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Table of Contents | |
CALCIUM AND ZINC
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Biol Trace Elem Res 1992 Nov;35(2):167-84 |
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Effect of calcium, copper, and zinc levels in a rapeseed
meal diet on mineral and trace element utilization in the rat.
Larsen T, Sandstrom B
National Institute of Animal Science, Animal Physiology and Biochemistry,
Foulum, Tjele, Denmark.
Mineral and trace element interactions were studied in a balance trial with
rats. Calcium, copper, and zinc were supplied to a rapeseed meal diet in a
factorial design. Animals were fed ad libitum, and absorption, excretion,
and retention of the elements were evaluated either as fractions of total
intake or in relation to nitrogen retention to account for differences in
food intake and lean body mass increment. The intrinsic content of minerals
and trace elements was sufficient to support growth at a rate that could be
expected from the rapeseed protein quality. However, when calcium was
included in the diet, the intrinsic dietary level of zinc appeared to be
limiting, despite the fact that the zinc level was twice the recommended
level. Additional zinc supply reversed growth impairment. This calcium-zinc
interaction is believed to be owing to the formation of phytate complexes.
Calcium addition influenced the calcium, phosphorus, magnesium, zinc, and
iron--but not the copper--balances. The addition of calcium reduced the
availability of the intrinsic zinc, whereas no effect was seen in the
zinc-fortified groups. The availability of intrinsic copper was in a similar
way significantly impaired by addition of dietary zinc, whereas
copper-supplied groups were unaffected by zinc addition. Intrinsic iron
availability was also dependent upon zinc addition, although in a more
ambiguous way. Thus, addition of extrinsic minerals to a diet high in
phytate can result in significant impairments of growth and mineral
utilization.
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