Browsing by Subject "Aquaculture feeds"

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Effects of low dietary levels of saponins on two common culture fish - common carp (Cyprinus carpio L.) and Nile tilapia (Oreochromis niloticus (L.))
(2001) Francis, George; Becker, Klaus
Saponins are a group of compounds present in many wild plants and cultivated crops and are commonly found in traditional medicinal preparations. Feeding experiments using saponin-supplemented (commercial Quillaja saponin) feeds were conducted in two commonly cultured fish species, namely common carp (Cyprinus carpio L.) and tilapia (Oreochromis niloticus (L.)). Quillaja saponins (QS) at dietary levels of 150 mg kg-1 and 300 mg kg-1 significantly increased body weight gain in common carp and Nile tilapia compared to controls. When fed to tilapia fry QS (700 mg kg-1) altered the normal 1:1 sex ratio. In separate, in vitro measurements it was found that QS stimulated the release of leutinising hormone (LH) from cultured tilapia pituitary cells, but apparently this did not happen in vivo since serum levels of LH were not found to be elevated in the saponin fed fish. Dietary saponins were also found to affect serum and muscle cholesterol levels. Adult tilapia - but not tilapia fry - fed a dietary level of 300 mg kg-1 QS were found to have significantly higher muscle cholesterol levels than fish fed the control diet. In tilapia fry, the average serum cholesterol levels in males showed a steady increase from dietary QS levels of 0 to 700 mg kg-1, while no such trend existed among the females. Supplementation with 50 and 100 mg kg-1 of Yucca schidigera butanol extract (containing steroidal saponins) did not significantly promote the growth of carp despite showing initial promise. The purified haemolytic fraction of triterpenoid Gypsophila saponin extract (isolated using column chromatography) did not produce any toxic effects in carp at dietary levels up to 250 mg kg-1 in a preliminary feeding trial. A growth promoting effect was however evident at the very low level of about 5 mg kg-1 when the purified fraction was used. More research needs to be done to determine the mechanisms of action of QS and to test whether saponins from other sources have similar effects.