Animal droppings are essential for agriculture because they are rich in organic matter and nutrients that support plant growth. The application and management of manure from domestic animals is essential for the sustainability of agricultural practices. Nevertheless, diseases and unbalanced nutrient contents in unprocessed manure can seriously endanger the environment and public health. This study examines the physical, chemical, bacteriological, and faunal diversity of fresh and decomposing horse dung mixed with agricultural waste. The mixture was analysed on the first day of the composition process and repeated eight months before field application. Frequent assessments of fresh and mature manure have been conducted to monitor faunal diversity. In addition, a light trap was used for an entire year to count the most common scarab species (Phyllanthus excavatus). The levels of faecal coliform bacteria and Streptococcus, total nitrogen, accessible phosphorus, potassium, organic matter, and carbon decreased in the mature manure mixture. Other measurements indicating a notable increase included total viable heterotrophic bacteria and Actinomyces, as well as total potassium, available nitrogen, and total phosphorus. The fresh mixture contained many insect species, including various species of ants, cockroaches, immature fly stages, earwigs, beetles, and woodlice. In contrast, woodlice and multiple stages of scarab species dominated the mature mixture. A high prevalence of the scarab Phyllognathus excavatus was observed, especially in October and November. Exploring the role of terrestrial biota and associated microflora on soil fertility and nutrient cycling dynamics is crucial for sustainable agricultural practices.