When it comes to ruminant nutrition most people think of things like crude protein, energy, and possibly mineral content. Although these factors are important, roughage intake can often be overlooked. A minimum amount of roughage is important to keep the rumen functioning as it should.
The purpose of the rumen is to degrade complex structural fibers found in plants. Once it does that it metabolizes them to provide nutrients for the animal to make meat and milk that can be consumed by humans. They can produce better with plants that have lower fiber levels and are more digestible.
The quality and availability of roughage can have a direct effect on the success of a cattle enterprise. Providing better quality roughage can reduce the cost of feeding high-producing animals. But just how are you to go about providing better roughage for your animals? Well here are some things for you to consider.
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.
By mixing the material it 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. While the stomach is supposed to have some acidity too much can be detrimental and even deadly to the animal. 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 rumen and a slower process time will require more than say a goat with a smaller rumen. o 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. But it is believed that extensively they can tolerate somewhere in the 20%-30% area.
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 in a native pasture select forage each day they can manipulate their diet as needed. If they eat something one day that makes their rumen more acidic one day then the next they can search for another forage higher in fiber to balance it out.
How animals can get roughages?
There are 3 types of roughages that you can feed your animals. They are grazed roughages (such as pasture and range). preserved roughages ( hay and silage), and crop residues or by-products ( straw and hulls). 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.
Here in the state of Texas the percentage of roughages must be listed on the label in the ingredient 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”.
