This manual describes the use of the transfer model to estimate the concentration of dioxins in egg yolk fat and body fat of the laying hen based on oral exposure to feed contaminated with dioxins and dioxin-like PCBs using contamination levels of individual congeners. For estimations based on total TEQ levels in feed only, the user is referred to the transfer model dioxins (total TEQ) laying hen. The model has several input fields (left side) and output fields (right side). The input and results can be saved using the button “Report (*.docx)”. Source information and a citation suggestion are provided (top).

Step1: Contamination level of feed
The user needs to provide the contamination levels of the individual dioxins and dioxin-like PCBs in feed (expressed in ng/kg 88% dry matter) in one of the following ways:

• the user can download an Excel template, fill in the contamination levels and upload the file;
• the user can directly enter the values in the input fields of the individual congeners in the tabs Dioxins and Dioxin-like PCBs.

To reset the contamination levels all at once, the “Reset contamination levels” button at the bottom of the input fields can be used.  

Step 2: Feed intake
The user first has to select the type of feed that is contaminated with dioxins.

a)    This can either be:

• Total compound feed (blend of various raw materials and additives)
• Compound feed ingredients

When compound feed ingredients are selected, a drop down menu will appear to select the contaminated compound feed ingredient.

b)    After selecting the contaminated feed (ingredient), a default feed intake value is provided (in kg 88% dry matter per day) for the laying hen¹. The user can adjust this default value to the value corresponding to the actual feeding regime.

Step 3: Exposure period of laying hen to contaminated feed
To estimate the concentration in egg yolk fat and body fat, the user has to enter the duration of the exposure of the animals to the contaminated feed and the time elapsed after exposure, if applicable (both expressed in days).

Step 4: Regulatory limit (optional)
Regulatory limits (for instance maximum levels) (expressed in pg total TEQ/g egg yolk fat and in pg total TEQ/g body fat) can be inserted. These limits will be plotted in the output graph for egg yolk fat (red line) and/or body fat (orange line).

Step 5: Running model
The “Run model” button, present at the bottom of the input fields, can be used to run the model. After changing a value in any of the input fields, the “Run model” button has to be used to update the results.

Step 6: Results
After running the model the results will appear in the output field. The user can select “Plot egg yolk fat” and/or “Plot body fat”. The top graph displays the TEQ concentration in egg yolk fat (in pg TEQ/g egg yolk fat, solid lines) and/or in body fat (in pg TEQ/g body fat, dashed lines) versus time. The gray lines depict the dioxin and/or dioxin-like PCB’s concentration in egg yolk fat/body fat based on the sum of all individual congener transfer models. The black lines show the model calculations based on total TEQ model, i.e. based on the total TEQ concentration in feed (ingredient). When the user selects “Display individual congeners”, additional lines for the concentration of the included individual congeners (expressed in pg TEQ/g egg yolk fat and/or body fat) will be displayed.

Above the bottom graph, the user can select a specific day after the beginning of the exposure period using the scroll. The graph shows the individual congeners as percentages of the TEQ sum of all congeners present in the contaminated feed (ingredient) and estimated in in egg yolk fat.

Several tools for viewing the graphs become visible on the right top of the graphs when hoovering anywhere in the graphs. The option ‘toggle spike line’ can for example be used to view when the regulatory limit is crossed. The option ‘show closest data on hoover’ will the display the exact x and y-values when hoovering the plotted result. The tool ‘compare data on hoover’ shows the TEQ concentrations for all plotted lines simultaneously.  

Step 7: Saving input and output
Using the “Report (*.docx)” button, present at the bottom of the input fields, input data and the results of the model run can be stored locally as a report file in word. Input data and results are not stored at the website.

Step 8: Citation suggestion
At the top of the model page the references that describe the model are listed, as well as a citation suggestion. Please use the suggested citation when referring to the model.

 ¹ Van Raamsdonk LWD, Kan CA, Meijer GAL, Kemme PA (2007) Key figures for some farm animals and their consumption patterns [in Dutch]; https://research.wur.nl/en/publications/kengetallen-van-enkele-landbouwhuisdieren-en-hun-consumptiepatron.