Emmanuel Kolawole Ajani

Growth, physiological, antioxidants, and immune response of African catfish, Clarias gariepinus (B.), to dietary clove basil, Ocimum gratissimum, leaf extract and its susceptibility to Listeria monocytogenes infection

ABSTRACT Clove basil, Ocimum gratissimum, is a native plant to Africa and grows virtually in tropical and subtropical regions. It has good aroma and its leaves have become used as a spicy and in traditional medicine. The use of plant leaves in fish diets may deteriorate their growth because it may content anti‐nutritional factors. Thus, it is better to use plants leaves extract. In the current study, clove basil leaves extract (CBLE) was administrated to African catfish, Clarias gariepinus (B.) to evaluate its effect on growth performance, physiological, antioxidants, and innate immunity variables. Fish (10.7±0.5g) were fed on diets enriched with 0.0, 5, 10, or 15g CBLE/kg diet for 12 weeks. After the feeding trial, fish were further exposed to pathogenic bacteria (Listeria monocytogenes) for 14 days. Fish performance and feed intake were significantly enhanced with increasing CBLE levels and its optimum level is found to be 12g/kg diet. It is noticed that the dietary CBLE in African catfish diets increased significantly the intestinal villi length, villi width, and absorption area in a dose‐dependent manner and fish weight was highly correlated with villi length, villi width, and absorption area (R2 = 0.91, 0.91, and 0.92, respectively). On the other side, Dietary CBLE has significant modulatory effect on hemato‐ and physiological variables of African catfish in a dose‐dependent manner. In this regard, blood glucose and cholesterol levels decreased significantly; mean while total protein, albumin, and globulin increased significantly in fish fed high CBLE levels (10–15g/kg diet). Furthermore, activities of aspartate aminotransferase and alanine aminotransferase, alkaline phosphatase, urea, and creatinine levels were significantly elevated with increasing dietary CBLE levels and their maximum values were detected in fish fed 15 g CBLE/kg diet. Antioxidants and immunity variables were significantly enhanced by CBLE supplementation. Additionally, fish mortality after bacterial challenge was highest in fish fed the control diet (85%) than those fed CBLE‐enriched diets. The lowest fish mortality was observed in fish fed 15g CBLE/kg diet (13.5%). This study evoked that CBLE administration enhanced the performance, feed utilization, antioxidant, and innate immunity properties of African catfish with optimum level of 12g/kg diet. Also, its supplementation enhanced fish challenge against L. monocytogenes. HIGHLIGHTSAfrican catfish fed on diets enriched with ethanolic extract of clove basil leaves (CBLE) for 12 weeks.After CBLE feeding, fish were exposed to pathogenic bacteria, Listeria monocytogenes, for 14 days.Dietary CBLE has significant modulatory effect on hemato‐ and physiological variables of African catfish.Also, CBLE supplementation improved significantly fish performance and welfare up to 12g/kg diet.CBLE supplement has antioxidant and immuno‐activity and elevated the fish resistance against pathogenic bacteria.

Optimum dietary Ca/P ratio and phytase for growth and bone mineralization in juvenile Clarias gariepinus fed soya bean-based diet.

The research investigated the interactive effect of five phytase graded levels of 0 FTU/g (P0), 250 FTU/g (P1), 500 FTU/g (P2), 750 FTU/g (P3), 1000 FTU/g (P4) and four graded levels of roasted soya bean substitution at 25%, 50%, 75% and 100% in place of fish meal, respectively. All basal diets contained 0.20% calcium without added inorganic phosphorus, wheat and amino acids supplements so that the phosphorus, calcium, and Ca/P ratios of the five (5) were: S0 (1.31%, 1.85%, and 1.41), S1 (1.15%, 1.64%, and 1.43), S2 (1.01%, 1.28%, and 1.27), S3 (0.75%, 0.99%, and 1.30), and S4 (0.43%, 0.68%, and 1.59). 1092 fish of average weight 11.55 ± 0.2 g were randomly allocated to all experimental diet and fed 3% body for 84 days. There was no significant difference in final weight, weight gain and FCR S3P1 and S0P0 (P>0.05). Fish fed low phosphorus diet (100% soya bean) showed reduced total weight and weight gain compared to high (0%, 25%, 50%) and medium phosphorus diet (75%) with phytase addition (P 0.05), and PER (r=-0.210, P>0.05). Ca/P of S3P1 (1.41 ± 0.02) was not different from S0P0 (1.41 ± 0.01). Bone phosphorus, calcium and zinc were higher in 250 FTU/g compared to 0 FTU/g, 500 FTU/g, 750 FTU/g and 1000 FTU/g. In conclusion, Phytase improved growth performance (r=0.05) of juvenile Clarias gariepinus with optimum at 250 FTU/g; however, Ca/P affected performance (r=-0.431) and should range between 1.41-1.46 for optimum phytase activity.

