Hay is a stable roughage for almost—if not all—hobby farmers with four-legged livestock. We rely on it during the winter when grass is gone or covered with snow and throughout the rest of the year when our animals may have limited access to pasture for various reasons.

At first blush, hay is not complicated. It’s cut and dried plant matter, after all. But herein lies the secret. The type of plant and when it was cut can make for drastically different nutrient profiles.

Let’s take a deeper look into this all-around roughage.

Types of Hay

The two most commonly encountered types of livestock hay in the U.S. are grass and legume hays. And several specific types exist within these two classifications. There is also mixed hay, which, true to its name, is a mix of both grass and legume types.

Grass Hays

Grass hays are true grasses. These include (among others):

• timothy grass
• orchard grass
• brome
• Bermuda
• Sudan
• fescue

The types of grass hay you’re most likely to encounter depend on where you and your livestock are in the country. Grass species fall into cool-weather and warm-weather types, describing which conditions they grow best in.

For example, if you’re farther north, you may typically see timothy grass hay. Timothy is a cool weather grass. Contrast this with more southern locales, where brome or Bermudas grass (both warm weather grasses) tend to grow.

Legume Hay

Legume hay is made from a different type of plant than simple grass. Botanically speaking, legumes are nitrogen-fixers. Symbiotic bacteria within their root systems utilize environmental nitrogen for growth, benefitting both the bacteria and the plant. Grass does not do this.

Common types of legume hay include alfalfa, clover and lespedeza (among others).

Nutritionally, there are a few large differences between grass and legume hays. Generally, legumes are higher in calcium and protein content as compared to grass hays, and are typically higher in overall caloric content. For this reason, legume hay like alfalfa is a great option to feed young growing animals. Same goes for adults that have higher energy requirements, such as pregnant animals and seniors with lower body condition scores due to health issues.

Alternatively, if you have over-conditioned animals (a nice way of saying fat animals), you may consider cutting their calories by feeding only grass hay.

Because of their general nutritional superiority, legume hays also tend to be more expensive than grass hays. Knowing the pros and cons of each type of hay impacts both your animals and your pocket book.

Read more: Should you measure hay by the bale or by volume?

Time of Cutting

In many parts of the U.S., the growing season occurs over several months through late spring into early fall. This means that a field of crop grown for hay can be cut up to three or four times during a single season.

This creates further choice in what you purchase: first-cutting versus second-cutting versus third-cutting, etc.

How young or old a plant is when cut also impacts its nutritional content, as based on leaf to stem ratio. Generally, the more leaves within a certain hay cutting, the more nutritious it is. When you evaluate whether to purchase a certain type of hay, ask about what cutting it is and look for leaves.

Based on your animals’ requirements, this can help you make a choice on what to buy.

Read more: These are the 20 machines and tools you’ll need for baling hay.

But How Do You Know for Sure?

Of course, all of this is to say that you can’t be totally sure of your hay’s nutritional value just by looking at its leaves, knowing what cut it is and its type. Laboratory analysis of your hay is a fantastic way to really understand what you’re feeding your animals.

To grab an adequate sample of your hay to submit for analysis, you need a tool called a hay corer, also called a hay probe. Many small operations don’t have one. Contact your local extension agent to grab one on loan.

Refer to the National Forage Testing Association for details on how and where to send your sample. Their website contains a wealth of information, including useful and easy to understand infographics.

Once you’ve mailed in a sample, results in terms of percentages will be returned. But terms like dry matter and acid detergent fiber can seem bizarre, intimidating and unhelpful. So talk to your extension agent and veterinarian about what they mean in relation to your herd’s nutritional requirements.

In this way, a little homework can reap a large payoff in understanding exactly what you’re feeding your animals.