apoptotic actions of IGF-1 are not required to for IGF-1 to block effects of heat shock on

development to the blastocyst stage after heat shock (Jousan and Hansen, 2007).

 Hernandez and Fonseca (2002) were the first researchers to test whether addition of IGF-1

to embryo culture could affect subsequent embryo survival following transfer to recipients.

Their results indicated that there was no effect of IGF-1 on the survival of frozen-thawed in vitro

produced embryos. However, only 10 recipients were used per treatment group and these low

numbers severely limit the conclusions that can be derived from this study. In a more recent

field trial (Block et al., 2003) in which more than 200 heat-stressed lactating Holstein cows were

used as recipients, IGF-1 treatment increased pregnancy rates at day 53 and day 81. In addition,

recipients that received IGF-1 treated embryos had an increased proportion of viable calves and

IGF-1 had no effect on calf birth weights or sex ratio.

 Questions for Dissertation

 While supplementation of embryo culture medium with IGF-1 can increase pregnancy and

calving rates following the transfer of embryos to heat-stressed, lactating dairy cows, several

questions remain unanswered: The first is what actions does IGF-1 exert during embryo

development in vitro that allows for increased embryo survival after transfer? As described

above, it is well recognized that IGF-1 can have many effect on embryo development in vitro.

However, despite all of the research related to the effects of IGF-1 on embryo development, cell

number and apoptosis, no study has analyzed the effects of IGF-1 on gene expression in bovine

blastocysts. Since culture conditions can affect gene expression in bovine embryos, it may be

possible that IGF-1 acts to improve embryo survival by altering the abundance of certain genes.

The second question is what actions does IGF-1 have on post-transfer embryo development that

allow for improved embryo survival? It is hypothesized that one action of IGF-1 is to increase

concepts length and IFN-T in the uterus around the time of maternal recognition of pregnancy.