Nitrogen retention during late gestation in the rat in response to marginal zinc intake

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Abstract
This study was conducted to characterize nitrogen retention in response to marginal dietary zinc during gestation. Long-Evans rats were randomly assigned to one of two dietary groups on day 1 of gestation. The dams were fed a basal diet supplemented with either restricted or control levels of zinc. Feces and urine were collected for 24 h on day 20 of pregnancy, and their nitrogen and zinc contents were determined. Urinary and fecal nitrogen excretions were similar for zinc-restricted and control dams, whereas fecal zinc excretions were depressed by feeding the zinc-restricted diet. Mean zinc and nitrogen retentions were negative for the zinc-restricted and positive for the control groups. Multiple stepwise regression analysis showed that nitrogen retention on day 20 depended on both dietary nitrogen and zinc intakes. Zinc-restricted offspring weighed 12% less and the maternal plasma zinc concentrations were reduced by 66% when compared with the control group values on day 22. Marginal dietary zinc and the associated anorexia limited fetal growth without causing excessive nitrogen excretion or severe weight loss.