The silvopastoral system (SPS) has been suggested to ensure sustainability in animal production systems in tropical ecosystems. The objective of this study was to evaluate pasture characteristics, herbage intake, grazing activity and milk yield of Holstein×Zebu cows managed in two grazing systems (treatments): SPS dominated by a graminaceous forage (Brachiaria decumbens) intercropped with different leguminous herbaceous forages (Stylosanthes spp., Pueraria phaseoloides and Calopogonium mucunoides) and legume trees (Acacia mangium, Gliricidia sepium and Leucaena leucocephala), and open pasture (OP) of B. decumbens intercropped only with Stylosanthes spp. Pastures were managed according to the rules for organic cattle production. The study was carried out by following a switch back format with 12 cows, 6 for each treatment, over 3 experimental years. Herbage mass was similar (P>0.05) for both treatments, supporting an average stocking rate of 1.23 AU/ha. Daily dry matter intake did not vary (P>0.05) between treatments (average of 11.3±1.02 kg/cow per day, corresponding to 2.23±0.2% BW). Milk yield was higher (P<0.05; 10.4±0.06 kg/cow per day) in the SPS than in the OP (9.5±0.06 kg/cow per day) during the 1st year, but did not significantly differ (P>0.05) in subsequent years. The highest (P<0.05) values for herbage mass and milk yield were observed during the 3rd year. In the SPS, with moderate shade (19% shade relative to a full-sun condition), the grass CP was higher (P<0.05) than in the OP, although the NDF content and digestibility coefficient were not modified. The animals spent more time (P<0.05) idling in the SPS than in OP. The higher legume proportion in the SPS was associated with the higher CP level in B. decumbens relative to the OP, which could explain the better (P<0.05) performance of the cows in silvopastoral areas during the 1st year. However, during the 2nd and 3rd years, similarities in the legume percentages of both systems resulted in similar (P>0.05) milk yields. Low persistence of Stylosanthes guianensis was observed over the experimental period, indicating that the persistence of forage legumes under grazing could be improved using adapted cultivars that have higher annual seed production. The SPS and a diversified botanical composition of the pasture using legume species mixed with grasses are recommended for organic milk production.

A reproductively efficient beef cow herd is fundamental to meeting the protein and specifically, red meat demand of an ever increasing global population. However, attaining a high level of reproductive efficiency is underpinned by producers being cognisant of and achieving many key targets throughout the production cycle and requires significant technical competency. The lifetime productivity of the beef bred female commences from the onset of puberty and will be dictated by subsequent critical events including age at first calving, duration of the postpartum interval for each successive calving, conception and pregnancy rate and ultimately manifested as length of intercalving intervals and number of calves weaned over her lifetime. Puberty in heifers is a consequence of the interactive effects of genetics and both pre- and post-weaning nutrition. Early onset of puberty is essential to achieving the first main reproductive target for beef cow herds; first calving at 2 years of age. In calved heifers and mature cows, the onset of ovarian activity, postpartum is a key event dictating the calving interval. Again, this will be the product mainly of prepartum nutrition, manifested through body condition and the strength of the maternal bond between cow and calf, though there is increasing evidence of a modest genetic influence on this trait. Following the initiation of postpartum ovarian 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. Cows and heifers should be maintained on a steady plane of nutrition during the breeding season, but the contribution of significant excesses or deficiencies of nutrients including protein and trace elements is likely to be minor where adequate pasture is available. While, increased efforts are being made internationally to genetically identify and select for more reproductively efficient beef cows, this is a more long-term strategy and will not replace the need for a high level of technical efficiency and management practice at farm level.

