Clearing up confusion on protein and energy supplements

Adele Harty
SDSU Extension Cow/Calf Field Specialist

Differentiating between protein and energy supplements is key to developing an effective cattle supplementation program, but it can be very confusing. With the multitude of feed options available, understanding types of feeds and nutrient requirements will help ensure cattle perform optimally.

All feeds contain energy and protein, but feeds are differentiated based on the amount of each nutrient in the feedstuff. Frequently, the biggest challenge is determining whether a protein or energy supplement is needed. The only way to know for sure is to sample feeds and send them to a commercial laboratory for a nutrient analysis. Once deficiencies are identified, supplemental feeds can be evaluated to determine which one will meet animal nutrient requirements with little or no modifications or addition of storage and handling equipment, at the most economic price.

As a general baseline, rumen microbes require a diet that contains a minimum of 7 percent crude protein. The rumen microbes utilize the nitrogen in the protein to grow, multiply, and digest the fiber components of the forage. This level of protein does not take into consideration the requirements of the cow herself. That being said, protein supplements are frequently necessary to improve forage digestibility by rumen microbes when cows are being fed low quality forage or grazing dormant pasture.

A protein supplement can be any feed that will increase the protein content of the basal diet. Examples of protein supplements include by-product feeds such as distiller’s grains and corn gluten feed. Other common protein sources are alfalfa hay, soybean meal, range cubes, molasses lick barrels, protein blocks and liquid protein supplements. The protein levels on these feeds can range from slightly less than 20 percent up to 48 percent for the soybean meal. Some of the commercial products, including molasses lick barrels, protein blocks and liquid protein supplements may contain a higher level of protein, but a portion of the protein is supplied by a non-protein-nitrogen source, such as urea or biuret. Read feed tags to determine the protein source in commercial feeds.

Energy supplements are characterized by low protein content, normally less than 20 percent. Traditional energy supplements typically consist of grains that are high in starch content such as corn, barley, and oats. The challenge with providing these energy supplements with a low quality forage diet, is that starch interferes with forage digestion in the rumen by changing the rumen pH and making it a more favorable environment for those microbes that are more efficient at starch digestion. This decrease in rumen pH results in a decreased number of microbes for forage digestion. Fortunately, there are other energy supplements available that decrease the potential for these negative associate effects. They are characterized as a high fiber energy source, many of which are by-product feeds such as soyhulls, wheat middlings, and sugar beet pulp. These high fiber supplements provide additional energy without changing the rumen environment.

To drive home the importance of identifying and knowing the difference between the two types of supplements, one must understand that if the wrong type of supplement is used, efficiency decreases and there is a potential for negative impacts. For instance, you observe cattle that have been grazing dormant forage have manure that is piling up, has well defined rings, and appears dry. This is an indicator that they are short on protein and not utilizing the feed as well as they should be. Additionally, over time, body condition has decreased. In this situation, if an energy supplement is used rather than a protein supplement and inclusion levels are greater than 10 percent of the diet dry matter, a negative associative effect can result. This simply means that the inclusion of the energy supplement can decrease forage digestibility and overall nutritive value of the ration. On the other hand, if a protein supplement is used, it results in increased efficiency of the rumen microbes and increased efficiency in forage digestion and utilization and overall improved performance.

When evaluating a feeding program make sure all nutrient goals are being met and that the appropriate supplement type is being utilized to overcome shortfalls. Read the feed tag or the feed analysis sheet to determine whether it is a protein or energy supplement by determining the main nutrient that this feed will be adding to the ration. In addition to making sure you have the right type of supplement, evaluate options on a cost per unit of nutrient basis to focus on the most economic option.