The effect of reproduction on the interaction of dietary protein and calcium

Abstract

1. Rats were maintained from the age of 3 weeks until the end of a second reproductive cycle on diets having different protein values and Ca concentrations. 2. Reproductive performance was judged from the number of viable young, their size, body composition and rate of growth during suckling. 3. The size and quality of the bones of the mothers and offspring were assessed from radiographs, histological appearance, total weight of ash, ash/cm3and ash:organic matter ratios of dry fat-free bone. 4. At the end of gestation the mean numbers and total weights of foetuses were low when the mothers had received diets of low protein value: there were smaller differences in the body-weight, water, ash and N contents of the individual foetuses. 5. When 0.44% Ca was included in the diet of low protein value, only one (three rats) of the six litters born survived beyond 1 week of age. 6. At weaning, the young born of and suckled by the protein-calorie deficient dams were only about half the weight of those from mothers receiving the high-protein diets; Ca deficiency produced relatively minor changes. 7. All the mothers lost weight during lactation irrespective of the protein value or Ca concentration of the diet; their bones had lower radiographic densities and less ash/cm3than is usual in non-pregnant rats of similar age. 8. The interaction of protein and Ca and their relative importance in maintaining the skeletal structure of mother and offspring during pregnancy and lactation are discussed.