Compost derived substances decrease feed protein N mineralization in swine cecal digestion

Objectives of this study were to investigate urban biowastes as sustainable source of soluble biobased products (SBO) for use in animal diet and, possibly, to assess product chemical nature-performance relationships. Thus, five different materials sourced from biowastes processed by anaerobic and/or aerobic fermentation were treated to yield five different SBO. The products were first characterized for their chemical nature. Afterwards, they were tested as diet supplements to modulate pig’s cecal fermentation of a protein feed. In vitro fermentation of the protein feed was performed using the cecal content collected from slaughtered pigs as incubation liquor. The experimental plan comprised 29 treatments distributed over the 5 SBO used at 5-6 doses each in the 0.1-1.4% concentration range, compared to a SBO free control. During the 24 h in vitro fermentation, gas and liquor samples were analyzed for total gas volume vs. time production, and for ammonia and volatile fatty acids concentration. The results showed the investigated SBO to be significantly different for both their chemical composition and in their effects on the measured fermentation indicators. All materials showed significant effects already at the lowest 0.1% concentration. However the SBO isolated from composted residues decreased ammonia production, whereas the SBO isolated from the digestate of the food residues’ anaerobic treatment had the opposite effect. Ammonia production was found to be directly correlated with isobutyric and isovaleric production. The results clearly pointed out reduced proteolysis and N mineralization by 7-17% caused by compost sourced SBO. These findings have relevant implications for the economics and environmental impact of the animal production industry