121 Opportunities and Challenges of Applying Recent Advances in Dairy Cattle Protein Nutrition to Beef Cattle Nutrition

Abstract

Ruminant protein nutrition is greatly affected by the fermentation in the rumen because the microbial population in the rumen converts a majority of protein provided in the diet to microbial protein. This has both positive and negative consequences on ruminant protein nutrition. On one hand, the ruminant can survive and thrive under conditions of poor protein quality, even with low concentrations of true protein in the diet. On the other hand, this can lead to reduced efficiency of nitrogen utilization and requires a more complicated approach for precisely meeting the amino acid requirements of the ruminant animal compared to non-ruminants. Because of the inefficiency of nitrogen utilization associated with milk protein production, high cost of high-protein feedstuffs, and the negative consequences of excess environmental nitrogen, a significant focus in the protein nutrition of dairy cattle in recent years has been to reduce dietary crude protein levels. Therefore, the goal is to reduce crude protein intake while maintaining high levels of milk production. To achieve this goal, dairy cattle nutritionists have increasingly used ration formulation models to predict microbial and rumen undegradable protein flow to meet a predicted metabolizable protein requirement. In addition to formulating for metabolizable protein, dairy cattle nutritionists are increasingly formulating for essential amino acids. The essential amino acids that are attracting the most attention are primarily methionine and lysine since these have been shown to be first-, second-, or co-limiting in a wide range of diets. There are also commercial options available to supplement for these limiting amino acids beyond formulating with complementary feedstuffs. The use of these approaches can result in reduced dietary nitrogen intake while maintaining or increasing productivity under commercial conditions; however, the most successful application comes when farms have excellent management and when farm managers and nutritionists agree to embrace this formulation philosophy. Although there are large differences in dairy and beef production systems, there could be important areas of overlapping understanding that could inform both dairy and beef cattle nutritional management. While there is much still to learn about dairy cattle protein nutrition, recent advances will be reviewed and the opportunities and challenges that exist in applying these nutritional approaches to beef cattle nutrition will be discussed.