Editorial: International Cow Fertility Conference 'New Science - New Practices' in Westport, Ireland, in 2014.

As the world population continues to expand, the demand for increased global food production and particularly highquality protein will also increase. Ruminants have the unique ability to convert forage to high-quality milk and animal protein. Efficient reproduction is critical to sustainable dairy and beef cows systems and is therefore central to global food production as well as the economic success of individual dairy and beef farms. In Europe, milk quotas, which have been in place since the mid-eighties, will be abolished in 2015. While this affords opportunities to expand milk production, sustained expansion must be based on profitable, efficient, environmental and cow welfare-friendly systems. With the average dairy and beef cows surviving only three and five lactations, respectively, good cow fertility is a major challenge facing dairy and beef producers and animal health professionals. This proceedings of the International Cow Fertility Conference ‘New Science – New Practices’ has not only a major focus on accumulating the most up-to-date scientific information but also on translating this information into practice at herd level. Across the world milk production systems can be divided into two broad categories: (1) intensive confined systems largely based on total mixed rations (TMRs) using highyielding cows and largely all-year around calving systems and (2) pasture-based systems generally using lower yielding cows. Pasture-based systems have a prerequisite for compact calving close to the onset of the grazing season, which in turn demands high fertility. Examining long-term trends in cow fertility and milk yield it is tempting to conclude that it is impossible to achieve good levels of fertility in highproducing cows. Drackley and Cardoso (2014) concluded that the 6 to 8-week period centered on parturition is critical to the welfare and profitability of individual cows. Fertility of high-producing cows is compromised by a difficult transition from non-lactation to lactation. Deficiencies in either nutritional or non-nutritional management increase the risk of periparturient metabolic disorders and infectious diseases, which decrease subsequent fertility. A primary factor impeding fertility is the extent of negative energy balance (NEB) in the early postpartum period, which may inhibit timing of first ovulation, return to cyclicity and oocyte quality. In particular, pronounced NEB during the first 10 days to 2 weeks appears to be critical for later reproductive success. Butler (2014) outlines the unique nutritional challenges faced by pasture-based systems of milk production, particularly the challenge of achieving grass dry matter intakes to meet the combined demands of maintenance and genetic milk production. The roles of specific metabolic hormones and metabolites in regulating reproductive function and nutritional strategies to improve herd fertility are discussed. Achieving the appropriate body condition score (BCS) at parturition and minimising BCS loss between calving and onset of the breeding season are key goals for pasture-based dairy systems. A large number of systems studies have demonstrated that adding more supplementary concentrate feed will not improve fertility but increased milk production. As with pasture-based milk production systems, high levels of reproductive efficiency are also key drivers underpinning the biological and economic sustainability of beef cow enterprises. Diskin and Kenny (2014) shows that lifetime productivity of the beef bred female commences from the onset of puberty that dictates subsequent events including age at first calving, duration of the postpartum interval, conception and pregnancy rate and ultimately inter-calving intervals. In calved heifers and mature cows, the onset of postpartum cyclicity is a key event dictating the calving interval. Again, this is the product mainly of prepartum nutrition, manifested through BCS and the strength of the maternal bond between cow and calf. Following the initiation of postpartum cyclicity, conception and subsequent pregnancy rate is generally a function of bull fertility in natural service herds and heat detection and timing of insemination in herds bred through artificial insemination (AI). Knowledge of the endocrine and physiological regulation of the postpartum anoestrous interval has increased dramatically in the past 2 decades, particularly with the advent of ultrasound scanning. Crowe et al. (2014) conclude that the recommencement of dominant follicle growth occurs at Animal (2014), 8:s1, pp 1–4 © The Animal Consortium 2014 doi:10.1017/S1751731114000846 animal