Variation in the phosphorus content of bone samples obtained from the last three ribs of cattle.

Variation in the phosphorus content and specific gravity of bone samples taken from the 11th, 12th and 13th ribs of cattle was examined in relation to the selection of a site for the acquisition of such samples by biopsy, in experiments where changes in skeletal phosphorus storage required to be monitored. The degree of mineralisation of the 11th rib was significantly higher than that of the 12th, which in turn was greater than that of the 13th. It was concluded that valid comparisons may be made between bone samples obtained during an experimental regime, provided they are taken from the same numbered rib; it is recommended that the 13th rib be avoided in such studies.