Verotoxin-producing Escherichia coli (VTEC) is the etiologic agent of hemolytic-uremic syndrome (HUS), which typically affects children ranging in age from six months to five years old. Transmission is produced by consumption of contaminated food, by direct contact with animals or the environment and from person to person. In previous studies we determined that the environment of a dairy farm is a non-animal reservoir; thus, we proposed to study the survival of 4 VTEC isolates (O20:H19; O91:H21; O157:H7 and O178:H19) in sterile water troughs and bovine feces by viable bacteria count and detection of virulence genes by PCR. It was demonstrated that the survival of different VTEC isolates (O157 and non-O157) varied in terms of their own characteristics as well as of the environmental conditions where they were found. The main differences between isolates were their survival time and the maximal counts reached. The competitive and adaptive characteristics of some isolates increase the infection risk for people that are visiting or working on a farm, as well as the risk for reinfection of the animals and food contamination.

La extracción y mantenimiento de ovocitos bovinos es una práctica rutinaria en la reproducción bovina de hoy, buscan mantener las células viables durante un largo periodo de tiempo para poderlas manipular, en algunos casos madurar y realizar fertilizaciones in vitro y demás técnicas que garanticen el éxito de los procesos reproductivos. En el presente trabajo se evaluó la posibilidad de utilizar el agua de coco como base para la elaboración de un medio de conservación alternativo para ovocitos bovinos, probando concentraciones distintas de agua de coco al M₁:31%, M₂:38.8% y M₃:46.5(artículo no publicado) a partir de las citadas preparaciones se evaluó la viabilidad de los ovocitos mediante la tinción de eosina nigrosina al 2%, los ovocitos muertos poseen sus membranas permeables a las tinciones, por tal razón se determina la viabilidad de los ovocitos vivos, teniendo en cuenta el principio que se tiene con los espermatozoides (Agüero, 2012), los cuales se mantuvieron en los tres medios con su respetiva concentración y observados con una diferencia de 10 horas en pruebas pareadas. El medio 2 (M₂) con concentración de agua de coco del 38.8% y el medio 3 (M₃) con concentración de agua de coco de 46.5%, brindaron la mejor recuperación de ovocitos viables después de un periodo de 30 horas en el mantenimiento de las células in vitro, ya que el agua de coco es rica en proteínas, azúcares, vitaminas, sal, lípidos neutros y aminoácidos. Además está dotada de sustancias que pueden inducir la división celular y electrolitos que promueven la supervivencia y viabilidad de gametos masculinos y femeninos. El agua de coco es un buen soporte vital para la conservación de ovocitos bovinos debido a su fácil adquisición es posible utilizarla en la reproducción bovina. | The extraction and maintenance of bovine oocytes is a routine practice in the bovine reproduction of today, they look for to maintain the viable cells during a long period of time to be able to manipulate them, in some cases to mature and to realize in vitro fertilizations and other techniques that guarantee the success of the reproductive processes. In the present work the possibility of using coconut water as a basis for the development of an alternative conservation medium for bovine oocytes was evaluated, testing different concentrations of coconut water at M₁: 31%, M₂: 38.8% and M₃: 46.5 (unpublished article) from the aforementioned preparations the viability of the oocytes was evaluated by staining 2% eosin nigrosin, the dead oocytes have their membranes permeable to the stains, for this reason the viability of the live oocytes is determined , taking into account the principle that we have with sperm (Agüero, 2012), which were maintained in the three media with their respective concentration and observed with a difference of 10 hours in paired tests. Medium 2 (M₂) with coconut water concentration of 38.8% and medium 3 (M₃) with 46.5% coconut water concentration, provided the best recovery of viable oocytes after a period of 30 hours in the maintenance of cells in vitro, since coconut water is rich in proteins, sugars, vitamins, salt, neutral lipids and amino acids. It is also equipped with substances that can induce cell division and electrolytes that promote the survival and viability of male and female gametes. Coconut water is a good life support for the conservation of bovine oocytes due to its easy acquisition it is possible to use it in bovine reproduction. | dalys.benitez@campusucc.edu.co | yeisson.lopezn@campusucc.edu.co

