The study investigates the effects of supplementing graded level of hydrolysed yeast on Nile tilapia (Oreochromis niloticus ). A high-fiber (7.7±0.3% CF), isoproteic (29.8±0.09% CP) and isoenergetic (3415.5±31.1 kCal/g) diets were formulated and supplemented with graded level (Control – ‘0.0’, HL0.5 – ‘0.5’ g/kg, HL1.0 – ‘1.0’ g/kg and HL2.0 – ‘2.0’ g/kg) of hydrolyzed yeast (Hilyses®, ICC Animal Nutrition , Sao Paulo, Brazil) in a 14- weeks feeding trial.
Despite no differences in most growth parameters, a positive trend was observed in feed efficiency (t=2.535 , P<0.024), protein efficiency ratio (t=2.572 , P<0.022), and the feed cost/ kg fish (t=-2.074 , P<0.047). Protein deposition, protein retention and energy re tention efficiency were responded linearly with the increasing dosage of hydrolyzed yeast (t=2.179 , P<0.0 47; t=3.056 , P <0.009; and t=2.154 , P<0.049, respectively) . Among haematological parameters, only haematocrit content decreased significantly with the increasing level of the yeast. The expression of all four target genes i.e., Insulin Like Growth Factor-I (IGF-I), Glyceraldehyde 3-Phosphate (G- 3-P), Ghrelin, and Hepcidin were significantly different among the treatments, and linearly increased with the increasing level of dietary Hilyses® (Table 1). Similar results were also observed in villi length (t= 3.006, P<0.009).
It can be concluded from the study that dietary supplementation of graded level of hydrolyzed yeast (Hilysis®) significantly improved feed utilization, protein and energy retention, intestinal health reflecting in the higher expression of growth (IGF-1), cellular glucose production (G -3-P), iron homeostasis (hepcidin), and hunger ( Ghrelin) genes.