Excellent reproductive performance in both males and females is fundamental to profitable dairy and beef production systems. In this review we undertook a meta-analysis of genetic parameters for female reproductive performance across 55 dairy studies or populations and 12 beef studies or populations as well as across 28 different studies or populations for male reproductive performance. A plethora of reproductive phenotypes exist in dairy and beef cattle and a meta-analysis of the literature suggests that most of the female reproductive traits in dairy and beef cattle tend to be lowly heritable (0.02 to 0.04). Reproductive-related phenotypes in male animals (e.g. semen quality) tend to be more heritable than female reproductive phenotypes with mean heritability estimates of between 0.05 and 0.22 for semen-related traits with the exception of scrotal circumference (0.42) and field non-return rate (0.001). The low heritability of reproductive traits, in females in particular, does not however imply that genetic selection cannot alter phenotypic performance as evidenced by the decline until recently in dairy cow reproductive performance attributable in part to aggressive selection for increased milk production. Moreover, the antagonistic genetic correlations among reproductive traits and both milk (dairy cattle) and meat (beef cattle) yield is not unity thereby implying that simultaneous genetic selection for both increased (milk and meat) yield and reproductive performance is indeed possible. The required emphasis on reproductive traits within a breeding goal to halt deterioration will vary based on the underlying assumptions and is discussed using examples for Ireland, the United Kingdom and Australia as well as quantifying the impact on genetic gain for milk production. Advancements in genomic technologies can aid in increasing the accuracy of selection for especially reproductive traits and thus genetic gain. Elucidation of the underlying genomic mechanisms for reproduction could also aid in resolving genetic antagonisms. Past breeding programmes have contributed to the deterioration in reproductive performance of dairy and beef cattle. The tools now exist, however, to reverse the genetic trends in reproductive performance underlying the observed phenotypic trends.

There is strong evidence that the gonads modulate the hypothalamic–pituitary–adrenal axis. To investigate these sex differences at the adrenal glands of sheep we compared the cortisol response to ACTH (experiment 1) and measured the relative expression of oestrogen receptor alpha (ERS1), androgen receptor (AR), melanocortin 2 receptor (MC2R) and steroid acute regulatory protein (STAR) mRNA in adrenal glands (experiment 2) of gonadectomised rams and ewes either with or without sex steroid replacement. In experiment 1 six castrated adult rams and four ovariectomised adult ewes were used in two ACTH trials. On each trial blood samples were taken every 15 min for 4 h through an indwelling jugular catheter and each animal received 0.5 mg of an ACTH analogue i.v., immediately after the sample at 1 h from the beginning of the trial. Four days after the first trial the males received 100 mg of Testosterone Cyclopentilpropionate (TC) i.m. and the females received 2.5 mg of Oestradiol Benzoate (EB) i.m. At 72 h after TC or EB administration the second trial was performed. In experiment 2 the adrenal glands were obtained from gonadectomised adult rams (n=8) and adult ewes (n=8). Four rams received 100 mg of TC i.m. and four females received 0.5 mg of EB i.m. Blood samples were taken at 0, 12, 24, 48 and 72 h relative to steroid replacement and the animals were thereafter slaughtered. Cortisol, testosterone and 17β-oestradiol were determined by radioimmunoanalysis. The transcripts of ERS1, AR, MC2R and STAR were determined by real-time reverse transcription PCR in adrenal tissue. Cortisol secretion was higher in female sheep than in male sheep, and higher in EB-treated than non-treated ewes. No difference in cortisol secretion was observed between TC-treated and non-treated rams. Gonadectomised rams treated with TC presented greater AR mRNA and MC2R mRNA expression than males without the steroid replacement. Gonadectomised ewes treated with EB tended to present lower AR mRNA than the ones without steroid replacement. Gonadectomised rams with TC also had greater AR mRNA, ERS1 mRNA and MC2R mRNA expression than ewes treated with EB. The relative amount of STAR transcript was not different among the different groups. The results confirm sex differences in ACTH-induced cortisol secretion in sheep, as well as in the expression of the receptor proteins for both 17β-oestradiol and testosterone in the sheep adrenal gland. However, the underlying mechanisms for sex steroid modulation remain unresolved.

