title: Effect of low levels of dietary available phosphorus on phosphorus utilization, bone mineralization, phosphorus transporter mRNA expression and performance in growing pigs.
abstract: A study was conducted to examine the effects of different dietary levels of available phosphorus (aP) on P excretion, bone mineralization, performance and the mRNA expression of sodium-dependent P transporters in growing pigs. Sixty-day old growing pigs (n = 54) with an average initial BW of 19.50 ± 1.11 kg were randomly allocated to a control diet (C) containing 0.23% available phosphorus (aP), T1 containing 0.17% aP and T2 containing 0.11% aP. There were 6 pens per treatment with 3 pigs per pen. Body weight and feed intake were measured weekly. At the end of each week, one pig from each pen was housed in a metabolic crate for 24 h to collect fecal and urine samples and then sacrificed to obtain third metacarpal (MC3) bones and jejunal and kidney samples. Bones were scanned by Dual Energy X-ray Absorptiometry (DEXA). Fecal and urine samples were sub-sampled and analyzed for P content. The expression of P transporter mRNA in jejunum and kidney samples was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Data were analyzed using GLM procedure of the Statistical Analysis System (SAS Institute version 9.2). Pigs fed the T2 diet had reduced (P < 0.05) average daily gain (ADG) and gain to feed (G:F) compared to those fed the C diet during week 2. Overall, ADG and G:F were also reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C and T1 diets. Bone mineral density (BMD) and bone mineral content (BMC) were reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet throughout the experiment. At week 1, jejunal mRNA expression of Na (+)-dependent phosphate transporter 2 (SLC34A2) was increased (P < 0.01) in pigs fed the T2 diet compared to C diet. Renal mRNA expression of Na(+)-dependent phosphate transporter 1 (SLC34A1) and SLC34A3 were increased (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet at week 2 and was accompanied by lower (P < 0.05) urinary P in pigs fed the T2 diet during week 2 and week 3. In conclusion, growing pigs are highly sensitive to low dietary P as shown by reduced ADG, bone mineralization and urinary P level, but moderate reduction in dietary P up to 0.17% aP in the diet has the potential to reduce environmental pollution by reducing P concentration in swine manure and without compromising performance.
authors.affiliation: a Department of Animal Science , University of Manitoba , Winnipeg , Manitoba , Canada.
authors.forename: Bishwo B
authors.initials: BB
authors.lastname: Pokharel
authors.affiliation: a Department of Animal Science , University of Manitoba , Winnipeg , Manitoba , Canada.
authors.forename: Alemu
authors.initials: A
authors.lastname: Regassa
authors.affiliation: a Department of Animal Science , University of Manitoba , Winnipeg , Manitoba , Canada.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Nyachoti
authors.affiliation: b Department of Poultry Science , University of Georgia , Athens , Georgia , USA.
authors.forename: Woo K
authors.initials: WK
authors.lastname: Kim
mesh_terms: D015502:Absorptiometry, Photon; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D015519:Bone Density; D002113:Calcification, Physiologic / Q000187:drug effects*; D005243:Feces; D007408:Intestinal Absorption / Q000187:drug effects; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D016226:Phosphorus, Dietary / Q000493:pharmacokinetics / Q000494:pharmacology*; D012333:RNA, Messenger; D060888:Real-Time Polymerase Chain Reaction; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa / Q000235:genetics*; D034421:Sus scrofa / Q000254:growth & development* / Q000378:metabolism
chemical_list: D016226:Phosphorus, Dietary; D012333:RNA, Messenger; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D010758:Phosphorus
keywords: Bone mineralization; P excretion; P transporters; performance; pigs