Influence of different calcium supplies on performance of fattening heifers and on calcium and phosphorus concentrations in blood plasma and candal vertebra

3 Groups of 24 crossbreed heifers intially weighing on average 295 kg were fed rations based on maize silage, soya bean oil and hay until weighing 450 kg. Each heifer was given 50 g daily of an almost Ca- and P-free mineralmi x. This mineral feed was given to heifers of group 1 without further supple ment, to heifers of group 2 in combination with 50 g ground limestone, and to heifers of group 3 in combination with 100 g ground limestone. Thus, all animals received equal amounts of all nutrients, except Ca. All heifers pe rformed well and showed daily weight gains of about 1000 g, without signifi cant differences in any of the usual performance traits. Neither concentrat ions of Ca or inorganic P in blood plasma nor concentrations of Ca, P or Mg in the candal vertebra were significantly affected by the level of Ca inta ke. Relative consumptions of Ca per kg weight gain were 16, 35 and 54 g, re spectively. It is concluded that official recommendations for Ca supply dur ing final fattening include large safety margins which could be reduced.