Herd Reproductive Performance Research Articles

Decision making for sexed semen and beef semen in dairy production

Breeding strategies using sexed semen on younger and supe­rior animals and beef semen on older and inferior animals are becoming widely used in the dairy industry because it bal­ances the number of replacements produced and required while bringing extra income of selling crossbreed beef calves that are more valuable than dairy calves. The value proposition also implies genetic improvement because of greater breed­ing selection and shorter intergenerational interval, which can be captured in improved milk productivity. The best semen-type breeding strategy is farm specific and dependent on herd reproductive performance and ever-changing market condi­tions. Hence, the need to use models and projections to assert the optimal semen-type breeding strategy that optimizes the net return of each farm under specific market conditions. We analyzed the economic value of using alternative breeding strategies using sexed, beef and conventional semen using 2 ap­proaches. A short-term approach contained in a user-friendly decision support tool, the Premium Beef on Dairy Program, assessed the income from calves over semen costs over a breed­ing cycle whereas a long-term approach, using the Animal Life Cycle submodule of the Ruminant Farm Simulation Model, included additionally breeding, rearing and feed costs, and slaughter, heifer and milk sales revenues. Important in the long-term evaluation was the milk value change as a proxy for genetic improvement. Both approaches consistently pointed out that the advantage of the sexed/beef semen is positively related to herd reproductive performance. The greater the reproduc­tive performance the more the economic opportunity. With medium to high reproductive performance (above ~20% 21-d pregnancy rate), the Premium Beef on Dairy Program found the maximum income from calves over semen cost occurred when sexed semen was used in the first 2 heifer breedings and first and second lactation superior cows, while the rest of the heifer breedings were made with conventional semen and the rest of the cow breedings were made with beef semen. These results were consistent in the long-term analysis, which indi­cated that even a slightly more aggressive breeding approach using sexed semen in all heifer breedings resulted in the best net return in the long-term when the extra value of increased milk productivity became the most important economic factor. Although the short-term analysis did not include the herd dy­namics and milk changes, it still produced the right trend and directionality for decision making. The recommendation is to use the Premium Beef on Dairy user-friendly tool according to a herd’s reproductive performance and market conditions, and repeat the analysis constantly as the management and market circumstances change. When a deep and long-term analysis is necessary, the use of the Life Cycle Assessment submodule from the RuFaS is critical. Thus, both approaches are useful and complementary.

Temporal trends in estimated breeding values for daughter fertility in Holstein and Jersey cows in the Australian dairy industry

Context Milk yield and fertility are negatively genetically correlated in dairy cows, so selection for milk yield would be expected to result in genetic deterioration in fertility unless there is concurrent selection for fertility. Aim The main study aim was to describe temporal trends in estimated breeding values (Australian Breeding Values, ABVs) for daughter fertility for Holstein and Jersey cows in Australian dairy herds. Methods A retrospective descriptive study was conducted using milk recording and ABV data from cows in commercial dairy herds. Calvings and lactations from 1980 to 2022 were used, along with ABVs for cows that calved over that period and for sires of those cows. Herd-year mean estimated breeding values were calculated for each breed as the means for cows of that breed that calved in the herd that year. Key results Daughter fertility ABVs declined (i.e. deteriorated) markedly in Holsteins in the Australian dairy industry, commencing before 1980. Rates of decline were most rapid in sires, less rapid in cows and least rapid at herd level. Selection pressure for cows with higher daughter fertility ABVs due to cow culling decisions was probably occurring within Australian herds but any such effect was minimal. The decline in cow daughter fertility ABVs is being reversed, but recovery of herd means in the study population has been slow. The rate of decline in daughter fertility ABVs in Jersey cows was less than for Holsteins. Conclusions Over a period of genetic deterioration, then recovery for a trait, genetic trends in sires are not closely related to genetic trends at herd level. The rapid decline in daughter fertility ABVs for sires probably resulted in substantial reductions in herd reproductive performance and cow longevity in Holstein herds in the Australian dairy industry. Under current trends, it will be a considerable time before the adverse effects of the decline in daughter fertility ABVs are fully reversed. Implications An important ongoing task for animal breeding is to identify and monitor traits that may become important for farmers and community in future but may be declining genetically under current selection decisions.

