Phosphorus turnover in sheep

Abstract

Rumen fluid, serum, and parotid salivary inorganic phosphorus concentrations in sheep given four levels of dietary phosphorus (0.42–4.02 g/day) were directly related to phosphorus intake. There was a very high correlation (r = +0.91; P < 0.001) between inorganic phosphorus concentrations in centrifuged rumen fluid and in parotid saliva. Serum inorganic phosphorus concentrations were positively correlated with those of saliva (r = +0.64; P< 0.05) and also with those in centrifuged rumen fluid (r = +0.75; P<0.01). The range in the mean daily saliva volumes collected from one parotid gland in each sheep was 3.2 to 4.2 l/day. The calculated minimum total salivary phosphorus secretion ranged from 3.0 g/day on the lowest dietary phosphorus intake to 5.3 g/day on the highest, the corresponding ratios of salivary to dietary phosphorus being from 7.24 to 1 .32 g/g. It appeared that salivary phosphorus was the major source of phosphorus to the rumen, and was also the principal determinant of rumen fluid inorganic phosphorus levels.