Effect of varying dietary zinc intake of weanling mouse pups during recovery from early undernutrition on tissue mineral concentrations, relative organ weights, hematological variables and muscle composition.

Because growth is an early sign of zinc (Zn) deficiency in young animals, it is often assumed that the occurrence of normal growth indicates adequate Zn status. In an earlier study we found that both marginal (10 micrograms Zn/g) and low (5 micrograms Zn/g) dietary Zn intake resulted in altered composition of gain in mouse pups that had been previously undernourished (L) from d 10 to 21 of suckling and rehabilitated from d 21 to 40 with high protein recovery diets. Therefore we examined several tissues, organs and biochemical measures to identify other variables that might be sensitive to either marginal or low dietary Zn intake in mice. After undernutrition in the suckling animal, liver Zn concentrations were lower; they normalized when the pups were subsequently fed recovery diets irrespective of dietary Zn intake (5-110 micrograms Zn/g). Bone Zn was 30% lower in pups fed low Zn, and 30% higher in pups given Zn-supplemented recovery diets (110 micrograms Zn/g) compared with controls (40 micrograms Zn/g). Thus bone Zn concentration was highly correlated with dietary Zn intake and lower liver Zn was highly correlated with undernutrition. Most organs of L pups recovered in proportion to body weight; the exceptions were brain, kidney and gastrocnemius muscle. At d 21 or 40, brain weight was most conserved and kidney weight was stunted during either protein or Zn deprivation. Gastrocnemius muscle weight in L pups was stunted to a much greater degree than other tissues, although proximate analysis showed muscle composition was similar among groups. These data support previous reports that adequate dietary Zn is essential for optimal recovery from early undernutrition.