Development and evaluation of a dynamic simulation model of reproductive performance in pasture based suckler beef systems

The reproductive performance of a beef cow herd is largely a factor of efficient animal management strategies and genetics. The complex and cumulative nature of individual management decisions on a farm system's performance over multiple years mean that robust evaluation is time consuming and costly. A dynamic deterministic simulation model (Grange Reproductive Management Model; GReMM) with the capacity to replicate herd inventory dynamics over multiple reproductive cycles was developed using the Stella Architect dynamic modelling platform. The model is representative of a pasture-based spring calving suckled beef cow herd and is initialised by specifying individual farm parameters with respect to reproductive management, such as the breeding season duration, nutrition and management of the cow and calf postpartum. The focus was on the key factors which affect the duration of the postpartum anoestrus interval (PPAI); body condition score of the cow at calving (BCSc), postpartum nutrition (PPN), access of the suckling calf to the dam and, exposure of the dam to a fertile male. Model output was displayed in the form of a shift in calving distribution, the number of calves produced per cow bred per year and, percentage of cows culled due to barrenness. Three management scenarios were investigated to represent a herd implementing current industry best practice (BASE), a herd implementing intensive levels of reproductive management (Intensive reproductive management; IRM) and a herd implementing poor levels of reproductive management (Poor reproductive management; PRM). When evaluated in terms of calving distribution over six production cycles, both PRM and IRM showed a shift in the calving spread with a higher proportion of animals calving earlier and later, respectively, in the calving season compared to the BASE. This resulted in a 5% increase and a 14% decrease in six-week calving rates relative to BASE by year six, for IRM and PRM, respectively. Correspondingly, culling rates due to barrenness reduced by 0.9% and increased by 3.3% relative to BASE for IRM and PRM, respectively. The model developed offers a realistic and intuitive dynamic simulation model capable of investigating practical on-farm management decisions on herd reproductive performance.

203 Development and evaluation of a dynamic simulation model of farm management strategies affecting the reproductive performance of a suckled beef cow herd

Abstract Reproductive output in suckled beef cow systems is underpinned by a combination of genetics and the impact of efficient animal management strategies which given their cumulative nature, are difficult to evaluate. A dynamic simulation model (Grange Reproductive Management Model; GReMM) was developed replicating the reproductive performance of a suckled beef cow herd over multiple production cycles using the Stella Architect dynamic modelling platform (isee systems, Ventana, Lebanon, USA). Model inputs for farm parameters include dates and duration of breeding seasons in addition to nutrition and management of the periparturient beef cow. Specific management parameters pertaining to the duration of the postpartum anoestrus interval (PPAI), such as the body condition score of the cow at calving (BCSc), level of postpartum nutrition (PPN), management of the suckling calf and bio-stimulation of the dam pre-breeding are modelled. Outputs are displayed in the form of shifts in calving distribution, calving rates and calves per cow per year. Scenario analysis consisted of the implementation of a BASE scenario representative of current industry best practice (Normal reproductive management; NRM: BCSc, 2.75; PPN, 100 MJ ME/d; ad libitum suckling). Two further scenarios were developed representing a more intensively managed herd, with high levels of nutrition pre and post calving in addition to alternative reproductive management strategies (Intensive reproductive management; IRM), and a herd with a low level of nutritional management pre and postpartum (Poor reproductive management; PRM). Outputs generated in terms of calving distribution over six production cycles, indicated that a shift in the calving spread towards later in the calving season occurred in the PRM scenario, and a small improvement in reproductive efficiency evident in the IRM scenario over NRM. The model developed offers a decision support tool with the capability of evaluating practical on-farm management decisions on herd reproductive performance.

Herd and environmental determinants of reproductive performance in Swedish dairy herds, 2001–2009

This was a retrospective cohort study of Swedish dairy herds. Summary measures of production and reproductive performance, details of soil, moss mineral concentrations, and temperature and rainfall measurements at each herd location were available for the period September 2001 to August 2009. A Bayesian mixed-effects regression model including spatial and non-spatial heterogeneity terms was developed to quantify associations between hypothesised explanatory variables and mean herd breeding interval, defined as the difference between mean calving to last service interval and mean calving to first service interval for each fiscal year.Mean herd breeding intervals were shorter in herds with greater than 80% Swedish Red Cattle, herds with lower mean age at first calving, herds comprised of older cows and in larger herds. None of the soil composition or moss mineral concentration estimates were associated with mean herd breeding interval and the effect of temperature and rainfall on mean herd breeding interval was small. We conclude that environmental conditions (soil composition, moss mineral concentrations, environmental temperature and rainfall) had relatively minor effects on dairy herd reproductive performance in Sweden between 2001 and 2009.

The development of reproductive management practices in New Zealand: what will the future hold in a consumer-focused, environmentally-conscious, export-driven marketplace?

