|POWELL, J MARK|
|Macleod, M -|
|Vellinga, T -|
|Opio, C -|
|Falcucci, A -|
|Tempio, G -|
|Steinfeld, H -|
|Gerber, P -|
Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2013
Publication Date: April 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/57152
Citation: Powell, J.M., Macleod, M., Vellinga, T., Opio, C., Falcucci, A., Tempio, G., Steinfeld, H., Gerber, P. 2013. Feed-milk-manure nitrogen relationships in global dairy production systems. Livestock Science. 152(2-3):261-272. Available: http://dx.doi.org/10.1016/j.livsci.2013.01.001. Interpretive Summary: With the anticipated increase in global demand for food, especially for animal products, and in an effort to improve the sustainability of animal agriculture, there is an urgent need for practices that enhance nitrogen use efficiency (NUE) and reduce environmental nitrogen loss from agricultural production. The objectives of this study were (1) to determine feed-milk-manure nitrogen relationships for the global dairy herd, (2) to evaluate how well regional and production system estimates (from models) correspond to actual measurements made under experimental and commercial farm conditions and (3) to evaluate how well estimates of nitrogen excreted in manure and NUE by lactating cows correspond to Intergovernmental Panel on Climate Change (IPCC) Tier 1 estimates of these parameters. We found that estimates (from models) of NUE-milk and manure nitrogen corresponded well to actual measurements under experimental and on-farm conditions. However, estimates of manure nitrogen were 30 to 50% lower than IPCC Tier 1 values for Africa, Middle East, Latin America and Asia. In other words, the amount of nitrogen in manure is being grossly overestimated in these regions of the world. The results of this study should enhance regional, production system and global determinations of dairy manure nitrogen loss during collection, storage, and land application, and the amounts of manure nitrogen actually recycled through crops and pastures.
Technical Abstract: Nitrogen (N) inputs from fertilizer, feed, and animal manure sustain productive agriculture. Agricultural systems are limited however in their ability to incorporate N into products, and environmental N losses may become local, regional and global concerns. The forecast increases in global demand for food, especially for animal products, necessitate an urgent search for practices that enhance N use efficiency (NUE) and reduce environmental N loss from agricultural production. The objectives of this study were to (1) determine feed-milk-manure N relationships for the global dairy herd, (2) evaluate how well regional (Africa, Central-South America, Asia, and Europe-North America-Oceania) and production system (confinement, grazing, hybrid confinement-grazing, and hybrid grazing-confinement) determinations of these relationships correspond to measurements made under experimental and commercial farm conditions, and (3) evaluate how well determinations of N excreted in manure (Nex) and NUE by lactating cows correspond to Intergovernmental Panel on Climate Change (IPCC) Tier 1 estimates of these parameters. Data on dairy cattle populations, feed and milk production from 144 countries were used in a Life Cycle Assessment (LCA) model to determine dry matter intake (DMI), N intake (NI), the percent of NI secreted as milk N (NUE-milk), the percent of NI used by the whole-herd (NUE-herd), and Nex. On a global basis, an average lactating animal cow weighs approximately 420 kg, and per animal unit (AU=1000 kg live weight) daily DMI and NI are 21.0 kg and 477 g, respectively, annual milk production is 5345 kg/AU, and NUE-milk and NUE-herd are 16.0 and 15.6%, respectively. There was great regional and production system variation in herd structures, production parameters, NUE and Nex. Determinations of NUE-milk and Nex corresponded well to measurements under experimental and on-farm conditions. The present study determinations of Nex were 30 to 50% lower than IPCC Tier 1 values of Nex for Africa, Middle East, Latin America and Asia. The apparent accuracy of LCA model calculations of Nex should enhance regional, production system and global determinations of Nex loss during collection, storage, and land application, and the amounts of Nex actually recycled through crops and pastures.