The objective of this study was to define different terminal sire flock environments, based on a range of environmental factors, and then investigate the presence of genotype by environment interactions (G×E) between the environments identified. Data from 79 different terminal sire flocks (40 Texel, 21 Charollais and 18 Suffolk), were analysed using principal coordinate and non-hierarchical cluster analyses, the results of which identified three distinct environmental cluster groups. The type of grazing, climatic conditions and the use of vitamins and mineral supplements were found to be the most important factors in the clustering of flocks. The presence of G×E was then investigated using data from the Charollais flocks only. Performance data were collected for 12 181 lambs, between 1990 and 2010, sired by 515 different sires. Fifty six of the sires had offspring in at least two of the three different cluster groups and pedigree information was available for a total of 161 431 animals. Traits studied were the 21-week old weight (21WT), ultrasound muscle depth (UMD) and log transformed backfat depth (LogUFD). Heritabilities estimated for each cluster, for each trait, ranged from 0.32 to 0.45. Genetic correlations estimated between Cluster 1 and Cluster 2 were all found to be significantly lower than unity, indicating the presence of G×E. They were 0.31 (±0.17), 0.68 (±0.14) and 0.18 (±0.21) for 21WT, UMD and LogUFD, respectively. Evidence of sires re-ranking across clusters was also observed. Providing a suitable strategy can be identified, there is potential for the optimisation of future breeding programmes, by taking into account the G×E observed. This would enable farmers to identify and select animals with an increased knowledge as to how they will perform in their specific farm environment thus reducing any unexpected differences in performance.

The objective of the present study was to compare genetic gain and inbreeding coefficients of dairy cattle in organic breeding program designs by applying stochastic simulations. Evaluated breeding strategies were: (i) selecting bulls from conventional breeding programs, and taking into account genotype by environment (G×E) interactions, (ii) selecting genotyped bulls within the organic environment for artificial insemination (AI) programs and (iii) selecting genotyped natural service bulls within organic herds. The simulated conventional population comprised 148 800 cows from 2976 herds with an average herd size of 50 cows per herd, and 1200 cows were assigned to 60 organic herds. In a young bull program, selection criteria of young bulls in both production systems (conventional and organic) were either ‘conventional’ estimated breeding values (EBV) or genomic estimated breeding values (GEBV) for two traits with low (h 2=0.05) and moderate heritability (h 2=0.30). GEBV were calculated for different accuracies (r mg), and G×E interactions were considered by modifying originally simulated true breeding values in the range from r g=0.5 to 1.0. For both traits (h 2=0.05 and 0.30) and r mg⩾0.8, genomic selection of bulls directly in the organic population and using selected bulls via AI revealed higher genetic gain than selecting young bulls in the larger conventional population based on EBV; also without the existence of G×E interactions. Only for pronounced G×E interactions (r g=0.5), and for highly accurate GEBV for natural service bulls (r mg>0.9), results suggests the use of genotyped organic natural service bulls instead of implementing an AI program. Inbreeding coefficients of selected bulls and their offspring were generally lower when basing selection decisions for young bulls on GEBV compared with selection strategies based on pedigree indices.

The discovery of progesterone (P4) and elucidation of the mechanisms of P4 action have an important place in the history of endocrinology and reproduction. Circulating P4 concentration is determined by a balance between P4 production, primarily 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 dairy cattle. During timed artificial insemination (AI) protocols, elevations in P4 are achieved by increasing number of CL by creating accessory CL or by supplementation with exogenous P4. Dietary manipulations can also alter circulating P4, although practical methods to apply these techniques have not yet been reported. Elevating P4 before the 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 regression, can dramatically reduce fertility. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI. Our recent meta-analysis and manipulative study indicated small fertility benefits (3% to 3.5%) mostly in primiparous cows. Thus, previous research has provided substantial insight into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve reproductive success.

