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Development of a new model for partitioning excretion of nitrogen between urine and faeces in cattle production

Project: Research

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There is currently a strong focus on ammonia emissions from livestock production, partly as a result of demands for a national reduction of 24% by 2020. There is therefore a strong focus on correct estimation of emissions and the effect of any interventions. Correct distribution of the excretion of nitrogen (N) in faeces and urine, respectively, is absolutely essential for subsequent prediction of ammonia emission, as the emission can be attributed to a fixed proportion of inorganic N in urine as opposed to organically bound N in faeces, where emission is calculated as being zero. In the Danish standard normative system for livestock manure content of nutrients, the excretion of N in faeces is calculated on the basis of dry matter intake and N content in the diet, and excretion of N in urine is subsequently calculated as a difference. The equation for predicting the excretion of N in faeces (and thus N in urine) for dairy cows is based on data from digestibility experiments published in the period 1973-1996. This is data that is 20-40 years old and thus at a completely different production level than the modern dairy cow. When the equation today is used to predict the effect of e.g. increased milk yield and dry matter uptake, we therefore have to extrapolate far beyond the production level on which the equation is based. For young stock, the model is even based on data for a completely different animal, namely sheep on maintenance. This is not sustainable with the political and business focus that is on these data today.
The project is financed by the Danish Milk Levy Foundation, the Danish Cattle Levy Foundation and Aarhus University Public Sector Consultancy.
Effective start/end date01/01/201731/12/2021

ID: 198241799