Phosphorus utilization in juvenile Clarias gariepinus fed phytase-supplemented diets based on soya bean (oil-extracted) and full-fat (roasted): A comparison

ABSTRACT The effect of microbial phytase on phosphorus utilization in juvenile Clarias gariepinus (initial fish body weight 11.55 ± 0.2 g) was tested on two different diets based on oil-extracted soya bean (Experiment 1) and roasted soya bean meal (Experiment 2) using a 5 × 5 experimental design for 84 days. The basal isonitrogenous and isocaloric diets for oil-extracted and roasted soya bean were formulated to replace fish meal at 25% (S1E), 50% (S2E), 75% (S3E), 100% (S4E); and 25% (S1), 50% (S2), 75% (S3), 100% (S4), respectively. Each treatment was replicated four times. Microbial phytase was supplemented in each replicate at 250 FTU/g (P1), 500 FTU/g (P2), 750 FTU/g (P3), and 1,000 FTU/g (P4). Basal controls, which included a fish meal-based diet (S0), were not supplemented with phytase (P0). The result in Experiment 1 showed that there was a significant increase in whole-body protein and reduction in fat with phytase compared to a diet without phytase (P < 0.05). Serum total protein declined significantly with phytase supplementation (P < 0.05). Serum phosphorus and glucose were higher with phytase supplementation compared to control (P < 0.05). Bone minerals declined significantly with increasing level of soya bean compared to fish meal diet (P < 0.05). In Experiment 2, serum phosphorus was improved with phytase compared to control with no phytase (P > 0.05). A significant reduction in whole-body protein and increase in fat was observed for fish fed phytase diets compared to diets with no phytase, regardless of soya bean level (P < 0.05); however, ash content was improved with phytase (250 FTU/g) compared to control (P < 0.05). Phytase supplementation improved bone phosphorus (250 FTU/g), calcium (250 FTU/g), magnesium (250–500 FTU/g), and zinc (250–1,000 FTU/g) compared to control (P < 0.05). In conclusion, the research has demonstrated that improved bone phosphorus (P) and growth could be achieved with the supplementation of dietary phytase.

Effect of Smoking Time and Temperature on the Proximate Composition and Quality of Milkfish Steaks

ABSTRACT The effect of three smoking durations (60, 90, and 120 min) and two smoking temperatures (60°C and 70°C) on proximate composition and quality of brackish cultured milkfish steaks of 3 cm size was studied. No significant difference was observed in the sensory properties across all the samples, except in the overall acceptability of sample smoked at 60°C for 60 min. There was significant difference in the values obtained for the textures of all the samples. The L*a*b* values showed a significant difference in the raw and smoked samples. The moisture content showed significant difference in all six samples. Naphthalene, fluorine, and anthracene were detected in the raw sample and in all the smoked samples with significant difference, except for naphthalene. The effect of smoking on the sensory properties and the moisture content of a smoked fish sample are dependent on the smoking time and temperature. Polycyclic aromatic hydrocarbon (PAH) concentration in smoked fish can be a factor, based on both water pollution and the smoking procedure. Benzo-a-pyrene and PAH4, which are acceptable indicators of total PAH presence in smoked foods, were not detected in all the smoked samples, thereby indicating the products to be safe for consumption.

