Meeting Abstract

P3.147  Tuesday, Jan. 6  Calcium intake, bone metabolism and reproductive output of white-footed mice (Peromyscus leucopus) BOOHER, C.M.**; HOOD, W.R.; Auburn University, Alabama; Auburn University, Alabama cmb0011@auburn.edu

The ossification of mammalian fetal and neonatal skeletons requires a significant amount of calcium transfer from maternal sources via the placenta during pregnancy and milk during lactation. Many mammals meet elevated calcium demand at this time by increasing bone resorptive activity, which mobilizes calcium stored in the skeleton. Consequently, maternal bone mineral content and density may be reduced to detrimental levels. When dietary calcium intake is low, females have been shown to rely more heavily on skeletal stores, resulting in relatively greater reduction of bone. To address the potential trade-off between maternal skeletal maintenance and offspring production when calcium availability is low, we provided either a low-calcium diet or a standard diet to reproducing white-footed mice and assessed 1. changes in bone mineral density and bone mineral content of the femur, tibia and lumbar vertebrae using dual-energy x-ray absorptiometry 2. changes in bone resorption activity using bone marker assays and 3. differences in offspring production relative to calcium intake. Females consuming the low-calcium diet produced more pups and experienced greater bone loss than females on the standard diet, suggesting that not only are resources preferentially allocated to offspring production, but relatively more is apportioned when calcium availability is low. Our results corroborate with life history theory regarding short-lived animals that experience fluctuating resource abundance.