Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy EFFECT OF INSULIN-LIKE GROWTH FACTOR-1 ON DEVELOPMENT AND POST- TRANSFER SURVIVAL OF BOVINE EMBRYOS PRODUCED IN VITRO By Jeremy Block May 2007 Chair: Peter J. Hansen Major: Animal Molecular and Cellular Biology In vitro embryo production has great potential as a tool for optimizing genetic selection, improving fertility and enhancing breeding schemes in beef and dairy production systems. Despite its potential, the use of in vitro embryo production is limited by several technical problems, including reduced embryo survival following transfer. One approach for improving survival post-transfer of in vitro produced embryos is to modify culture media with growth factors. Recently, the addition of IGF-1 to bovine embryo culture increased pregnancy and calving rates in heat-stressed, lactating dairy cows. A series of experiments was conducted to determine how IGF-1 promotes the survival of in vitro produced bovine embryos after transfer. The production of embryos in vitro can alter several aspects of embryo physiology, including gene expression. An experiment was conducted to determine whether addition of IGF- 1 to embryo culture could alter the abundance of several developmentally important gene transcripts. Treatment of embryos with IGF-1 increased the relative abundance of transcripts for Na/K, DcII, Bax, and IGFBP3, while decreasing the abundance of Hsp70 and IGF-1R transcripts. In contrast, IGF-1 supplementation had no effect on blastocyst cell number, cell allocation, or the proportion of apoptotic blastomeres.