Effect of particle size on physio-chemical properties of clinoptilolite as feed additive

As livestock feed additive, clinoptilolite can adsorb water and minerals in the digestive track, improving nutrient ingestion, reducing manure nutrient levels and lowering the environmental impact during land spreading. The particle size distribution of the zeolite powder can influence its effectiveness as feed additive: a finer size exposes more surfaces for greater adsorption while a coarser size can improve flowability and handling. This project measured the effect of the particle size distribution on the physico-chemical properties of zeolite powder used as a feed additive. In the laboratory, three zeolite (90%+ clinoptilolite) powders were prepared, each having a different particle size distributions (+250 mu m, -250 mu m or mixed). The effect of particle size on mineral exchange over time was tested by exposing duplicate samples to a 0.05 M NH4Cl solutions without and with a sodium phosphate buffer, at 22 degrees C and a pH of 7, for up to 3 days. The effect of acidic conditions found in the stomach of animals, was tested by exposing triplicate samples to a 0.05 M NH4Cl solution at 39 degrees C and a pH of 1.5, for 1 and 24 h. Both tests measured mineral and heavy metal desorption and ammonium adsorption. Using a shear box, the angle of friction of zeolite powder, against itself and galvanized steel sheeting, was measured for the three particle size distributions wetted to three humidity levels (0%, 5% and 10%). Under neutral pH, 22 degrees C and after one day, the +250 mu m samples adsorbed significantly more ammonium followed by the mixed samples and the -250 mu m samples (158, 143 and 78 C mol(+)/kg of zeolite, respectively). After 3 days, the mixed particle size adsorbed 5% less NH4+, compared to the others. Under a pH of 1.5 and at 39 degrees C, clinoptilolite samples adsorbed 17% less NH4+ than at neutral pH and room temperature, but released a low amount of heavy metals expected to have no impact on meat quality. Particle size distribution and moisture content did not significantly affect the friction between zeolite particles and therefore its flowability. Zeolite's high wall friction indicates funnel flow when being discharged from a storage bin. (c) 2006 Elsevier Inc. All rights reserved.