M. S.

Three experiments, each with 24 pregnant female rats as subjects, were conducted. Four experimental diets contained either 7.5 mg tryptophan or 500 mg tryptophan/100 g and either 7.5 ppm or 50 ppm zinc. Dams on the low zinc diets throughout gestation consumed less food and gained less weight than those on the high zinc diets. Reproductive success was less on the low zinc diet. The incidences of maternal mortality, fetal mortality, and reabsorptions were higher in the dams fed a low zinc diet. There were no significant differences in water intake, urine volume, fetal weight, or fetal nitrogen content which were dependent upon dietary treatment. Dams on the low zinc diets had acute renal nephrosis which was most severe when dietary tryptophan levels were high. Fetal zinc content was higher in fetuses from dams fed the high zinc diets. Although the dams on the low zinc diet did exhibit signs of zinc deficiency, the deficiency was not severe enough to affect fetal weight. Diets containing between 6 and 9 ppm were not sufficient for normal parturition. / M. S.