The truth about what roughages does for cattle

Roughages are an important but often overlooked part of a cow’s diet. Most of the time people only focus on things like crude protein, energy, and possibly even mineral content. While those are vital for the overall production of cattle roughages play just as important a role.  Consuming a certain amount of roughage is important to keep the rumen functioning in allowing the digestion of things like protein, energy, and minerals.

The rumen, mainly the microbes, needs to be taken care of if the animal is to produce. The purpose of the rumen is to degrade complex structural fibers found in plants. When it does that it then metabolizes them to make the nutrients that the animal needs. In order to keep them going the microbes need to be fed just like the animal themselves.

The quality and availability of roughages can have a direct impact on the success of a cattle ranch. There are many factors that can affect the quality of roughages. Things like rainfall, stage of maturity, and how they are managed can all affect the quality.

What are roughages?

A general definition of roughage is a feed ingredient that has a high concentration of slowly degradable fiber.  The tradeoff here is that being high in fiber they are low in total digestible nutrients. Roughages include the vegetative part of plants as well as feeding stuff of low total digestible nutrient content on a dry matter basis.

For a ruminant, the term roughage is any feed ingredient that has what is called “long roughage”. Long roughage contains particles that are from 3/8in to 1 1/2in or longer. The length is important because the longer fibrous material will need to be re-chewed by the animal. They will remain in the rumen for a greater time period than the shorter material.

The crude fiber content will also play a role in defining if it is roughage or not. According to the National Research Council, roughage feedstuffs have a minimum crude fiber content of 18%. The maximum total digestible nutrient of the feedstuff should also be 70%.

What do roughages do?

Roughages provide for what is called the “roughage effect”. What this means is that the long coarse fiber materials rub against the wall of the rumen. By doing this the muscles in the wall of the rumen expand and contract. This expansion and contraction stir and mixes the food that is in the rumen.

Mixing the material allows the microorganisms there to break down more of the food. The more contact the microorganisms make with the mix the more completely it can break them down. Breaking them down more allows more of the nutrients to be absorbed and used by the animal.

Another benefit of roughage in the diet is that the coarse material has to be regurgitated and chewed again in order to be metabolized by the microorganisms. This is commonly known as the animal “chewing its cud“.  Along with breaking the material down more the production of more saliva is also of benefit.

A ruminant’s saliva contains buffers that help to keep down the acidity in the rumen. An animal’s stomach should have some acidity, but too much can be harmful and even fatal. The fiber-digesting microorganisms in the rumen work best in a neutral to a slightly acidic environment.  This is typically a problem with animals that are being fed an all-concentrate diet.

How much do they need?

The amount of roughage that a ruminant requires will depend on the species. For example, a cow with a larger capacity of the rumen and a slower process time will require more than say a goat with a smaller rumen. You should look at which animals you will be feeding to determine the amount that you will need.

When it comes to measuring the amount of roughage there are 2 ways to go about it: Acid Detergent Fiber or Neutral Detergent Fiber. The Acid Detergent Fiber, or ADF, measures the cellulose and lignin content of a feed. Cellulose is a digestible form of fiber, while lignin is an indigestible form. ADF is a good test for measuring the energy value of forages whereas the NDF is superior in valuing a feed’s roughage effect. This is because this test measures the cellulose, hemicellulose, which is a poorly digestible material, and the lignin content of the feed.

When it comes to cattle the minimal NDF values have been studied very extensively, mostly from the dairy industry. The minimum recommended NDF level here is 25%, below this, the rumen environment can become very volatile and potentially dangerous to the animal’s health. With sheep and goats, the minimum amount has not been studied. There is a consensus that they are able to tolerate between 20% and 30%.

I should point out that there is a difference between a ruminant selecting a diet in the pasture that is 25% NDF over one that you are feeding them. When animals are in a native pasture grazing forage each day they can manipulate their diet as needed. If they eat something one day that makes their rumen more acidic one day than the next they can search for another forage higher in fiber to balance it out.

How animals can get roughage?

There are 3 types of roughages that you can feed your animals. Grazed roughages (such as pastures and rangelands), preserved roughages (hay and silage), and crop residues or by-products (straw and hulls) are all available.  They can be fed in either a fresh, dried, or ensiled state.

If you are having to provide roughages in a supplement it is important to look a little deeper than what will be on the feed tag. The crude fiber listed on the feed tag does not represent the ADF and NDF values. You will have to do a little more digging to find that stuff out.

The higher the crude fiber the more roughages that should be in the ration. Animals that are on a feedlot-type ration and are being fed hay along with it should have a feed that is at least 16% crude fiber for cattle and 14% for smaller ruminants. Cottonseed hulls, soybean hulls, and rice hulls are some good sources to use.

A Texas label must list the percentage of roughages in the ingredients section. If the roughage level is low and the crude fiber content is high the fiber is from a source that will probably not give much of a roughage effect. I go into a little more detail on what to look for in a previous post “How to read a feed tag”.

Some alternatives to forage roughages

There are sometimes certain conditions that traditional roughages may not be available. Things like the current drought that is going on in most of the country forages are either lacking in quality or just missing altogether. Add to that the possibility of there not being enough hay for this winter and producers may have to get creative when it comes to supplementing roughages to their cattle.  Here are some options that you can consider.

In cattle diets, cottonseed hulls are an excellent source of fiber. A majority of their use is found in the southern U.S., where cotton is primarily grown. They are low in protein (3.7%), calcium, phosphorus, and energy but they are high in fiber (44%). During times of scarcity, cottonseed hulls provide palatable roughage. In grain mixes, they increase bulk density and crude fiber content.

Another alternative is to use corn stalks. The leftover grain after harvesting. It can winter non-lactating mature cows very effectively. However, if you will be grazing first-cow heifers and fall-calving cows then you will need to provide additional energy and protein alternatives. Too many downed ears per acre can lead to excessive grain consumption. This increase can lead to digestive disturbances like acidosis and founder.