As the world population continues to expand, the demand for increased global food production and particularly high-quality 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 high-yielding 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 high-producing cows. Drackley and Cardoso (Reference Drackley and Cardoso2014) 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 (Reference Butler2014) 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 (Reference Diskin and Kenny2014) 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. (Reference Crowe, Diskin and Williams2014) conclude that the recommencement of dominant follicle growth occurs at about the same time (~day 7) postpartum in both beef and dairy cows, irrespective of the duration of the subsequent postpartum anoestrous interval. The lack of ovulation of dominant follicles during the postpartum period is associated with infrequent LH pulses, with both maternal–offspring bonding and low BCS at calving being implicated as the main causes of delayed resumption of cyclicity in nursed beef cows. In dairy cows the normal pattern of early resumption of cyclicity is influenced by NEB, dystocia, retained placenta and uterine infections. First ovulation, in both dairy and beef cows, is generally silent and is generally (>70%) followed by a short inter-ovulatory interval. The key to optimising resumption of ovulation in both beef and dairy cows is appropriate pre-calving nutrition so that cows calve down in optimal BCS (2.75 to 3.0; scale 0 to 5) with postpartum body condition loss restricted to <0.5 BCS units.

Reproductive disease in the first 2 months after calving is very common and spans severe clinical illnesses to unapparent yet substantial impairment of fertility. LeBlanc (Reference LeBlanc2014) concludes that these conditions result from compromised immune response to bacterial infection or persistent inflammation that impairs reproductive function. The degree of mobilisation of fat and how effectively it is used is a risk factor for metabolic and infectious disease. Release of non-esterified fatty acids (NEFA) has direct effects on liver and immune function but also produces pro-inflammatory cytokines (tumour necrosis factor-α and interleukin-6), which contribute to systemic inflammation and to insulin resistance. Inflammatory disease of the reproductive tract can be a function of both local and systemic inflammatory stimuli and regulation as well as regulation of fat metabolism.

Following calving, the re-establishment of regular oestrous cycles, detection of oestrus and insemination, the establishment and maintenance of pregnancy are the key reproductive events in the annual cycle of the cow. Lonergan and Forde (Reference Lonergan and Forde2014) conclude that while there is substantial evidence for the oviduct having an influence on the quality of the developing embryo, evidence for a two-way dialogue is weak. However, successful growth and development of the post-hatching blastocyst and pregnancy establishment are a result of the two-way interaction between a competent embryo and a receptive uterine environment. Progesterone (P4) plays a key role in reproductive events associated with establishment and maintenance of pregnancy through its action on the uterus. Elevated concentrations of P4 in the immediate post-conception period have been associated with an advancement of conceptus elongation, an increase in interferon-τ production and, in some studies, higher pregnancy rates in cattle.

Wiltbank et al. (Reference Wiltbank, Souza, Carvalho, Cunha, Giordano, Fricke, Baez and Diskin2014) also discusses the pivotal role of P4 in the establishment of pregnancy. Circulating P4 is determined by a balance between P4 production, by the corpus luteum (CL) and P4 metabolism, primarily by the liver. The volume of luteal tissue and number and function of large luteal cells are primary factors determining P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in high-producing dairy cattle. During timed AI protocols, elevations in P4 are achieved by increasing number of CL by creating accessory CL or by supplementation with exogenous P4. Elevating P4 before timed AI generally decreases double ovulation and increases fertility to the timed AI. Near the time of AI, slight elevations in circulating P4, possibly due to inadequate luteal lysis, can dramatically reduce fertility. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. A recent meta-analysis and manipulative study indicated small fertility benefits (3% to 3.5%), mostly in primiparous cows following P4 supplementation.

Lucy et al. (Reference Lucy, Butler and Garverick2014) reviews endocrine and metabolic mechanisms linking early embryonic and foetal development with parturition, uterine involution and lactation in dairy cows. The competing processes of milk production and restoration of reproductive function can be at odds, particularly if the unique homeorhetic processes that typify early lactation become imbalanced and the cow experiences metabolic disease. Glucose is an important molecule involved in the process, because it is a major component of cow’s milk and also a molecule that coordinates homeorhetic mechanisms that can impinge upon postpartum uterine health and the subsequent establishment of pregnancy. Associated metabolites such as NEFA and β-hydroxy butyrate as well as insulin and IGF1 may also play a role in controlling tissue function. The first 30 days postpartum may be the most critical in terms of the impact that metabolites and metabolic hormones have on reproduction. Circulating NEFA leaves a metabolic imprint on the composition of the oocyte and function of follicular cells that appears to have long-term consequences. The slow rate of embryonic or foetal growth in lactating cows with low blood concentrations of P4 and glucose may be an important mechanism explaining pregnancy loss.

