443 Awardee Talk: Calcium and phosphorus requirement estimates for gestating and lactating sows

Abstract Calcium and phosphorus are minerals involved in biological functions and essential structural components of the skeleton. The body tightly regulates Ca and P to maintain homeostasis. Maternal demand for Ca and P increases during gestation and lactation to support conceptus growth and milk synthesis. Litter size and litter average daily gain have a large impact on Ca and P requirements for sows because as they increase, the requirements increase due to a greater demand on the sow. The objective of this review was to summarize published literature on Ca and P requirements in gestating and lactating sows derived from empirical data and factorial models. A total of 9 empirical studies and 7 factorial models were reviewed for determining the Ca and P requirements in gestation. For lactation, there were 6 empirical studies and 7 factorial models reviewed. Empirical studies determined requirements based on the observed effect of Ca and P on bone mineralization, sow and litter performance, and milk characteristics. Factorial models generated equations to estimate Ca and P requirements using the main components of maintenance, fetal and placental growth, and maternal retention in gestation. The main components for factorial equations in lactation include maintenance and milk production. In gestation, the standardized total tract digestibility (STTD) P requirement estimates from empirical studies range from 5.4 to 9.5 g/d with total Ca ranging from 12.9 to 18.6 g/d to maximize bone measurements or performance criteria. According to the factorial models, the requirements increase throughout gestation to meet the demands of the growing fetuses and range from 3.3 to 5.1 g/d of STTD P on d 45 of gestation and increase to 7.6 to 10.6 g/d on d 114 of gestation. The modeled total Ca requirement estimates increase from 9.2 to 17.7 g/d on d 45 gestation to 18.4 to 38.2 g/d on d 114 of gestation. During lactation, STTD P requirement estimates from empirical studies ranged from 8.5 to 22.1 g/d and total Ca ranged from 21.2 to 50.4 g/d. For the lactation factorial models, STTD P requirements ranged from 14.2 to 25.1 g/d for STTD P and 28.4 to 55.6 g/d for total Ca for parity 1 sows with a litter size of 15 pigs. The large variation in requirement estimates make it difficult to define Ca and P requirements for reproducing sows; however, a minimum level of 6.0 and 22.1 g/d of STTD P, and 12.9 and 50.4 g/d of total Ca during gestation and lactation, respectively, appears to be adequate to meet basal requirements. The limited data and high variation indicate a need for future research evaluating Ca and P requirements for reproducing sows.