Growing animals

Recirculating systems can make aquaculture feasible in locations where conditions would otherwise not be conducive to successful operations. Such systems can also be used to reduce transportation costs by making it possible to grow animals near markets. In areas where there are concerns about pollution or the use of exotic species, closed systems provide an alternative approach to more extensive types of operations. 

Mechanism of Action. The mechanisms by which antibiotic adrninistration at subtherapeutic levels enhance growth rate and efficiency of gain in growing animals have not been clarified. Possible modes of action include disease control, nutrient sparing, and metaboHc effects. There is extensive evidence that the principal benefit from subtherapeutic use of antibiotics results from the control of harmfiil microorganisms. 

Animal nutritionists have developed formulas to guide them in recommending the amount of food to feed animals in captive situations such as in zoos. First, the number of calorics needed to maintain the animal while at rest is determined—this is called the basal metabolic rate (BMR). In general, a reptile s BMR is only 15 percent that of a placental mammal, while a bird s is quite a bit higher than both a reptile s and a mammal s. For all animals, the number of calories they should receive on a maintenance diet is twice that used at the basal metabolic rate. A growing animal should receive three times the number of calories at the BMR, while an animal in the reproductive phase should receive four to six times the BMR. 

Surface interactions play an important role in the ability of certain animal cells to grow and produce the desired bioproducts. An understanding of the dynamics of cell surface interactions in these "anchorage-dependent" cells (cells that function well only when attached to a surface) will be needed, for example, to improve the design of bioreactors for growing animal cells. 

Bone is very sensitive to dietary factors such as the amount of calcium present in the diet and the availability of that calcium when all other nutrients are present in adequate amounts (46, 47). This is especially true of the growing animal which is utilized in most bioavailability studies. Adult animals, however, may also be used. Krook et al (48) caused osteoporosis in adult dogs in 42 weeks by feeding a low-calcium high-phosphorus diet. The bones were radiologically normal after 28 weeks of calcium repletion (48). The ash contents of the vertebral bones of these dogs were much more responsive to dietary calcium and phosphorus manipulation than were the humeri and femora (48). 

The animals receive a battery of clinical measurements, much like those people receive when they leave samples of blood and urine for testing after a medical examination. It turns out that body weight -reduced weight gain for growing animals or weight loss for adults -is a particularly sensitive indicator of toxicity. Its measurement does not provide much of a clue about the nature of the toxic effect that is occurring, but it is considered an adverse response in and of itself. In some cases it is due to reduced food consumption (and this is why food consumption is measured carefully), because the addition of the... 

Required to some degree in young, growing animals, and/or sometimes during illness. 

All growing animal tissues need cholesterol for membrane synthesis, and some organs (adrenal gland and gonads, for example) use cholesterol as a precursor for steroid hormone production (discussed below). Cholesterol is also a precursor of vitamin D (see Fig. 10-20a). 

In the growing animal body, a significant portion of proteins consumed is required for the creation of new tissue. This results in an increasing... 

More recent studies of the effect of methylphenidate on the growing animal brain have produced even more ominous results with direct connections to emotional and behavioral development. Carlezon and Konradi (2004), from Harvard s Department of Psychiatry, observed that some children are being treated with psychiatric drugs as early as age 2. They summarized their research ... 

Molybdate is known to induce copper deficiency, ft was found that the administration of molybdenum compounds, particularly with added sulfate, impaired copper metabolism in ruminants. Tetrathiomolybdate has been used to treat patients who were intolerant to D-penicillanune, trientine, and zinc. Tetrathiomolybdate seems to act both by blocking the intestinal absorption of copper and keeping it in a metabolically inert chelated form, which is not taken up by the liver. However, it induces only a modest cupriuresis. There are also known toxic effects of tetrathiomolybdate on the skeletal system of growing animals. Thus one should be extremely careful in administering this compound. It should be considered as an experimental drug. 

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