Interactive effects of dietary saponin with cholesterol and tannin on growth and biochemical responses in Labeo rohita (Hamilton, 1822) fingerlings

The present study assessed the possible interaction of saponins with the phenolic antinutritional factor tannin and the animal-origin diet component, cholesterol, in the context of plant-based aquafeed formulation with the addition of cholesterol. An in vitro analysis evaluated the ability of saponin to neutralize cholesterol and tannin. The results revealed that the neutralizing capacity of cholesterol and tannin at 0.5% saponin concentration was 49.84% and 40.32%, respectively. In the second experiment, a feeding trial was conducted for 45 days in Labeo rohita fingerlings. Twelve fish each (average weight 5.28 ± 0.34 g) were randomly distributed into six treatment groups in triplicates. Six iso-nitrogenous (30% CP) and isolipidic (6%) purified diets were prepared: control (C), saponin (CS; C + 0.5% saponin), cholesterol (CC; C + 1% cholesterol), tannin (CT; C + 1.25% tannin), saponin and cholesterol (SC; C + 0.5% saponin and 1% cholesterol), and saponin and tannin (ST; C + 0.5% saponin and 1.25% tannin). The group fed 0.5% saponin and 1% cholesterol showed the maximum weight gain (%), specific growth rate, and protein efficiency ratio with the lowest FCR value, which was similar (P > 0.05) to the control. The addition of tannin (1.25%) to the saponin (0.5%) containing diet (ST group) partially restored growth performance. The HSI value significantly increased due to the feeding of saponin but decreased in the SC and ST groups compared to the saponin-fed (CS) group. The blood parameters like hemoglobin content, RBC, and leucocyte counts were higher (P < 0.05) in the SC and ST groups compared to the CS group, although significantly (P < 0.05) lower than that of the control (C) group. Serum total protein, albumin, and globulin values in the CS group decreased but improved in the SC and ST groups. Serum transaminase enzymes (SGPT, SGOT), total bilirubin, and creatinine were increased in the saponin-fed CS group but reduced in the SC and ST groups. In conclusion, saponins had an unambiguous interaction with tannin and cholesterol in both in-vitro and in-vivo conditions. Further, adding (1%) cholesterol into saponin (0.5%) containing aqua-feeds can negate the effect of saponin.