Functional linseed fibres and their impacts on silver catfish (Rhamdia quelen) nutrition

This study was conducted with the objective of evaluating the combination of different ratios of soluble and insoluble linseed fibre for silver catfish (Rhamdia quelen). For this, the soluble and insoluble fractions were concentrated separately and combined in four ratios (1:0.5, 1:1, 1:2, 1:4), which were added to silver catfish diets and evaluated in a bioassay. After 45 days of receiving the experimental diets, the animals were submitted to biometry to collect data and tissues. The experimental design was completely randomized, with five treatments and four replications and the means were compared by Tukey's test (p < .05). Diets 1:2 and 1:4 provided higher weight gain, specific growth rate and crude protein deposition to the fish, whereas only the 1:4 diet reflected higher crude body protein. The 1:0.5 diet altered the trypsin activity in the intestine, and, together with the 1:4 diet, it provided a higher intestinal villi height. Body yield, somatic and digestive parameters, chymotrypsin activity and glucose, glycogen and liver protein were not altered, regardless of the experimental diets. In conclusion, the results indicate that linseed fibre acts effectively as a growth promoter in silver catfish diets, with the use of 1:2 and 1:4 ratios optimizing its prebiotic action.     

Ovulation induction in jundiá (Rhamdia quelen,Heptapteridae) using carp pituitary extract or salmon GnRH analogue combined with dopamine receptor antagonists

Jundiá (Rhamdia quelen) is an important species for aquaculture in temperate and subtropical climates. In the present study, the results of different forms of GnRH analogue treatments on ovulation in jundiá have been compared with those from treatment with carp pituitary. Seven out of eight females ovulated in groups treated with carp pituitary (4.0 mg kg^?1 BW) and Ovaprim (0.5 mL kg^?1 BW). Injection with sGnRHa (10 μg kg^?1 BW) combined with metoclopramide (20 mg kg^?1 BW) caused a significantly lower rate of ovulation with three out of eight females responding. None of the fish injected with sGnRHa (10 μg kg^?1 BW) alone ovulated. Mean PGSI [(weight of stripped egg mass/BW of the female before stripping) × 100] and mean fertilization rate values were high and similar between treatment groups. The obtained results indicate that in jundiá, there is a strong dopamine inhibitory tone on gonadotropin secretion. The gonadotropin releasing activity of sGnRHa can be potentiated by dopamine receptor antagonists and the combined treatment is effective in inducing ovulation. In this regard, domperidone proved to be more potent than metoclopramide.     

Effect of sex and protein level on the intermediary metabolism,growth, deposition of nutrients and profile of volatile compounds of silver catfish (Rhamdia quelen)

This study aimed at evaluating the intermediary metabolism, growth, nutritional deposition and volatile compounds of fillet of female and male silver catfish created in cages having commercial diets at two levels of crude protein. A total of 1,200 silver catfish were randomly distributed in 12 cages with initial weight of 130.05 ± 0.14 g and visually sexed. Commercial diets with 280 g/kg and 320 g/kg of crude protein were offered twice a day in the amount of 30 g/kg their biomass/day, for 90 days. At the end of the experimental period, biometry was performed to collect data, blood and tissue for later determination of plasma metabolites, hepatic metabolites, digestive enzymes, volatile compounds, deposition of nutrients and calculation of growth variables. There were metabolic differences due to the sex of silver catfish, reflecting greater productive efficiency on the females. For the plasma metabolites, in male, there were higher values of triglycerides and free amino acids than in female. For hepatic glucose, males fed with diet containing 280 g/kg of crude protein showed higher values. For protein and free amino acids, the interaction between males that received 320 g/kg of crude protein was higher. In males, there were higher values of AST and hepatic glycogen than in females. In turn, hepatic ammonia was higher in females. There was greater activity of acid protease enzymes and trypsin in the silver catfish that received diets containing 320 g/kg of crude protein. Regardless of sex, in this cultivation phase, diets with 320 g/kg of crude protein provided better performance to silver catfish. The profile of volatile compounds suggests mild odour for the fillet of silver catfish, which can be a competitive advantage of the species.     

Effect of supplementation of dietary fibre concentrates on biochemical parameters,stress response,immune response and skin mucus of jundiá (Rhamdia quelen)

The aim of this study was to assess the effects of different dietary fibre concentrates (DFC: Mucilage = MG; pectin = PN or β‐glucan+mannan = βg+M), on biochemical parameters, stress and immune response and skin mucus of jundiá (Rhamdia quelen). The fish (7.16 ± 0.06 g) were fed with Control diet (0 g/kg of DFC); diet supplemented with 5 g/kg of commercial prebiotic (CP 5) or diets supplemented with 5 or 10 g/kg of MG; PN or βg+M. After 8 weeks of the feeding trials, biochemical parameters (cholesterol, glucose, albumin and total protein), cortisol, immunoglobulin IgM and mucoproteins of skin mucus were assessed. Results demonstrated that supplementation with PN increased cholesterol levels (p<.05). After application of the stressor, most fish, except those in the PN and 10 g/kg MG groups, showed significant increases (p<.05) in cholesterol, glucose and albumin levels. The jundiás showed no difference in cortisol levels after application of the stressor (p>.05). IgM levels were significantly high in fish supplemented with DFC (p<.05). However, the concentration of mucoproteins in skin mucus was not influenced in the different treatments (p>.05). The results showed that supplementation with DFC promoted beneficial effects on the metabolism of jundiá.     

