antibiotics over the counter is a common practice driven by farmers' experience -based antibiotic usage (Bâtie et al. 2022; Carrique-Mas et al. 2015; Truong et al. 2019) as it is also in human medicine (McKinn et al. 2021). Moreover, in Vietnam, people without a practice certificate or veterinary training sell drugs (usually to a relative of the shop owner) and are therefore not allowed to issue prescriptions. In countries where over-the-counter drugs are highly regulated, the rate of self-medication is significantly lowerthan in Southeast Asia, where drugs are widely available. Self-medication leads to antibiotic misuse and overuse (Nepal and Bhatta 2018) . Changing farmers' habits (especially among the older generation and for small scale farms) was perceived as difficult in Vietnam because they are using antibiotics according to their own experience or their neighbor's experiences. The implementation of this essential regulation in the fight against ABR will therefore require the development of tailored solutions. Solutions to improve the implementation of the newregulations Several respondents stressed the need to clarify regulations and strengthen sanctions to improve their implementation. These sanctions should be more clearly defined, stricter, and systematic. This would require clear guidance, a distribution of tasks, and more resources for the authorities, including technical and human capacities (Jamrozik and Selgelid 2020). Participants suggested random on-farm feed inspections or targeting drug sellers to incur a domino effect. We also identified an informal flow of antibiotics leading to the sale and usage of banned substances. This informal flow has already been described in aquaculture systems (Brunton et al. 2019), and producers have reported using banned substances (Pham-Duc et al. 2019). Respondents also raised drug quality concerns, including the presence of diluted antibiotics, which led to higher antibiotic dosages or that expose the chickens to sub- therapeutic dosages. This finding was consistent with a previous study conducted among farmers in the Mekong Delta (Yen et al. 2019) and is also an issue in other Southeast Asia countries (Pham-Duc and Sriparamananthan 2021). This is a worrying situation as counterfeit or sub-standards antibiotics contribute to the emergence of ABR (Kelesidis and Falagas 2015). Mostrespondentsbelievethat reducingtheproportionofsmall-scale farmsin favor of large- scale farms and integrated systems would help to alleviate the ABR burden. Small-scale farms have often been blamed for antibiotic misuse and overuse in Vietnam and worldwide (Ducrot et al. 2021) and identified as stakeholders whofail to comply with regulations due to their lack of adaptability (Pham-Duc and Sriparamananthan 2021). The solution of reducing the number of small scale farms is in line with the government's strategy outlined in the agriculture development plan for 2025 (Prime Minister 2021). This was also true in 2003, during the highly pathogenic avian influenza crisis, when industrial production was pushed through partnership between the public and agro-industrial sectors, because integrated farms were perceived as implementing better biosecurity (Figuié, Pham, and Moustier 2013). However, this study demonstrated that, due to consumer preference for the local market, only the most competitive ones developed. Also, as one respondent pointed out, increasing the size of farms does not always result in a reduction in ABU, and increasing size without adequate training can have negative consequences for ABU control. Moreover, intensive systems were also reported as heavy users of antibiotics, especially in prophylaxis (Bâtie et al. 2022; Luu et al. 2021). Onthe other hand, poor biosecurity in small-scall farms in Vietnam can also be challenging with outdoor systems and low farmers technicity (Thi Dien et al. 2023). Small-scale production has