Inhibition of protease activities in discus Symphysodon spp. by three plant meals

Based on biochemical assays and electrophoretical methods, the inhibitory effects of three plant meals (soybean meal, wheat meal, winged bean meal) on digestive alkaline proteases of discus were investigated. Casein assays revealed that increasing levels of soybean meal caused a linear inhibitory effect on activity of protease. SDS-PAGE images revealed that trypsin and chymotrypsin were the inhibited enzymes. Soybean showed the lowest inhibition rate followed by wheat meal and raw winged bean. There was a quadratic relationship between wheat meal levels and its inhibition of protease acitivity. The highest inhibitory effect was obtained with the winged bean meal with inhibition of caseinolytic activities ranging from 3.6–98.6%. Results from this study showed the potential of both soybean meal and wheat meal as ingredients for practical diet for discus, while demonstrating the need for further improvement in processing method for winged bean meal.     

Effects of the probiotic, Lactobacillus acidophilus, on the growth performance, haematology parameters and immunoglobulin concentration in African Catfish (Clarias gariepinus, Burchell 1822) fingerling

This experiment was carried out to evaluate the effects of the probiotic, Lactobacillus acidophilus , on the growth performance, haematology parameters and immunoglobulin concentration in African catfish Clarias gariepinus fingerling. Two experimental diets were formulated to contain 35 g kg⁻¹ crude protein and 10 g kg⁻¹ lipids accordingly and fed three times daily for 12 weeks to 25 C. gariepinus fingerlings per fibreglass tank in 12 replicates each. The control diet was prepared with no probiotic supplementation whereas the second diet was prepared supplemented with a probiotic, L. acidophilus , containing about 3.01 × 10⁷ colonies/g of diet. The results show that growth performance [specific growth rate (SGR) and relative growth rate (RGR)], nutrient utilization [protein efficiency ratio (PER) and feed conversion ratio (FCR)] and survival were significantly ( P <0.05) higher in fish maintained on the probiotic-supplemented diet compared with those on the control diet. Haematology parameters (packed cell volume, haemoglobin, erythrocyte sedimentation rate, red blood cell and white blood cell, total serum protein, Ca²⁺, Mg²⁺, Cl⁻, glucose and cholesterol) and total immunoglobulin concentrations were also significantly better in fish fed the probiotic-supplemented diet than in the control. Although the water quality parameters monitored were better in the fish fed the probiotic-supplemented diet than in the control, the parameters were not significantly different ( P >0.05). From the results of this experiment, we conclude that L. acidophilus can be used as a probiotic agent in African catfish culture, to enhance fish health, survival and better feed efficiency and growth performance.     

Effectiveness of single and combined use of selected dietary probiotic and prebiotics on growth and intestinal conditions of striped catfish (Pangasianodon hypophthalmus,Sauvage, 1978) juvenile

Aquaculture International - Single or combined effect of yeast, galactooligosaccharide (GOS), mannanoligosaccharide (MOS), and β-glucan was evaluated on the growth performance, nutrient...     

In vivo and in vitro protein digestibility in juvenile bagrid catfish Mystus nemurus (Cuvier and Valenciennes 1840) fed soybean meal‐based diets

In vivo and in vitro protein digestibility of 0% to 60% soybean meal protein (SBM) substitution from fishmeal protein was conducted for bagrid catfish Mystus nemurus juveniles. Seven experimental diets containing 35% protein and 15% lipid were fed to bagrid catfish to determine the in vivo protein digestibility. In vitro methods were determined using pH stat, pH shift, spectrophotometric assay and sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) with different enzyme mixtures (crude intestinal extract of bagrid catfish, Lazo 1‐enzyme, Hsu 3‐enzyme, Saterlee 4‐enzyme). In vivo and in vitro protein digestibility decreased with increased SBM protein substitution with highest tolerance level of 10% (in vivo). pH stat and pH drop methods showed the highest degree of hydrolysis (DH) and relative protein digestibility (RPD) using Saterlee 4‐enzyme system. However, pH stat method showed highest correlations (r² = 0.9263) with the in vivo results using crude intestinal enzyme extract compared to other enzyme systems. The highest correlation of the in vitro methods using crude intestinal enzyme extracts of bagrid catfish was determined using spectrophotometric assay (r² = 0.9284) followed by pH stat (r² = 0.9263), SDS‐PAGE (r² = 0.8348) and pH drop (r² = 0.6777). All the in vitro methods tested are suitable to rapidly determine protein digestibility for bagrid catfish except for pH drop.     

