Relationships between iron and zinc metabolism: predictive value of digestive absorption on tissue storage

The responses of animals to intake of a trace element could vary if it is ingested with a single test meal or due to chronic intake. The metabolic relationships between zinc (Zn) and iron (Fe) were assessed in the young animal by comparing their digestive absorption studied at the beginning of the study with their tissue storage after two months of being fed on experimental diet. Diets supplied adequate intakes of Fe (45 and 300mg/kg diet) and Zn (14 and 45 mg/kg). A significant effect of Fe supply (p < 0.0001) but not of Zn was displayed on Fe absorption; both Fe and Zn diet concentrations influenced Zn absorption (p < 0.01, p < 0.0001). Fe and Zn organ contents significantly correlated with the amount absorbed during the metabolic balance (p < 0.0001). There was a positive correlation between liver, bone, and muscle Fe and Fe absorption (mg/d)(p < 0.0001), and Fe absorption and bone and muscle Zn (p < 0.04) and a negative one with liver Zn (p < 0.0001); a positive correlation was displayed between Zn absorption (mg/d) and Zn organ content (p < 0.0001). There was no correlation between Zn absorption and Fe tissue content (p > 0.05). This study suggests that interactions occur at every step of Fe and Zn metabolism; Fe is more efficient in altering Zn storage than the reverse. The organism seems to be unable to diminish the consequences of an unbalanced diet and digestive absorption. Care must be taken to give the young growing balanced diets.