Digestible phosphorus requirement of grower pigs

Abstract

Phosphorus excretion may have a major impact on the environment if it is not managed properly. The success of management strategies for reducing P excretion of pigs is dependent partly on more accurate estimates of P requirements, specifically digestible instead of total P requirements. Performance and metabolism studies were conducted to determine digestible P requirements of grower pigs based on performance, plasma and bone P, and P excretion and retention variables, using 200 pigs (23 ± 0.9 kg) and 20 barrows (54 ± 3.1 kg), respectively. Pigs were fed one of five concentrations of dietary digestible P (0.19, 0.24, 0.33, 0.35, and 0.38%). Increasing digestible P quadratically increased average daily gain (ADG) (P < 0.01), feed intake (P < 0.05), and feed efficiency (P < 0.001). Barrows had a higher ADG than gilts (0.890 vs. 0.838 kg d-1; P < 0.05); however, digestible P requirement was higher for gilts than for barrows (6.92 vs. 6.17 g d-1 or 0.36 vs. 0.32% in diet; P < 0.05). In barrows, increasing digestible P intake quadratically increased P in plasma and urine (P < 0.01), and linearly increased P in faeces (P < 0.01), suggesting that P excretion depends on excess P intake. Using regression analysis, digestible P requirements were 6.45 g d-1 with ADG, 7.46 g d-1 with bone P, 6.01 g d-1 with plasma P, 3.61 g d-1 with urinary P, 5.86 g d-1 with retained P, and 5.11 g d-1 with retained N. Feeding P closer to pig requirements will reduce P excretion.