Feed companies that add antibiotics to feed benefit more than others. Indeed, if feed is perceived as less efficient because of the absence of antibiotics, farmers will switch to a feed supplier knowntoaddantibiotics to feed to maximize their production. Respondents reinforce the fact that, for regulations to be effective, they mustbeappliedby everyone at the sametime.

'Enforcement is one of the issues because of the violation of certain (…). If one of them uses it illegally, that means that somehow, they have the benefit of market competitiveness. ' (IW34, international partner)

####### Scale-related management discrepancies

Thepredominanceofsmall-scalefarms in Vietnamwasperceivedbyrespondentsasamajor barrier. Stakeholders reported that they had poor farming management practices, which were accentuated by intermittent production. Indeed, some farmers produced a few hundred chickens for the Lunar New Year and then stopped their production after selling the batch. Farmers treated their chickens themselves or according to the experience of other farmers and bought drugs without a prescription based on their own experience. This practice was confirmed by a family commercial farmer that explained not always following the recommendations of the health professional, because they relied more on their own or other farmer's experience and wanted to treat their animals immediately. However, the household farmer reported calling the veterinarians and the family commercial farmers going or calling the veterinarian for unknown disease. Respondents raised that small-scale farmers aged between 50 and 60 showed less willingness to change compared to the younger generation. Moreover,there wasinsufficient control oversmall-scale farms becausethegovernmentdid not have the humanand financial capacity to inspect them all.

'Even if wedon't put antibiotics in feed, they can still buy drugs from drug agencies and add it themselves. ' (IW29, feed company)

Additionally, some drug sellers sold antibiotics without the proper qualifications. This is made possible by the limited control capacity of Sub-DAHLP to inspect all small drugstores. Integrated and large-scale farms were perceived to be more compliant with legislation. Firstly, they were more aware of regulatory changes and had time to adapt due to their direct link with integrators. Integrators, drug, and feed companies were also better prepared for regulatory change because in-company veterinarians were qualified to write out prescriptions underthenewregulation. Also, respondentsexplained that it wasmoredifficult for a large farm to add antibiotics to feed and to mix them themselves than for small scale farms. Government or contract farm integrators carried out more on-farm inspections due to the products being sold in supermarkets where drug residue tests are performed.

####### Technical and financial barriers to the implementation of regulations at local level

Locally, respondents stressed the technical and financial barriers to implementing the new regulations. First, in some areas, there were not enough certified veterinarians for the number of farmers, especially given the large number of small-scale farms. Thus, due to a shortage of