Yeasts are single-cell eukaryotic microorganisms that are largely employed in animal nutrition for their beneficial effects, which are owed to their cellular components and bioactive compounds, among which are mannans, β-glucans, nucleotides, mannan oligosaccharides, and others. While the employment of live yeast cells as probiotics in poultry nutrition has already been largely reviewed, less information is available on yeast-derived products, such as hydrolyzed yeast (HY) and yeast culture (YC). The aim of this review is to provide the reader with an overview of the available body of literature on HY and YC and their effects on poultry. A brief description of the main components of the yeast cell that is considered to be responsible for the beneficial effects on animals’ health is also provided. HY and YC appear to have beneficial effects on the poultry growth and production performance, as well as on the immune response and gut health. Most of the beneficial effects of HY and YC have been attributed to their ability to modulate the gut microbiota, stimulating the growth of beneficial bacteria and reducing pathogen colonization. However, there are still many areas to be investigated to better understand and disentangle the effects and mechanisms of action of HY and YC.

To support the overall health of horses, it is essential to maintain an optimal gut health (GH) status, which encompasses several physiological and functional aspects, including the balance and functionality of intestinal microbial populations and, accordingly, the effective digestion and absorption of nutrients. Numerous biotic and abiotic stressors can lead to an imbalance of GH, such as the quality of forages and the composition of diet, e.g., the inclusion of high energy-dense feeds to meet the energy requirements of performance horses. To support the digestive function and the intestinal microbial populations, the diet can be supplemented with feed additives, such as probiotic yeasts, that promote the ability of cellulolytic bacteria in the hindgut to digest the available fiber fractions, finally increasing feed efficiency. Among the different yeasts available, S. cerevisiae is the most used in horses’ nutrition; however, results of digestibility trials, as well as data on intestinal and fecal microbial populations, are sometimes contradictory. Therefore, the purpose of this review is to summarize the effects of S. cerevisiae on in vivo and in vitro digestibility, providing an updated overview of its effects on the intestinal and fecal microbial population.

Phytogenic feed additives have replaced the use of antibiotic growth promoters (AGP) in the diet of poultry particularly broiler chickens. Researchers are moving towards the use of natural products such as herbs, spices, plants and plant products, which possess influential effects on growth performance parameters, immune response and treatment of various diseases. Aloe vera is a well-known medicinal plant and is being used for commercial and therapeutic purposes such as antimicrobials, antitumor, anti-inflammatory, immunomodulator, wound healing, antioxidant and antiprotozoal agents. From a few last decades, the use of Aloe vera has been increased as a natural additive to broiler diet. Based on the review of literature, Aloe vera can improve immune response, growth performance in the broiler, as well as an excellent alternative of AGPs and anticoccidial drugs. It can be used for broiler diet in the form of gel, powder, ethanolic extract and aqueous extract. This review provides information about the use of Aloe vera in broiler production with reference to the effects on growth performance, immune system, intestinal microflora and coccidiosis in broiler chickens.

This study investigated the effects of yeast-derived nucleotides (YN) supplementation via drinking water on growth performance, intestinal morphology, barrier function, and cecal microbiota in broiler chickens. A total of 480 one-day-old male Ross 308 broilers were randomly assigned to three groups: control (CTR), and two treatment groups receiving YN at 90 g/100 kg (T1) or 180 g/100 kg (T2) in drinking water for 42 days. Growth performance parameters were recorded throughout the trial, and intestinal samples were collected on days 21 and 42 for histomorphological evaluation, gene expression analysis, and microbiota profiling using 16S rRNA gene sequencing. YN supplementation significantly improved body weight on day 21 and average daily gain during the grower phase in the T2 group. Carcass weight was also significantly increased in T2 at day 21. Intestinal morphology analysis revealed improved villus-to-crypt ratio on day 21 in both treatment groups, and gene expression analysis demonstrated upregulation of tight junction-related genes (ZO-1, OCLN, CLDN3) in T2, indicating enhanced intestinal barrier integrity. No differences were observed in mucous layer thickness or MUC2 expression. Microbiota analysis showed a significant increase in alpha diversity indices over time, consistent with normal microbial maturation. While T1 increased Shannon and Simpson indices compared to CTR, no significant changes were observed for T2. Beta diversity was not affected by treatment, although a clear temporal shift in microbial community composition was evident between days 21 and 42. In conclusion, administering yeast-derived nucleotides via drinking water improved early growth performance and intestinal health in broilers, particularly at higher inclusion levels. This mode of administration offers a practical, flexible alternative to feed-based supplementation, allowing targeted use during critical growth periods or under stress conditions. These findings support the functional role of YN as a dietary strategy to promote gut health and performance in poultry production.