Physico-Chemical Status of Eleyele Reservoir, Ibadan, Nigeria

Eleyele reservoir is a vital resource for fishery, domestic water supply and flood control. Unfortunately, the reservoir is fast being degraded due to various anthropogenic activities around its catchments. Hence, this study evaluates spatio-temporal variations in the physico-chemical parameters of the reservoir. Eleyele reservoir was stratified into five zones (S1-S5) based on hydrological features and three sampling points were randomly selected per zone. Water samples were collected bi-monthly from each station for 24 months covering wet (May-November) and dry (December-April) seasons. Water parameters were analysed for alkalinity (mg/L), phosphate (mg/L), Dissolved Oxygen (DO, mg/L), Biological Oxygen Demand (BOD, mg/L), Chemical Oxygen Demand (BOD, mg/L) and temperature (°C) following standard procedures. Highest and least alkalinity (103.63 ± 14.87; 96.25 ± 11.41) and phosphate (2.00 ± 0.69; 1.94 ± 0.66) were recorded in S2 and S4, respectively. Temperature and DO ranged from 26.53 ± 2.20 (S5) to 26.86 ± 2.45 (S1) and 4.24 ± 0.84 (S2) to 5.39 ± 0.82 (S5), respectively. Alkalinity were 99.72 ± 12.41 and 100.91 ± 16.14, phosphate (1.71 ± 0.55; 2.10 ± 0.61), temperature (28.20 ± 2.34; 25.53 ± 1.74) and DO (4.48 ± 0.98; 4.85 ± 0.97) in dry and wet seasons, respectively. The mean values obtained for Biological Oxygen Demand (4.29 ± 2.23 mgl-1), temperature (26.64 ± 2.36), conductivity (0.270 ± 0.21 μScm-1), alkalinity (100.42 ± 14.69), hardness (69.18 ± 30.94 mgl-1) and ions were within desirable limits for aquatic life. Crucial steps should be taken to reduce agricultural activities and anthropogenic discharges into the Reservoir.

Biological Treatments of Fish Farm Effluent and its Reuse in the Culture of NileTilapia (Oreochromis niloticus)

Aquaculture wastewater collected from a catfish farm in Ibadan metropolis was treated with duckweed, Lemna minor (Td) for two weeks and thereafter used in the culture of Nile tilapia (O niloticus). The performance of O niloticus raised in Lemna minor treated waste water was compared with bacteria-treated waste water, Bacillus sp. (Tb) and well water (Tc) as control (untreated). The Bacillus sp. was isolated from the catfish wastewater, and was positive to Gram’s staining, catalase and glucose fermentation test. Nile tilapia juveniles (n=54) of an average initial weight of 10.43 ± 0.04 g were stocked in triplicates per treatment and fed to satiation twice daily for 8 weeks. There was significant difference (P<0.05) in the quality of waste water in all the treatments. Compared to initial waste water, Td showed a significant reduction in biological oxygen demand, BOD (1.23 ± 0.03 mg/L vs. 36.80 ± 1.89 mg/L), chemical oxygen demand, COD (2.20 ± 0.06 mg/L vs. 58.81 ± 1.89 mg/L), sulphate (0.50 ± 0.06 mg/L vs. 5.53 ± 0.33 mg/L) and phosphate (5.40 ± 0.31 mg/L vs. 18.43 ± 0.78 mg/L) after 2 weeks of treatment. The level of phosphate, BOD, COD, nitrate, and TSS were lowest in Td compared to Tb and Tc (P<0.05). The lowest level of ammonia was obtained in Tc (0.15 ± 0.10 mg/L), compared to Td (0.15 ± 0.10 mg/L) and Tb (0.66 ± 0.28 mg/L). The highest percentage weight gain (WG) of 34.37 ± 0.60% and the lowest feed conversion ratio (FCR) of 1.59 ± 0.03were recorded in fish raised in Td (P<0.05). Oreochromis niloticus juveniles raised in Td also had the highest specific growth rate (SGR) of 0.23 ± 0.01% compared to 0.19 ± 0.00% recorded in fish raised in both Tb and Tc. Fish raised in Tc had the highest survival rate (100 ± 0.00%) compared to the fish cultured with Tb (77.80 ± 2.30%) and Td (72.20 ± 1.95%). The research findings suggest that Lemna minor could be used in fish culture with positive effect on water quality and growth performance.

Assessment of the impact of Abiotic factors on the fish assemblages in a tropical estuary creek

Fish assemblage structures of Badagry creek, Nigeria in relation to abiotic (physical and chemical) variables were studied for 2 years period (November, 2011 – September, 2013). Environmental parameters were monitored in sampling stations randomly selected in each of the three zones established in the creek (3 stations per zone). Fishermen catches were monitored in three major landing sites around the creek (one site per zone). The physico-chemical parameters investigated were within the tolerance limits for aquatic life. Conductance, Salinity and Water depth data showed significant differences (p 0.05) in physicochemical parameters measured seasonally. The survey of fish in the Badagry creek recorded more estuarine and near-shore marine species with a total of 4,045 fish individuals comprising 36 species from 22 families. Dominant fishes included Tilapia zillii (15.2%), Chrysichthys nigrodigitatus (11.3%) and Ethmalosa fimbriata (11.2%). Fish diversity indices in dry season were higher than wet season. Water depth was found to be the most important abiotic factor determining the abundance of species ecological categories. The other abiotic factors tested also showed some influence on the species (ecological categories) abundance, suggesting the importance of environmental parameters in determining fish distribution and abundance.