Abstract
This trial was conducted to assess the possibility of replacing maize (Zea mays L) with varying levels of whole cassava (Manihot esculent crantz) root meal (WCRM) in the diet of hybrid catfish (Heterobranchus, bidorsalis x Clarias gariepinus). The effect of replacement on growth variables andnutrient utilization of the WCRM as a replacement for maize were also determined. Four practical diets with varying replacement levels of maize at 0 (Ao), 33 (B33), 66(C66), and 100% (D100) were formulated andfed to hybrid catfish fingerlings for 32weeks. Fish were fed twice daily at 5% body weight/day. Optimum growth, nutrient utilization of the fish were assessed. The results obtained from the study indicated thatWCRM can completely replace maize with the best result at 66% inclusion. The highest values of growth performance were: final weight 12,782±601.21g, mean weight gain 12041.43±312.66g, and daily weightgain 78.78±10.28g. The nutrient utilization indicated the best feed conversion ratio (FCR) 1.71±0.40; Gross feed conversion efficiency (GFCE), 68.95±5.161; protein intake (PI), 12975.88±306.11g, proteinefficiency ratio (PER) 1.98±0.11; and nitrogen metabolism (NM) 10782.98±314.12g/100g were recorded in diet C66. However, growth and nutrient utilization variables varied significantly (p0.05) from the control value. Dietary WCRM at 100% inclusion produced similar results in the mean weight gain (MWG), mean daily weight gain (MDWG), Gross Feed Conversion Efficiency (GFCE), Protein Intake (PI), and survival as the control diet. It could therefore be concluded that WCRM can replace maize in the diet of hybrid catfish effectively up to 100% with the optimal performance at 66% level of inclusion. Fish farmers can therefore explore the use of WCRM as an alternative to maize meal in hybrid catfish diet with better profit margins.
Highlights
Over the past decades aquaculture has grown in leaps and bounds in response to an increasing demand for fish as a source of protein globally (Akinrotimi et al, 2007a)
The lipid content of the cassava root meal used in this work is close to the range 7.00 - 8.20% for cassava and rice grain meal employed by Ufodike and Matty, (1984) in the diet of rainbow trout
It has been documented that 50% replacement of maize with cassava meal in broiler diet showed no depression in growth or unfavourable feed conversion ratio (Essers et al, 1995) and that the best growth performance was recorded in layers fed 10% cassava meal
Summary
Over the past decades aquaculture has grown in leaps and bounds in response to an increasing demand for fish as a source of protein globally (Akinrotimi et al, 2007a). This is because production from capture fisheries has reached its maximum potential possible, as the catch is dwindling with each passing day (Gabriel et al.,2007). According to Olurin et al (2006), maize is the major source of metabolisable energy in most compounded diets for catfish species. To relieve the food feed competition between man and animal and for profit maximization, cassava is very appropriate for this purpose
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