Introduction which is unavailable to the pig Jongbloed, 1987.

Livestock Production Science 67 2000 113–122 www.elsevier.com locate livprodsci The effects of microbial phytase, organic acids and their interaction in diets for growing pigs A.W. Jongbloed , Z. Mroz, R. van der Weij-Jongbloed, P.A. Kemme IDTNO Animal Nutrition , P.O. Box 65, 8200 AB Lelystad, The Netherlands Received 4 February 1999; received in revised form 1 October 1999; accepted 14 February 2000 Abstract One hundred and ninety-two crossbred pigs from 22 to 45 kg BW were used to investigate the effects of Aspergillus niger phytase, organic acids, and their interaction, on animal performance, nutrient digestibility and urine composition. Pigs were housed in pens of six animals each, and had ad libitum access to the pelleted feed and water. A basal diet was either or not 21 21 supplemented with 410 phytase units kg , and with lactic acid 0, 16.0 and 32.0 g kg or formic acid 0, 8.0 and 16.0 g 21 kg . The respective levels of lactic acid and formic acid were of the same acid equivalency. There were four replicates for the basal diet either or not supplemented with microbial phytase, and three replicates for the other treatments. The Ca and 21 digestible P contents of the basal diet were 6.0 and 1.0 g kg , respectively. The apparent total tract digestibilities of DM, OM, ash, Ca, Mg and P were calculated using Cr O as an indigestible marker. Osmolarity, pH, Ca, Mg, and P content were 2 3 analysed in freshly voided urine. Microbial phytase very positively affected animal performance. Also, their daily gain and feed conversion ratio were significantly enhanced by the organic acids, but there was no synergistic effect. The apparent total tract digestibility of DM, ash, Ca and P were significantly enhanced by microbial phytase. Also, the apparent total tract digestibility of DM, OM, ash, Ca and P were significantly enhanced by the organic acids. A synergistic effect of organic acids and microbial phytase was found for ash, P and Mg digestibility. Formic acid and phytase increased digestible P 21 content by 0.20 g digestible P kg of diet. No differences in the effect due to the doses of supplemented organic acids were observed on animal performance, digestibilities and urine characteristics. Microbial phytase affected Ca and P content in urine, but had no effect on pH, osmolarity and Mg content. The acids had no effect on urine parameters.  2000 Elsevier Science B.V. All rights reserved. Keywords : Pigs; Microbial phytase; Phosphorus; Organic acids; Digestibility

1. Introduction which is unavailable to the pig Jongbloed, 1987.

During the last decade, numerous experiments have A total of 60 to 70 of P in plant ingredients, shown that microbial phytase can partly render commonly used in pig diets, is present as phytate P phytate P available to pigs Cromwell et al., 1995; ¨ Dungelhoef and Rodehutscord, 1995; Jongbloed et al., 1996. Supplementation of phytase to pig diets Corresponding author. Tel.: 131-320-237-312; fax:131-320- 21 . 500 FTU kg ; activity of phytase is expressed 237-320. E-mail address : a.w.jongbloedidtno.nl A.W. Jongbloed. as FTU usually results in the enhancement of the 0301-6226 00 – see front matter  2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 0 0 0 0 1 7 9 - 2 114 A .W. Jongbloed et al. Livestock Production Science 67 2000 113 –122 digestibility of phytate-bound P up to 40 synergistic interactive effect with phytase. On the Jongbloed et al., 1996. This implies that 60 of the other hand, Radcliffe et al. 1998 showed an phytate phosphorus is still unavailable. Jongbloed improved P digestibility by using 1.5 or 3.0 of 1987 reviewed that lowered intestinal pH increases citric acid, but no significant interaction was ob- the solubility of P and phytate and improves P served between microbial phytase and citric acid. absorption in the small intestine. In addition to their This lack of consistency in the conclusions implies a effect on intestinal pH, supplementary organic acids need for further research. can also bind various cations along the intestine and Therefore, the objective of this study was to may act as chelating agents Ravindran and Kor- investigate the effects of microbial phytase, organic negay, 1993, resulting in increased intestinal ab- acids at two doses, and their possible interactions on sorption of minerals Table 1. However, there is a the apparent total tract digestibility of some nutrients scarcity of experimental data on synergistic effects of and performance of grower pigs. microbial phytase in the presence of various acids. The efficacy of microbial phytase is found to be pH-dependent Simons et al., 1990. The highest activity was observed at two pH optima, i.e. 5.0 to

2. Materials and methods