THE EFFECT OF DIETARY CALCIUM ON THE EFFICACY OF MICROBIAL PHYTASE IN RATIONS FOR GROWING PIGS

A 3-week balance trial with 30 (5 x 6) castrated, growing, male pigs (16.0 kg b.w.) housed individually in stainless-steel metabolic cages was carried out to evaluate the efficacy of a microbial phytase supplement (Natuphos(R), BASF AG, Ludwigshafen, Germany; 1000 U/kg) on the utilization oi phosphorus of plant origin (barley/soybean meal/sunflower meal), as influenced by dietary calcium. The experimental diets contained the same amounts of phytate phosphorus, total phosphorus at a marginal deficient level (4 g/kg) and increasing calcium levels (5-8 g/kg). The microbial phytase supplement significantly improved the apparent absorption and retention of phosphorus and calcium. Increasing dietary calcium levels progressively reduced the phytase effect on apparent phosphorus absorption. Simultaneously, the utilization of the absorbed phosphorus was improved by the increasing calcium supply. The best overall utilization of the dietary phosphorus was achieved by a feeding level of 7 g Ca/kg diet. Thus, the reduction of the phosphorus output in pig manure caused by a dietary phytase supplement can be further improved and optimized by an appropriate calcium supply.