Two trials were conducted in order to assess the efficacy of microbial phytase supplementation in improving the bioavailability of certain nutrients in the diet of early weaned piglets. In trial I, a low-phosphorus, corn-soybean meal diet supplemented with phytase significantly improved the apparent digestibilities of phosphorus (P, p = 0.0004) and calcium (Ca, p = 0.04). The average daily gain (ADG) and feed conversion ratio (FCR) were also improved by supplemental phytase. In trial II, addition of acetic acid to the low-P plus phytase diet further improved the apparent digestibilities of P and Ca (gp = 0.01, p = 0.02, respectively). Furthermore, the apparent digestibility of copper was also significantly improved by acetic acid addition. As a consequence, the piglets fed this treatment showed the best growth performance. Acidification of a diet which provided the NRC recommended levels of available P significantly improved the apparent digestibilities of protein and most of the minerals (P, Fe, Zn, Cu and Mn) but it was not reflected in improved growth performance. These results indicate that microbial phytase not only released P from the phytic acid molecule but it also cleaved other minerals bound to this complex.

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