The rearing period has a key influence on the later performance of cattle, affecting future fertility and longevity. Producers usually aim to breed replacement heifers by 15 months to calve at 24 months. An age at first calving (AFC) close to 2 years (23 to 25 months) is optimum for economic performance as it minimises the non-productive period and maintains a seasonal calving pattern. This is rarely achieved in either dairy or beef herds, with average AFC for dairy herds usually between 26 and 30 months. Maintaining a low AFC requires good heifer management with adequate growth to ensure an appropriate BW and frame size at calving. Puberty should occur at least 6 weeks before the target breeding age to enable animals to undergo oestrous cycles before mating. Cattle reach puberty at a fairly consistent, but breed-dependent, proportion of mature BW. Heifer fertility is a critical component of AFC. In US Holsteins the conception rate peaked at 57% at 15 to 16 months, declining in older heifers. Wide variations in growth rates on the same farm often lead to some animals having delayed first breeding and/or conception. Oestrous synchronisation regimes and sexed semen can both be used but unless heifers have been previously well-managed the success rates may be unacceptably low. Altering the nutritional input above or below those needed for maintenance at any stage from birth to first calving clearly alters the average daily gain (ADG) in weight. In general an ADG of around 0.75 kg/day seems optimal for dairy heifers, with lower rates delaying puberty and AFC. There is some scope to vary ADG at different ages providing animals reach an adequate size by calving. Major periods of nutritional deficiency and/or severe calfhood disease will, however, compromise development with long-term adverse consequences. Infectious disease can also cause pregnancy loss/abortion. First lactation milk yield may be slightly lower in younger calving cows but lifetime production is higher as such animals usually have good fertility and survive longer. There is now extensive evidence that as long as the AFC is >23 months then future performance is not adversely influenced. On the other hand, delayed first calving >30 months is associated with poor survival. Underfeeding of young heifers reduces their milk production potential and is a greater problem than overfeeding. Farmers are more likely to meet the optimum AFC target of 23 to 25 months if they monitor growth rates and adjust feed accordingly.

Livestock breed-related public good functions are often used to justify support for endangered breed conservation despite the fact that little is known about such non-market values. We show how stated preference techniques can be used to assess the non-market values that people place on livestock breeds. Through the application of a case study choice experiment survey in Zamora province, Spain, the total economic value (TEV) of the threatened Alistana–Sanabresa (AS) cattle breed was investigated. An analysis of the relative importance of the non-market components of its TEV and an assessment of the socio-economic variables that influence people’s valuation of such components is used to inform conservation strategy design. Overall, the findings reveal that the AS breed had significant non-market values associated with it and that the value that respondents placed on each specific public good function also varied significantly. Functions related with indirect use cultural and existence values were much more highly valued than landscape maintenance values. These high cultural and existence values (totalling over 80% of TEV) suggest that an AS in situ conservation strategy will be required to secure such values. As part of such a strategy, incentive mechanisms will be needed to permit farmers to capture some of these public good values and thus be able to afford to maintain breed population numbers at socially desirable levels. One such mechanism could be related to the development of breed-related agritourism initiatives, with a view to enhancing private good values and providing an important addition to continued direct support. Where linked with cultural dimensions, niche product market development, including through improving AS breed-related product quality and brand recognition may also have a role to play as part of such an overall conservation and use strategy. We conclude that livestock breed conservation strategies with the highest potential to maximise societal welfare would be those that secure the breed-related functions that people value most, with appropriate in situ conservation interventions and strategies being identified accordingly.

