Effects of diet and management on nutrient balance in open feedlots and wet corn gluten feed and roughage levels in finishing cattle diets

Nutrient management is an escalating concern for beef feedlots. Nitrogen volatilization to the atmosphere is a major concern, and nutritional and manure management programs can play a role in reducing N losses. Two experiments were conducted. In the first, two methods to increase manure N and decrease N losses were evaluated: (1) 30% dietary corn bran inclusion and (2) monthly pen cleaning frequency. Corn bran inclusion in finishing diets reduces diet digestibility and increases organic matter (OM) excretion onto the pen surface. Additional OM on the pen surface may “trap” N in manure via microbial immobilization and reduce N losses. More frequent pen cleaning may result in less exposure of manure N to surrounding air and subsequent volatilization. An interaction between diet and pen cleaning frequency on N balance in the feedlot was observed. Pens cleaned monthly and cattle fed bran resulted in the greatest reduction in N volatilization losses; however, performance was depressed with corn bran inclusion. Regardless of pen cleaning frequency, feeding corn bran resulted in more N recovered in composted manure. The second experiment was designed to evaluate alfalfa hay (AH) and wet corn gluten feed (WCGF) combinations in dry-rolled corn-based diets for effects on performance and N balance. Three levels of AH (0, 3.75, and 7.5%) and two levels of WCGF (0 and 35%) were evaluated. Addition of intermediate levels (i.e., 20–50%) of WCGF to finishing diets maintains cattle performance due to the combination of steep and bran, and reduced acidosis. Fiber addition to diets in the form of WCGF may reduce the need for conventional levels of roughage and reduce N losses by increasing OM excretion. Feed efficiency improved as AH was removed in diets containing 35% WCGF, suggesting no value of AH in these diets. Manure and compost N was greater with WCGF addition to diets, likely as a result of greater OM excretion. More manure OM was removed from pens fed WCGF; however, N losses were not reduced, presumably as a result of greater N excretion and the effects of warm summer feeding months on NH 3 volatilization