PSVI-21 Digestible Phosphorus Requirements of Growing Pigs Determined in Experiments Are Greater Than Those Estimated Using Modeling Approach

Abstract

Abstract Sufficient supply of dietary phosphorus (P) is critical for maximizing muscle and bone growth of pigs. The objective was to compare standardized total tract digestible (STTD) P requirements of growing pigs determined in the experiments and those estimated using modeling approach. Fifty-two experiments in the literature that empirically determined P requirements of pigs were employed. The basis for the determination of P requirements were growth performance (average daily gain or gain to feed ratio; n = 34) and bone development (n = 23). Based on the STTD P in the feed ingredients provided in NRC (2012) and ingredient composition used in the experiments, P requirements presented as total P, available P, and true total tract digestible P were converted to STTD P requirements. To obtain STTD P requirements (g/d) suggested by NRC (2012) for grow-finishing pigs (body weight > 20 kg), mean body weight and sex indicated in the experiments were input into the NRC model. The statistical model for comparing the empirical data with the NRC requirements included the basis for determining P requirements in the experiments as a fixed variable and body weight as a random variable. To quantify the deviations between NRC STTD P requirement estimates and empirically determined STTD P requirements, mean percentage difference was calculated. The STTD P requirements empirically determined based on growth performance were greater than the NRC STTD P requirement estimates (5.89 vs. 4.61 g/d, SEM = 0.27; P < 0.001). Moreover, the bone development-based STTD P requirements were greater than the NRC STTD P requirement estimates (6.63 vs. 4.46 g/d, SEM = 0.42; P < 0.001). In conclusion, the standardized total tract digestible P requirements suggested by the NRC are less than the experimentally determined requirements.