The metabolic state of pregnant mammals influences the offspring’s development and risk of metabolic disease in postnatal life. The metabolic state in a lactating dairy cow differs immensely from that in a non-lactating heifer around the time of conception, but consequences for their calves are poorly understood. The hypothesis of this study was that differences in metabolic state between non-lactating heifers and lactating cows during early pregnancy would affect insulin-dependent glucose metabolism and development in their neonatal calves. Using a mixed linear model, concentrations of glucose, IGF-I and non-esterified fatty acids (NEFAs) were compared between 13 non-lactating heifers and 16 high-yielding dairy cows in repeated blood samples obtained during the 1st month after successful insemination. Calves born from these dams were weighed and measured at birth, and subjected to intravenous glucose and insulin challenges between 7 and 14 days of age. Eight estimators of insulin-dependent glucose metabolism were determined: glucose and insulin peak concentration, area under the curve and elimination rate after glucose challenge, glucose reduction rate after insulin challenge, and quantitative insulin sensitivity check index. Effects of dam parity and calf sex on the metabolic and developmental traits were analysed in a two-way ANOVA. Compared with heifers, cows displayed lower glucose and IGF-I and higher NEFA concentrations during the 1st month after conception. However, these differences did not affect developmental traits and glucose homeostasis in their calves: birth weight, withers height, heart girth, and responses to glucose and insulin challenges in the calves were unaffected by their dam’s parity. In conclusion, differences in the metabolic state of heifers and cows during early gestation under field conditions could not be related to their offspring’s development and glucose homeostasis.

The evolution of hyper-prolific pig breeds has led to a higher within-litter variation in birth weight and in BW gain during the nursery phase. Based on an algorithm developed in previous research, two populations from a pool of 368 clinically healthy piglets at 6 weeks of age were selected: a low (LP) and a high (HP) performing population and their development was monitored until the end of the nursery phase (10 weeks of age). To understand the cause of the variation in growth between these populations we characterized the LP and HP piglets in terms of body morphology, behaviour, voluntary feed intake, BW gain, and apparent total tract and ileal nutrient digestibility. Piglets were housed individually and were fed a highly digestible diet. At selection, 6 weeks of age, the BW of LP and HP piglets were 6.8±0.1 and 12.2±0.1 kg, respectively. Compared with the LP piglets the HP piglets grew faster (203 g/day), ate more (275 g/day) from 6 to 10 weeks of age and were heavier at 10 weeks (30.0 v. 18.8 kg, all P<0.01). Yet, the differences in average daily gain and average daily feed intake disappeared when compared per kg BW0.75. Assuming similar maintenance requirements per kg BW0.75 the efficiency of feed utilization above maintenance was 0.1 g/g lower for the LP piglets (P=0.09).The gain : feed ratio was similar for both groups. LP piglets tended to take more time to touch a novel object (P=0.10), and spent more time eating (P<0.05). At 10 weeks, LP piglets had a higher body length and head circumference relative to BW (P<0.01). Relative to BW, LP had a 21% higher small intestine weight; 36% longer length, and relative to average FI, the small intestinal weight was 4 g/kg higher (both P=<0.01). Apparent total tract and ileal dry matter, N and gross energy digestibility were similar between groups (P>0.10). We concluded that the low performance of the LP piglets was due to their inability to engage compensatory gain or compensatory feed intake as efficiency of nutrient utilization and feed intake per kg BW0.75 was unaffected. LP piglets tend to be more fearful towards novel objects. The morphological comparisons, increased body length and head circumference relative to BW imply that LP piglets have an increased priority for skeletal growth.

This in vitro study aimed at understanding how abiotic, that is chemical and electrochemical potentials, and biotic factors combine to impact the outputs of rumen volatile fatty acid (VFA). Using a 48-run design optimized by means of an exchange algorithm, the curvilinear effects of pH, Eh and partial pressure of dihydrogen (H2) on fermentation yields were investigated in 6-h batch cultures of mixed rumen microbes, fed on glucose so as to bypass the enzymatic hydrolysis and conversion steps preceding the glycolytic pathway. The role played by rumen microbiota in the expression of these effects was explored by testing three inocula grown on feeds supplying a microflora adapted to fibre, slowly degradable or readily degradable starch as the dominant dietary polysaccharide. Data were fitted to 2nd-order polynomial models. In fibre-adapted cultures, the yields of major VFA were mainly influenced by pH and H2 partial pressure, in opposite ways. In wheat grain-adapted cultures, the VFA yields underwent the opposite influences of pH, in a curvilinear way for propionate, and Eh since acetate production yield was not significantly modified by any factor. In maize grain-adapted cultures, acetate production yield was not modified by any factor but H2 in a quadratic way when the production yields of higher VFA underwent opposite influences of pH and Eh. In conclusion, the effects of environmental factors were dependent on the nature of the inoculum, a major source of variation, and more particularly on its adaptation to high- or low-fibre diets. These effects were loosely interrelated, the pH being the most active factor before the Eh and H2 partial pressure.

