This research was conducted to determine the minimum endogenous losses, the nutritional requirement of phosphorus (P) for maintenance, the biological availability of P from dicalcium phosphate and the variation of plasma P concentration in swine of 20 kg LW. The pigs were fed diets containing different levels of total phosphorus (.30, .40, .51, .65 and .73%). Twenty commercial crossbred barrows were maintained in metabolic cages for a seven-day period of adaptation and seven days of total collection of feces, urine and blood samples. In the first day of the collection period, each animal was injected intravenously with 7.4 MBq of 32P as metabolic tracer. The values of endogenous fecal P were of 8.59, 8.43, 9.81, 11.28, and 12.75 mg P/kg LW•day, of P retained were 25.68, 67.05, 108.29, 131.56, and 135.88 mg P/kg LW•day, and of absorption P were 34.55, 75.93, 124.41, 162.97, and 175.00 mg P/kg LW•day, respectively, for diets A, B, C, D and E. The minimum endogenous fecal loss was 23.92 mg /kg LW•day and the daily P requirement for maintenance of pigs, in diets supplemented with dicalcium phosphate, was 38.58 mg P/kg LW•day. The biological availability of P from dicalcium phosphate was 90.30%.
radiophosphorus; swine; nutrition; true absorption
