Fe-deficiency anemia has been produced in rhesus monkeys (Wolcott et al., 1973; Mandell and George, 1991). Weanling rhesus monkeys (3 months old) were found to be less Fe-deficient if they were raised in the nursery than if they were mother-reared (Bicknese et al., 1993), and multiparous dams were more likely to have Fe-deficient weanlings than primiparous dams. Formula-fed infant rhesus monkeys have been shown to develop Fe-deficiency anemia at the age of 3-5 months even if the formula was fortified with Fe (Kriete et al., 1995). Another study, however, showed no anemia at that age in infant rhesus monkeys fed Fe-fortified formula exclusively from birth (Lonnerdal et al., 1999). Differences in Fe endowment at birth, growth rate, number of bleedings, and Fe concentration in the formulas used might explain the disparate findings. Fe deficiency has also inadvertently been produced in monkeys fed diets low in protein (Sood et al., 1965).
The Fe requirements of nonhuman primates have not been well established. Infant rhesus monkeys fed infant formula exclusively up to 5.5 months of age showed no signs of anemia (Lonnerdal et al., 1999). The formula contained Fe at 12 mg·L-1, and average consumption was 400 ml·d-1, so it appears that an Fe intake of about 5 mg·d-1, or about 3-10 mg·BWkg-1·d-1, given in formula meets the Fe requirement during infancy. Rhesus milk contains Fe at about 1.1-1.8 mg·L-1 during the first month of lactation and slightly less after that (Lonnerdal et al., 1984). Assuming that milk intake by nursed rhesus infants is similar to that by formula-fed infants, the “true” Fe requirement might be substantially lower than that estimated for formula-fed infants.
Fe-deficiency anemia has been produced in adult female baboons (Papio spp.) (Huser et al., 1967) and newborn squirrel monkeys (Saimiri sciureus) (Amine et al., 1972), and an Fe-deficient diet developed for 4-year-old capuchins (Cebus albifrons) produced a negative Fe balance (Wolfe et al., 1989). But the minimal Fe requirement for those species cannot be deduced from the studies.
Although Fe-deficiency anemia is of concern in most colonies, it should be recognized that giving primates high-Fe diets can result in Fe overload. Hemosiderosis has been observed in lemurs in captivity (Gonzales et al., 1984); signs were most pronounced in the black lemur (Eulemur macaco) and least in the ring-tailed lemur (Lemur catta). It was later found that all 49 lemurs in the colony that had been necropsied during a 10-year period had hemosiderosis and that severity increased with age (Spelman et al., 1989). A suggested explanation was that captive lemurs received diets high in Fe (commercial monkey diets) and in ascorbic acid (citrus fruits), which enhanced Fe absorption, while they received few inhibitors of Fe absorption, such as tannins (polyphenols), that are constituents of the diet consumed in the wild (leaves, fruits, and bark). Because hemosiderosis can lead to liver and kidney disease, the authors suggested that lemur diets should be modified to reduce this risk. Marmosets (Callithrix jacchus), too, develop hemosiderosis in captivity; it is also believed to be caused by high-Fe diets (Miller et al., 1997). When a diet lower in Fe (100 mg·kg-1) was fed, liver Fe was only one-tenth that of animals fed a high-Fe diet (500 mg·kg-1), demonstrating that lowering the Fe content of the monkey diet can reduce the risk of hemosiderosis. Experimental hemosiderosis has been induced in rhesus monkeys by injections of Fe dextran (Nath et al., 1972). Cebus monkeys, loaded with Fe dextran, were found to be a useful model for study of the effectiveness of Fe chelators in Fe overload. Desferroxamine, administered intramuscularly, and desferrithiocin, administered intramuscularly or orally, were found to significantly promote Fe excretion (Wolfe et al., 1989). To test new orally active Fe chelators, marmosets (Callithrix jacchus) have been Fe-overloaded by intraperitoneal injections of Fe hydroxide polyisomaltose (Sergejew et al., 2000).
Copper (Cu) is associated with a number of proteins, including many important enzymes. The Cu-containing enzymes are commonly divided into amine oxidases, ferroxidases, cytochrome c oxidase, dopamine ß-hydroxylase, superoxide dismutases, and tyrosinase. The known Cu-binding proteins are metallothionein, albumin, transcuprein, and blood-clotting factor V (Turnlund, 1999).
Cytochrome c oxidase might be the most important enzyme in the mammalian cell because it is the terminal link in the mitochondrial electron-transport chain and regulates the formation of ATP. Other Cu-containing enzymes are part of the body’s antioxidant defense system, are involved in melanin formation, and function in the cross-linking of collagen and elastin during formation of connective tissue (Linder, 1996). In studies of the development of age-related macular degeneration in elderly (20 years old and older) rhesus macaques, monkeys with diagnosed drusen (hyaline excrescences in the basal choroid layer of the eye) exhibited alterations in concentrations and activities of the free-radical defense system, particularly of enzymes associated with Cu (Olin et al., 1995b). Cardiovascular defects in Cu deficiency include weakened heart and blood-vessel structure, impaired use of energy by the heart, reduced ability of the heart to contract, altered ability of blood vessels to grow and regulate their diameter, and altered structure and function of the blood cells. Those defects result principally from impaired effectiveness of the enzymes that are Cu-dependent (Saari and Schuske, 1999).
Copper is usually added to manufactured feeds in the form of cupric sulfate, CuSO4, a form that is highly bioavailable. Cupric carbonate, CuCO3, a form sometimes used in rations, is intermediate in Cu bioavailability. Copper in