NDF, is an estimate of total fiber. The normal range is from 40% on early-bloom legume hay to 72% on late-cut grass hay. Cattle, sheep, horses and other ruminants need fiber.

Samples 1 and 4 would generally be adequate for growing animals with little additional supplement. Sample 2 is adequate for non-lactating, idle adult animals, and animals fed Sample 3 may need some additional concentrate, especially over winter.

It is also worthwhile to look at the forage’s mineral content. Phosphorus is often low in forage. Levels approaching 0.25% P on a dry-matter basis are at the critical level. Samples 2 and 4 are low in P. Lactating cows and growing animals have higher P requirements.

Thus, animals fed hay from samples 1 and 3 need little additional P supplement (except for milking dairy cows), while animals fed sample 2 and 4 should receive additional P.

The calcium level in Sample 1 is high, indicating a high level of legume in the hay, while the other three samples are likely primarily grass. Lactating cows and growing calves will have the highest requirements, needing about 0.39% and 0.45% calcium, respectively. All samples except No. 3 meet these requirements.

One can see that individual hays would need differing supplements depending on the type of animal being fed. Some hays could be more cost effectively fed to certain animals. The only way to know what is needed or to most effectively use the hay is to test the forage and determine its contents.

Undersander is a University of Wisconsin-Madison Extension and research forage agronomist.

This article published in the September, 2010 edition of WISCONSIN AGRICULTURIST.

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