Effect of different levels of yeast cell wall on performance and cecal microbial population of Japanese quail

Introduction: Poultry nutrition constitutes approximately 60 to 70 percent of poultry farming expenses. Consequently, it is crucial to develop cost-effective poultry production using scientific nutritional principles. Yeast and its derivatives are recommended additives in poultry diets to enhance performance. Yeast cell walls, making up 25 percent of the yeast cell's dry weight, not only serve a protective function but also participate in metabolic processes. These cell walls contain mannoproteins, beta-glucan, mannan oligosaccharide, chitin, and N-acetylglucosamine. Notably, beta-glucan, with its helical structure, can absorb mycotoxins, thereby playing a significant role in improving livestock and poultry health by detoxifying their feed. Mannan oligosaccharide has been shown to prevent pathogen colonization in the digestive tract. As prebiotics, oligosaccharides promote the growth of beneficial anaerobic bacteria in the gut, indirectly reducing pathogen populations and enhancing intestinal health. This study aimed to examine the impact of varying levels of yeast cell wall on the performance and blood parameters of Japanese quails.
Materials and methods: In this experiment, 360 one-day-old Japanese quails were studied using four levels of yeast cell wall supplementation (0, 0.5, 1, and 1.5 g/kg). The study followed a completely randomized design with 4 treatments and 6 replications each. Throughout the experiment, performance traits such as feed intake, body weight gain, and feed conversion ratio were assessed. At the conclusion of the study, intestinal samples were collected to analyze tissue structure, while cecal contents were sampled to evaluate the microbial population. Blood samples were drawn from the jugular vein, and the serum was stored at −20°C for later analysis of blood parameters, including triglycerides, cholesterol, glucose, HDL, and LDL, as well as serum liver enzymes (AST, ALT, and ALP). These measurements were conducted using Pars Azmoon commercial kits and a Mindray autoanalyzer.
Results and discussion: The experiment results indicated that yeast cell wall consumption increased feed intake and enhanced weight gain in birds aged 22 to 35 days and throughout the entire rearing period (P<0.05). Additionally, it lowered the feed conversion ratio during this age range (P<0.05). The yeast cell wall consumption led to an increase in lactobacilli populations and a decrease in Escherichia coli populations in the cecum (P<0.05). Carcass components, such as digestive tract weight, breast and thigh weight, forestomach, gizzard, liver, small intestine length (duodenum, jejunum, ileum), cecum length, blood parameters (triglycerides, cholesterol, glucose, HDL, and LDL), and serum liver enzymes (Alanine Aminotransferase, Alkaline Phosphatase, and Aspartate Aminotransferase) remained unaffected by the treatments (P>0.05). Among the duodenum and jejunum histological characteristics, villus height and the villus height to crypt depth ratio increased with yeast cell wall consumption (P<0.05). The benefits of yeast cell walls are largely attributed to the active immune function due to beta-glucan and mannan oligosaccharides in yeast products. Incorporating yeast products in poultry diets has been shown to boost immunity, balance microbial populations, and promote gastrointestinal health and development. These additives enhance nutrient digestion and absorption, thereby improving growth and overall bird performance. Mannan oligosaccharides in the yeast cell wall effectively bind pathogenic bacteria, exhibiting prebiotic properties. Balancing pathogenic and beneficial bacteria enhances villus length and reduces crypt depth, serving as biomarkers for improved intestinal morphology. Improved intestinal morphology boosts digestive enzyme activity, enhancing digestion. Longer villi signify a more mature epithelium with increased absorptive function due to a larger absorptive area. The development of intestinal morphology reflects the health status of the animal's digestive tract. Greater villus height increases enzyme activity at the villi ends, resulting in improved digestibility.
Conclusions: The study results indicated that administering 1 to 1.5 g/kg of yeast cell wall enhanced the microbial population in the cecum and improved the histological features of the duodenum, although it did not affect the birds' overall performance.