ESTIMATION OF DIGESTIBLE PHOSPHORUS REQUIREMENTS IN GROWING-FINISHING PIGS BY CARCASS ANALYSIS

72 piglets were used in an experiment, in which 2 diets (1% Ca and 0.77% tP(A) 0.74% Ca and 0.57% tP(B) were used in the growing period. These 2 groups were subdivided during the finishing period on 2 diets with the same P-content of 0.38% tP (unsupplemented) but two different Ca/P ratio's: 1.3 (C) vs 2.0 (D). Some pigs were slaughtered and analysed at 18, 35 and 95 kg. In the growing period the following differences were observed: better feed/gain on feed B, lower contents of Ca and P in bones on feed B, higher Ca digestibility on feed B, lower urinary P-excretion on feed B. In the finishing period the following phenomena were observed: lower zoo-technical performances on feed D, a very similar bone mineral content at 95 kg irrespective of the Ca/P ratio. There is no ''carry-over'' effect of P from the ample supply in the growing period to the marginally supplied finishing period. A wide Ca/P ratio has an important negative influence on the low-P diet. With regard to the polluting P-emission, the feed combination BC is the most favourable, since the overall retention coefficient is the highest.