Young rats were fed diets containing 12 mg Zn/kg and varied levels of
sodium phytate for 21-day ad libitum feeding periods. In experiment 1, Ca levels were 0.3, 0.5, 0.8 and 1.0%, and
phytate:Zn molar ratio varied between 0 and 50. In experiment 2, Ca was maintained at 0.3%, Mg levels were 0.07, 0.22 and 0.37%, and
phytate:Zn molar ratios were 0, 10, 20 and 30 at each Mg level. Major response criteria were
body weight gain and tibia Zn accumulation.
Weight gain was not influenced by Ca level in the absence of
phytate or by
phytate at 0.3% Ca; it was increasingly depressed as
phytate was increased and by each increase in Ca in the presence of
phytate. Total tibia Zn content was decreased at the highest Ca level in the absence of
phytate; increasing the
phytate progressively depressed tibia Zn at all Ca levels. Mg and
phytate additions did not affect
weight gain. Tibia Zn tended to be depressed by Mg and by
phytate but these effects were significant only at the highest levels of the combined additions. These data corroborate and extend previously published findings on Ca and
phytate effects on Zn utilization and show bone Zn accumulation to be a more sensitive criterion than
weight gain in this connection. They also indicate that Mg exerts a less pronounced effect on Zn utilization in
phytate-containing diets than does Ca.