title: Response to dietary phosphorus deficiency is affected by genetic background in growing pigs.
abstract: Concern over the environmental effect of P excretion from pig production has led to reduced dietary P supplementation. To examine how genetics influence P utilization, 94 gilts sired by 2 genetic lines (PIC337 and PIC280) were housed individually and fed either a P-adequate diet (PA) or a 20% P-deficient diet (PD) for 14 wk. Initially and monthly, blood samples were collected and BW recorded after an overnight fast. Growth performance and plasma indicators of P status were determined monthly. At the end of the trial, carcass traits, meat quality, bone strength, and ash percentage were determined. Pigs fed the PD diet had decreased (P < 0.05) plasma P concentrations and poorer G:F (P < 0.05) over the length of the trial. After 4 wk on trial, pigs fed the PD diet had increased (P < 0.05) plasma 1,25(OH)(2)D(3) and decreased (P < 0.05) plasma parathyroid hormone compared with those fed the PA diet. At the end of the trial, pigs fed the PD diet had decreased (P < 0.05) BW, HCW, and percentage fat-free lean and tended to have decreased LM area (P = 0.06) and marbling (P = 0.09) and greater (P = 0.12) 10th-rib backfat than pigs fed the PA diet. Additionally, animals fed the PD diet had weaker bones and also decreased (P < 0.05) ash percentage and increased (P < 0.05) concentrations of 1alpha-hydroxylase and parathyroid hormone receptor mRNA in kidney tissue. Regardless of dietary treatment, PIC337-sired pigs consumed more feed and gained more BW than their PIC280-sired counterparts (P < 0.05) during the study. The PIC337-sired pigs also had greater (P < 0.05) HCW, larger (P < 0.01) LM area, and tended to have (P = 0.07) greater dressing percentage. Meat from the PIC337-sired pigs also tended to have greater (P = 0.12) concentrations of lactate but decreased (P = 0.07) concentrations of total glucose units 24 h postslaughter. Although plasma 1,25(OH)(2)D(3) concentrations were elevated (P < 0.05) in all the animals fed the PD diet, this elevation due to P deficiency tended (P = 0.09) to be greater in the PIC337-sired pigs after 12 wk on the treatment. The PIC337-sired pigs had stronger (P < 0.01) bones with greater ash percentage than the PIC280-sired pigs. The difference in the strength of the radii between the PIC337-sired pigs fed the PA and PD diets was greater than their PIC280-sired counterparts, which resulted in sire line x treatment interactions (P < 0.05). These data indicate differing mechanisms of P utilization between these genetic lines. Elucidating these mechanisms may lead to strategies to increase efficiency of growth in a more environmentally friendly manner.
authors.affiliation: Department of Animal Science, Iowa State University, Ames, IA 50010, USA.
authors.forename: L S
authors.initials: LS
authors.lastname: Alexander
authors.forename: A
authors.initials: A
authors.lastname: Qu
authors.forename: S A
authors.initials: SA
authors.lastname: Cutler
authors.forename: A
authors.initials: A
authors.lastname: Mahajan
authors.forename: S M
authors.initials: SM
authors.lastname: Lonergan
authors.forename: M F
authors.initials: MF
authors.lastname: Rothschild
authors.forename: T E
authors.initials: TE
authors.lastname: Weber
authors.forename: B J
authors.initials: BJ
authors.lastname: Kerr
authors.forename: C H
authors.initials: CH
authors.lastname: Stahl
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition / Q000187:drug effects / Q000235:genetics; D015519:Bone Density; D004032:Diet / Q000662:veterinary; D005260:Female; D005786:Gene Expression Regulation; D007668:Kidney / Q000378:metabolism; D008460:Meat / Q000592:standards; D010758:Phosphorus / Q000172:deficiency*; D016226:Phosphorus, Dietary / Q000494:pharmacology*; D013552:Swine / Q000235:genetics* / Q000254:growth & development*
chemical_list: D016226:Phosphorus, Dietary; D010758:Phosphorus