Using basic approaches to address applied problems in dairy reproduction.

Poor reproductive efficiency is a worldwide problem affecting the dairy industry. There is substantial evidence for an association between high milk production and lower conception rates observed in cows compared to heifers. However, whether the decline in fertility is due directly to the level of milk production or other factors associated with lactation is unclear. There are various checkpoints along the developmental axis which could, in part, contribute to reduced fertility including suboptimal follicle development associated with poor oestrus exhibition, suboptimal oocyte quality, altered sperm transport and fertilization and/or a suboptimal reproductive tract environment incapable of supporting normal embryo development. The challenge is deciphering where the major problems lie. Evidence for the relative contributions of oocyte quality, embryo quality and the reproductive tract environment is discussed in this paper.