Given the euryphagic nature of the species (Bruton 1979b), it is not surprising that it is able to efficiently utilize a wide variety of ingredients (Rouhani, 1993; Fagbenro, 1998; Fagbenro, Adeparusi and Fapohunda, 2003) and hence in some quarters is considered as an ideal “bio-waste management instrument” (Sambhu, 2004). Tables 5a and 5b list the calorific value and digestible energy of various plant and animal-based feed ingredients for C. gariepinus. The data clearly illustrate the wide spread of ingredients that can be used as feeds or feed ingredients for Clarias species.
The North African catfish has been translocated for aquaculture purposes to many countries (Welcomme, 1988) and is or was farmed, either in its pure form or as a hybrid, in 23 African countries, four countries in Europe, ten in Asia and one in South America. Total production of North African catfish in 2007 amounted to some 47 428 tonnes, of which 92 percent was produced in three countries, Nigeria (79 percent), the Netherlands (9 percent) and Hungary (4 percent) (FAO Fishstat, 2009). The species is produced in widely different farming systems ranging from highly intensive tank culture under flow-through or recirculating conditions to intensive, semi-intensive and extensive (small and large-scale, poly- or monoculture) pond-culture systems. It is therefore not surprising that a wide range of feeds is used in the farming of this species, including dry feeds, ranging from single ingredient dry feeds such as maize bran, to farm-made mixed feeds to formulated, floating or slow-sinking, extruded feeds, as well as single ingredient or mixed moist, farm-made feeds.
Clarias gariepinus is a highly valued foodfish in many African countries (Figure 8). In Africa, the high cost of formulated commercial fish feeds is a major constraint to the expansion and growth of the aquaculture sector (Hecht, 2007), and this has prompted a concerted effort, particularly in Nigeria, to seek suitable alternative feed ingredients. The aim of this work has principally been to reduce production costs by minimizing the use of or replacing conventional feed ingredients such as fishmeal and soybean meal. The findings of this research are summarized in Table 6. It should be noted that the inclusion levels of various feedstuffs are of course predicated by the protein and essential amino acid (EAA), lipid and essential fatty acid (EFA) and carbohydrate requirements. Some of the non-conventional ingredients that have been successfully tested as feed ingredients for catfish include fish silage (Fagbenro and Jauncey, 1994, 1995; Fagbenro, Jauncey and Haylor 1994); hydrolyzed feather meal; maggot, termite and toad meal (Madu and Ufodike, 2003; Dada and Akinwande, 2004; Ayinla, 2007); dried water fern (Azolla pinnata) (Fasakin and Balogun, 1998); cassava leaves and peanut vines (Bureau, de la Noue and Jaruratjamorn, 1995); grasshopper meal (Nnaji and Okoye, 2004); rumen epithelial meal (Sotolu and Adejumoh, 2008); pigeon pea meal (Ogunji et al., 2008); winged bean meal (Fagbenro 1999a,b,c) and numerous others such as duckweed, periwinkle meal, sweat potato peel meal, garden snail meal, cassava meal, jackbean seed meal, etc. However, in most cases the high manufacturing cost of the alternative meals seriously limits their use (Ayinla, 2007). It would appear that meat and bone meal cannot be used at the same high levels at which poultry by-product meal is used to replace fishmeal in the diet of C. gariepinus. Goda, El Haroun and Chowdhury (2007) suggest that this may be due to a deficiency in methionine, lysine and isoleucine and high levels of saturated fat that may contribute to reduced palatability. The only study that suggests that soybean meal could possibly wholly replace fishmeal is the work by Goda, El Haroun and Chowdhury (2007). It is however generally accepted that catfish feeds should contain at least 8–10 percent fishmeal (percent dry weight), although in Asia it has been shown that golden apple snail meal (Pomacea canaliculata) can replace 100 percent of the dietary fishmeal component of commercial feeds (Phonekhampheng, Hung and Lindberg, 2009).
In Africa, over 90 percent of feeds used by farmers are farm-made, moist or dry feeds (Hecht, 2007; Ponzoni and Nguyen, 2008). Moist ingredients that are commonly used for catfish feeds in Africa and Asia include chicken entrails, minced poultry farm mortalities, abattoir waste, butchery sweepings, fish market waste (mainly fish entrails), maggots, termites, earthworms, trash fish, hotel or restaurant kitchen waste and live juvenile tilapia. In most instances, these moist ingredients are mixed with milled oilseed cakes (soy, cotton, sunflower, palm kernel) and relatively inexpensive ingredients such as maize, wheat or rice bran and dried brewery waste. Gabriel et al. (2007) provide a succinct overview of alternative ingredients that have been tested as ingredients for farm-made feeds in sub-Saharan Africa. However, many farmers use moist ingredients such as chicken offal as a stand-alone feed and claim to achieve FCRs of around 1.3:1 (Ayinla, 2007). However, recent trials in Uganda have found that the use of chicken offal results in unacceptably high abdominal fat deposition (Matsiko and Mwanj, 2008). However, it should be noted that fish with low abdominal fat content are least preferred in many other regions in Africa. There is some evidence to suggest that juvenile catfish fed on mixed moist feeds (34 percent moisture) have poorer performance indices (weight gain, specific growth rate, FCR, protein efficiency ratio) than juveniles fed on a dry diet using the same ingredients (Fagbenro, 1994; Fagbenro and Jauncey,1994; Fagbenro, Jauncey and Krueger, 1997).
