Feeding thermophile-fermented compost improves the water and muscle quality of cherry salmon by altering the microbiota in the gut

Improving the quality of recycling is necessary to build a sustainable society. Here, the effect of the oral administration of the compost, which was fermented from unused marine resource under high temperature condition, on the breeding result and the quality of the internal and external of Oncorhynchus masou as a freshwater fish model. Compost exposure improved the water quality, such as reduction of the total nitrogen content and suspended solids in the water. The fish body with ascites decreased significantly, although the rearing conditions were similar. Structural equation and causal inference based on machine learning data estimated the relationship among the water conditions and the muscle N-acetyl glutamate, a rate-determining factor of the urea cycle, and the fecal Sphingomas. These results emphasise that feeding compost modulate the relationship between the intestinal bacteria, internal metabolism, and water quality as the environmental load.