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Nitrogen in livestock systems

The international scientific community keeps warning against greenhouse gas (GHG) emissions and the serious consequences of a drastic transformation of the nitrogen cycle over the last 40 years (FAO, 2006). Nitrogen compounds are emitted towards the environment in increasing amounts, leading to damages for biodiversity, climate, water quality and human health.
In that context, livestock systems are primarily concerned as they are both nitrogen consumers through feeding and nitrogen suppliers through animal excretion. The reduction of nitrogen emissions and the improvement of nitrogen recycling at the livestock system scale are therefore considered as major challenges for future evolutions in agriculture (FAO, 2006; Galloway et al., 2008).

Factors influencing gaseous emissions in dairy systems

In France, livestock systems are the first source of ammonia emissions (NH3, 74%) and the second source of nitrous oxide emissions (N2O, 8,6%; CITEPA, 2014). These gaseous emissions are caused by the volatilization of nitrogen excreted in manure, which depends on nitrogen amount and form in the diet, and are therefore directly linked to manure management (housing, storage, spreading, grazing).
Deep litter systems are widely used in France for cattle, leading to the production of farm-yard manure for which references on gaseous emissions are scarce and very variable in the literature, both at the house and storage levels. Similarly, ammonia emissions at pasture, generally weak but very variable, depend on numerous factors like climate, soil characteristics, stocking rate, grazing time…, which are difficult to analyze.

This project therefore aims at acquiring new knowledge on ammonia and GHG emissions and potential interactions over the chain of manure management (housing, storage, grazing).

A thesis combining a meta-analysis of the literature and experiments

The period of work in France has just started (February 2015). Three experiments are planned in the experimental dairy farm in order to evaluate the consequences of feeding different diets on nitrogen use by dairy cows and resulting gaseous emissions (housing, storage, grazing). A meta-analysis of a database from the literature will also be conducted in order to identify main variation factors of ammonia and GHG emissions in dairy barns.

The first experiment will consist in a comparison of lactating cows’ performances and nitrogen use efficiency when fed with a maize silage and soybean meal diet or with fresh grass. The cows will be conducted on a straw deep litter during 4 weeks and gas emissions (CO2, CH4, NH3, N2O) will be measured at the barn level.

At the same time, a second experiment will be conducted to measure ammonia (NH3) and nitrous oxide (N2O) emissions from dairy cows at pasture using different measurement methods.

A third experiment will aim at measuring gaseous emissions (CO2, CH4, NH3, N2O) from farm-yard manure produced in barns during their storage period (3 months).

All these results will help to propose animal management strategies both more efficient in terms of nitrogen use and more environmentally friendly.

The thesis of João Gabriel Rossini Almeida is a sandwich thesis partially conducted in Brazil (State University of Santa Catarina, Lages) with a stay of 1 year in the Syslait team of UMR Pegase.

Contact

Nadège Edouard, Dairy Systems team (nadege.edouard[at]rennes.inra.fr)

References

• CITEPA, 2014. Inventaire des émissions de polluants atmosphériques et de gaz à effet de serre en France – Format SECTEN. 333 p. [lien]
• FAO, 2006. Livestock’s long shadow, environmental issues and options. 7, 416 p. [lien]
• Galloway J.N., A. R. Townsend, J. W. Erisman, M. Bekunda, Z. Cai, J. R. Freney, L. A. Martinelli, S. P. Seitzinger, M. A. Sutton, 2008. Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions, Science 320, 889-892. (DOI)