Milk and milk solids production per cow is increasing annually in dairy systems. Peak milk production is in early lactation when the uterus and ovary are recovering from the previous pregnancy. The competing processes of milk production and restoration of reproductive function can be at odds, particularly if unique homeorhetic mechanisms that typify early lactation become imbalanced and cows experience metabolic disease. Homeorhesis leads to an increase in the synthesis of glucose that is irreversibly lost to milk lactose. Irreversible loss of glucose during lactation can invoke an endocrine and metabolic state that impinges upon postpartum uterine health, oestrous cyclicity and subsequent establishment of pregnancy. The first 30 days postpartum may be most critical in terms of the impact that metabolites and metabolic hormones have on reproduction. Depressed immune function caused in part by the postpartum metabolic profile leads to a failure in uterine involution and uterine disease. Oestrous cyclicity (interval to first ovulation and subsequent periodicity) is affected by the same hormones and metabolites that control postpartum immune function. Slower growth of the embryo or foetus perhaps explained by the unique metabolic profile during lactation may predispose cows to pregnancy loss. Understanding homeorhetic mechanisms that involve glucose and collectively affect postpartum uterine health, oestrous cyclicity and the establishment of pregnancy should lead to methods to improve postpartum fertility in dairy cows.

Despite the widespread adoption of hormonal synchronization protocols that allow for timed artificial insemination (AI), detection of estrus plays an important role in the reproductive management program on most dairies in the United States. Increased physical activity is a secondary sign of estrus in dairy cattle, and a new generation of electronic systems that continuously monitor physical activity to predict timing of AI have been developed and marketed to the dairy industry. A variety of management and physiologic challenges inhibit detection of behavioral estrus on farms, but the prevalence of anouvular cows near the end of the voluntary waiting period is particularly problematic. Only 70% of lactating Holstein cows were detected in estrus when using an activity monitoring system, with the remaining 20% of cows classified as anovular and 10% ovulating without showing signs of activity. Mean time of AI in relation to ovulation based on the activity monitoring system was acceptable for most of the cows with increased activity, however, variability in the duration of estrus and timing of AI in relation to ovulation could result in poor pregnancy outcomes in some cows. Use of a Presynch–Ovsynch protocol for submission of cows for first AI has been widely adopted by dairies in the United States, and a combined approach in which AI based on activity is followed by submission of cows not detected with activity to timed AI after synchronization of ovulation may be an effective strategy for submission of cows to first AI. Based on a field trial on a large commercial dairy in the United States, the activity monitoring system detected 70% of cows with increased activity after the second PGF2α injection of a Presynch–Ovsynch protocol, however, cows inseminated to increased activity had fewer pregnancies per AI (P/AI) compared with cows with increased activity after the second PGF2α injection that received timed AI after completing the Presynch–Ovsynch protocol. Based on an economic model comparing reproductive management programs with varying levels of AI to estrus v. timed AI, the rate of estrus detection and the P/AI to inseminations based on AI to detected estrus v. timed AI affected the decision to inseminate based on activity v. timed AI. In conclusion, an activity monitoring system detected increased activity in about 70% of lactating Holstein cows on a large commercial dairy in the United States, however, synchronization of ovulation and timed AI was beneficial to inseminate cows not detected with increased activity by the activity monitoring system.

