In vitro fertilisation (IVF) can be used to improve herd genetics by combining gametes from superior animals, resulting in significant commercial returns for the cattle industry. Adoption of IVF in breeding programs has been limited as pregnancy rates are lower compared to traditional technologies such as artificial insemination and embryo transfer. Improving IVF culture conditions to support the metabolic activity of oocytes and spermatozoa will increase the proportion of viable preimplantation embryos. It has been demonstrated previously that the combination of glutamine (Gln), proline (Pro) and Isoleucine (Ile) support bovine oocyte maturation, whilst Cystine (Cys2) caused a significant reduction in nuclear maturation rates. These amino acids (AAs) could also affect oocytes and/or spermatozoa during fertilisation. Therefore, the aim of this study was to investigate the effects of in vitro supplementation of Gln, Pro, Ile and Cys2 during fertilisation on the formation of 2 pronuclei (2PN).
Bovine oocytes matured in TCM199 were fertilised in FERT-TALP supplemented with either 1 mM Gln, 0.4 mM Pro, 0.28 mM Ile or 0.07 mM Cys2 for 20 h. The %2PN for oocytes supplemented with 1 mM Gln (56.5 ± 2.4), 0.4 mM Pro (57.7 ± 6.6), 0.28 mM Ile (60.3 ± 3.8) was not significantly different to those in FT alone (60.9 ± 2.0). However, the %2PN was significantly reduced with the addition of Cys2 (42.5 ± 1.1) compared to FT alone (P≤0.05). Our results suggest that the addition of Gln, Pro or Ile individually, during IVF does not increase the %2PN, though further investigation is required to determine whether supplementation with these AAs during fertilisation affects embryo development. Furthermore, Cys2, which is often used in multiple culture media formulations, caused a reduction in the proportion of zygotes following IVF, and these deleterious effects on fertilisation are yet to be determined.