Effects of Dietary Fibre Concentrates on growth performance and digestive enzyme activities of jundiá (Rhamdia quelen)

This study was conducted to investigate the prebiotic effect of different Dietary Fibre Concentrates (DFC) (Mucilage =MG; Pectin = PN or β‐glucan + mannan = βg + M) on growth and somatic parameters, body composition and digestive enzyme activities of jundiá (Rhamdia quelen). After acclimation, fish (7.16 ± 0.06 g) were allocated into 24 tanks (30 fish per tank) and triplicate groups were fed with Control diet (0 g kg^?1 of DFC); diet supplemented with 5 g kg^?1 commercial prebiotic (CP) or diets supplemented with 5 or 10 g kg^?1 diet of MG; PN or βg + M. At the end of the trial (8 weeks), growth was significantly (P < 0.05) higher in fish fed diets supplemented with DFCs and did not differ from animals supplemented with CP. The animals that were fed Control diet presented a body protein content higher compared to those supplemented with diets containing pectin or β‐glucan + mannan (P < 0.05). However, fish fed diets added with β‐glucan + mannan yielded a higher level of protein deposited in the whole body. The activity of digestive enzymes was lower in the group supplemented with Pectin. Results indicate that supplementation with DFCs in the diet had positive effects on the performance of jundiá and are prebiotic potential candidate.     

Simultaneous effect of sex and dose on efficacy of clove oil,tricaine methanesulfonate, 2‐phenoxyethanol and propofol as anaesthetics in guppies,Poecilia reticulata (Peters)

We studied the simultaneous effect of sex and dose on anaesthesia efficacy to estimate, if possible, the lowest effective dose (LED) for clove oil, tricaine methanesulphonate (MS‐222), 2‐phenoxyethanol (2‐PE) and propofol in mature guppies. LED is the lowest dose needed to reach A5 stage in a mean time of 3 min, with mean recovery (R5) time of 5 min. We used four doses/anaesthetic: 25, 50, 75 and 100 mg/L for clove oil; 120,140,160 and 180 mg/L for MS‐222; 800, 1,000, 1,200 and 1,400 mg/L for 2‐PE, and 7.50, 8.25, 10.00 and 11.25 mg/L for propofol. Each dose was tested on 10 females and 10 males. Morbidity, mortality and behavioural changes were checked on two control groups (10 males and 10 females/group). Sedation (A3), A5 and R5 times were recorded. Significant interactive effect dose*sex on A5 time was found for each anaesthetic agent (p_dose*sex < .05). Except for MS‐222 (p_dose*sex = .284), significant interactive effect dose * sex on R5 time was found (p_dose*sex < .05). A5 time in females tended to be greater than in males, but, in general, R5 times were longer in males. Body size differences between males and females could explain these differences in MS‐222 on A5 time and for clove oil, 2‐PE and propofol on R5 time. No dose simultaneous meet LED′s conditions relating to both A5 and R5 times; therefore the lowest doses inducing A5 in a mean time of 3 min could be a safe guideline for anaesthetic procedure in both male and females.     

A Comparison between dietary effects of Cuminum cyminum essential oil and Cuminum cyminum essential oil,loaded with iron nanoparticles,on growth performance,immunity and antioxidant indicators of white leg shrimp (Litopenaeus vannamei)

This study evaluates the effect of dietary cumin essential oil's (CEO) and cumin essential oil's loaded iron nanoparticles (CEO‐loaded NPs) on growth performance, haematological parameters and antioxidant status of white leg shrimp. Shrimps with the initial weight of 3.38 ± 0.014 g were allocated into 15 fibreglass tanks (300 L, 60 shrimps per tank) and were fed with five experimental diets containing 0 g/kg CEO (the control diet), 5 g/kg CEO, 10 g/kg CEO, 5 g/kg CEO‐NPs and 10 g/kg CEO‐NPs for 56 days. After 56 days of culture, the shrimps fed with CEO and CEO‐loaded NPs supplemented diets showed a more significant increase in growth performance (p < .05) than in the control diet. Total haemocyte count (THC) value, large‐granule cells (LGC), hyaline cells (HC)%, superoxide dismutase (SOD) and Alkaline phosphatase (AKP) activity were significantly higher (p < .05) in the shrimps fed with CEO and CEO‐loaded NPs supplemented diets than the shrimps fed with the control diet. Glutathione peroxidase (GPX) enzyme activities along with the glucose and cholesterol concentrations significantly decreased in the shrimps fed with the CEO and CEO‐loaded NPs supplemented diets more than those fed with the control diet. The results suggest that the dietary CEO‐loaded NPs can improve the growth performance, the health status and the antioxidant capacity of L. vannamei.