CHAPTER 3
 THE EFFECT OF IGF-1 SUPPLEMENTATION DURING IN VITRO BOVINE EMBRYO
 CULTURE ON SUBSEQUENT IN UTERO DEVELOPMENT TO DAY 14 OF GESTATION

 Introduction

 Early embryo development is coordinately regulated by several molecules secreted by the

maternal reproductive tract, and in some cases, the embryo itself. Among such molecules,

growth factors play an important role during preimplantation embryo development as they can

regulate mitogenesis, differentiation, metabolism and apoptosis (Kane et al., 1997; Diaz-Cueto

and Gerton, 2001; Hardy and Spanos, 2002). Despite their actions on early embryo

development, growth factors are not routinely included in embryo culture medium. This may

help to explain why embryos produced in vitro differ from their in vivo derived counterparts in

terms of metabolism (Khurana and Niemann, 2000), gene expression (Bertolini et al., 2002a;

Lazzari et al., 2002; Lonergan et al., 2003) and survival and development after transfer Farin and

Farin, 1995; Hasler et al., 1995; Drost et al., 1999; van Wagtendonk de-Leeuw et al., 1998,

2000).

 One growth factor that modifies embryonic physiology is insulin-like growth factor-1

(IGF-1). Addition of IGF-1 to culture medium can reduce the proportion of blastomeres that are

apoptotic (Byrne et al., 2002b; Sirisathien and Brackett, 2003), alter the abundance of some

developmentally important genes (Chapter 2), and increase cellular resistance to heat shock

(Jousan and Hansen, 2004, 2006). Also, IGF-1 can increase development of bovine embryos to

the blastocyst stage (Palma et al., 1997; Prelle et al., 2001; Byrne et al., 2002b; Makarevich and

Markkula, 2002; Moreira et al., 2002b; Block et al., 2003; Sirisathien et al., 2003b; Chapter 4; )

and increase blastocyst cell number (Byrne et al., 2002b; Moreira et al., 2002b; Sirisathien et al.,

2003b), although these effects are not always observed (Prelle et al., 2001; Chapter 2)