Miguel Jover

Growth of mediterranean yellowtail (Seriola dumerilii) fed extruded diets containing different levels of protein and lipid

Young Mediterranean yellowtail were maintained for 10 months in three different weight groups (114, 141 and 192 g initial mean liveweight) and fed four extruded diets containing two protein levels (45 and 50% CP) and two lipid levels (14 and 17%) according to a factorial design. Survival at the end of trial was around 70% and was unaffected by treatment. Final mean liveweights were 1044, 1098, 1336 and 1163 g for groups fed 45/14, 45/17, 50/14 and 50/17 protein/lipid diets, respectively. The effect of lipid level was not significant, but the growth of fish fed diets containing 50% CP was higher than those fed the 45% CP diets. Nutritive parameters such as, feed intake, feed conversion ratio and PER were not affected by diets. Body composition and nutrient retention values were similar for fish fed various diets. Viscerosomatic index was higher for fish fed diets containing 17% lipid and hepatosomatic index was higher for those fed 50% CP or 12% lipid. Dressout percentage was higher for fish fed diets containing 50% CP.

Growth of European sea bass fingerlings (Dicentrarchus labrax) fed extruded diets containing varying levels of protein, lipid and carbohydrate

Sea bass fingerlings (2.78 g) were fed eight extruded diets for 90 days, in which part of the protein was replaced by lipid (Trial 1) or carbohydrate (Trial 2), so that crude protein (CP) varied between 40 and 55%, lipid from 6 to 18% and carbohydrate between 20 and 35%. The effect of protein level on growth and feed conversion was significant (P < 0.01). The best performance was obtained with 45% CP in both experiments, with relative weight gain of 539 vs. 416, 476 and 326% in Trial 1, and 536 vs. 376, 466 and 520% in Trial 2, for 40, 50 and 55% CP, respectively. The overall results suggest that the percentage of carbohydrate in sea bass diets should not exceed 30%, and that lipid content can vary between 12 and 14%.

Growth of dentex fingerlings (Dentex dentex) fed diets containing different levels of protein and lipid

Abstract Dentex fingerlings weighing 2.5 g initial live weight were fed 12 extruded diets containing four crude protein levels (40%, 45%, 50% and 55%) and three crude lipid levels (12%, 17% and 22%) according to a factorial design, for 6 weeks. Survival was high (84–92%) and specific growth rate (SGR) values were 3.4%, 3.9%, 4.3% and 4.1% day −1 and food conversion ratio (FCR) were 2.2, 2.1, 1.5 and 1.9 for fish fed the diets containing 40%, 45%, 50% and 55% crude protein, respectively. With respect to lipid levels, SGR values were 4.2%, 4.0% and 3.6% day −1 and FCR were 1.7, 1.8 and 2.3 for 12%, 17% and 22% crude lipid, respectively. The effects of protein and lipid levels were significant; final live weight, SGR, FCR and PER values were best for fish fed 50% crude protein and poorest for those fed 22% lipid diets. The best growth performance was observed in fish fed diets containing 50/12 and 50/17 protein/lipid ratios. The results indicate that optimum growth and nutrient utilisation of dentex fingerlings can be obtained when they are fed a diet containing around 50% crude protein with a lipid level ranging from 12% to 17%, and having a crude protein/gross energy ratio from 22 to 25 g MJ −1 .

Molecular and physiological study of the artificial maturation process in European eel males: From brain to testis

European eel males can be artificially matured (1.5IU hCG/g fish), but the regulatory mechanisms of their reproductive development are practically unknown. Spermatogenic stages (S1-S6), biometric characters [eye index (EI), gonadosomatic index (GSI), hepatosomatic index (HSI)] and sperm quality parameters (motility, viability and head spermatozoa morphometry) were analysed. Moreover, the present study evaluated the expression of GnRHs (mammal and chicken II Gonadotropin Release Hormone I) and gonadotrophins (FSHbeta and LHbeta) during hormonal treatment, as well as 11-ketotestosterone (11-KT) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) plasma levels. One week was enough to observe the S2 of gonad development, but it was necessary to reach the 7th week of treatment to obtain animals that presented the most advanced stage of development (S6). Differential regulation of the two GnRH expressions was found, supporting the main role of mGnRH in the control of gonadotrophin release. One hCG injection was enough to dramatically decrease the FSHbeta expression, being close to zero during the rest of the treatment. LHbeta expression and 17,20beta-P registered a significant increase in the same stage of development, S3/4, confirming the role of this gonadotrophin in the last steps of maturation and 17,20beta-P in the spermatozoa maturation. The 11-KT increased with GSI, and the highest 11-KT values coincided with the advanced steps of spermatogenesis prior to spermiation. Being consistent with the known role of the steroid in these processes. Furthermore, this study supports a role for 11-KT in stimulating eye growth, presenting high values when EI increased. Sperm production was obtained from the 4th week of treatment, but it was in the 8th week when a significant increase was observed in sperm quality [viability, high motility (>75%)].

Ionic composition and physio-chemical parameters of the European eel (Anguilla anguilla) seminal plasma

Looking for good sperm diluting media, physio-chemical parameters and ionic composition of the eel seminal plasma were studied in relation with sperm motility.