Effect of Lactobacillus acidophilussupplementation on growth performances,digestive enzyme activities and gut histomorphology of striped catfish (Pangasianodon hypophthalmusSauvage, 1878) juveniles

The influence of dietary supplementation of Lactobacillus acidophilus, on growth performance, digestive enzyme activities, gut histomorphology and gut microflora were evaluated in juveniles striped catfish (Pangasianodon hypophthalmus). Five experimental diets were formulated by supplementing 0, 10³, 10⁵, 10⁷ and 10⁹ CFU/g L. acidophilus in fishmeal and casein‐based semi‐purified diet. Triplicate groups of striped catfish (21.69 ± 0.18 g) were stocked in 15 fiberglass tanks with stocking density of 25 individuals per tank and fed twice daily at 2.5% of the fish body weight for 12 weeks. Weight gain, specific growth rate, feed conversion ratio and the protein efficiency ratio were significantly higher in fish fed with 10⁵ and 10⁷CFU/g L. acidophilussupplemented diets compared with the other treatment groups. Compared with the control and fish fed low (10³ CFU/g) L. acidophilus supplementation, those fed with 10⁵ and 10⁷ CFU/g had significantly higher (p < 0.05) apparent protein digestibility. Inclusion of L. acidophilus at 10⁷ CFU/g diet significantly increased amylase, protease and lipase activities. Microscopic analysis showed that the villi length in both the anterior and posterior gut and microvilli length in the posterior gut increased significantly in fish fed L. acidophilus supplementation at 10⁵ and 10⁷ CFU/g of diet. The fish fed L. acidophilus supplemented diets significantly increased the total lactic acid bacteria counts in the gut of striped catfish compared with the control‐fed group. Based on gut histomorphology and growth performance, inclusion of L. acidophilus at 10⁵ CFU/g appears to have the most positive effect on striped catfish farming.     

Galactooligosaccharide and a combination of yeast and β-glucan supplements enhance growth and improve intestinal condition in striped catfish <Emphasis Type="Italic">Pangasianodon hypophthalmus</Emphasis> fed soybean meal diets

The effects of galactooligosaccharide (GOS) and a combination of yeast and β-glucan (YβG) supplementation of dietary soybean meal (SBM) on the growth and digestive performance of striped catfish Pangasianodon hypophthalmus were evaluated. Four isonitrogenous (30% protein) and isocaloric (19 MJ/kg diet) diets were formulated to contain 100% fish meal (FM) protein, 55% FM protein/45% SBM protein, FM-SBM supplemented with 1% GOS, and a combination of 1% yeast and 0.1% β-glucan, respectively. Each diet was fed for 12 weeks to three groups of 30 striped catfish fingerlings (average weight 16.45?±?0.07 g) maintained in circular fiberglass tanks (600 l). Growth, feed utilization, and muscle protein composition of fish improved significantly after supplementation with either GOS or YβG compared to the unsupplemented SBM diet, but were similar to those of fish fed the FM diet. Nutrient digestibility, digestive enzyme activities, villi and microvilli length were significantly increased in fish fed the supplemented SBM diets. The gut microbiota ranking profile showed that supplementing the SBM diet with YβG and GOS gave a ranking of Verrucomicrobia, Spirochaetes, Bacteriodetes, and Actinobacteria phyla similar to that of the FM diet. Thus, diet containing 45% protein from soybean supplemented with either GOS or YβG can be recommended to improve the growth and digestive performance of striped catfish.     

Effect of varying dietary lipid and protein levels on growth and reproductive performance of female swordtails Xiphophorus helleri (Poeciliidae)

We conducted a study to determine the effect of dietary protein and lipid levels on the growth and reproductive performance of a freshwater ornamental species, the swordtail (Xiphophorus helleri). Two protein levels (20% and 30%) with four lipid levels (8%, 12%, 16%, 20%) within each protein levels were tested through formulation of practical diets labelled as 20P8L, 20P12L, 20P16L, 20P20L, 30P8L, 30P12L, 30P16L and 30P20L respectively. Results showed that dietary protein level significantly influenced final weight, weight gain and specific growth rate, while dietary lipid did not influence any of these growth parameters. More specifically, increasing dietary lipid levels from 8% to 12–16% in both 20% and 30% protein levels significantly improved swordtail growth performance. Dietary protein levels positively influenced gonadosomatic and hepatosomatic indexes. Both dietary protein and lipid significantly influenced female muscle protein content. Significantly highest fry production was obtained from diets 30P12L and 30P16L, respectively, while diet 20P8L resulted in the lowest fry production. This present study indicates the dietary protein and lipid requirements for female swordtails for optimized growth and reproductive performances to be at 30% and 12% respectively.     

Characterization of protease activity in developing discus Symphysodon aequifasciata larva

The activity of different protease classes was monitored in developing discus (Symphysodon spp.) larvae using a combination of biochemical assays and substrate SDS–PAGE techniques. Results showed the presence of alkaline proteases of serine proteases such as trypsin with a significant increase in activity levels detected beginning 3 days after hatching. Other alkaline proteases such as metallo‐proteases and chymotrypsin, a type of serine protease, were only detected in older larval stages, at around 20–30 days after hatching. Acidic protease activity was very low during the first 20–25 days of development before showing a significant (P < 0.01) rise. This is despite the formation of a stomach observed 10 days after hatching. Based on the development of the protein digestive system observed, the use of microdiets to replace Artemia should be considered 25 days after hatching.