Abstract:
Unconventional and underutilised protein-rich feedstuffs such as Baobab (Adansonia digitata) Seed Meal (BSM) could effectively replace the expensive soyabean meal, except for the presence of antinutritional factors. Processing has been reported to reduce BSM antinutrients, increase its nutritional composition and enhance its utilisation by animals. However, information on utilisation of processed BSM in the culture of Clarias gariepinus is limited. The growth performance and physiological response of C. gariepinus juvenilesfed differently processed BSM-based diets were therefore investigated.
Crude protein (CP; %), saponins (mg/100g) and oxalates (mg/100g) of Raw (RBSM), Autoclaved (ABSM), Toasted (TBSM), Soaked in Water (SWBSM), Soaked in Liquor (SLBSM), Soaked in Alkali (SABSM) and Soaked in Pulp (SPBSM) samples were determined using standard methods. Apparent Digestibility Coefficient for CP (ADCCP;%) of the meals by C. gariepinus (n=315, 18.54±0.04g, 15 fish tank-1) were determined using standard procedures. Each of the two processed BSM with best ADCCP were made into 12 isonitrogenous (36% CP) diets. These were used to replace soyabean meal at 0 (control), 20, 40, 60, 80 and 100% for growth trial. Clarias gariepinus (n=495, 24.04±0.25g, 15 fish tank-1) were randomly allotted in triplicates to treatments in a 2×6 factorial arrangement in completely randomised design and fed twice daily at 5% body weight for 16 weeks. Mean Weight Gain (MWG; g) and Food Conversion Ratio (FCR) were calculated. Blood (5 mL) was sampled to determine Packed Cell Volume (PCV; %) and Alanine Aminotransferase (ALT; IU/L). Immunocompetence indices: Catalase (U/mg protein) and respiratory burst activity (H2O2;U/mg protein) were assessed using standard methods. Data were analysed using descriptive statistics, ANOVA and Polynomial regression at α0.05.
The CP ranged from 22.8±0.1 (TBSM) to 26.8±0.1 (SABSM). Saponins (61.7±2.9) and oxalates (171.7±10.4) were significantly least in TBSM, and highest in SABSM (213.3±5.8) and RBSM (276.7±10.4), respectively. Highest ADCCP were recorded in SABSM (85.8±0.4) and SPSBM (81.32±0.10) while the least was obtained in SLBSM (59.4±1.9). The MWG were 102.1±22.3 and 97.3±32.6 while FCR were 1.9±0.2 and 1.9±0.3 in SPBSM and SABSM, respectively. Significantly highest MWG (152.9±12.2) and least FCR (1.6±0.1) were recorded in 20% SABSM while least MWG (59.1±9.3) and highest FCR (2.2±0.3) were obtained in 100% SABSM. Optimal dietary inclusion level of SPBSM and SABSM relative to MWG were 7.7% (R2=0.5) and 13.4% (R2=0.7), respectively. The PCV were 22.0±3.4; 21.7±4.2 and ALT 34.1±9.8; 31.3±7.0 in SPBSM and SABSM, respectively. The PCV ranged from 16.0±1.4 (60% SPBSM) to 25.5±6.4 (40% SPBSM) while ALT varied from 29.0±4.1 (0% BSM) to 38.7±13.9 (60% SPBSM). Least and highest H2O2 (48.1±9.1, 48.4±10.0) andcatalase(18.2±2.3, 18.9±2.0) were obtained in SPBSM and SABSM, respectively. Catalase varied from 17.5±1.5 (20% SABSM) to 20.5±2.0 (100% SABSM) while H2O2 ranged from 41.8±7.1 (20% SABSM) to 57.0±6.3 (100% SPBSM).
Baobab seed meal based diets soaked in alkali and pulp were best digested by Clarias gariepinus. Soyabean meal could be replaced optimally at 13.4% and 7.7% inclusion for soaked in alkali and pulp baobab seed meal, respectively for improved fish growth and health.