The purpose of this study was to verify the effect of dietary Ca2+ on growth and survival of silver catfish fingerlings (Rhamdia quelen) exposed to different water pH (5.5; 7.5 and 9.0). Silver catfish fingerlings were randomly placed in a termo-regulated water re-use system with twelve 250 L tanks, two 1000 L biofilters and a 2000 L reservoir with medium flow of 3.84 L min-1 tank. Stocking density was 0.16 fingerlings L-1. To prepare the treatment diets, the control diet (0.08% Ca2+) was supplemented with CaCO3 to yield experimental diets with 0.64; 0.95 and 2.39% Ca2+. There were three replicates/treatment. Survival was higher than 93.9% in all treatments. Exposure of silver catfish fingerlings to alkaline or acid water reduced growth, and this effect was not ameliorated by dietary Ca2+ supplementation. Moreover, best dietary Ca2+ range for silver catfish fingerling growth is 0.08-0.64%, mainly when fingerlings were maintained in water with neutral pH. | Coordenação de Aperfeiçoamento de Pessoal de Nível Superior | A proposta deste estudo foi verificar o efeito de diferentes níveis de Ca2+ na dieta no crescimento e na sobrevivência de alevinos de jundiá (Rhamdia quelen) expostos a diferentes faixas de pH da água (5,5; 7,5 e 9,0). Os alevinos de jundiá foram distribuídos aleatoriamente em densidade de estocagem de 0,16 alevinos/l, num sistema de recirculação de água termo-regulada, com 12 caixas de cimento amianto impermeabilizado de 250 l, 2 biofiltros de 1000 l e 1 reservatório de água elevado de 2000 l. Para o preparo dos diferentes tratamentos, a dieta controle (0,08% Ca2+) foi suplementada com CaCO3 para formulação das demais dietas, com 0,64; 0,95; e 2,39% Ca2+, com 3 repetições por tratamento. A sobrevivência foi superior a 93,9% em todos os tratamentos, não havendo diferença significativa. A exposição de alevinos de jundiá em águas ácidas ou alcalinas reduziu o crescimento, sendo que tais efeitos não foram compensados pela adição de Ca2+ na ração. Os resultados demonstram que dietas com níveis de Ca2+ em torno de 0,08-0,64% são as mais adequadas para o crescimento de alevinos de jundiá, principalmente quando os alevinos são mantidos em água com pH neutro.

The goal of this study was to determine the effect of the liquid extract of Yucca schidigera on water quality and survival of Pacific red snapper Lutjanus peru during its transfer from wild to laboratory conditions. Three experimental groups (0.00; 0.25 and 0.75 mg of Y. schidigera liquid extract per liter of culture) were tested with four replicates using water recirculating systems. The liquid extract was dispensed every 72 h during 28 days. It was proved that Y. schidigera extract could be effective to reduce ammonia nitrogen caused by biogenic source (excretion of fish juveniles) diminishing mortality of Pacific red snapper during acclimatization process. It is recommended the use of yucca extract concentration at a dose of 0.75 mg L-1 to reduce ammonia concentration in marine water for holding red snapper juveniles. | El objetivo de este estudio fue determinar el efecto del extracto líquido de Y. schidigera sobre la calidad del agua y prevención de la mortalidad del pargo rojo del Pacífico L. Peru, durante la transferencia del medio silvestre a condiciones del laboratorio. Se utilizaron tres tratamientos: extracto líquido concentrado 100% de Y. schidigera natural fue administrado en baja concentración (0,25 mg L-1) y alta concentración (0,75 mg L-1), además de un grupo control sin extracto. El extracto líquido fue administrado cada 72 h durante 28 días. Se encontró que el extracto Y. schidigera reduce la concentración de amonio producto de la excreción de los juveniles y la mortalidad del huachinango durante la aclimatación en un sistema de recirculación. Se recomienda el uso del extracto de yuca en una concentración de 0,75 mg L-1 para reducir el amonio y para una densidad máxima de 10,9 kg m-3 y con aireación.

