Influence of Timing of Short-term Supplementation during Gestation on Congenital Abnormalities of Manganese-deficient Rats

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Abstract
The effects of short-term supplementation with manganese during pregnancy were studied in an attempt to differentiate various abnormalities of manganese-deficient offspring in terms of critical periods during gestation. Three groups of manganese-deficient female rats were given a manganese-supplemented ration for a period of 24 hours on day 14, day 16, or day 18. Control groups received either no supplementation or the manganese-supplemented ration throughout the study. Deficient females supplemented with manganese for 24 hours on day 14 gave birth to young whose survival to 28 days approached that of normal controls; none of these young were ataxic. In contrast, only 11% of the offspring of unsupplemented rats survived to this age, and 81% were ataxic. Supplementation on day 16 also resulted in a survival rate in the young comparable to that of the controls, but 67% of the survivors were severely ataxic. Supplementation on day 18 improved survival to 39%, with a high incidence (84%) of ataxia. Similar differences were observed in results of body-righting tests. Measurements of body and tibia lengths showed that one day of supplementation during gestation was sufficient to prevent the disproportionate tibial shortening observed in manganese-deficient young. One day of supplementation also appeared to have a mitigating effect upon the incidence of tibial epiphyseal abnormalities, although it did not prevent them entirely. The results show that one day of supplementation, if it occurred on day 14, was sufficient to prevent ataxia in the young, but not when given on days 16 or 18, and in addition suggest that the post-natal mortality and ataxia of manganese-deficient young develop through different congenital pathways.
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