Abstract
The study was conducted to assess the effects of a postbiotic, Saccharomyces cerevisiae fermentation product (SCFP) and a commercial phytogenic feed additive (PFA) as alternative to antibiotic growth promoter(AGP) on growth performance, gut microbiota, intestinal morphology, and immune response of commercial broiler chickens at a Food and Agriculture Organization (FAO) classified sector 3 commercial poultry farm. One-day-old mixed sex Vencobb 430 Y chicks (n=4800) were randomly divided into four dietary treatment groups for 35 days experimentation encompassingT1 (positive control, PC) basal diet supplemented with bacitracin methylene disalicylate as an AGP at 500 g/MT; T2 (negative control, NC) basal diet without a growth promoter; T3 basal diet supplemented with commercial PFA at 500 g/MT; T4 basal diet supplemented with SCFP at 1.25 kg/MT.At day 35, ADG and FCR were significantly improved in PFA and SCFP groups compared to the NC group. The levels of blood glucose, total protein, albumin, triglyceride, cholesterol, and uric acid in serum showed no significant variation across different dietary treatments. From day 21 of the study, log cfu count and DNA concentration of pathogens (Enterohaemorrhagic Escherichia coli, Salmonella) decreased significantly in the AGP, PFA, and SCFP groups compared to the NC group. Whereas the log cfu count and average DNA concentration of Lactobacillus was significantly increased in PFA and SCFP groups, but not in AGP group. Increased Lactobacillus concentration in PFA and SCFP groups downregulated the virulence gene expression of pathogens (Enterohaemorrhagic E. coli and Salmonella). The duodenal and jejunal villi height was significantly higher in PFA and SCFP groups, although ratio of villi height to crypt depth in the duodenum, jejunum and ileum did not show significant differences among the groups. On day 28, antibody titers against the IBDV and NDV were significantly higher in SCFP groups than other groups. The present study did not identify any modulation of the cell mediated immune response in the chickens. In conclusion, addition of SCFP at 1.25 kg/MT or PFA at 500 g/MT in diet could produce better nutrient utilization ability, reduction of pathogens and their virulence gene expression, increased Lactobacillus count, but incorporation of SCFP increased antibody titre against two fatal viral infections such as NDV and IBDV which was not detected with PFA.