The objective of this research was to evaluate the effects of ingestion rations with different phosphorus levels, by goats in growth, on metabolism and endogenous losses of phosphorus. Eighteen Saanen animals, males, castrated, from 4 to 5 months of age, body weight average of 25 ± 1.2 kg, were housed, for 45 days, in metabolism cages. The animals received rations with three levels of P (0.08, 0.15 and 0.38% in dry matter) and similar levels of crude protein, metabolizable energy and Ca:P ratio. After 38 days of experiment, animals received injection of radiophosphorus (7,4 Mbq of 32P). They were sampled blood, feces, urine. It was used a randomized design, being made the regression analysis for ingested P. The average P intake ranged from 20.9 to 132.3mg kg-1 BW and it influenced the fecal excretion P. The amount of fecal endogenous P ranged from 7.6 to 45.4 mg kg-1 BW and it was influenced by dry matter and plasma inorganic P too. The net P requirements for maintenance was 6.87 mg/kg- BW.
goats; phosphorus absorption; metabolism; nutritional requirements
