Manuel García-Ulloa

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.

SEASONAL LEVELS OF HEAVY METALS IN SOFT TISSUE AND MUSCLE OF THE PEN SHELL Atrina maura (SOWERBY, 1835) (BIVALVIA: PINNIDAE) FROM A FARM IN THE SOUTHEASTERN COAST OF THE GULF OF CALIFORNIA, MEXICO

The pen shell ( Atrina maura ) is a filter-feeder bivalve that may accumulate metals in its body. The objective of this study was to determine seasonal concentrations of copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), lead (Pb), arsenic (As), zinc (Zn), and mercury (Hg) in soft tissue and muscle of A. maura cultivated in a farm located in the southeastern coast of the Gulf of California from summer 2011 to summer 2012. Except for Cu, the higher metal concentrations were found during the dry season (winter 2011-spring 2012). The mean values in soft tissue fluctuated from 0.064 ± 0.01 µg/g (dry weight [dw]) for Hg to 485.66 ± 71.12 µg/g (dw) for Zn, while for muscle they varied from 0.058 ± 0.03 µg/g (dw) for Hg to 64.83 ± 4.90 µg/g (dw) for Zn. Concentrations of cadmium (18.15 µg/g in soft tissue and 1.82 µg/g in muscle, wet weight [ww]) and lead (2.31 µg/g in soft tissue, ww) exceeded the permissible limits (36.3, 3.64, and 2.31 times, respectively) recommended by the sanitary regulations of the official mexican standards. The results suggest that variation of metal levels in cultivated pen shell could be influenced by seasonality and anthropogenic activities such as agriculture and aquaculture developed around the culture zone. Continual monitoring of metals in farmed pen shell is recommended.

Crecimiento y supervivencia del callo de hacha Atrina maura (Bivalvia: Pinnidae) cultivado en la costa sureste del Golfo de California, México

espanolEl crecimiento y la supervivencia de bivalvos representan herramientas importantes para evaluar su cultivo. Se describe el crecimiento y la supervivencia del callo de hacha Atrina maura cultivado durante 15 meses (febrero 2008-mayo 2009) en Isla Los Redos, en la costa sureste del Golfo de California, Mexico. El promedio inicial de la altura de la concha y el peso corporal de las semillas (n= 2500) fueron 28,41 ± 4,96 mm y 0,3 ± 0,2 g, respectivamente. Los organismos se mantuvieron 4 meses en suspension y 11 meses sembrados en arena hasta la cosecha. Se realizaron biometrias de 50 especimenes cada mes. En promedio, los valores de crecimiento finales fueron de 220,48 ± 12,41 mm para la altura de la concha y 284,26 ± 54,45 g para el peso. Se encontraron diferencias significativas en el peso total durante la duracion del cultivo. El promedio de la tasa diaria de crecimiento registro un valor de 0,48 mm d-1 y 0,63 g d-1 para la altura de la concha y el peso corporal, respectivamente. La supervivencia final fue de 88,72%. Los resultados muestran que A. maura alcanzo la talla comercial (≥ 200 mm) despues de 9 meses de cultivo en Isla Los Redos, Sinaloa, Mexico. Esta informacion contribuye con conocimiento basico para posteriores estudios en el desarrollo del cultivo de A. maura. EnglishThe evaluation of growth and survival of bivalves represents an important tool in culture. Growth performance and survival of the pen shell Atrina maura cultivated in Isla Los Redos, at the southeastern coast of the Gulf of California, Sinaloa, Mexico, during 15 months (February 2008-May 2009), were described. The mean initial shell height and body weight of seeds (n= 2,500) were 28.41 ± 4.69 mm and 0.3 ± 0.2 g, respectively. Pen shells were cultured in suspension for 4 months, and 11 months in bottom system until harvesting. Biometrics of 50 specimens were measured every month. The average final shell height and weight were 220.48 ± 12.41 mm and 284.26 ± 54.45 g, respectively. There were significant differences among the total weight of each month. The mean daily growth of shell height and body weight were 0.48 mm d-1 and 0.63 g d-1, respectively. Final survival was 88.72%. Results show that A. maura reached the commercial size (≥ 200 mm shell height) after 9 months of culture in Isla Los Redos, Sinaloa, Mexico. This information contribute with basic knowledge for further studies on farming of the pen shell A. maura.

Primer registro de Perkinsus sp. (Protozoa, Apicomplexa) en el callo de hacha Atrina maura en Sinaloa, México

We evaluated the presence of the protozoan Perkinsus sp. by determining of its prevalence and level of infection in Atrina maura during 2012. Pen shells were collected per season beside an oyster farm located at Estero La Piedra, Sinaloa, Mexico, and analyzed by Rays fluid thioglycollate medium and polymerase chain reaction. The higher prevalence (90%) and infection level (2.3) were obtained when temperature and salinity were higher. The Mackin scale showed a non-infected to moderate infection range. PCR was positive to Perkinsus sp. This is the first record of the presence of Perkinsus sp. in A. maura in Sinaloa, Mexico.

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.