Endogenous losses of phosphorus by sheep

Abstract

Twelve sheep were fed semisynthetic roughage diets at three rates to study the effects of intake of dry matter, concentration of phosphorus and the physical form of two low-P barley straws upon the faecal losses of P. The sheep were in negative P balance throughout the experiement. The absorption of dietary P increased with P intake and was unaffected by differences in the physical form of the roughage. For each barley straw diet, endogenous faecal P increased with dry matter intake, and was higher when the roughage was ground than chopped. Over the whole experiment, daily endogenous faecal P ranged from 8.5 to 31.5 mg/kg live weight. Endogenous faecal P was related to P intake or to dry matter intake and plasma inorganic P. The concentration of faecal endogenous P was negatively related to the intake of each diet. It is concluded that the concentration of inorganic plasma P and the rate of salivary secretion are responsible for the endogenous faecal excretion of P and the regulation of P balance in sheep fed low-P diets. © 1989, Cambridge University Press. All rights reserved.