Preparation of altrenogest microcapsules suitable for field use

Altrenogest has been widely used in synchronization of estrus of pigs, but the existing preparations are inconvenient to use for they have to be administered individually. In order to simplify its administration and improve its stability, altrenogest microcapsules were successfully prepared by intra-liquid desiccation using ethyl cellulose as the capsule material in this study. The average particle size of the optimal altrenogest microcapslue was 76.8 µm which is less than 200 µm, so they are suitable for use in animal feed. The yields, encapsulation levels and drug loading capacity were 20 %, 84 % and 53 %, respectively. The drug release in artificial gastric juice was relatively rapid with 50 % in the first hour and 60 % by hour 2 and the release curve fit the power function equation. Extended exposure (10 d) to light (4500 lux), high humidity (95 %) and high temperature (60 ℃) did not change the concentration of encapsulated drug. The prepared altrenogest microcapsules are suitable as a feed additive and could simplify the use of this drug for the synchronization of estrus for swine production.