ENVIRONMENTAL BENEFIT AND BURDEN OF POSTBIOTICS IN ANIMAL NUTRITION

The EU Sustainability Goals (NP/EFSA/FEEDCO/2022/02) heavily relies on feed additives. The revision of the feed additives regulation is one of the goals of the Farm to Fork strategy. Its primary objective is to encourage innovation in feed additives, especially those that help reduce the use of antibiotics, improve animal welfare, and lessen the environmental impact of animal production. This will support the shift to a more sustainable livestock farming system. Postbiotics are soluble compounds, either products or metabolic by-products, secreted by living micro-organisms (yeast and bacteria) or released upon their lysis, which confer physiological benefits to the host. These substances are currently the subject of research. Postbiotics, however, remain a novel concept in the domain of animal science. It is hypothesized that yeast-derived postbiotics may have a positive effect on growth performance and gastrointestinal health in poultry. The objective of this research was to evaluate the benefit of postbiotics in animal nutrition that pass through hydrolyzed yeast (HY) and yeast nucleotides (YN) as a form of postbiotics. The final goal is to do yeast fermentation in order to understand the procedure involved in generating a postbiotic. The first study was conducted after writing a literature review on yeast and its derived products to better comprehend their mechanism of action in poultry and to define the state of the art. An in vivo trial was conducted on broilers using hydrolyzed yeasts (K. marxianus). The findings revealed that the treatment had no significant impact on the broilers’ performance, meat quality, and gut health. The role of hydrolyzed yeasts (HY) on gene expression, with specific attention to the adiponectin system and tight junctions was analyzed. Taken together, determining the segment-specific changes in expression provides a deeper understanding of the molecular mechanisms underpinning pathophysiological changes in the gut of broiler chickens with various etiologies. Additionally, the increased levels of tricarboxylic acid (TCA) cycle interme-diates (2-oxoglutarate and citrate) in untargeted metabolomic treated cecal samples may point to a slight shift in the bacterial community, which metagenomic approaches might be able to explain in the future. The goal of the second trial was to examine the impact of yeast nucleotides (YN) on production performance and gastrointestinal health. In vivo study was performed on broilers using YN (S. cerevisiae). The supplementation of the basal diet with YN showed significant effects on production performance and slaughtering performance while given in drinking water. YN also showed a statistically significant effect on the villous height to crypt depth (VH/CD) ratio and tight junction proteins (Zonula occludens (ZO-1), Occludin (OCLN), Claudin-3 (CLDN3)), indicating an impact on the morphology and gut health of younger broilers during the growing phase. The third trial was conducted to understand the complexities of yeast fermentation process which may lead to the production of a novel yeast-derived postbiotic. Particular attention has been reserved for yeast fermentation, factors affecting fermentation, the end products of fermentation, and their strict connection to the emerging concept of postbiotics. The yeast growth curves were monitored, enabling a comprehensive examination of the lag, exponential, and stationary phases of fermentation in real-time with high throughput. The maximum growth rate, lag time, and cell density were obtained from the growth curves by utilizing nonlinear regression models to extract key characteristics. The preliminary results showed that the simple media molasses (MY) group (1/4 dilution) showed maximum growth rate, lag time, cell density and biomass at all three temperatures as compared to the molasses oligo element vitamin mix groups (MOVY). The metabolomic analysis gave a list of significant metabolites (including nucleotide metabolism intermediates, amino acids, arginine metabolism intermediates, biotin, pyridoxine, d-glucose and d-oxoglutarate) present in both groups at 30 ̊ C. The results opened a path that may lead to optimization of yeast additives, precise yeast fermentation scrutiny, accenting its usefulness in optimizing industrial fermentation processes and helping further understand the key role of postbiotics in animal nutrition.