Browsing by Person "Richter, Nahid"

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Evaluation of suitability of non-toxic and detoxified Jatropha curcas L. meal as feed for fingerling common carp, Cyprinus carpio L., with reference to phytase application
(2012) Richter, Nahid; Becker, Klaus
Jatropha curcas L. is a hardy plant which can thrive on marginal degraded lands. Jatropha seeds contain about 300-350g kg-1 oil, which is used as fuel or in transesterified form as a substitute for diesel; they also have considerable protein quality. However, Jatropha contains antinutrients such as lectins, trypsin inhibitors and phytic acids at high levels and in toxic varities phorbolesters cause detrimental effect. Common carp fed heat-treated non-toxic Jatropha meal (JM) has been shown to have higher weight gain and protein efficiency ratio than those fish fed untreated JM. However, these parameters were significantly lower in the aforementioned trial when compared to fish fed a fish meal (FM) based diet. Reduced growth performance in fish fed non-toxic JM might be attributable to the deficiency of some essential amino acids such as lysine, to high levels of phytic acids or the presence of antinutrients. These may indicate the need for additional processing of JM for common carp. This work was therefore conducted to test various ways of further improving the nutritional quality of JM to increase the levels of inclusion in diets for common carp. In the first experiment, four diets based on 50% replacement of FM with defatted non-toxic JM were formulated, one with no further JM treatment, the second with 80% aqueous ethanol extraction before diet formulation, the third supplemented with 1% L-lysine and the fourth with 500 FTU phytase (5000G, Natuphos). These were compared to a standard, FM based diet. The results showed that diets with 500 FTU/kg phytase or 1% L-lysine could maintain common carp?s growth performance at a level comparable to fish fed a FM diet. Fish fed diets containing JM and ethanol treated JM had significantly lower growth performance than the control. The addition of 1% L-lysine or 500 FTU phytase enhanced percent body weight gain, food conversion efficiency and specific growth rate to a level comparable to those of the control. Furthermore, the addition of 500 FTU phytase significantly increased whole body Mg, P and K to the levels of those fish fed Diet Control. When the level of JM replacement was increased from 50% to 75% while at the same time supplementing the diets with inorganic phosphorus (Experiment 2), however, a significant decrease in body weight gain of common carp was observed both with and without 500 FTU phytase. In a third experiment, the effect of JM diets with added phytase but without phosphorous supplementation was therefore investigated in more detail. At the end of the eight week trial, phytase supplementation had not affected body mass gain (BMG), food conversion ratio (FCR) and specific growth rate (SGR) of fish. However, whole body phosphorous (P), P gain and P retention were significantly improved in fish fed JM with phytase supplementation when this was compared to the fish fed JM without phytase. Moreover, fish fed JM diets indicated higher O2 consumption per gramme body mass gain than carp fed FM diets. Energy expenditure per gramme protein retained was significantly higher for fish fed JM with or without phytase addition, indicating that the utilisation of JM was associated with higher energy costs for the fish. In the final experiment, the nutritional quality of non-toxic JM was compared to that of the toxic variety once appropriate measures had been taken to detoxify the latter. FM was replaced with either of the two at 75% of total dietary protein, for each Jatropha variety once without further supplementation and once supplemented with 500 FTU phytase and 1% lysine. The results of this experiment indicated that there was no significant differences in final body mass (FBM), % BMG, feed intake (FI), FCR and specific growth rate (SGR) of fish fed diets Control and non-toxic, supplemented JM. However, fish fed diets based on detoxified or non-toxic, unsupplemented Jatropha showed significantly inferior growth parameters when compared to carp fed the first two diets (p<0.05). Whole body P was significantly higher in fish fed the Control and non-toxic JM diets (with/without phytase and lysine) than fish fed either of the two detoxified JM diets (p<0.05). The depressed growth performance in the group fed detoxified JM could imply that the detoxification process was not complete and traces of phorbolesters may still be present in the diets. This work has shown that, given proper treatment, JM can act as a suitable replacement for FM at high levels in diets for common carp. The results of this work suggest that phytase addition to enhance phosphorous availability and lysine supplementation to correct the essential amino acid imbalance are two factors that have significant effects in improving JM suitability for common carp.