The New Zealand (NZ) economy and its dairy industry are sensitive to global consumer perception of farming practices used to generate milk products because milk exports account for >25% of national export earnings and >90% of milk produced is exported as products. Astute management of product image and market risk is, therefore, important for the viability of the industry and country. More than 95% of milk produced in NZ comes from strictly seasonal, pasture-based systems, with associated constraints on reproductive performance. Increasing herd sizes, operational changes and genetic selection priorities have further challenged dairy farmers to achieve optimal levels of herd fertility. Reproductive management practices have developed to address the need to maintain a 365-day inter-calving interval, essentially through maximizing the number of cyclic cows during the breeding period and minimizing the duration of the seasonal calving period. Aspects of the hormonal interventions developed and routinely used to achieve these objectives have been the subject of product quality and market risk concerns forcing the industry to explore alternative ways of achieving reproductive performance goals. One approach has been to exploit the inherently high level of fertility in NZ dairy herds. This approach has seen the inclusion of fertility-related traits in the national genetic evaluation system to prevent further decline in genetic fertility. More recently, a nationally coordinated extension program has been adopted to support farmers and their advisors to identify, prioritize and improve on key management areas for incremental gains in herd reproductive performance. Advances in automation and bio-sensing are yet to make a significant impact, but remain potentially valuable additions in supporting the dairy farmer to manage the areas having the largest effects on reproductive performance.

A decision-support tool for investment analysis of automated oestrus detection technologies in a seasonal dairy production system

Context Advances in automated oestrus detection have made this an attractive technology to help reduce manual oestrus detection labour on dairy farms. Aims A decision-support tool was created to help farmers estimate the investment outcome of adopting automated oestrus detection technologies in a seasonal dairy production system. Methods A decision-support tool was created using Excel 2011 (Microsoft Inc., Redmond, WA, USA). The tool allows farmers to input both current herd reproductive management costs and performance and automated oestrus detection technology system costs and performance to receive herd-specific estimates of investment benefit. The investment analysis outputs include the net present value (NPV), internal rate of return (IRR), and payback period associated with automated oestrus detection adoption. Two different automated oestrus detection technologies were compared with visual oestrus detection aided by tail paint with a 72.0% oestrus detection rate (sensitivity) to demonstrate the value of the investment analysis tool. The alternative scenarios, technology one and technology two, were compared over an eight-year investment period. Key results Technology one, with a 62.4% oestrus detection rate, resulted in a negative NPV and IRR (–NZ$182567 and –100% respectively), indicating a poor investment. Technology two, with an oestrus detection rate of 91.0%, provided a positive NPV and IRR (NZ$177890 and 38.7% respectively), indicating a beneficial investment. The payback period for technology one was estimated as >10 years, whereas technology two’s payback period was <1 year. Conclusions The investment tool results are dependent on farm-specific and automated oestrus detection inputs. Implications Farmers can use farm-specific inputs in the tool to aid them when considering adoption of new automated oestrus detection technologies.

Effect of mature size and body condition of Nelore females on the reproductive performance

The size and body condition of cows can affect their reproductive efficiency. However, few studies reported genetic correlations between these traits in beef cattle. Thus, we estimated the genetic parameters and correlations between weight (MW), height (MH) and body condition score (BCS) of cows and reproductive traits (SC: scrotal circumference, AFC: age at first calving, GL: gestation length, DC: days to calving, and CI: calving interval) in Nelore animals. In addition, it has also obtained direct and correlated responses aiming at determining whether changes in cow size and body condition may affect the herd reproductive performance. A series of two-trait Bayesian analyzes were performed including MW, MH or BCS with each of the reproductive traits. The heritability estimated for MW, MH and BCS were 0.46 ± 0.02, 0.35 ± 0.01 and 0.17 ± 0.02, indicating an involvement of additive gene action mainly in cows' size determination. For the reproductive traits of females, heritability ranged from 0.05 ± 0.00 for CI to 0.18 ± 0.01 for GL, and was 0.37 ± 0.01 for SC. Low repeatability were estimates for GL (0.19 ± 0.00), DC (0.19 ± 0.00) and CI (0.05 ± 0.00). The MW was positive correlated with AFC (0.23 ± 0.08), CI (0.25 ± 0.15) and, with lower magnitude, of GL (0.14 ± 0.03). Null genetic correlations were obtained between MW with SC (0.03 ± 0.03) and DC (−0.01 ± 0.04). The MH showed positive and low genetic association with all female reproductive traits, but negative with SC (−0.08 ± 0.03). Negative and favorable genetic correlations were estimated between BCS and females reproductive traits, but unfavorable with SC (−0.13 ± 0.06). In summary, the negative impact of increase the size of Nelore females on their reproductive performance is expected to be small in tropical regions. The use of sires with high genetic breeding values for SC should result in slight reduction of BCS of cows, but no effective genetic response in female size is expected. Selection based on BCS should promote little improvement in reproductive efficiency of cows.

