Altered lactational performance in rats fed low carbohydrate diets and its effect on growth of neonatal rat pups.

The possibility that low carbohydrate diets fed to nursing rat dams altered milk composition and impaired neonatal growth and development was explored. Pregnant control dams fed a 62% glucose diet were paired at parturition with experimental dams fed diets with either severe (0% glucose) or moderate (6% glucose) carbohydrate restriction. At birth half of the littermates of each pair were cross-fostered so that each dam nursed a litter consisting of one-half deficient and one-half control pups. All pups born to dams fed the 0% glucose diet died within 24 h of birth whether they were nursed by control or deficient dams. Control pups cross-fostered to these deficient dams died by the second day; the 0% glucose diet failed to support milk production. In contrast, the dams fed the 6% glucose diet produced milk, but its composition was significantly lower in carbohydrate and lipid than was milk of control dams. This altered milk composition was associated with retarded postnatal growth and development. Control pups cross-fostered to 6% glucose dams showed decreased survival (83% vs. 97%) and significantly reduced body weight (10 g vs. 12 g) at d 7. Conversely, 6% glucose pups cross-fostered to control dams showed improved survival (54% vs. 29%) and significantly increased body weight (9 g vs. 7 g) at d 7. These data showed that carbohydrate-restricted diets altered milk production and/or composition, which, in turn, reduced growth and increased mortality in the pups nursed by dams fed these diets. The results demonstrate that an adequate source of dietary carbohydrate is important for optimal lactational performance.