Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots
Cowley, F., Jennings, J., Cole, A., Beauchemin, K. (2019). Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots, 59(11), 2082-2092. http://dx.doi.org/10.1071/AN19259
Plain language summary
Overfeeding of nitrogen to feedlot cattle is considered low-risk (in terms of cost and effects on production), but excreted excess dietary nitrogen is of significant environmental concern. Our ability to formulate the protein content of grain-finishing rations is becoming more precise but there are still barriers to adoption on-farm. Precision feeding of protein needs to account for variations in production system, and will enable us to improve nitrogen use efficiency, and reduce nitrogen intake and wastage in the feedlot.
© CSIRO 2019 Open Access.Formulating diets conservatively for minimum crude-protein (CP) requirements and overfeeding nitrogen (N) is commonplace in grain finishing rations in USA, Canada and Australia. Overfeeding N is considered to be a low-cost and low-risk (to cattle production and health) strategy and is becoming more commonplace in the US with the use of high-N ethanol by-products in finishing diets. However, loss of N from feedlot manure in the form of volatilised ammonia and nitrous oxide, and nitrate contamination of water are of significant environmental concern. Thus, there is a need to improve N-use efficiency of beef cattle production and reduce losses of N to the environment. The most effective approach is to lower N intake of animals through precision feeding, and the application of the metabolisable protein system, including its recent updates to estimation of N supply and recycling. Precision feeding of protein needs to account for variations in the production system, e.g. grain type, liveweight, maturity, use of hormonal growth promotants and β agonists. Opportunities to reduce total N fed to finishing cattle include oscillating supply of dietary CP and reducing supply of CP to better meet cattle requirements (phase feeding).