The minimum content of magnesium in the diet for a normal pregnancy in the rat

Abstract

Reduction of the quantity of Magnesium in diets of Western countries and the importance of this element in cellular physiology suggested the determination of the minimal requirement for normal embryofetal development in rats. Four groups of female CD white rats, each composed of 16 animals, were fed for 15 days before mating and for the duration of pregnancy with one of the following diets: standard diet containing 4200 ppm Mg; purified diet containing 1000, 500, or 250 ppm Mg. All females were sacrificed on the 21st day of pregnancy, and fetuses removed for morphological examination. The three groups of animals fed a purified diet had weight increases similar to the group fed the standard diet. Levels of maternal plasma Mg correlated with the reduction of Mg concentration in the diet during pregnancy and the following values were found at term: standard, 2.4 ±0.6 mg/dl; 1000 ppm, 1.8±0.4. mg/dl; 500 ppm, 1.4±0.5 mg/dl; 250 ppm 0.8±0.3 mg/dl. Fetuses from the corresponding groups had the following plasma Mg values: 4.6±0.8mg/dl; 4.2±1.2 mg/dl; 3.5±0.7 mg/dl; 2.9±0.5 mg/dl. The principal parameters regarding fertility were not affected as a result of feeding the purified diet. But fetuses from rats fed the diet containing 250 ppm Mg ahd a lower weight than controls (p<0.05) and showed retardation in skull and tail vertebrae ossification. These results suggest that the minimum requirement of Mg for a normal pregnancy and embryofetal development is between 500 and 250 ppm of the diet.