Biogas production from cattle manure offers a promising and sustainable solution for managing livestock waste in the rural areas of the Vietnamese Mekong Delta (VMD), where smallholder cattle farming is common. The study aims to evaluate the impact of organic loading rates (OLR) of cattle manure (CM) on biogas production through anaerobic digestion under the tropical conditions typical of smallholder farming. Additionally, the research seeks to assess the stability, suitability, and continuous operational performance of biogas digesters in relation to the size of the cattle herd in each household. Nine biogas digesters achieved steady-state operation, with various numbers of cattle in households being monitored continuously over 13 weeks to assess daily biogas production. The results of the study can be categorized into three groups based on cattle herd size: Group 1 (two cattle), Group 2 (three cattle), and Group 3 (four cattle). The volume of the biogas digester is approximately 6.3 m³, which is typically suitable for households with three cattle, operating at an OLR of 5.78–6.00 kg-VS day-1. Under these conditions, the digesters demonstrated stable performance and achieved high biogas yields of 270–310 L kg-VSadded-1. In contrast, households with four cattle experienced a higher OLR of 7.52–8.67 kg-VSadded day-1, which resulted in lower biogas yields of 156–219 L kg-VSadded-1. These findings suggest that the digester volume used in this study is not appropriate for households raising more than three cattle, as overloading can impair performance and reduce methane productivity. The study established the optimal digester volume corresponding to herd size to maximize biogas production efficiency. For future strategies, it is recommended to use post-digestion effluent (biogas effluent - BE) for cultivating Napier grass (Pennisetum purpureum). This approach is a crucial step towards creating a closed-loop circular economy in cattle farming systems