In global terms, animal feeds and forages contain a wide range of contaminants and toxins arising from anthropogenic and natural sources. In this article, the distribution of heavy metals, radionuclides, mycotoxins, plant toxins, antibiotics and microbial pathogens in cereals, complete feeds and forages is reviewed. The impacts on farm livestock productivity and on the safety of resulting edible products are also considered. Evidence is provided to demonstrate that feeds contain a variety of substances as co-contaminants and that there are regional differences in the nature of the compounds involved. It is concluded that the options for remedial action are limited. Furthermore, although many developing countries lack appropriate legislation, change in this respect is inevitable as regulatory controls for feeds imported into Europe and America are strengthened.
However, triacylglycerol depots have other functions. Subcutaneous depots serve as insulation against cold in many terrestrial animals, as is obvious in the pig, which is surrounded by a layer of fat, and it is especially true for marine mammals. In the latter and in fish, the lipid depots are less dense than water and so aid buoyancy with the result that less energy is expended in swimming. More surprisingly, perhaps, triacylglycerols together with the structurally related glyceryl ether diesters and wax esters are the main components of the sonar lens used in echolocation by dolphins and some whales. In spite of their hydrophobic nature, triacylglycerols are the major transport lipid in plasma in association with lipoproteins where their biological inertness is a virtue.
Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more  or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.  [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography .  : 10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity.