Effect of different levels of humic acid on the growth and nutrient uptake of teak seedlings

A greenhouse experiment to study the effect of humic acid (HA) on the growth and nutrient uptake of Teak (Tectona grandis L.f.), a tropical hardwood, was conducted in Ibadan, Nigeria. The plants were grown for four months in top soils (0–30 cm) collected from an Alfisol (high organic matter) and an Oxisol (low organic matter) in Southern Nigeria. Three levels of HA, viz:, 50, 500, and 1000 mg/kg were added to the two soils. The results indicated that HA was beneficial to the growth and nutrient uptake of teak seedlings. Plant monthly growth rates, and height and total dry matter yield increased significantly (p = 0.05) over the controls in the two soils at the three HA application levels. Effects of adding 500 mg/kg and more of HA to the Alfisol were less beneficial while plant parameters and nutrient uptake tended to increase with increasing amounts of HA in the Oxisol. A significant positive correlation was established between rate of HA application and plant height (r = 0.57), stem diameter (r = 0.77) and total dry matter yield (r = 0.67) in the Oxisol, whereas the HA application rate was significantly correlated only with height (r = 0.57) and root/shoot ratio (r = 0.56) in the Alfisol. The addition of HA to the two soils increased the uptake by seedlings of N, P, K, Mg, Ca, Zn, Fe, and Cu, while Mn was decreased.     

Evaluation of Cassia fistula meal as a replacement for soybean meal in practical diets of Oreochromis niloticus fingerlings

This study was undertaken to determine the replacement value of Cassia fistula seed meal (CFM) for soybean meal (SBM) in practical diets of Oreochromis niloticus fingerlings. Five practical diets (350 g kg^?1 crude protein) containing 0 g kg^?1 (control), 170 g kg^?1 (diet II), 340 g kg^?1 (diet III), 509 g kg^?1 (diet IV) and 670 g kg^?1 (diet V) substitution levels of CFM for SBM were formulated and fed to triplicate groups of O. niloticus fingerlings (mean initial weight of 10.22 ± 0.03 g) for 70 days. Fish mortality increased linearly with increase in inclusion levels of CFM in the diet. Growth and diet utilization efficiency were depressed in fish fed diets containing CFM at varying inclusion levels. Feed conversion ratio, specific growth rate and protein efficiency ratio of O. niloticus fed on diet containing 170 g kg^?1 substitution level of CFM were similar (P > 0.05) to the control diet. Digestibility of the different diets decreased with increase in inclusion levels of CFM. Fish fed diet containing 670 g kg^?1 CFM had significantly lower carcass protein. However, no significant differences were observed in carcass protein and lipid contents between fish fed the control diets and diet containing 170 g kg^?1 CFM. The most efficient diet in terms of cost per unit weight gain of fish was obtained in 170 g kg^?1 CFM dietary substitution.     

Induced Breeding of Two Clariid Catfishes Clurius gariepinus and Heterobranchus bidorsalis Using Tilapia Pituitary Extracts

Induced breeding trials of two clariid catfishes, Clarias gariepinus and Heterobranchus bidorsalis , were conducted using five doses (2, 4, 6, 8 or 10 mg/kg) of acetone-dried tilapia pituitary (ADTP) extracts. Oocyte maturation and ovulation were induced in female catfishes by single intramuscular injection of 6–10 mgkg ADTP; optimum results were obtained with 8 mgkg in both catfishes. At ambient temperature (27 ± 1 C). ovulation occurred within 14–18 h post-injection resulting in 16–20% increase in egg diameter. Fertilization and hatching percentages increased ( P < 0.05) with increases in hormone dosage. Survival of fry fed a mixed zooplankton diet was high (ranging from 79% to 85%) after 30 d of rearing.     

Dietary ascorbic acid reduced micronucleus and nuclear abnormalities in <Emphasis Type="Italic">Clarias gariepinus</Emphasis> (Burchell 1822) exposed to hospital effluent

Hospital effluents contain myriad of mutagens and genotoxins capable of increasing DNA damage in aquatic biota. African mudfish, Clarias gariepinus, are exposed to genotoxins when cultured in swamps and derelict water bodies often contaminated by effluents. Moreover, its DNA is susceptible to xenobiotic-induced lesions since it lacks l-gulonolactone oxidase and hence cannot synthesize l-ascorbic acid. This study investigated 96-h acute toxicity and protective effects of dietary ascorbic acid (AA) against micronucleus (MN) and abnormal nuclear (NAs) formation in C. gariepinus exposed to sub-lethal concentrations of hospital effluent. Six concentrations (0.5–3.0%) of the effluent were selected to determine the 96-h acute toxicity of the effluent in C. gariepinus, after range finding test. Fish were exposed to sub-lethal concentrations (0.08–1.30%) of the 96 h LC₅₀. Two other groups were exposed to the 96 h LC₅₀ (1.30%) of the effluent +50 and +100 mg/kg of dietary ascorbic for 7 days, and MN and NAs assessed in peripheral erythrocytes. The 96 h LC₅₀ (1.30%) was 1.18 times more toxic than the 24 h LC₅₀ (1.54%), indicating that the toxicity of the effluent increased with exposure duration. MN, nuclear bud, enucleated, fragmented nucleus (apoptosis), and necrotic erythrocytes significantly increase in effluent treated fish. Dietary AA reduced MN from 6.35-fold (1.30% treated group) to 3.72-fold (1.30% + 50 mg AA) and 3.54-fold (1.30% + 100 mg AA). Also, AA reduced total NAs from 2.26-fold (1.30%) to 1.40-fold (1.30% + 50 mg AA) and 1.06-fold (1.30% + 100 mg AA) compared to the control. Heavy metals and physicochemical parameters analyzed in the tested effluent possibly induced the mortality and cytogenotoxicity in C. gariepinus, and this was ameliorated by dietary AA.     

