Environmental pollution generated by phosphorus excreted by ruminants: quantitative aspects of phosphorus availability, absorption, metabolism and excretion

Abstract

Phosphorus metabolism has been target of a great number of studies in the last decades. The Laboratory of Animal Nutrition (LANA-CENA-USP) has done several experiments concerning the phosphorus metabolism by domestic animals using the isotopic dilution technique. Phosphorus is very important for animals due to the great number of functions in which it is involved in the animal organism. However, the exploitation of dietary is relatively low, mainly in ruminants, being part of it excreted with an endogenous fraction. Thus, phosphorus is the diet constituent that more contributes for the environmental pollution. The objective of this project is to evaluate the environmental pollution potential of phosphorus from ruminant farms using the biomathematical model to estimate the metabolic kinetics of that nutrient. For in such a way, it is planned to carry through: (i) research and standardization of the database produced in the innumerable studies of phosphorus metabolism by ruminants in the LANA-CENA-USP, (ii) adjustment of the data for the biomathematical model, and (iii) estimative of potential of ambient pollution by phosphorus from excretions of bovines, sheep and goats, fed different sources and levels of phosphorus. After the database creation, these will be classified according to qualitative (animal species, characteristics of the animals, alimentary regimen, type of source) and quantitative aspects (number of animals, age, live weight, P content in the diet, Ca:P ratio, dry matter intake). With the data of the experiments and with the consent of respective responsibles, the parameters of the metabolism will be recalculated for standardization of the calculations and posterior adjustment by the biomathematical model with four compartments. The results will be statistically treated to estimate the phosphorus losses to the environment. (AU)