title: Effects of dietary calcium:phosphorus ratios on apparent absorption of calcium and phosphorus in the small intestine, cecum, and colon of pigs.
abstract: Thirty-two crossbred barrows were used to investigate the effects of dietary Ca:total P (tP) ratios in phytase-supplemented diets on the apparent absorption of P and Ca in the small intestine, cecum, and colon. Three Ca:tP ratio treatments (1.5:1, 1.3:1, or 1.0:1) were created by adjusting the amount of ground limestone added to the basal low-P grower (.39% tP including .07% added inorganic P) and finisher (.32% tP without added inorganic P) diets. All low-P ratio diets were supplemented with Natuphos phytase at 500 units/kg. A positive control diet without phytase supplementation contained adequate P and Ca to meet dietary requirements. At 123 kg, the pigs were slaughtered and the contents of ileum, cecum, and colon were collected. Lowering the dietary Ca:tP ratio in the diets containing phytase linearly increased (P < .01) the apparent absorption (% and g/d) of P in the small intestine, but Ca absorption was not affected. Pigs fed the low-P diet with a Ca:tP ratio of 1.0:1 had an apparent absorption (g/d) of P or Ca similar to that of pigs fed the control diet, which was adequate in Ca and P. Averaged across all diets, the apparent absorption of P was highest when measured at the cecum, and the apparent absorption of Ca was highest when measured at the colon. In conclusion, lowering the dietary Ca:tP ratio to 1.0:1 in a low-P diet containing phytase increased the apparent absorption of P in the small intestine. Furthermore, a significant amount of P was absorbed in the cecum.
authors.affiliation: Department of Animal Science, University of Missouri, Columbia 65211, USA.
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: D W
authors.initials: DW
authors.lastname: Bollinger
authors.forename: D R
authors.initials: DR
authors.lastname: Ledoux
authors.forename: T L
authors.initials: TL
authors.lastname: Venum
mesh_terms: D010832:6-Phytase / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002136:Calcium, Dietary / Q000494:pharmacology*; D002432:Cecum / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D010758:Phosphorus / Q000276:immunology*; D016226:Phosphorus, Dietary / Q000494:pharmacology*; D013552:Swine / Q000378:metabolism*
chemical_list: D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D010758:Phosphorus; D010832:6-Phytase; D002118:Calcium