The on-going intensification of aquaculture in tropical countries has made it essential to develop suitable diets for catfish using alternative protein sources, traditionally; fish meal (FM) has been the main source of dietary protein for fish. Fish meal is often utilized in aqua feeds because it offers a balanced source of indispensable amino acids, essential fatty acids, vitamins, minerals and generally enhances palatability (Kaushik et al., 1995). In recent years, its increasing cost, decreasing availability in the market and poor quality have stimulated several studies on its partial or complete substitution with alternative protein sources (Kaushik et al., 1995; Fournier et al., 2004). Presently, most of the commercial feed depends mostly on soybean meal as a fish meal replacer. However, over dependency on this conventional protein source will cause hike in price since it’s a human food. Therefore, utilization of other inexpensive plant protein source would be beneficial in reducing the feed cost and contribute to food security (Sofia, 2007).

The fingerlings of Clarias gariepinus for this study were obtained from the research farm of the Fisheries Department, University of Agriculture Makurdi. The experiment which lasted for 56days was carried out also in an earthen pond at the departmental research farm. Hapas made from nets measuring 1x1x1 were mounted on a kuralon rope and set across the pond surface and properly staked to the dyke of the pond using bamboo sticks. Stones were attached to the four bottom corners of the hapas to serve as sinkers. This enables the bottom surface of the hapas to spread uniformly and to extend properly. The extension made easy inflow and outflow of water through each hapa and was immersed in the pond water half way to enable ease of access.

 

The feed ingredients used in the feed formulation were Fish meal, Soybean meal, Maize meal, Vitamin and Mineral premixes and were purchased from the Makurdi Modern market, they were then processes and grinded into meal for storage. Matured seeds ofJatropha curcas however, were obtained from the ripped fruits of locally grown Jatropha curcas plant at Kyado in Ukum local government area of Benue state. Soon after harvesting the fruits, the seeds were manually removed from the husk, cracked and the shells carefully removed to obtain the kernel. The kernel was grounded and defatted using Hexane. The kernel meal obtained was heated and autoclaved at 121 ℃ for 30mins and then washed four times using methanol. The meal obtained was dried under sun to remove methanol so as to obtain the detoxified Jatropha kernel meal. 35% crude protein control diet was formulated using Pearson square method with fish meal added at 26% level of inclusion (Table 1), the other experimental diet were formulated by simply substituting detoxified Jatropha kernel meal at 0%, 25%, 50%, 75%, and 100% substitution levels (Table 1). The diets so formed were pelletized using a pelleting machine after weighing appropriately and thorough mixing of the ingredients.

Protein requirement is given high priority in any nutritional study because it is the single nutrient that is required in the largest quantity for growth and development and also the most expensive ingredient in diet formulation (Lovell, 1989; NRC, 1993). A number of study have been conducted on the replacement of fishmeal with convention and unconventional protein source for African catfish production (Tiamiyu et al., 2006; Solomon et al., 2007; Solomon and Okomoda, 2012; Tiamiyu et al., 2007;Tiamiyu et al., 2013). To our knowledge, this is the first study on the replacement of Fishmeal by Detoxified Jatropha Kernet Meal in the diet of Clarias gariepinus. The results on the growth performance and nutrients utilization of Clarias gariepinusfingerlings fed the different experimental diets shows that the fish body mass increased four to five times within 8 weeks. This is an indication that the protein quality of Jatropha curcas kernel meal was effectively utilized by the fingerlings of Clarias gariepinus. Detoxification process used may have contributed significantly to the suitability of the different diets for feeding of African catfish, Fakunle et al. (2013), stated that toxic component or anti-nutritional factors in Jatropha seed or kernel meal may cause irritation of digestive tract which is capable of decreasing feed intake and growth. Boiling, cooking and chemical treatment are among the methods used in removing anti-nutritional factors in Jatropha kernel meal.

 

Feed utilization was higher in fish fed Diet III with 50:50 % fishmeal and jatropha meal compared to the other experimental diets. Contrary to the outcome of this study, Fakunle et al. (2013) reported a better performance in African catfish fed diet containing graded level of boiled jatropha kernel meal as replacement for soybean meal, however Kumar et al. (2011), reported better growth of Cyprinus carpio fed detoxified Jatropha kernel meal (60min) replacing 50% of the diet’s fishmeal, and they envisaged the cause of differences in observations for the different diet to be factors such as acceptability of diets, presence of toxic and antinutritional factors and digestibility of protein and energy in the diets, since the present study used same detoxification process, hence, nutrient and amino acid compensation gotten from both fishmeal and detoxified Jatropha kernel meal in the Diet III must have led to better growth of the fish compared to other diets. Significantly lower growth response of fish fed Diet IV (75%) and Diet V(100%) might be because of several factors such as lower digestibility of protein and energy in the diets (Kumar et al., 2011) resulting from lower quality protein and energy availability from the detoxified Jatropha kernel meal. Antinutritional factors such as phytate and lactin may still be available insufficient amount to adversely affect the feed utilization of the diet leading to lower growth performance. The reduction in growth performance observed from the fish fed diets with higher ratio of plant protein (i.e. Diet IV and V), is in agreement with data on Clarias gariepinusfed other plant based feed stuff as reported by Gomes et al. (1993), Hasan et al. (1997), and Kumar et al. (2010, 2011), this is likely due to the carnivorous nature of the experimental fish, hence reduction in growth may give strong indication of their tolerance to the antinutritional factor present in the plant protein. Similar observation was made for common carp and rats with Jatropha meal as reported by Becker and Makkar (1998) and Rashid et al. (2008) respectively, reduce growth of this animal also includes reduction in feed intake and diarrhea. A low FCR values means that little of the diets were needed by the fish to gain flesh. Fish fed diet III had the lowest FCR which means they require 2.43 Kg of feed to build up 1 Kg of their flesh and lesser than control diet with 100% fishmeal which require 2.54 Kg of feed to build 1 Kg of flesh, thus feeding cost of the fish will be reduced (FAO, 2006). Hence Jatropha kernel meal may be a good feed ingredient to supplement the protein requirement of fish most especially where fish meal is found less abundant and costly (Maker and Becker, 1999). This is because the cost of acquisition of Jatropha curcas (though not determined in the study) are expected to be lower when compared to purchasing fishmeal.

 

The protein efficiency ratio (PER) is based on the weight gain of the test organism divided by the protein consumed for a particular diet during the period of the experiment (Wikipedia, 2011). It is the measure of growth using the dietary protein as an index and so a high PER value will be obtained if the weight gain is high compared to the dietary protein consumed. The variation in PER of the various diets suggest that the bulk of the protein consumed was converted to weight gain however Diet III had the highest value.

 

Carcass composition of the fingerings fed all the various diets had more protein retained in the body at the end of the experiment. This showed that the protein to energy ratio used in the feed was at the right proportion as a result, there was no sparing of protein for energy (Mooneye and Facade, 2003). A confirmation of the good quality can be seen in the reduction in fat content of the fingerings fed the various diets when compared to result of the initial fat content of the fingerlings. This result to the non fatty fleshed fish produced. The present study has therefore shown that Jatropha curcas kernel meal can replace fishmeal up to 50% without affecting growth and nutrient utilization significantly, however beyond this growth and stored protein reduces as the level of inclusion increases.