Abstract:
The study was carried out with the objective to study the effect of two local plant extracts on fresh quality of Nile tilapia (0. niloticus) for 12 hours’ period at room temperature. Nile tilapia were exposed to various concentrations of two plant extracts (T vogelii and A. corlaria) to determine the potential crude concentration for sedation. Extractions were made by grinding 50g of plant material with.500ml of water followed by crushing and filtering. Induction times of anesthesia to three pre-determined stages (I-IIl) were recorded for different concentrations of plants extracts. When fish Iost the total equilibrium (III), it was placed in a fresh water tank and the recovery time was recorded; Each concentration of the plant extract was tested in two replicate fish. Tephrosia was more effective and statistically the potential to induce sedation stage III was different (p<0.05) for both plants. Tephrosia gave the best induction time at 9ml plant extract/L, fish attained Ill within 7.27 minutes with recovery time 27 minutes. A conaria showed some sedative properties but was less effective due to longer induction time, at 25ml/l plant extract fish attained stage III within 19.9 minutes with recovery time 47.86· minutes: 10 experiment 2.the established concentration of each plant extract were used as killing methods to evaluate their effect 911 the fresh quality of Nile tilapia (0.niloticus). Whole fish-were used eviscerated and these were divided into two groups; whereby each group was killed using a different method: Tephrosia, and Albizia Rigor mortis and muscle pH were assessed besides t11~sedative potential of plant extracts. Rigor mortis did not differ among' treatments, during 12 hour period (p>O.O5); however fish killed by Albizia had faster onset of rigor compared to that of Tephrosia, andafter six hours all animals were in rigor stage Analysis showed that-rigor mortis was affected by time (p<O,OS). pH values obtained from the study had no significant difference.for all the three slaughtering methods (p>.0.05), but there was subsequent low muscle pH.This research is evidence of how plant extracts have a significant effect on fresh quality of Nile. tilapia fish and thus a basis for demoting the use of these plant extracts in the culture of Nile tilapia
