title: Quantitative relationships between standardized total tract digestible phosphorus and total calcium intakes and their retention and excretion in growing pigs fed corn-soybean meal diets.
abstract: An experiment was conducted to determine the quantitative relationships between standardized total tract digestible P (STTD P) and total Ca intakes with their retention and excretion by growing pigs fed corn-soybean meal diets. Forty-eight crossbred barrows (BW = 22.7 ± 2.9 kg) were allotted to 1 of 8 diets, housed individually in pens for 3 wk, and then moved to metabolism crates and allowed 4 d for adaptation and 5 d for collection of urine and fecal samples. Eight corn-soybean meal diets were formulated for similar NE, fat, and AA concentrations but to increase the STTD P from 0.16 to 0.62% using monocalcium phosphate. Dietary treatments were formulated for a constant Ca:STTD P ratio (2.2:1). The STTD P intake increased (P < 0.001) from 64 to 242% of the daily requirement (4.59 g/d of STTD P). Fecal and total excretion of P and Ca were linearly associated with mineral intake (P < 0.001). Constant urinary P excretion of 0.03 g/d P was observed, but at 4.96 g/d of STTD P intake, the urinary P excretion increased (P < 0.001). In contrast, Ca excretion in urine decreased (P < 0.001) with Ca intake, but constant excretion of 0.40 g/d Ca was reached at 17.97 g/d of Ca intake. The daily intakes of STTD P and Ca moderately explained the variation in urinary excretion of P (R2= 0.41) and Ca (R2= 0.64). The absorption and retention of P increased linearly (P< 0.001) with dietary P intake, whereas absorption and retention of Ca showed a quadratic response (P < 0.001). Absorption and retention of P and Ca were highly predictable from the STTD P and Ca intakes, with of 0.87 and 0.90, respectively. The femur mineral content (FMC) increased by 2.71 g with STTD P intake (P < 0.001) but reached a plateau (29.54 g of FMC) at 8.84 g/d of STTD P intake. The FMC was highly predictable from the STTD P intake (R2 = 0.89). The FMC affected the urinary P excretion ( P< 0.01), but moderately (R2= 0.19) explained the variation in urinary P. In conclusion, constant excretion of P in urine was observed but excretion increased linearly at STTD P intake levels above the requirement for maximum growth of growing pigs. The FMC increased with STTD P intake, but a plateau was reached at a STTD P intake level above the requirement. Dietary STTD P was used for growth and accumulated in bones until a plateau was reached and excess was excreted in urine. The predictability of P and Ca excretion in urine from the dietary STTD P and Ca intakes was moderate.
authors.forename: N A
authors.initials: NA
authors.lastname: Gutierrez
authors.forename: N V L
authors.initials: NV
authors.lastname: Serão
authors.forename: A J
authors.initials: AJ
authors.lastname: Elsbernd
authors.forename: S L
authors.initials: SL
authors.lastname: Hansen
authors.forename: C L
authors.initials: CL
authors.lastname: Walk
authors.forename: M R
authors.initials: MR
authors.lastname: Bedford
authors.forename: J F
authors.initials: JF
authors.lastname: Patience
mesh_terms: D015502:Absorptiometry, Photon; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001826:Body Fluids; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D002151:Calorimetry; D005243:Feces / Q000737:chemistry; D005269:Femur / Q000737:chemistry; D005526:Food, Formulated; D065569:Gastrointestinal Absorption / Q000502:physiology; D041981:Gastrointestinal Tract / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D013025:Glycine max / Q000378:metabolism; D013552:Swine / Q000378:metabolism*; D003313:Zea mays / Q000378:metabolism
chemical_list: D016226:Phosphorus, Dietary; D002118:Calcium