Division 4.9.1 Techniques for monitoring N and P excretion

United Kingdom

Technique	Description
Calculation by using a mass balance of nitrogen and phosphorus based on feed intake, crude protein content of the diet, total phosphorus and animal performance.	The mass balance is calculated for each animal category reared on the farm, coinciding with the end of a rearing cycle, on the basis of the following equations: N_excreted = N_diet – N_retention P_excreted = P_diet – P_retention N_diet is based on the amount of feed ingested and on the crude protein content of the diet. P_diet is based on the amount of feed ingested and on the total phosphorus content of the diet. The crude protein and the total phosphorus contents can be obtained by one of the following methods: in the case of external feed supply: in the accompanying documentation; in the case of self-processing of feed: by sampling of feedstuff compounds from the silos or the feeding system for analysing the total content of phosphorus and crude protein or, alternatively, in the accompanying documentation or using standard values of total content of phosphorus and crude protein of the feedstuff compounds. N_retention and P_retention can be estimated by one of the following methods: statistically derived equations or models; standard retention factors for the nitrogen and phosphorus contents of the animal (or of eggs, in the case of laying hens); analysis for nitrogen and phosphorus contents of a representative sample of the animal (or of eggs, in the case of laying hens). The mass balance considers especially any significant changes to the diet commonly applied (e.g. change of a compound feed).
Estimation by using manure analysis for total nitrogen and total phosphorus contents.	The total content of nitrogen and phosphorus of a representative composite sample of manure is measured — and the total excretion of nitrogen and phosphorus is estimated — based on records for the volume (for slurry) or weight (for solid manure) of manure. For solid manure systems, the nitrogen content of litter is also considered. In order for the composite sample to be representative, samples must be taken from at least 10 different places and/or depths to make the composite sample. In the case of poultry litter, the bottom of the litter is sampled.

Technique

Description

Calculation by using a mass balance of nitrogen and phosphorus based on feed intake, crude protein content of the diet, total phosphorus and animal performance.

The mass balance is calculated for each animal category reared on the farm, coinciding with the end of a rearing cycle, on the basis of the following equations:

N_excreted = N_diet – N_retention
P_excreted = P_diet – P_retention

N_diet is based on the amount of feed ingested and on the crude protein content of the diet. P_diet is based on the amount of feed ingested and on the total phosphorus content of the diet. The crude protein and the total phosphorus contents can be obtained by one of the following methods:

in the case of external feed supply: in the accompanying documentation;
in the case of self-processing of feed: by sampling of feedstuff compounds from the silos or the feeding system for analysing the total content of phosphorus and crude protein or, alternatively, in the accompanying documentation or using standard values of total content of phosphorus and crude protein of the feedstuff compounds.

N_retention and P_retention can be estimated by one of the following methods:

statistically derived equations or models;
standard retention factors for the nitrogen and phosphorus contents of the animal (or of eggs, in the case of laying hens);
analysis for nitrogen and phosphorus contents of a representative sample of the animal (or of eggs, in the case of laying hens).

The mass balance considers especially any significant changes to the diet commonly applied (e.g. change of a compound feed).

Estimation by using manure analysis for total nitrogen and total phosphorus contents.

The total content of nitrogen and phosphorus of a representative composite sample of manure is measured — and the total excretion of nitrogen and phosphorus is estimated — based on records for the volume (for slurry) or weight (for solid manure) of manure. For solid manure systems, the nitrogen content of litter is also considered.

In order for the composite sample to be representative, samples must be taken from at least 10 different places and/or depths to make the composite sample. In the case of poultry litter, the bottom of the litter is sampled.