Effect of feeding cooked-extruded diets, containing different levels of protein, lipid and carbohydrate on growth of red swamp crayfish (Procambarus clarkii)

Abstract Two nutritional trials were conducted with juvenile red swamp crayfish Procambarus clarkii using eight cooked-extruded diets containing different levels of protein, lipid and carbohydrate: H20 (22/5/41), H25 (26/6/36), H30 (30/6/33), H35 (35/6/28), G25 (25/14/21), G30 (32/11/21), G35 (35/8/24), G40 (41, 6, 22), respectively. In the first experiment, crayfish were kept in individual containers and all diets were given for a period of 165 days. In general, lower lipid diets led to better growth and survival, protein levels of 22, 26 and 30% protein were adequate. After 105 days mortality decreased and weight remained stable for animals fed most diets, except for those containing 22% protein which increased. A good final weight was also obtained with diets containing 22, 26 and 30% crude protein. In the second trial, only diets H20, H25 and H30 were used. Crayfish were stocked in collective tanks and fed the test diets for 150 days. Growth was better than in the previous experiment, and the three diets gave similar final liveweights, survival and total weight. In summary, the optimum nutrient levels for red swamp crayfish growth under our experimental conditions were 22–26% crude protein, 6% lipid and 36–41% carbohydrate, with 10–12 MJ/kg (2.4–2.9 Mcal/kg) of energy content and 17–21 g/MJ (4.1–5.0 mg/kcal) of protein/energy ratio.

Improvement of European eel sperm cryopreservation method by preventing spermatozoa movement activation caused by cryoprotectants.

Sperm production has been obtained from European and Japanese eels, but its quality and quantity tend to be changeable. So, its cryopreservation has been tried in both species. Dimethyl sulfoxide (Me(2)SO) is the best cryoprotectant for European eel sperm, but increases the medium osmolality, inducing the activation of spermatozoa motility. To avoid this, different combinations of pH (6.5 and 8.5) and NaHCO(3) concentrations (20, 40 and 80mM) were tested with two Me(2)SO concentrations (5% and 10%). Foetal bovine serum (FBS, 25%v/v) was added as a membrane protector to all the freezing media used in the different experiments. The highest Me(2)SO and NaHCO(3) concentrations at pH 6.5 caused the best post-thawing motility (26+/-4%). A second experiment was carried out testing media with Me(2)SO 10% with additional NaHCO(3) concentrations (100 and 120 mM). The highest post-thawing motility (38+/-3%) was found in the media containing NaHCO(3) 100mM, but no significant difference was observed compared with the best in the previous experiment (NaHCO(3) 80 mM). In a parallel experiment, aiming to improve the protection against the cryopreservation process, bovine serum albumin (BSA, 5%w/v) was added instead of FBS. Lower motilities were registered with BSA as membrane protector. Spermatozoa activation caused by addition of Me(2)SO can be prevented using high NaHCO(3) concentrations, improving the cryopreservation process. This effect seems be based on some of the products dissociated from NaHCO(3) in aqueous solution, affecting the intracellular pH, essential in the sperm motility.

Effects of pH, Sodium Bicarbonate, Cryoprotectants and Foetal Bovine Serum on the Cryopreservation of European Eel Sperm

The main objective of the present study was to evaluate the influence of pH and bicarbonate concentration in the activation or inhibition of European eel (Anguilla anguilla) spermatozoa and to evaluate the effect of different cryoprotectants: dimethyl sulphoxide (DMSO), acetamide, ethylene glycol, propanol, glycerol and methanol (MeOH). The effect of these factors was evaluated comparing the percentage of motile cells, the percentage of alive cells (by Hoechst staining) and the spermatozoa morphometry pre- and post-cryopreservation (by computer-assisted morphology analysis). Based on the above findings, three cryoprotectants (DMSO, MeOH and glycerol) were chosen and evaluated in two media (P1 and P1 modified) with different concentrations of NaHCO(3) and in the presence or absence of foetal bovine serum (FBS). The effect of these factors was evaluated comparing the percentage of alive and motile cells post-cryopreservation. DMSO was the cryoprotectant showing better results in relation to the percentage of spermatic alive cells post-freezing and caused a smaller modification of the head spermatozoa morphology. The combination of P1-modified medium with DMSO and containing FBS increased slightly but significantly the percentage of motile spermatozoa post-cryopreservation.

Media and methods for the cryopreservation of European eel (Anguilla anguilla) sperm

Different media and protocols were assayed for European eel sperm cryopreservation.

The effect of dietary soybean meal on growth, nutrient utilization efficiency, and digestibility of juvenile common dentex, Dentex dentex (Actinopterygii: Perciformes: Sparidae).

Background. The aim of this work was to study the growth of juvenile dentex fed on cooking-extruded diets, determine the level of substitution of fishmeal by soybean meal may be without affecting the growth in this species and its digestibility. MaterialsandMethods. The availability of defatted soybean meal as a substitute for fish meal was evaluated in juvenile (41 g on average) dentex by feeding diets containing 0%-60% soybean meal, for 97 days. Results. Survival at the end of the experiment was high (80%) except for the fish fed diets with 50% and 60% substitution. Growth, feed gain ratio, and protein efficiency ratio (PER) were slightly reduced at higher soybean meal levels. Fish fed diets containing 0% to 40% of soybean meal grew significantly more and FCR was lower than fish fed other diets. No differences were obtained for protein digestibility coefficients of experimental diets (20%, 30%, 40%, and 50% SBM). Conclusion. The results confirm the best protein level for optimum growth seems to be around 50% and 12% lipid level, and maximum soybean meal substitution of 40%.