Effects of copper, zinc and selenium status on performance and health in commercial dairy and beef herds: retrospective study

A retrospective study using analysis of plasma copper and zinc, and erythrocyte glutathione peroxidase from 2 080 dairy and beef cow herds was conducted to evaluate the relationship between trace-element status and production, reproduction and health in cows and their calves. Classification of the herd status as deficient, marginal, low-adequate or high-adequate was based on the lower tercile of individual values. Odds ratios for each disorder in herds were calculated by multivariable stepwise logistic regression. Inadequate copper status was not associated with adult disorders, but was an important risk factor for poor calf performance or health. Selenium deficient status was associated with most studied disorders in cows, and both deficient and marginal herd status were strongly associated with poor health of calves, particularly with increased risks of myopathy and infectious diseases. Zinc insufficiency was strongly associated with low milk production and impaired locomotion in dairy herds, and was also associated with diarrhoea and poor growth in calves. Because a low-adequate status increased the risk of many disorders in adults and calves, we propose to classify herds as deficient and marginal when the lower terciles of plasma zinc concentration are below 12 and between 12 and 14 lmol/l respectively

Valores bioquímicos no soro de cabras relacionadas ao estado fisiologico e raça, no nordeste semi-arido. III. Zinco e cobre.

Estudaram-se os microelementos zinco e cobre, para estabelecer os seus níveis normais em cabras criadas na região semi-arida do nordeste. Com essa finalidade, foi utilizado um lote de 153 animais das raças mestiças Anglo-nubiana, Canindé-repartida, Marota, Moxotó e animais SRD durante os vários estados fisiologicos: antes, inicio, termino da prenhez e lactação

Testing asset pricing models with Euler equations: it's worse than you think

This paper reexamines the small sample properties of Hansen's (1982) Generalized Method of Moments (GMM) and Hansen and Jagannathan's (1989) estimation-free tests on simulated data from a more plausible consumption based asset pricing model. Previous studies are incomplete and misleading. A continuous distribution of consumption growth produces a near nonidentification in the GMM criterion function, severe bias in coefficient estimates, misleading parameter confidence intervals even for very large samples and far worse overrejection problem in GMM tests of restriction than previously thought. Further, estimation-free methods advocated by Kocherlakota (1990) may also have very poor finite sample properties.Prices ; Statistics

Design Issues of Heavy Fuel APUs Derived from Automotive Turbochargers Part III: Combustor Design Improvement

Heavy fuel combustion problems with startup and operation may significantly reduce the microturbine efficiency in small APUs (Auxiliary Power Units). The use of commercial automotive-derived turbochargers solves the design problems of compressors and turbines but introduces large issues with combustors. The radial combustor proved to be the best design. Unfortunately, high-pressure injection is not practical for small units. For this reason, primary air and low-pressure fuel spray are heated and mixed. In any case, a high air swirl must achieve a satisfactory combustion efficiency. This swirl should be almost eliminated at the turbine intake. CFD analysis of the combustor design was, therefore, performed with several different geometries and design solutions. In the end, a large offset of the fresh pipe from the compressor proved to be the best solution for a high swirl in the combustion region. The combustion tends to eliminate the swirl, but an undesired tumble motion at the turbine intake takes place. To eliminate the tumble, two small fins were added to straighten the flow to the turbine