Hervey Rodríguez-González

Growth of fresh-water prawn Macrobrachium tenellum (Smith, 1871) juveniles fed isoproteic diets substituting fish meal by soya bean meal

Growth parameters (standard length, weight, specific growth rate and daily we ight gain) of prawn Macrobrachium tenellum juveniles fed 40% crude protein isoproteic diets substituting fish m eal with soya bean meal at various levels (20, 40, 60, 80 and 100%) were evaluated for 45 days under laboratory conditions. Experimental diets were compared with a 100% fish meal based di et. Total survival was recorded for all the treatments at the end of the experiment. There were no significant differences (p � 0.05) for all the growth parameters among the dietary treatments. The initial mean weight (0.36 ± 0.10 g) increased almost three times (1.00 ± 0.13 g) after 45 days. The final specif ic growth fluctuated from 1.82% BW/d for the 60% soya bean meal inclusion diet, to 2.62% for the 100% fish meal diet. The mean final survival was 91.66%. Growth performance of M. tenellum juveniles was not affected by the dietary soya bean meal levels tested.

Bioprocessing of common beans in diets for tilapia. In vivo digestibility and antinutritional factors

BACKGROUND Bioprocessing of ingredients by solid-state fermentation is a low-cost technique for preparing diets. It is performed by adding microorganisms such as Rhizopus oligosporus to bean grains, achieving minimal degradation of nutrients and a significant improvement in digestibility. In particular, fermentation induces favorable changes in beans by reducing enzyme inhibitors, such as phytates and tannins. RESULTS Fermentation significantly (P < 0.05) increased the protein content and digestibility of dry matter and protein compared with whole bean grains, and decreased the content of lipids, ash and phytic acid. Hardening did not have a significant (P > 0.05) effect on the chemical content of beans and digestibility of diets. The dehulled bean meal significantly (P < 0.05) increased protein and lipid content and digestibility of dry matter and protein of beans, and decreased fiber, ash and tannin content. The chemical content of beans and digestibility of ingredients compare favorably with those reported by other authors, indicating the benefits of fermentation and dehulling. CONCLUSION We concluded that bean meal obtained from fermentation or dehulling represents a low-cost alternative for diets for tilapia.

Apparent digestibility coefficient of chickpea, maize, high-quality protein maize, and beans diets in juvenile and adult Nile tilapia ( Oreochromis niloticus )

The objective of our study was to assess the apparent digestibility of plant ingredients in diets for juvenile (50 g) and adult (220 g) Nile tilapia (Oreochromis niloticus). Dietary dry matter and protein apparent digestibility coefficients of four plant-derived feedstuffs (chickpea, maize, high-quality maize protein, and beans) were tested. The beans diet had the lowest apparent digestibility coefficient of dry matter (ADCDM) (69.41%), while no significant differences were detected in ADCDM among the other diets; ADCDM was significantly higher in adults compared with juveniles (77.02 vs. 73.76%). Apparent dry matter digestibility coefficient of ingredients (ADCI) was significantly higher in the chickpea (70.48%) and high-quality protein maize (71.09%) ingredients, and lower in the beans (52.79%) ingredient. Apparent dry matter digestibility coefficient of ingredients was significantly higher in juveniles compared with adults (72.56 vs. 56.80%). The protein digestibility of diet (ADCCP) was significantly higher in the reference diet (93.68%), while the lowest corresponded to the maize (87.86%) and beans (87.29%) diets. Significantly lower apparent digestibility coefficient of protein (ADCICP ) was obtained with the high-quality maize protein (59.11%) and maize (49.48%) ingredients, while higher ADCICP was obtained with the chickpea and beans ingredients (71.31 and 63.89%, respectively). The apparent digestibility coefficient of ingredient crude protein ADCICP was significantly higher in juveniles compared with adults (67.35 vs. 53.46). Digestibility is generally higher in juveniles, and we recommend using chickpea as an ingredient in diets for Nile tilapia.

Stocking Density for Nursery Production of Redclaw Crayfish, Cherax quadricarinatus, in a Recirculating System

Redclaw crayfish, Cherax quadricarinatus, early juveniles were reared at different stocking densities in a closed recirculation system using 12-L plastic containers as rearing tanks. Initial stocking densities were 1.0, 1.5, 2.0, 2.5, and 3.0 per liter (66, 89, 111, 133, and 156 crayfish/m2, respectively). Rearing period was 42 days. Each density was tested with five replicates. Shelter (0.112 m2) was added to double the surface area of rearing tanks. Animals were fed ad libitum twice a day with a commercial diet containing 35% crude protein. There were no significant differences (P < 0.05) in length and specific growth rate (SGR) among stocking densities. Final weight and daily weight gain, however, were significantly higher at the density of 66 per m2 (1.0 per liter). Total biomass at harvest increased with density. Survival was affected by stocking density from day 28 onward, decreasing with density from 62.7 ± 7.6% obtained at 66 crayfish/m2 to 44.85 ± 8.18% at 156 crayfish/m2.

Channel Catfish (Ictalurus punctatus, Rafinesque, 1818): current status and problematic from the perspective of a developing country

Channel catfish is a Mexican native species with a huge aquaculture potential. There is little information about its dynamics, distribution and productive systems. In the present, it is described the current status of channel catfish in Mexico regarding its historical and actual distribution on the country. It is also reported an analysis of the main problematic on the national catfish productive system. On a general level, there are no records indicating neither channel catfish productive potential nor the extension of its natural habitat. On a particular level, water quality and availability were detected as the major concern for Mexican producers while food supply represents the higher expense on the productive system. There is a great heterogeneity on both grow-out and breeding systems; much of the productive dynamics follows a trial and error model and there is no consensus for channel catfish production. The success of different production methods cannot be assessed since there are no records of most relevant productive events. The need for optimization and homogenization of the channel catfish productive system, as well as the correct characterization of domestic and wild populations, becomes an evident issue in order to maximize the productive potential through fishing and aquaculture.

Novel single nucleotide polymorphisms in candidate genes for growth in tilapia ( Oreochromis niloticus )

The objective of the present work was to identify and validate single nucleotide variations located in candidate genes to growth traits in tilapia (Oreochromis niloticus). Two transitions were identified in the promoter region of the growth hormone gene (GH); eight nucleotide changes were identified in introns and promoter region of the IGF-I gene; and a transition (T/C) was identified in the Myogenin gene (MyoG). The highest genotypic frequency (0.8) for GHpA1 and MyoG was found in the GG and TT homozygous individuals, while the highest frequency (0.9) for GHpB1 was observed in the CT heterozygous fish. There was no genotypic frequency in the CC homozygous tilapia for the GHpB1 and MyoG markers. Based on their allelic frequencies, validation as novel single nucleotide polymorphisms (SNP) of those variations located at O. niloticus GH and MyoG genes was possible. These new markers will allow their association with growth traits in tilapia to be exploited in order to determine their potential use as assisted-selection markers.