Effect of zinc supplemented as either an organic or an inorganic source and of microbial phytase on zinc and other minerals utilisation by weanling pigs

Thirty-six pigs, weaned at 28 days of age at an average body weight of 9.3 kg were used in a 19-day experiment to assess the bioavailability of Zn. A Zn–methionine complex with a molar methionine to Zn ratio of 2:1 was compared to Zn sulphate using a basal diet based on maize and soya bean meal supplemented with or without microbial phytase. Six experimental diets were formulated: the basal diet containing 32 mg Zn/kg, the basal diet supplemented with 20 mg Zn/kg from either sulphate (ZnSO4·7H2O) or the organic source (ZnOrg), and the same three previous diets supplemented with 1200 units (U) of microbial phytase per kilogram. The replacement of ZnSO4 by the organic source did not modify Zn retention, the concentration of Zn in bone and plasma or plasma alkaline phosphatase (AP) activity. The addition of microbial phytase considerably improved Zn bioavailability. Considering plasma AP activity, plasma Zn concentration, bone Zn concentration and Zn retention, the effect of adding 1200 U phytase/kg in the basal diet largely exceeded the effect of adding 20 mg Zn/kg. When phytase was added to the basal diet, these indicators of Zn status increased by 198, 269, 111 and 189%, respectively. Dietary phytase and Zn also modified the utilisation of Ca, P, Mg, Fe and Cu by piglets.