Microtechnology for hormone release in programmed animal reproduction

IGNACIO RINTOUL; ANDREA POPIELARZ; RICARDO GRAU

Rosario, Argentina

Simposio; V International Symposium of the International Commission of Agriculture and Biosystems Engineering; 2009

Instituto Nacional de Tecnologías Agropecuarias (INTA) y Universidad Nacional de Rosario

Selected for oral presentation. The control of the estrous cycle and ovulation in bovine breeders significantly improves the livestock cattle business. Controlled hormones release through loaded polymer matrices may control the estrous cycle and artificially induces ovulation. Hormones release from biocompatible, biodegradable and injectable microbeads is an interesting alternative to the existing intravaginal devices. Some advantages of this technology are the possibility to perform massive artificial insemination at very low product and labor costs, fast and economic genetic improvement, delivery, feeding and vaccination programming and optimization. In addition, storage, transportation, application and dosage of microbeads are easier than using intravaginal devices. Moreover, aseptic conditions and the actions for introduction, retire and final deposition of intravaginal devices can be avoided. Polyvinyl alcohol and dropping/gelling technique were selected as polymer matrix and microencapsulation technology, respectively. The effects of chemical composition and dropping/gelling conditions on the geometry and size distribution of microbeads and the dissolution - diffusion processes of progesterone through the matrix were studied. A procedure for microbeads production that maximizes the spherical shape, minimizes the polydispersity of results and regulates the pore size for hormone release was developed. Statistical methods were applied for experimental design. The dissolution of progesterone crystals and subsequent diffusion though the polymer matrix was regulated by reversible and irreversible crosslinking at the bulk and surface of the microbeads. Those polymeric crosslinking strategies allowed to produce microbeads loaded at 5, 20, 33 and 50 wt% of progesterone. The swelling and the dissolution of the polymer matrix could be varied between 50 to 90% and from 2 hours to 15 days, respectively. The rate of progesterone release could be also controlled. Microbeads loaded at 5wt% released progesterone (47mg/L h) at almost double rate than microbeads loaded at 50wt% (20 mg/L h). Finally, in-vitro results for hormone release are presented.