4.3.3. Influence of Knowledge about the Relevant Laws and Their Penalties on Farmer's Behavioral Choices

Figure 4 demonstrates the influences of knowledge about the relevant laws and penalties on farmers' behavioral choice. Farmers' VA use is closely related to their knowledge about relevant laws and their penalties. When farmers' knowledge about relevant laws and their penalties *ϕi*<sup>3</sup> = 1, there was a relatively high probability of improper VA use, fluctuating between 70% and 80%, as shown in Figure 4a,b. When the value of *ϕi*<sup>3</sup> changed from 1 to 3, the probability of proper VA use in the farmer group did not increase substantially, while the probability of improper use decreased by 5–10%. As can be seen from Figure 4c, when farmers had a relatively high level of knowledge about the relevant laws and their penalties, improper VA use still occurred at a probability of around 50%, which was similar to the probability of proper use. In fact, current pre- and post-slaughter pig quarantine in China

only focuses on foot-and-mouth disease, swine fever, swine vesicular disease, and other diseases. VA residues in live pigs are not strictly monitored. The testing of antibiotic residues only includes several common types of VAs. This has resulted in a low probability of discovering improper VA use by farmers, and consequently, there has been insufficient punishment. From the perspective of policy regulation, pig farmers in China is allowed to execute routine treatments by themselves, just like some advanced nations including The Netherlands (e.g., Kuipers et al., 2016 [21]). This and other similar permissions have allowed farmers in China more autonomy in medical related behaviors. Therefore, it is possible that farmers, driven by economic interests and endorsed with higher behavioral autonomy, deliberately choose improper VA use, despite knowing the penalties.

**Figure 4.** Simulation results of the changes of farmers' behavioral choices regarding VA use under the variation of their knowledge about relevant laws and their penalties: (**a**) the value of *ϕi*<sup>3</sup> (knowledge of relevant laws and their penalties) was set to 1; (**b**) the value of *ϕi*<sup>3</sup> was set to 3; (**c**) the value of *ϕi*<sup>3</sup> was set to 4.
