Bioavailability of different sources of phosphorus to growing pigs

Vegetable ingredients used in feed for growing pigs do not provide the amount of phosphorus (P) ideal to meet the nutritional requirements requiring the use of inorganic P sources with higher bioavailability of this mineral. This study aimed to evaluate the P balance of pigs fed diets with different P levels using three types of inorganic phosphates as source of P. The experiment was conducted at UNESP Jaboticabal, with 42 castrated males weighing on average 18 kg at the beginning divided in 7 treatments and distributed in individual metabolic cages. After an adaptation period of 5 days in the cage and to the experimental diets, feces and urine were collected separately for 10 days. Experimental diets soybean meal and corn were formulated to be iso-energetic and iso-protein, except for Ca and P. A basal diet with low P content and the experimental diets was corresponding to the basal diet supplemented with the equivalent of 0.1 and 0.2% P of different inorganic phosphates as source of P: DCP (dicalcium phosphate, 18% P); MDCP (monodicalcium phosphate, 20% P); MCP (monocalcium phosphate, 22.7% P). There was linear (P>0.05) response of final BW of pigs fed diets with different P levels using three types of inorganic phosphates as source of phosphorus. The pigs fed with MCP sources had higher (P>0.05) final BW than group fed with DCP. Phosphorus supplementations had linear effect on fecal P excretion for all P sources. Urinary P did not changed (P>0.05) with increasing P supplementation from both sources. P retained and P retention expressed as % of intake and as % of absorbed increased linearly (P<0.01) with supplementation of the basal diet with increasing level of either phosphate. Pigs fed with MDCP sources showed better response (P<0.05) for P absorbed, P retained and P retention compared with group fed with DCP source. However there was not difference (P<0.05) between pigs fed with MCP compared with MDCP and MDCP with DCP. The results of the present P balance study showed that the bioefficacy of MDCP and MCP P source relative to DCP was 136 and 169 % on a product-to-product basis for P retention expressed as % of intake when added to a P deficient diet. Supplementing MCP improves P absorption, P retained and P retention of the pigs when compared with DCP.