Soybean meal replacement by roquette (Eruca sativa Miller) seed meal as protein feedstuff in diets for African Catfish, Clarias gariepinus (Burchell 1822), fingerlings

Apparent digestibility coefficient (ADC) values for mechanically extracted meal derived from roquette (Eruca sativa) seeds were obtained. The digestibility of dry matter (DM), protein and energy was measured using an inert marker in the diets and by faeces collection using the dissection method. Soybean meal and roquette meal had similar ADC values for protein and energy. Roquette seed meal was thereafter evaluated as a protein source in diets (400‐g crude protein, 120‐g crude lipid and 18.00 MJ gross energy kg^?1 DM) fed to African catfish, Clarias gariepinus, fingerlings (10.4±0.4 g) to apparent satiation twice daily for 70 days. The test diets contained roquette seed meal as replacement for soybean meal protein in a control diet, providing 20%, 40% or 60% of the total protein. Catfish mortality was low (<10%) and not diet related. Substituting soybean meal protein with roquette seed meal protein providing 20% of total protein did not affect weight gain, growth response, feed conversion ratio, protein utilization or carcass composition of catfish. Catfish growth was, however, retarded and feed was poorly utilized only when roquette seed meal provided above 20% of total protein, caused by reduced energy digestibility, deficiencies in some essential amino acids and presence of antinutritional factors. Livers of catfish fed high dietary levels of roquette seed meal showed severe histological abnormalities.     

Comparative evaluation of heat-processed Winged bean (Psophocarpus tetragonolobus) meals as partial replacement for fish meal in diets for the African catfish (Clarias gariepinus)

Mature winged bean (Psophocarpus tetragonolobus) (cultivar Tpt26) seeds were roasted or autoclaved and their meals evaluated as a dietary protein source for the African catfish. Five dry practical diets (400 g protein/kg and 17.5 kJ gross energy/g dry diet) containing menhaden fish meal or each of the heat-processed winged bean meals as partial replacement (80%), (with or without 5 g -methionine/kg diet supplementation) for menhaden fish meal, were prepared and fed to triplicate groups of catfish fingerlings (5.8±1.2 g) to satiation for 70 days. No mortality occurred throughout the study and satisfactory diet acceptance was observed when the heat-processed winged bean meals replaced menhaden fish meal. Differences were found in weight gain, specific growth rate, feed and protein efficiency ratios, but were not significant (P>0.05). Digestibility of crude protein and gross energy content of the diets were high (>85%) and comparable to that of menhaden fish meal. Carcass composition of catfish did not vary significantly (P>0.05) between diet treatments. Results indicate that both autoclaved and roasted winged bean meals were acceptable as protein sources and can replace 80% of menhaden fish meal in catfish diets.     

Comparative Growth and Survival of Reciprocal Hybrids Between Clarias gariepinus and Clarias anguillaris

Reciprocal, interspecific hybrids of Clarias gariepinus and Clarias anguillaris were produced via hypophysation and dry stripping. Two-week-old fry (0.06 ± 0.02 g) of the parental Clarias species and their interspecific hybrids were stocked in duplicated 1 m³ hapas suspended in outdoor earthen ponds (16 m²) for a rearing period of 56 days. Growth and survival of the hybrids was intermediate to the faster growing and better surviving C. gariepinus and the more slowly growing and more vulnerable C. anguillaris parental lines. The weight gain attained by C. gariepinus, C. anguillaris, C. gariepinus (♂)?×?C. anguillaris (♀), and C. anguillaris (♂)?×?C. gariepinus (♀) were 3.18 g, 2.99 g, 3.16 g and 3.05 g, respectively. Among hybrids, the growth of C. gariepinus (♂)?×?C. gariepinus (♀) was higher than the reciprocal C. anguillaris (♂)?×?C. gariepinus (♀). Heterosis for growth was a negligible 0.65% and for survival was negative (?5%). C. gariepinus appears to be the best species for aquaculture in terms of growth rate and survival.