The rearing of replacement heifers is a key component of profitable dairy and beef cow operations. Wathes et al. (Reference Wathes, Pollott, Johnson, Richardson and Cooke2014) discuss key influences of heifer-rearing strategies on later performance including future fertility and longevity. Cattle reach puberty at a fairly consistent, but breed-dependent proportion of mature body weight. In general, an average daily gain of around 0.75 kg/day seems optimal for dairy heifers, with lower rates delaying puberty. Major periods of nutritional deficiency and/or severe calfhood disease will compromise development with long-term adverse consequences. First lactation milk yield may be slightly lower in younger calving cows but lifetime production is higher as such and animals usually have good fertility and survive longer. There is now extensive evidence that as long as age at first calving is >23 months, then future performance is not adversely influenced. On the other hand, delayed first calving (>30 months) is associated with poor survival.

In recent years, evidence has emerged that some of the observed decline in dairy cow fertility can be reversed by including fertility traits in breeding objectives. Berry et al. (Reference Berry, Wall and Pryce2014) points out that the required emphasis on reproductive traits within a breeding index to halt deterioration will vary, based on the underlying assumptions and the impact on genetic gain for milk production. Advancements in genomic technologies can aid in increasing the accuracy of selection, especially for reproductive traits and thus genetic gain. Elucidation of the underlying genomic mechanisms for reproduction could also aid in resolving genetic antagonisms.

In recent years, there has been renewed interest in crossbreeding of dairy cattle to address declining fertility, health and survival issues and capitalise on heterosis. Buckley et al. (Reference Buckley, Lopez-Villalobos and Heins2014) clearly illustrate, using a range of dairy breeds and in both grass-based and high input confinement production environments, that the net effect of crossbreeding is more profitable performance owing to lower replacement costs and higher herd productivity.

Detection of oestrus plays an important role in the reproductive management programme of most dairy herd. Fricke et al. (Reference Fricke, Carvalho, Giordano, Valenza, Lopes and Amundson2014) discusses the primary and secondary signs of oestrus and next generation electronic systems that continuously monitor physical activity to predict timing of AI. A variety of management and physiologic challenges inhibit detection of behavioural oestrus on farms, but the prevalence of anovular cows near the end of the voluntary waiting period is particularly problematic. In two experiments on a large commercial dairy in the United States, an activity monitoring system detected only 70% of lactating Holstein cows with increased activity with the remainder of cows being anovular or ovulating in the absence of activity. A combined approach in which AI, based on activity, is followed by submission of cows not detected with activity to timed AI after synchronisation of ovulation may be an effective strategy for submission of cows to first AI.

Bó and Baruselli (Reference Bó and Baruselli2014) report on the increased use of AI in beef herds in Brazil following the adoption of fixed-time AI (FTAI) protocols without oestrous detection. These FTAI protocols facilitate the application of AI in larger, extensively managed, herds and especially in suckled beef cows instead of restricting the breeding programmes to the heifers. FTAI treatments are widely used in South America, with about 3 and 8 million cows inseminated in the last season in Argentina and Brazil, respectively. The review outlines treatments available and some of the factors that may affect pregnancy rates in beef cattle.

Bisinotto et al. (Reference Bisinotto, Ribeiro and Santos2014) discuss recent advances in synchronisation of ovulation protocols for dairy cows that now permit AI at a pre-established time with acceptable fertility, which have become an integral component of breeding management in multiple production systems. The better understanding of ovarian biology of the dairy cow combined with improved control of both follicle growth and luteal lifespan has resulted in refinement of these programmes providing unique opportunities to manipulate follicle development, improve oocyte quality and enhance embryo survival. Ovsynch-type protocols requires that some fundamental physiological principles are respected, including: induction of ovulation to synchronise follicle growth in the first 2 days of the programmes such that a young antral follicle is recruited; maintenance of high concentrations of P4 during the development of the ovulatory follicle, effective lysis of the CL to result in very low concentration of P4 at AI; and having a healthy pre-ovulatory follicle of moderate diameter that is highly oestrogenic and responsive to gonadotropins to synchronously ovulate 12 to 18 h after AI.