There is a variable anoestrous period following parturition in the cow. Follicular growth generally resumes within 7 to 10 days in the majority of cows associated with a transient FSH rise that occurs within 3 to 5 days of parturition. Dairy cows that are not nutritionally stressed generally ovulate their first postpartum dominant follicle (~15 days), whereas beef suckler cows in good body condition normally have a mean of 3.2±0.2 dominant follicles (~30 days) to first ovulation; moreover, beef cows in poor body condition have a mean of 10.6±1.2 dominant follicles (~70 to 100 days) to first ovulation. The lack of ovulation of dominant follicles during the postpartum period is associated with infrequent LH pulses, with both maternal–offspring bonding and low body condition score (BCS) at calving being implicated as the predominant causes of delayed resumption of cyclicity in nursed beef cows. In dairy cows, the normal pattern of early resumption of ovulation may be delayed in high-yielding Holstein type cows generally owing to the effects of severe negative energy balance, dystocia, retained placental membranes and uterine infections. First ovulation, in both dairy and beef cows, is generally silent (i.e., no behavioural oestrus) and followed by a short inter-ovulatory interval (>70%). The key to optimizing the resumption of ovulation in both beef and dairy cows is appropriate pre-calving nutrition and management so that cows calve down in optimal body condition (BCS; 2.75 to 3.0) with postpartum body condition loss restricted to <0.5 BCS units.

There has been a long history of herd health and production management programmes in many dairy industries around the world, but evidence for the efficacy of such programmes is limited. In response to a perceived decline in fertility of dairy cows, a herd reproductive management programme (InCalf) was introduced in New Zealand in 2007. This programme uses a management cycle approach that includes an assessment of the current herd status, identification of areas for improvement, development of a plan, implementation of this plan and finally a review process. The programme uses facilitators who work with farmers either in a one-to-one manner or in a formalised group setting that involves a series of meetings over a 12-month period (the farmer action group). The hypothesis that involvement in a reproductive management programme would improve herd reproductive performance was tested using a herd-level controlled randomised study (the National Herd Fertility Study) involving herds in four geographic regions of New Zealand over 2 years. Within each region, herds were ranked on the basis of the 6-week in-calf rate (i.e. the proportion of the herd pregnant in the first 6 weeks of the seasonal breeding programme) in the year preceding commencement of the study and then randomly assigned to be involved in a farmer action group or left as untreated controls. The key outcome variable of the study was the 6-week in-calf rate. Pregnancy diagnosis was undertaken at 12 weeks after the start of the seasonal breeding programme, which allowed determination of conception dates and hence calculation of the 6-week in-calf rate. Additional measurements including heifer live weight and body condition score (pre-calving and pre-mating) were undertaken to test whether treatment resulted in measurable changes in some of the key determinants of herd reproductive performance. Involvement in the farmer action group of InCalf resulted in a 2 percentage point increase in the 6-week in-calf rate (P=0.05). The following additional observations were made in herds involved in the farmer action group relative to control herds: heifers had live weight closer to target; the pre-mating body condition score of cows was higher; and oestrous detection rates were higher. It was concluded that involvement in this herd reproductive management programme improved reproductive outcomes in this New Zealand study. However, to achieve substantial improvements in herd reproductive performance at the regional or national level a greater response to the programme and a high uptake of such programmes is required, as well as use of other industry-level tools such as genetic management programmes.