The objective of this study was to investigate the effect of water pH on survival and Na+ and K+ body levels of fingerlings of Rhamdia quelen, a freshwater catfish. Survival was 100% at pH 4.00 to 9.0 throughout the experiment (96h), and death of all fingerlings was observed only at pH 3.75 or lower and at pH 10.50. There was a significant correlation between water pH and body Na+ levels (but not K+ levels) 72h after transfer. There was a clear reduction in Na+ levels when the transfer was to pH outside the 5.0 - 9.0 range, which is in agreement with the fact that fishes exposed to such pH’s present loss of ions by diffusion and/or a decrease in absorption. Growth experiments with this species probably would present best results within the 5.0 - 9.0 pH range, in which the decrease of body Na+ levels is reduced.<br>O objetivo deste estudo foi analisar o efeito do pH da água na sobrevivência e níveis corporais de Na+ e K+ de alevinos de Rhamdia quelen, um peixe de água doce. A sobrevivência foi de 100% ao longo do experimento (96h) na faixa de pH de 4,0 a 9,0, e foi observado mortalidade total dos alevinos em pH abaixo de 3,75 (e inclusive) e em pH 10,5. Houve uma correlação significativa entre o pH da água e os níveis corporais de Na+ (mas não de K+) 72h após a transferência. Quando os alevinos foram transferidos para um pH fora da faixa de 5,0 - 9,0, houve uma nítida redução dos níveis corporais de Na+, concordando com o fato que peixes expostos a esses níveis de pH apresentam perda de íons por difusão e/ou uma redução na sua absorção. O crescimento dessa espécie, provavelmente, é estimulado dentro da faixa de pH 5,0 - 9,0, na qual a diminuição dos níveis corporais de Na+ foi menor.

Con el fin de estudiar el efecto de la espesura de la cubierta forestal en la disponibilidad de luz y agua para las plantas y su supervivencia, se plantaron brinzales de dos savias de Quercus petraea (Matt.) Liebl. (roble albar) y Quercus pyrenaica Willd. (melojo) en el interior de un pinar de Pinus sylvestris L. (pino albar) situado en el NE de la provincia de Madrid sometido previamente a tres tratamientos: clara del 33% de la densidad original, clara del 50% y ausencia de clara. Se midió la humedad volumétrica del suelo con un TDR y la disponibilidad de luz en el sotobosque por medio de fotografías hemisféricas. La supervivencia se midió al final del primer año y al comienzo del verano de los dos años siguientes. La reducción de la densidad del dosel incrementó la luz disponible en el sotobosque, la humedad de los primeros 10 cm de suelo y la supervivencia de las plantas de melojo, aunque no se apreció un efecto diferente según la intensidad de la clara aplicada. La mortalidad de las plantas de roble albar fue elevada en todos los tratamientos, y superior a la del melojo. Estos resultados apuntan a la necesidad de reducir la espesura del pinar albar en la zona de estudio antes de llevar a cabo plantaciones con melojo en su interior. | Information of tree-nurse shelterwood effects on survival of underplanted seedlings is particularly scant in Mediterranean forest ecosystems. To study light and water resources availability and survival associated to overstory density, two-year-old seedlings of Quercus petraea (Matt.) Liebl. (sessile oak) and Quercus pyrenaica Willd. (pyrenean oak) were planted in the understory of an even-aged Scots pine (Pinus sylvestris L.) plantation located in central Spain, which had been previously assigned to three density treatments: uncut, 33% thinned and 50% thinned of the original density, each replicated four times. Soil moisture was measured with a TDR during the first growing season after planting. Light conditions were estimated by hemispherical photography. Survival was measured at the end of the first growing season in the field and at the beginning of the next two growing seasons. The reduction in density after thinning had a positive effect on light availability and on near-surface soil moisture. Pyrenean oak had higher survival rates than sessile oak, which showed similarly high mortality rates in all three overstory treatments. Thinning had a positive effect on the survival of pyrenean oak, though irrespective of the intensity. Overall, these results point to the necessity to reduce canopy tree density in Mediterranean mountain pinewoods before carrying out enrichment plantations beneath.