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U.S. Plant, Soil and Nutrition Laboratory, Soil and Water Conservation Research Division, Agricultural Research Service, U. S. Department of Agriculture, Ithaca, New York 14850
Rats were placed on limited zinc intakes (<1 ppm) from day 1, 12, 15, or 18 of gestation. Two to three of the females in each of the groups deprived of zinc from day 1, 12, or 15 were moribund at parturition. None of the females deprived of zinc from day 18 was moribund, but three of the 12 females still had undelivered pups 6 hours after the first pup was born. Weight gain during pregnancy, birth weight of pups, mammary weight, and uterine weight (except day-18 females) but not ovarian weight were lower in the zinc-deprived groups than in the zinc-supplemented controls regardless of the length of deprivation. Zinc concentrations in the pup and neonatal liver were higher in the zinc-supplemented controls than in the zinc-deprived groups although uterine zinc was the same in all groups. Zinc must therefore be supplied through at least day 18 of pregnancy if the rat is to deliver a normal litter without difficulty.
KEY WORDS: zinc pregnancy parturition
Manuscript received 2 July 1971.