Early interest in selenium by nutritionists concerned its high concentration in
certain range plants and the consequent toxicosis in animals that grazed those plants.
More recently, the essential nature of selenium has become the center of attention, and
this element is now known to be required by laboratory animals, food animals (including
fish), and humans. Its role as an integral feature of glutathione peroxidase has been
established, and other possible functions are under active investigation.
The structural carbohydrates that constitute plant fibre represent a major feed resource. Herbivorous animals, unable to produce fibre-degrading enzyme systems of their own, have evolved a range of strategies (Hume and Sakaguchi, 1991) to make use of a consortium of microbes, including bacteria, protozoa and anaerobic fungi, for this purpose...
It should be clear from Chapter 6 that with the advent of optical ampliﬁers, ﬁber losses are no longer a major limiting factor for optical communication systems. Indeed, modern lightwave systems are often limited by the dispersive and nonlinear effects rather than ﬁber losses. In some sense, optical ampliﬁers solve the loss problem but, at the same time, worsen the dispersion problem since, in contrast with electronic regenerators, an optical ampliﬁer does not restore the ampliﬁed signal to its original state.
The Animal Production and Health Section of the Joint FAO/IAEA Division of
Nuclear Techniques in Food and Agriculture recognises that the trend towards
intensification of livestock production in developing countries presents both opportunities
and challenges. The potential opportunities are the flow-on benefits to the
producers and local economy while the potential challenges are the flow-on costs
to the environment, animal health and welfare.