Genetic background influences phosphorus utilization for growth and bone integrity in pigs

Phosphorus (P) in the excreta from pig production is of both economical and environmental concern. The objective of this study was to determine the affect of genetic background on P utilization by gilts sired by 2 different lines (PIC337 and PIC280). Gilts (n=94, 3wk of age) were allotted based on litter and BW into 2 groups and were fed either a P adequate (PA) or a 20% P deficient (PD) diet for 14wk. Growth performance and plasma concentrations of inorganic P (PP), parathyroid hormone (PTH), 1,25(OH) 2 Vitamin D (VitD), and alkaline phosphatase activity (AKP) were determined monthly. At trial completion, radial bones were collected for bone strength analysis, intermediate carpals were collected for ash % determination, and kidney tissue was collected for gene expression analysis by real‐time PCR. PIC337 PA pigs had higher (p≤0.05) ADG than PIC280 PA pigs and had the highest bone strength and ash % among all groups. Pigs fed the PD diet had significantly (p≤0.05) lower PP and higher VitD throughout the study, indicative of minor P deficiency. Pigs fed the PD also had greater expression of the 1α hydroxylase gene in the kidney than PA fed pigs (≈1.8 fold, p≤0.05). These data demonstrate an interaction between genetic background and dietary P utilization that could lead to the identification of genotype specific feeding programs and breeding strategies to produce more P efficient pigs.