Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

1 st WorkshopXIII International Feed Technology SymposiumINTRODUCTIONMeat is a very rich and suitable source of nutrients, including microelements, amongothers. The chemical composition of meat is dependent on the livestock feeding methodsand plane of nutrition. Mineral requirements of cattle depend on their age, physiologicalstate and feed intake as well as on the raising conditions employed [14]. Mineralsaccount for almost 1% and they have specific functions in terms of metabolism andbreeding technology [30]. Meat contains significant amounts of phosphorus, calcium,sodium and iron salts and low amounts of copper, zinc, aluminium and manganese.Iron is an essential component of a number of proteins involved in oxygen transport orutilization (hemoglobin, myoglobin, cytochromes and iron-sulphur proteins participatingin the electron transport chain). There are several mammalian enzymes that eithercontain iron or are activated by iron [16]. More than 50% of the iron in the body ispresent in hemoglobin. Since three quarters of the iron in the organism is contained inhemoglobin and myoglobin, it is quite natural that the highest iron concentrations arefound in the blood and organs having hematopoietic, hemolytic and storage functions.The iron requirement is about 50 mg/kg diet in beef cattle, due to the reports on youngcalves fed milk diets indicating that 40-50 mg Fe/kg is adequate to support growth andprevent anemia [4, 2]. Minimum requirements for complete feed mixtures (CFM) inbeef cattle are estimated at 20 mg/kg. The iron content in adult animals is variable acrossorgans and tissues. Total iron levels differ among individual animals.Iron occurs in meat as either heme iron or free iron and is stored in ferritin in ionic form.Iron resorption takes place through the intestinal mucous membrane providing andregulating maintenance of iron equilibrium in the body. Iron resorption in the digestivetract is dependent on the iron reserves in the body and therefore an equilibrium ismaintained between the course of iron resorption and size of iron reserves. The course ofresorption may be affected by diet components: it decreases substantially at low calciumand high phosphorus and phytic acid levels. Iron excretion from the organism is minimal(through urine and faeces).The first signs of iron deficiency in animal diet include anemia (hypochromicmicrocytic), languidness, reduced feed intake, weight loss, pale mucous membranes andatrophy of the papillae of the tongue [3, 4]. Anemia can develop in calves fedexclusively milk diets for extended periods of time lacking sufficient amounts of othernutrient supplements.Given the fact that anemia treatment in humans is also associated with iron intakesthrough beef meat and viscera, we deemed it important to determine the iron content ofthe muscular tissue, liver and kidneys following slaughter of the tested beef calves. Bothmeat and fish meat are good sources of iron in human diet (400-500 mg Fe/kg).Manganese functions as a component of the enzymes pyruvate carboxylase, arginase andsuperoxide dismutase and as an activator for a number of enzymes, including hydrolase,kinase, transferase and decarboxylase [13, 1]. Only glycosyltransferases are specificallyactivated by manganese. The mitochondrial concentrations of manganese imply thatmanganese is involved in partial regulation of oxidative phosphorylation.Manganese participates in oxidation and reduction processes, as well as in theconversion of fat, sugars and proteins. It influences growth, reproduction and thefunction of endocrine organs. High levels of manganese can reduce those of hemoglobin.307