This manual describes the use of the transfer model to estimate the concentration of PFOS and/or PFOA in milk, blood and the combined liver, kidney and muscle compartment (LKM) of the dairy cow based on oral exposure to feed contaminated with PFOS and/or PFOA. In this model, LKM is a lumped compartment based on the weighed sum of liver, kidney and muscle weight. 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 can provide the contamination level in feed for PFOS and/or PFOA (expressed in µg /kg 88% dry matter) in the contamination fields.
Step 2: Feed intake The user has to select the type of feed that is contaminated with PFOS and/or PFOA. For this, the user first chooses between a summer or winter feed regimen, and then the relevant type of feed.
a) This can either be:
- Total feed intake
- Grass
- Grass silage
- Maize silage
- Total compound feed (blend of various raw materials and additives)
- Compound feed ingredients
- Other
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)1. The user can adjust this default value to the value corresponding to the actual feeding regime. The user should be aware that whether the feed of the dairy cow is protein rich or protein poor can influence the default feed ingredient intake. The default values for compound feed ingredients used here are based on a protein-rich diet.
Step 3: Milk production To estimate the concentration of PFOS and/or PFOA in milk, a default value for milk production is provided (expressed in L/day)1. The user can adjust this default value to the value corresponding to the actual milk production.
Step 4: Exposure period of dairy cow to contaminated feed To estimate the concentration of PFOS and/or PFOA in milk, blood and the lumped compartment LKM, 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 5: Regulatory limit (optional) A regulatory limit for PFOS and/or for PFOA (for instance a maximum level) (expressed in µg/L milk) can be inserted. This limit will be plotted in the output graph for milk (black line for PFOS and blue line for PFOA).
Step 6: 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 7: Results After running the model the results will appear in the output field. The user can select “Plot milk”, “Plot blood” and/or “Plot LKM”. The graph displays the PFOS concentrations (black lines) and/or PFOA concentrations (blue lines) in cow milk (in µg/L milk, solid lines), in blood (in µg/L blood, dotted lines) and/or in LKM (in µg/kg LKM, dashed lines) versus time. These concentrations are based on the average Holstein dairy cow.
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 PFOS and/or PFOA concentrations for a maximum of 5 plotted lines simultaneously.
Step 8: 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 9: 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 In most models, an average food intake is provided as default based on Van Raamsdonk LWD, Kan CA, Meijer GAL, Kemme PA (2007) Key figures for some farm animals and their consumption patterns [in Dutch]; https://edepot.wur.nl/35188.