Seidel (Reference Seidel2014) highlights the fact that incremental improvements in flow cytometer/cell-sorting procedures resulting in faster speeds of sexing sperm and improved fertility. The fertility of sexed semen is unlikely to exceed 90% of unsexed semen for most situations for several years. Longer term prospects are encouraging; since sperm are evaluated one at a time, some defective sperm are discarded during sexing, and this may become more sophisticated, thus increasing fertility.

Butler and Hutchinson (Reference Butler and Hutchinson2014) present preliminary Irish results from a large-scale 2013 field trial, which suggests that significant improvements in the performance of sexed semen have been made, with conception rates of 87% of those achieved with conventional semen. The improved fertility of a sexed semen delivering a 90% gender bias has considerable implications for the future of breeding management in pasture-based dairy production systems. Sexed semen may facilitate faster, more profitable dairy herd expansion by increasing the number of dairy heifer replacements born. Biosecurity can be improved by maintaining a closed herd during the period of herd expansion. In a non-expansion scenario, sexed semen may be used to increase the value of beef output from the dairy herd though market prices for sexed semen will be important.

McGetrick et al. (Reference McGetrick, Reid and Carrington2014) discuss the potential to develop new improved semen diluents. This is based on the results of recent studies of bovine sperm as they progress towards maturity, capacitation and fertilisation. This could allow the use of reduced numbers of sperm per insemination, enhance the use of high genetic merit bulls, and facilitate the greater application of fresh and sex-sorted semen.

Smith et al. (Reference Smith, Oultram and Dobson2014) reviewed the use of dairy herd records, metabolic profiles and ultrasonography at veterinary fertility examinations to monitor and manage dairy herd fertility. The selection of timely key performance indicators that monitor specific events in the postpartum and service periods is vital to correctly identify problems, their potential causes and rectification. Cumulative sum charts are the timeliest monitors of oestrous detection, insemination outcome and relationship between postpartum events and fertility, with the point of inflection indicating when a change took place. Metabolic profiles and milk constituent data allow monitoring of nutritional adequacy and developments to offer new possibilities of on-farm systems for regular measurements of milk constituents (including progesterone) and energy status. Examination of the reproductive tract can be used to indicate individual and herd fertility status but the currently available detail is under used. Recent advances in ultrasonography can improve the diagnosis of reproductive tract pathophysiology still further, but the clinical use of these methods needs further evaluation.

McDougall et al. (Reference McDougall, Heuer, Morton and Brownlie2014) describes the outcome and evaluation of a planned animal health approach to dairy herd fertility following a controlled randomised study. The programme tested (InCalf) used a management cycle approach, that is, assessment of current performance against goals and objectives, identification of areas for improvement, development and implementation of a plan and review. Such an approach allowed for the identification of the economically important areas for improvement. Success of this approach provides industry leaders and service providers with confidence that if appropriately implemented, such planned animal health services have positive effects on herd performance.

Cabrera (Reference Cabrera2014) reviews the latest findings in dairy cattle reproductive economics with an emphasis on high-yielding, confined TMR systems. Dairy cows on confined systems improve their profitability as they improve reproductive performance due to higher milk production, more calves, lower replacement costs and lower relative reproduction costs. Most farms rely on a combination of oestrous detection and synchronisation/ovulation control programme, which appears to be economically effective. Use of alternative pregnancy diagnosis such as earlier blood or milk tests could be economically feasible if accurate. Opportunities for cow-level reproductive management exist within herd-defined reproductive programmes.

Shalloo et al. (Reference Shalloo, Cromie and McHugh2014) identifies significant costs associated with infertility in pasture-based dairy herds. A number of key variables associated with infertility were related to 6-week calving rate for both cows and heifers. These variables include: increase culling costs, the effects of sub-optimum calving dates, increased labour costs, and increased AI and intervention costs. A stochastic budgetary simulation model was used to simulate the overall economic effect at farm level. The costs associated with increased culling, calving date slippage, increased AI and intervention costs, as well as, increased labour costs (10%) were quantified as €13.2, €3.51, €4.56 and €29.6/cow per year. A 1% change in 6-week calving rate was associated with €7.46/annum for cows and €2.60/annum for heifers.