A PRELIMINARY REASSESSMENT OF THE REQUIREMENTS FOR MAJOR MINERALS BY GROWING PIGS

Forty-two mineral balances were measured in 50 kg pigs fed various die ts, including barley, maize or potato, and used to examine the presump tion that the current recommended dietary requirements for the major m inerals, especially phosphorus, are essential to the well-being of the pig, All the diets contained similar levels of all the mineral elemen ts, except potassium which was higher in the diets containing potato. The concentrations/kg dry matter were 11.0 g calcium, 6.9 g phosphorus , 0.96 g sodium, 1.5 g magnesium and 5.4 g potassium or 14.0 g potassi um in the diets containing potato. The apparent digestibility coeffici ents were calcium 0.39, phosphorus 0.45, sodium 0.72, magnesium 0.26 a nd potassium 0.70 or 0.80 and the gross efficiencies with which the in gested elements were retained were calcium 0.36, phosphorus 0.25, sodi um 0.32, magnesium 0.07 and potassium 0.22 or 0.16. The low efficienci es of utilisation of the digested minerals, especially phosphorus (0.5 3), suggested that a reduction in dietary phosphorus levels may be jus tified in terms of reducing the pollution of the environment with phos phorus caused by the application of pig slurry.