66 MARCH 2013 • WORLD AQUACULTURE • WWW.WAS.ORG T he African catish Clarias gariepinus is a major cultivated ish of high commercial value in Nigeria and is ideal for captive breeding (Adesulu and Syndeham 2007). Many limitations are associated with fry production and the development of better broodstock management techniques is crucial to improvement of fry yield and system eficiency. Effective ish seed production demands a thorough understanding of the special husbandry and particular nutritional requirements of broodstock, which greatly affect fecundity, survival, egg size and egg and larval quality. Medicinal plants have been used to enhance fertility and research has conirmed the pro-fertility effects of some herbs tested with animals and ish (Ofusori et al . 2007, Oluyemi et al . 2007, Adeparusi et al . 2010, Dada 2012). Sesame is found in the tropics and the seeds contain lignans such as sesamin, a phytoestrogen with antioxidant properties (Ashamu et al . 2010). Most plants rich in antioxidants can increase sperm counts, motility and enhance sperm morphology. Sesame seed has a positive effect on the reproductive performance of humans and animals (Ashamu et al . 2010) and may promote fertility or improve reproductive performance in ish. The objective of this study was to assess the possibility of improving reproductive performance of male African catish using different levels of sesame seed meal. Study Methods Five isonitrogenous diets containing 40 percent crude protein were formulated from practical ingredients (Table 1). Test diets were supplemented with 50, 100, 150 or 200 mg/kg sesame seed powder. A control diet was formulated without sesame seed powder. African catish broodstock (mean weight = 275 g) were acclimated to laboratory conditions for 14 days before stocking into 15 concrete tanks at 10 ish/tank. Each dietary treatment was evaluated in three tanks. Water quality was suitable for good African catish production (temperature 26.2 - 27.2, dissolved oxygen 4.0 - 4.2 mg/L, pH, 6.96 - 7.00). Fish were weighed every 15 days to calculate adjustments to daily feeding rate. Fish were fed at 3 percent of body weight daily in two equal meals between 0800 and 1800 hours. At the end of the 8-wk feeding trial, ten male ish were randomly selected from each dietary treatment, euthanized, and the testes removed to determine milt quality indices (milt volume, motility duration, percentage motility and spermatozoa concentration). One female African catish broodstock (850 g) was induced to spawn with an injection of 0.43 mL Ovaprim®. After 12 hours, the female was strip-spawned and 30 eggs were placed into each of ifteen 2-L plastic bowls. Eggs were fertilized with 1-mL of milt from males from each dietary treatment. The number of fertilized and unfertilized eggs were counted under a microscope (40× magniication) and used to make the following calculations: EF = NEI – NOE / TNE × 100 where EF = egg fertilization (in percent), NEI = number of eggs incubated, NOE = number of opaque eggs, and TNE = total number of eggs. Hatchability (percent) = number of eggs hatched / total number of eggs × 100 Survival (percent) = total number of hatchlings / total number of eggs × 100. Dietary Sesame Improves Reproductive Performance of Male African Catish Adekunle Ayokanmi Dada 1 TABLE 1. Ingredient composition and proximate composition of contol diet. INGREDIENTS g/kg diet Menhaden ish meal 250 Corn meal 100 Soybean meal 350 Blood meal 100 Cod liver oil 90 Vegetable oil 60 Vitamin-mineral premix 30 Corn starch 20 PROXIMATE COMPOSITION PERCENT Crude protein 40.4 Crude lipid 17.4 Ash 12.1 Gross energy (MJ/kg) 16.9 Vitamin premix was a Pfizer livestock product containing the following per kg of feed: A = 4500 IU, D = 11252 IU, E = 71 IU, K 3 = 2 mg, B 12 = 0.015 mg, panthothenic acid = 5 mg, nicotinic acid = 14 mg, folic acid = 0.4 mg, biotin = 0.04 mg, choline = 150 mg, cobalt = 0.2 mg, copper = 4.5 mg, iron = 21 mg, manganese = 20 mg, iodine = 0.6 mg, selenium = 2.2 mg, zinc = 20 mg, antioxidant = 2 mg.