EFFECTS OF THE REPRODUCTIVE-CYCLE AND AGE ON CALCIUM AND PHOSPHORUS-METABOLISM AND BONE INTEGRITY OF SOWS

The purpose of this study was to determine the effects of stage of the reproductive cycle and age can Ca and P metabolism and. bone integrit y of sows. Five-day balance studies were conducted with first-and fift h-parity sows, and sows were slaughtered during the last trimester of gestation, at the end of lactation, or during the last trimester of th e subsequent gestation. First-parity-sows we-re studied during their f irst gestation (n = II), first lactation (n = 10), or second gestation (n = 10). Fifth-parity sows were examined during their Mch gestation (n = 10), fifth lactation (n = 9), or sixth gestation (n = 9). All sow s were fed 1.9 kg/d of a common diet (.76% Ca and .63% P) during gesta tion and were allowed ad libitum access to the same diet during lactat ion. Digestibilities of Ca and P were much greater during lactation th an during gestation. During gestation, young sows absorbed and retaine d more Ca and P than did mature sows. However, during lactation, matur e sows consumed more feed, and therefore Ca and P, and retained more C a and P than did young sows. Bones of mature sows were larger, more mi neralized, and stronger than the bones of young sows. Bone weight and strength decreased during lactation and increased during the subsequen t gestation. Changes in weight and strength were greater in young sows than in mature sows.