Ultrafine Metallic Particles as Inducers of Digestive Processes in Rumen: Dry Matter Digestibility of Feed and...

The ban on the use of antibiotics in animal husbandry encourages an active search for highly effective alternatives with additional properties, one of which is ultrafine particles (UFP) of metallic nature. The objective of the presented work was to conduct a comprehensive analysis of newly synthesized UFP Co₃O₄ and Mn₂O₃, including determination of their biological activity on the model of luminescent bacterial strain and potentiating effect on rumen digestion in ruminants using an in situ method. In parallel, the activity of proteinase, lipase, amylase, and cellulase, as well as nitrogen forms, microbial biomass, and the number of protozoa in 1 mL of rumen fluid, were determined. The minimum inhibitory concentrations for Mn₂O₃ and Co₃O₄ UFP were 3.9 × 10^-2 and 1.2 × 10^-3 mg/mL, respectively. The digestibility coefficient with the introduction of Mn₂O₃ UFP (39.0 mg/kg dry matter of feed) increased relative to the control by 6.6% (p = 0.012); Co₃O₄ UFP (0.6 mg/kg) by 12.7% (p = 0.012). Cellulolytic, amylolytic, and lipolytic activities in the group with Mn₂O₃ UFP increased by 18.2%, 515.5%, and 122.6% times compared to control, respectively. Proteinase activity decreased by 7.7% compared to control. Similar indicators in the group with Co₃O₄ UFP were +35.1%, +210.3%, +74.2, and +8.8%. Other indicators changed accordingly. Thus, UFP Mn₂O₃ and Co₃O₄ demonstrated significant potential as effectors of digestive processes in the rumen, stimulating the reproduction of protozoa and the enzymatic activity of the microbiome, which in combination ensured an increase in the digestibility of dry matter of feed. In other words, they can be used in the future as feed additives for ruminants. However, to fully understand the mechanisms of their action, it is also necessary to analyze the microbiome and metabolic pathways in the rumen.