Voluntary intake of food

In previous chapters attention has been concentrated on the energy and nutrient requirements of farm animals for maintenance and various productive processes. An additional i mportant factor that must be considered is the quantity of food that an animal can consume in a given period of time. The more food an animal consumes each day, the greater will be the opportunity for increasing its daily production. An increase in production that is obtained by higher food intakes is usually associated with an increase in overaii efficiency of the production process, since maintenance costs are decreased proportionately as productivity rises. There are, however, certain exceptions to the generalisation for example, with some breeds of bacon pigs, excessive intakes of food lead to very fat carcasses, which are unacceptable to the consumer and therefore economically undesirable. 

Control mechanisms for the food intake of farm animals can be envisaged as operating at three levels. At the metabolic level, concentrations of nutrients, metabolites or hormones may stimulate the nervous system to cause the animal to start or stop feeding. At the level of the digestive system, the quantities of digesta may determine whether or not the animal ingests more food. Finally, external influences such as climatic variables and the ease with which food can be ingested will also influence food intake. In 

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It remains to be seen whether mandatory enrichment of cereal products with folic acid will reduce death from cardiovascular disease. But this, and the widespread voluntary enrichment of foods in other countries, means that intervention studies with folic acid supplements for cancer prevention are unlikely to yield useful results, because the control group will also be receiving a high intake of folic acid. 

Agricultural and Food Research Council (AFRC) 1991 Technical Committee on Responses to Nutrients, report no. 8. Voluntary Intake of Caftfe, Wallingford, CABI (see also Nutrition Abstracts and Reviews, Series B 61 815-23). 

Iodized Salt. Iodized table salt has been used to provide supplemental iodine to the U.S. population since 1924, when producers, in cooperation with the Michigan State Medical Society (24), began a voluntary program of salt iodization in Michigan that ultimately led to the elimination of iodine deficiency in the United States. More than 50% of the table salt sold in the United States is iodized. Potassium iodide in table salt at levels of 0.006% to 0.01% KI is one of two sources of iodine for food-grade salt approved by the U.S. Food and Dmg Administration. The other, cuprous iodide, is not used by U.S. salt producers. Iodine may be added to a food so that the daily intake does not exceed 225 p.g for adults and children over four years of age. Potassium iodide is unstable under conditions of extreme moisture and temperature, particularly in an acid environment. Sodium carbonate or sodium bicarbonate is added to increase alkalinity, and sodium thiosulfate or dextrose is added to stabilize potassium iodide. Without a stabilizer, potassium iodide is oxidized to iodine and lost by volatilization from the product. Potassium iodate, far more stable than potassium iodide, is widely used in other parts of the world, but is not approved for use in the United States. 

There are two aspects of food consumption palatability and voluntary intake (47, 48). Palatability connotes the appealing characteristics of the feed and is measured as the acceptability or relative amount eaten when a number of forages are offered in cafeteria style. Voluntary intake means the amount that is consumed when a single feed is offered to the animal. Often forages that are rejected in cafeteria feeding will be consumed to a great extent in a voluntary intake trial. 

Campling R C and Lean 1 J 1983 Food characteristics that limit voluntary intake. In Rook J A F and Thomas P C (eds) Nutritional Physiology of Farm Animals, London, Longman. 

Tomlinson, A.L. (1997) Voluntary food intake and apparent digestibility of grass chaff, and an assessment of mobile bag technique to study the dynamics of fibre digestion in equids. M.Sc. thesis. University of Wales, Aberystwyth, UK, 118 pp. 

At high environmental temperatures, food intake and oxygen consumption will fall, as will voluntary activity. Thus a reversal of the effect secondary to food intake noted for cold exposure may be expected. Whether or not adrenal activation occurs is of interest, since one tends to consider environmental temperatures other than those normally found in the individual s natural habitat to constitute a stress, but all environmental temperatures below body surface temperature will impose an obligatory heat loss on the animal, and may thus be considered stressful. 

Iodine-containing processed foods, such as bread, fish sauce and other foods, play an increasingly significant role in dietary iodine intake in many populations. It has even happened that producers of processed foods use iodized salt unknowingly (Harris et ai, 2003). The practice of processed foods containing iodine has grown to the extent that, in some countries with voluntary salt iodization, iodine-containing processed foods may be the primary source of dietary iodine intake. 

Irrespective of whether the use of iodized salt in the production of processed foods is compulsory or voluntary, the production of iodine-containing processed foods draws the producers of such foods into the iodine nutrition arena. It could therefore be expected that these producers are familiar with the basics of iodine nutrition, the benefits and risks involved, and how their product fits into the iodine nutrition program of the country. Particularly in countries where processed foods are the primary source, or are contributing a significant percentage of dietary iodine intake, these producers need to be educated and well-informed about iodine nutrition. 

The nationwide survey of iodine status in reunified Germany (Manz et ai, 2002) found an inadequate iodine intake, also among 50-70-year-old subjects, despite an increase in iodine intake for the last 20 years (Table 116.4). In Germany, the use of iodized salt in households and the food industry is voluntary, and since 1990 there has been a considerable increase in the production of iodized salt (Manz et ai, 2002). 

Peptide S, NPS or PEPS, a 20-peptide identified in the brain and in periphery via a strategy using an orphan G protein-coupled receptor as target. NPS injection in the brain of mice causes wakefulness, locomotion and arousal, and produces anxiolytic-like paradigms. Recently, it has been reported that NPS is a potent inhibitor of voluntary and fast-induced food intake in rats [B. Beck et al., Biochem. Biophys. Res. Commun. 2005, 332, 859]. 

Samuel Lefkovsky, The Physiological Basis of Voluntary Food Intake (Appetite ). 105... 

The data show clearly that the administration of amphetamine sulfate can cause in man and dog a loss of body weight which is associated with a reduction of voluntary food intake. When the caloric deficit which results from the decrease in dietary intake is calculated over a period of from two to four weeks, it is found that the loss of body weight is accounted for by the decrease in food intake. 

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