Effect of low levels of dietary available phosphorus on phosphorus utilization, bone mineralization, phosphorus transporter mRNA expression and performance in growing pigs

• Published in: Journal of environmental science and health. Part B, Pesticides, food contaminants, and agricultural wastes Vol. 52; no. 6; pp. 395 - 401
• Main Authors: Pokharel, Bishwo B., Regassa, Alemu, Nyachoti, Charles M., Kim, Woo K.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 03.06.2017; Taylor & Francis Ltd
• Subjects: Absorptiometry, Photon; Animal Feed - analysis; Animal Nutritional Physiological Phenomena; Animal wastes; Animals; Body weight; Bone Density; Bone mineral content; Bone mineral density; Bone mineralization; Bones; Calcification, Physiologic - drug effects; Data processing; Diet; Dual energy X-ray absorptiometry; Excretion; Feces; Gene expression; Hogs; Intestinal Absorption - drug effects; Jejunum; Kidney - drug effects; Kidney - metabolism; Kidneys; Livestock; Manures; Metacarpal; Mineralization; P excretion; P transporters; Pens; Phosphate; Phosphate transporter; Phosphates; Phosphorus; Phosphorus - metabolism; Phosphorus - pharmacokinetics; Phosphorus - urine; Phosphorus, Dietary - pharmacokinetics; Phosphorus, Dietary - pharmacology; Pig manure; pigs; Polymerase chain reaction; Real time; Real-Time Polymerase Chain Reaction; RNA, Messenger; Sodium; Sodium-Phosphate Cotransporter Proteins, Type IIa - genetics; Statistical analysis; Statistical methods; Sus scrofa - growth & development; Sus scrofa - metabolism; Swine; Urine; Weaning; pigs; performance; Bone mineralization; P transporters; P excretion
• ISSN: 0360-1234; 1532-4109
• DOI: 10.1080/03601234.2017.1292096

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.