title: A kinetic model of phosphorus metabolism in growing goats.
abstract: The effect of increasing phosphorus (P) intake on P utilization was investigated in balance experiments using 12 Saanen goats, 4 to 5 mo of age and weighing 20 to 30 kg. The goats were given similar diets with various concentrations of P, and 32P was injected to trace the movement of P in the body. A P metabolism model with four pools was developed to compute P exchanges in the system. The results showed that P absorption, bone resorption, and excretion of urinary P and endogenous and fecal P all play a part in the homeostatic control of P. Endogenous fecal output was positively correlated to P intake (P < .01). Bone resorption of P was not influenced by intake of P, and P recycling from tissues to the blood pool was lesser for low P intake. Endogenous P loss occurred even in animals fed an inadequate P diet, resulting in a negative P balance. The extrapolated minimum endogenous loss in feces was .067 g of P/d. The minimum P intake for maintenance in Saanen goats was calculated to be .61 g of P/d or .055 g of P/(kg(.75) x d) at 25 kg BW. Model outputs indicate greater P flow from the blood pool to the gut and vice versa as P intake increased. Intake of P did not significantly affect P flow from bone and soft tissue to blood. The kinetic model and regressions could be used to estimate P requirement and the fate of P in goats and could also be extrapolated to both sheep and cattle.
authors.affiliation: Animal Nutrition Laboratory, Centro de Energia Nuclear na Agricultura, Piracicaba, SP, Brazil.
authors.forename: D M
authors.initials: DM
authors.lastname: Vitti
authors.forename: E
authors.initials: E
authors.lastname: Kebreab
authors.forename: J B
authors.initials: JB
authors.lastname: Lopes
authors.forename: A L
authors.initials: AL
authors.lastname: Abdalla
authors.forename: F F
authors.initials: FF
authors.lastname: De Carvalho
authors.forename: K T
authors.initials: KT
authors.lastname: De Resende
authors.forename: L A
authors.initials: LA
authors.lastname: Crompton
authors.forename: J
authors.initials: J
authors.lastname: France
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle; D004435:Eating; D005243:Feces / Q000737:chemistry; D005260:Female; D006041:Goats / Q000254:growth & development* / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D010758:Phosphorus / Q000493:pharmacokinetics*
chemical_list: D010758:Phosphorus