281 Young Scholar Presentation: Digestibility of calcium and phosphorus in feed ingredients fed to gestating sows and growing pigs

Abstract

Abstract In practical diet formulation, values for standardized total tract digestibility (STTD) of Ca and P obtained in growing pigs are also applied to sows. However, gestating sows have reduced digestibility and retention of Ca and P compared with growing pigs, and the impact of microbial phytase on the digestibility of P and Ca is much less in sows than in growing pigs. Applying STTD values for Ca and P obtained in growing pigs to diets for gestating sows, therefore, results in an overestimation of the absorbed Ca and P in sows (Table 1). Further research, however, indicated that the digestibility of Ca and P in late gestating sows is greater than in sows in early or mid-gestation and retention of Ca and P was greater in late-gestation compared with earlier gestation periods, which indicates that digestion and absorption of Ca and P may be under hormonal control in sows (Table 2). It was also demonstrated that a wide Ca:P ratio decreased P digestibility in both growing pigs and sows in late-gestation, which demonstrates the need for not overfeeding STTD Ca. In follow-up research, it was demonstrated that several serum biomarkers may be used to predict if a sow is in a positive or a negative Ca and P state, but more research is needed to quantify this effect and to determine if biomarkers can be used in Ca and P requirement experiments. In conclusion, gestating sows have much lower digestibility of Ca and P than growing pigs, which demonstrates that digestibility values obtained in growing pigs cannot be used to accurately formulate diets for gestating sows. Likewise, effects of microbial phytase on digestibility of Ca and P are much less predictable in gestating sows than in growing pigs and phytase effects in sows are much smaller than in growing pigs.