PSXI-17 - Prediction models for phosphorus excretion of pigs

Abstract: The objective of the present study was to develop prediction equations for daily phosphorus excretion based on body weight (BW) and dietary phosphorus concentration of pigs. Four experiments were conducted using pigs with an initial body weight of 15 kg, 30 kg, 50 kg, and 78 kg. In the experiment 1, the experimental diets were mainly based on corn, soybean meal, whey powder, fish meal, and blood plasma. In the experiments 2, 3, and 4, the diets based on corn, soybean meal, and fibrous ingredients were formulated. All experimental diets were supplemented with commercial phytase at 500 FTU/kg. In all experiments, a total collection method and the marker-to-marker procedure were used for fecal and urinary collection. Fecal and urinary phosphorus excretions were determined. Correlation coefficients among BW, daily phosphorus intake, and daily phosphorus excretion of pigs were determined. Prediction equations for phosphorus excretion were developed using BW and dietary phosphorus concentration as independent variables. The BW had positive correlations with fecal and total phosphorus excretion (r = 0.78 and P < 0.001 for fecal phosphorus excretion and r = 0.78 and P < 0.001 for total phosphorus excretion). The prediction equations for predicting fecal phosphorus excretion and total phosphorus excretion were: fecal phosphorus excretion (g·pig^–1·d^–1) = –0.647 – 0.00065 × BW² + 0.270 × BW × dietary phosphorus concentration (R² = 0.81; P < 0.001); total phosphorus excretion (g·pig^–1·d^–1) = –0.619 – 0.00064 × BW² + 0.277 × BW × dietary phosphorus concentration (R² = 0.85; P < 0.001) where BW in kg and phosphorus concentration in %. The BW of pigs corresponding to the age was predicted using the NRC model. The mean phosphorus excretion of pigs weighing from 7 kg to 120 kg at day 22 to 180 was calculated using a developed estimation equation, with BW and total phosphorus requirement used as independent variables. Daily fecal and total phosphorus excretions were 3.77 g·pig^–1·d^–1 and 4.01 g·pig^–1·d^–1, respectively.