Effect of Yeast (Saccharomyces cerevisiae) on Blood and Intestinal Histopathology of Nile Tilapia (Oreochromis niloticus)

Background: Aquaculture advises against using antibiotics and synthetic hormones for tilapia fish growth due to concerns about antimicrobial resistance, environmental contamination, and disruption of the fish microbiome. The search for alternative fish growth promotion strategies has been an extensive one. The effect of yeast (Saccharomyces cerevisiae) on intestinal histology, biochemical parameters, and haematology indices of Oreochromis niloticus is examined in this study. Methods: To produce the experimental diet of 35% crude protein, yeast at varying quantities were added to the basal feed ingredient in the following amounts: 0, 5, 10 and 15 g/kg, which corresponded to the groups G1 (control), G2, G3, and G4, respectively. Twelve (12) concrete ponds, each with a capacity of 1,500 litres, were the culture structures for the experiment. Two hundred and forty mixed-sex Oreochromis niloticus fingerlings were stocked, and each pond was randomly allocated twenty fingerlings. Each parameter assessed was replicated 3 times. Results: The result on growth parameters showed that the highest final mean weight (86.33± 3.51 g), average daily growth (1.14±0.05 g), percentage mean weight gain (278.05±4.59%), and Specific Growth rate (7.41±0.08 g) were obtained in G3 fed with 10g/kg of Saccharomyces cerevisiae. While the lowest final weight (38.00±4.58 g), average daily growth (0.28±0.07 g), percentage mean weight gain (68.23±16.66%), Specific Growth rate (4.84±0.50 g) was obtained in G1, fish fed with control diet. The study's results on blood parameters indicate that the O. niloticus fed 5 g/kg of yeast in G2 had the highest mean values of Red Blood Cells at 4.49±0.23 × 106 μ/l, Haemoglobin at 3.73±0.20 g/dl, and Mean Cell Haemoglobin Content at 46.03±0.07. While the fish fed 15 g/kg of yeast in G4 had the lowest mean values of 3.48±0.35 × 106 μ/l, 3.73±0.31 g/dl, and 31.80±0.05, respectively. The greatest mean values of White Blood Cells at 10.53±0.35 × 103 μ/l, Parked Cell Volume at 15.50±0.50%, and Mean (red) Cell Volume at 38.08±0.06 were observed in fish fed with the control diet. Fish given 5 g/kg (G2) had the greatest levels of total protein, glucose, globulin, and cholesterol, with mean values of 62.00±0.93 g/dl, 14.30±0.20 g/dl, 48.00±1.00 and 3.34±0.05 g/dl respectively. Conclusion: The study suggests that increasing yeast concentration in O. niloticus diets increases mucosa surface area and promotes nutrient absorption, with minimal adverse effects on intestinal histology, biochemical parameters, and haematology indices of Oreochromis niloticus.