Amino acids are the building blocks of protein. Each protein is made up of a unique configuration of various amino acids. Not enough amino acids can reduce performance potential, and too many amino acids are excreted through urine – basically wasting producer’s money.
There are hundreds of amino acids found in nature, but only 20 amino acids are used by cattle to make protein. Half of those are essential, meaning cattle cannot synthesize them within the body, and they must be consumed in the diet or provided by rumen microbes. Regardless if an amino acid is classified as essential or non-essential, they are all critical to supporting cattle growth and development.
Although diets are formulated to meet protein requirements, cattle require amino acids, not protein. To meet amino acid requirements, diets are typically fed with excess protein to ensure adequate amino acid levels are offered. This method of meeting amino acid requirements has a few challenges.
First, some feed ingredients are low in certain amino acids. A diet could have adequate or excess protein levels and still be insufficient in an essential amino acid. For instance, diets high in corn tend to lack adequate lysine, while diets high in forage or soybean products tend to lack methionine. When amino acids are underfed, cattle will fail to meet their maximum performance potential and are more likely to experience negative health events. In beef cattle diets, histidine, methionine, lysine, and arginine tend to be the amino acids of most concern.
On the other hand, excess protein diets may exceed amino acid requirements for certain amino acids. In this case, cattle will expend energy metabolizing the excess protein, decreasing the efficiency of protein use by the animal and shifting energy away from growth. And all the excess protein will be excreted leading to increased urea output.
Regardless if amino acids are under- or over-fed, producers will end up wasting money on either cattle that don’t meet their maximum level of performance or on waste loss in the form of excess urea.
Beef cattle nutritionists are working to overcome the challenges with feeding protein to beef cattle by identifying specific amino acid requirements for beef production. A shift in formulating diets based on amino acids content allows for less protein to be fed in the diet and improved efficiency of protein use.
Rumen-protected amino acids are a tool available to help nutritionists formulate diets for amino acid content. Rumen-protected amino acids escape ruminal degradation and are utilized in the lower gut. Because many feed ingredients are limited in some essential amino acids, rumen-protected amino acids can be used to meet amino acid requirements without adding additional protein sources to the diet.
Extensive work has been done in dairy cattle on rumen-protected amino acids, but work in beef cattle is still limited. However, data indicates there is value in including rumen-protected amino acids in beef cattle diets.
In multiple studies, the addition of rumen-protected amino acids improved feed efficiency due to increased average daily gain. In finishing studies, cattle finished with higher final body weights and larger, more muscular, and leaner carcasses. Beef cows saw a shift in protein utilization away from body weight gain and towards milk protein production. Additionally, when cattle diets were formulated for amino acid content, nitrogen digestibility was enhanced, while urinary nitrogen excretion, urea, and nitrous oxide emissions were decreased.
Overall, including rumen-protected amino acids and formulating diets for amino acid enhanced protein utilization resulted in reduced urea output by cattle. Implementing these tools on-farm will help producers meet sustainability goals while also managing feed costs and tight margins.