The objective of this review paper was to summarise the latest findings in dairy cattle reproductive economics with an emphasis on high yielding, confined total mixed ration systems. The economic gain increases as the reproductive efficiency improves. These increments follow the law of diminishing returns, but are still positive even at high reproductive performance. Reproductive improvement results in higher milk productivity and, therefore, higher milk income over feed cost, more calf sales and lower culling and breeding expenses. Most high-yielding herds in the United States use a combination of timed artificial insemination (TAI) and oestrous detection (OD) reproductive programme. The ratio of achievable pregnancies between OD and TAI determines the economic value difference between both and their combinations. Nonetheless, complex interactions between reproductive programme, herd relative milk yield, and type of reproductive programme are reported. For example, higher herd relative milk yield would favour programme relying more on TAI. In addition, improved reproductive efficiency produces extra replacements. The availability of additional replacements could allow more aggressive culling policies (e.g. less services for non-pregnant cows) to balance on-farm supply and demand of replacements. Balancing heifer replacement availability in an efficient reproductive programme brings additional economic benefits. New technologies such as the use of earlier chemical tests for pregnancy diagnosis could be economically effective depending on the goals and characteristics of the farm. Opportunities for individual cow reproductive management within defined reproductive programme exist. These decisions would be based on economic metrics derived from the value of a cow such as the value of a new pregnancy, the cost of a pregnancy loss, or the cost of an extra day open.

The technology in current use for sexing sperm represents remarkable feats of engineering. These flow cytometer/cell sorters can make over 30 000 consecutive evaluations of individual sperm each second for each nozzle and sort the sperm into three containers: X-sperm, Y-sperm and unsexable plus dead sperm. Even at these speeds it is not economical to package sperm at standard numbers per inseminate. However, with excellent management, pregnancy rates in cattle with 2 million sexed sperm per insemination dose are about 80% of those with conventional semen at normal sperm doses. This lowered fertility, in part due to damage to sperm during sorting, plus the extra cost of sexed semen limits the applications that are economically feasible. Even so, on the order of 2 million doses of bovine semen are sexed annually in the United States. The main application is for dairy heifers to have heifer calves, either for herd expansion or for sale as replacements, often for eventual export. Breeders of purebred cattle often use sexed semen for specific matings; thawing and then sexing frozen semen and immediately using the few resulting sexed sperm for in vitro fertilization is done with increasing frequency. Beef cattle producers are starting to use sexed semen to produce crossbred female replacements. Proprietary improvements in sperm sexing procedures, implemented in 2013, are claimed to improve fertility between 4 and 6 percentage points, or about 10%.

Early embryo development following fertilization occurs in the oviduct. However, despite being the site of fertilization in cattle, it is possible to by-pass the oviduct by producing embryos in vitro and/or by transferring blastocysts recovered from one female into the uterus of another. While there is substantial evidence for the oviduct having an influence on the quality of the developing embryo, manifested in altered morphology, gene expression and cryotolerance, evidence for a two-way dialogue is weak. In contrast, 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 uterine endometrium. Elevated concentrations of circulating P4 in the immediate post-conception period have been associated with an advancement of conceptus elongation, an increase in interferon-tau production and, in some studies, higher pregnancy rates in cattle. This review summarizes current knowledge on the communication between the developing embryo and the maternal reproductive tract.

Sexed semen technology is now commercially available in many countries around the world, and is primarily used in dairy cattle breeding. Sperm are sorted by flow cytometry on the basis of a 4% difference in DNA content between sperm containing X and Y chromosomes. Despite reliably producing a 90% gender bias, the fertility of the sexed semen product is compromised compared with conventional semen. The negative implications of the reduced fertility of sexed semen are amplified in seasonal systems of dairy production, as the importance of fertility is greater in these systems compared with year-round calving systems. A review of the literature indicates that conception rates (CR) to 1st service with frozen-thawed sexed semen are ~75% to 80% of those achieved with conventional frozen-thawed semen. Preliminary results from a large-scale field trial carried out in Ireland in 2013 suggest that significant improvements in the performance of sexed semen have been made, with CR of 87% of those achieved with conventional semen. The improved fertility of a sexed semen product that delivers 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. The replacement heifer requirements for a herd could be met by using sexed semen in the 1st 3 weeks of the breeding season, with the remaining animals bred to beef sires, increasing the sale value over that of a dairy bull calf. Alternatively, very short gestation sires could be used to shorten the calving interval. Market prices have a considerable effect on the economics of sexed semen use, and widespread use of sexed semen should be restricted to well managed herds that already achieve acceptable herd fertility performance.