|Abstract for ISTA 2008 in Egypt
Treatment with saponins from Trigonella foenum-graecum and Quillaja saponaria influences sex ratio in Nile tilapia (Oreochromis niloticus) larvae
Stadtlander T1, Focken U1*, Levavi-Sivan B2, Dweik H3, Qutob M3, Abu-Lafi S3, Kerem Z2 and Becker K1
1University of Hohenheim, Germany; 2Hebrew University Jerusalem, Israel; 3Al-Quds University, Palestinian Authority
Nile tilapia production is one of the most rapidly increasing aquaculture industry sectors worldwide. Mixed sex culture is not sustainable on a long term basis because of the high rate of reproduction, increasing feeding competition in ponds and harvest of low percentage of large individuals. The most common method to prevent unwanted reproduction and subsequent overcrowding is an all male culture which is mainly achieved by synthetic hormone treatment with 17-a-methyl-testosterone (MT). Since the application of synthetic hormones in animal feed is prohibited in many countries, including the whole of the EU, due to environmental and health concerns, endocrine active plant derived substances with a similar effect could serve as a substitute for MT. .
In previous experiments saponin supplementation in fish diets has shown a potential to influence sex ratio and reproduction success.
During this experiment we tested the effects of steroidal saponins derived from fenugreek (Trigonella foenum-graecum, TS) and soap bark tree (Quillaja saponaria, QS) as feed supplement in mixed sex tilapia populations for their influence on sex ratio. Saponins were extracted by the conventional Soxhlet method with hexane/ethanol and fractionated and isolated by consecutive methanol concentrations of 40, 60 and 80% (TS) and 80% (QS). Extracted saponins and commercially available Quillaja saponin (Sigma) were added to the diets of Nile tilapia larvae in two different concentrations, 150 and 1000 ppm, respectively, with Sigma-saponin in 1000 ppm only. Fish were fed with experimental diets and standard diet as control for four weeks and afterwards raised on standard diets only.
Sex ratio was determined micro- and macroscopically after approximately 4 months.
Percentage of non-females ranged from 52% (40% TS, 150 ppm) to 73% (80% QS, 150 ppm) with two treatments (80% TS 150 ppm and 60% TS 150 ppm) being significantly different (p< 0.05) from the expected 50:50 ratio.
Although further work is needed to identify the most effective fraction, single saponin or mode of action of Trigonella saponins, it is obvious that plant derived saponins have a significant masculinization effect in tilapia larvae.
* Corresponding author:
Institute for Aquaculture Systems and Animal Production in the Tropics and Subtropics
University of Hohenheim
70599 Stuttgart, Germany