Source of maternal milk zinc for absorption by suckling rats
1980
Johnson, Phyllis E. | Evans, Gary W.
Female rats were mated at 90 days of age and fed throughout pregnancy and lactation on chow containing 39 p.p.m. Zn. A single oral dose of 0.5 mu Ci 65Zn was given either (i) immediately after parturition or (ii) on day 7 post partum; a 3rd group of dams received the same dose by injection 3 wk prior to mating. % of total 65Zn dose absorbed was 55 plus or minus 10, 12 plus or minus 2 and 45 plus or minus 6% in group (i)-(iii) dams resp., while in the pups which averaged 13/litter, it was 26 plus or minus 4, 7.4 plus or minus 1.5 and 4 plus or minus 2.2%; absorption of 65Zn by the suckling pups expressed as % of dam's absorption, was therefore 46, 62 and 8% resp. Results showed that when an adequate diet is provided to the dam during lactation, <10% of the Zn in her milk is Zn that was present in her body at parturition. It is inferred that more than or equal to 90% Zn ingested by rat pups via their dams' milk originates from the dams' current dietary sources. Dietary Zn is rapidly turned over by the lactating dam while Zn in body stores acquired before pregnancy and lactation is turned over more slowly. The lower absorption of the total dose by group (ii) pups compared with (i) pups was probably due to the higher Zn concn. in colostrum than in mature milk.
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