WSC, ESC and Starch in a Hay Test: What Buyers Need to Know About Fast Energy

WSC, ESC and starch are the figures on a hay test that tell you how much rapidly available carbohydrate, or fast energy, is in the feed. They matter when you are buying hay because different animals use that energy very differently. The same hay test can describe a feed that suits cattle well and is risky for a laminitis-prone horse. Knowing how to read these three numbers helps you match a listing to the animals you are feeding before you buy.

If you are purchasing hay through a marketplace, the feed test is one of the most useful pieces of information a seller can provide. Understanding what these results mean turns a test report from a page of numbers into a buying decision you can trust.

What each number measures

These three results describe slightly different pools of carbohydrate, and they overlap.

• ESC, or ethanol-soluble carbohydrates, is mostly simple sugars. It represents the fastest sugar fraction and is especially useful when you are assessing hay for horses.
• WSC, or water-soluble carbohydrates, is a wider sugar pool. It covers simple sugars plus fructans, and it includes the sugars measured by ESC. Because WSC captures more, it will usually read higher than ESC on the same sample.
• Starch is mostly grain, seed or plant energy reserve. High starch levels can be valuable energy, but they carry risk if an animal is overfed.

Read together, these figures tell you how much of the feed’s energy is fast and how readily available it is.

Why cattle and horses read the same test differently

This is the part that catches buyers out. A hay test does not have a single verdict, because the animal eating the hay determines whether the result is good or risky.

Cattle can make good use of sugars and starch as part of a balanced ration. The risk for cattle is feeding too much fast-fermenting carbohydrate without enough effective fibre, which can increase the chance of rumen upset. For cattle, fast energy is useful when it is balanced.

Horses need extra care, and some need a great deal of it. Ponies, easy keepers, laminitis-prone horses and horses with metabolic issues may not suit higher sugar and starch levels at all. For these animals, a lower WSC and ESC result is often what you are looking for, and a test showing high fast energy is a reason to assess the hay carefully before buying.

So a hay that is a sound buy for a commercial cattle operation may be exactly the hay an owner of a laminitis-prone pony should avoid. Same numbers, different decision.

Do not forget dry matter

When you are comparing two hay tests, check the dry matter results before you compare the carbohydrate figures. Feeds with different moisture levels are not directly comparable on an as-fed basis, and dry matter lets you compare like with like. Two tests can look different simply because one sample held more moisture, not because the feed is genuinely different.

Key takeaways

WSC, ESC and starch describe the fast energy in hay, and they overlap, with WSC the widest pool and ESC the fastest sugar fraction. Cattle can use fast energy well in a balanced ration, while many horses, particularly metabolic and laminitis-prone animals, need lower sugar and starch. Always compare hay tests on a dry matter basis. Match the feed to the animal before you buy.

Buy hay with confidence

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