A cross-sectional study to identify a set of risk factors for caprine herpesvirus 1 infection

BackgroundCaprine herpesvirus 1 (CpHV-1) causes neonatal mortality and reproductive failure in goats. Despite its impact on herd reproductive performance, few studies have investigated the risk factors associated with CpHV-1 infection. The aim of this cross-sectional study was to identify potential herd- and host-level risk factors associated with CpHV-1 prevalence in a goat population with heterogeneous seropositivity for CpHV-1.ResultsBlood samples and individual data from 4542 goats were collected from 255 herds in Piedmont, Italy. Enzyme-linked immunosorbent assay (ELISA) and serum neutralization tests were carried out to detect antibodies against CpHV-1. A mixed-effects model was applied to identify any statistical association between CpHV-1 seropositivity and a set of putative host-level and herd-level risk factors. A total of 630 samples tested were found positive by ELISA (prevalence = 13.9%; 95% confidence interval (CI) 12.9–14.9). Of the 255 tested herds, 85 were classified as positive for the presence of at least one gB-positive animal (herd prevalence 33.3%, 95% CI 27.5–39.2), with a within-herd prevalence between 0.7 and 100% (Q1 = 17.6%; median = 32.3%; Q3 = 50%) (Q = quartiles). The prevalence ratios showed a statistical association with the following risk factors: breeds other than Saanen, older age, larger herd size, meat and extensive herds, and co-existence of CAEV-infected animals.ConclusionsResults from this cross sectional study may help to elucidate the natural history of the infection and inform targeted strategies to control a disease with a potentially important impact on animal health and goat farming economy.

Testis specific histone 2B is associated with sperm chromatin dynamics and bull fertility-a pilot study

BackgroundBull fertility is the degree of sperm’s ability to fertilize and activate the egg and support embryo development, and this is critical for herd reproductive performance. We used the bull as a unique model organism for the study of male fertility because cattle genetics and physiology is similar to those of other mammals including humans. Moreover, reliable fertility data along with well-established in vitro systems are available for bovine. The objective of this original study was to ascertain evolutionary diversification and expression dynamics of Testis Specific Histone 2B (TH2B) in sperm from Holstein bulls with different fertility scores.MethodsThe intensity of TH2B was determined by using flow cytometry in sperm from 13 high and 13 low fertility bulls. Expression levels of TH2B were measured using immunofluorescence and Western blotting in sperm from five high and five low fertility bulls. Sequence identity, evolutionary distance and interactome of TH2B were evaluated by dotmatcher, STRING and Cytoscape. Data were analyzed using linear mixed effects model and regression plots were drawn.ResultsThe intensity of TH2B as measured by flow cytometry was significantly affected by an interaction between fertility group and fertility score (P = 0.0182). The intensity of TH2B in sperm from the high fertility group decreased (P = 0.0055) as fertility increased. TH2B was constantly detectable in sperm and expression levels of TH2B decreased in relation to fertility in sperm from the high fertility group (P = 0.018). TH2B biological functions include male gamete generation, chromosome organization, DNA packaging, DNA conformation change, chromatin organization, nucleosome organization, chromatin disassembly, spermatid nucleus elongation, spermatid nucleus differentiation, sperm motility, chromatin organization, chromatin condensation, chromatin silencing, nucleus organization, and chromatin remodeling (P < 0.05).ConclusionsWe elucidated the cellular localization and molecular physiology of TH2B using both computational and cell biology approaches. In addition to advancing the fundamental science of mammalian male gamete, the present findings can be potentially used to evaluate semen quality and predict male fertility in the future.Trial registrationThis study did not involve any live animals. We did not perform any anesthesia, euthanasia, or any kind of animal sacrifice. The cryopreserved semen samples were obtained from Alta Genetics, Inc., Watertown, WI, USA. All samples were preserved in liquid nitrogen.

The Analysis of Production and Culling Rate With Regard to the Profitability in a Dairy Herd

Abstract As milk prices move away from production costs, dairy farms are under increased pressure to find ways to protect profitability on the farm. Producers have some problems that they can improve. Improve the milk production, produce more milk to sell focused on quality (reduce the amount of high level of somatic cell count). The deterioration of animal health status (lameness, mastitis and different metabolic disorders) can have a serious impact on cow productivity, causing pain and discomfort, production losses and might result in a decision to cull the animal. Improving herd reproductive performance is an important aspect of profitable farm management. The aim of this work is to analyse milk production, reasons of culling and culling rate in different lactation on a dairy cattle farm.

Effect of diagnosis and treatment of clinical endometritis based on vaginal discharge score grading system in postpartum Holstein cows

In this study, the prevalence, effectiveness of diagnosis, and treatment based on vaginal discharge score (VDS) of clinical endometritis in cattle were evaluated. To detect clinical endometritis and classify its severity, vaginoscopy was performed during 21 to 60 days postpartum in 164 Holstein cows consisting of 229 lactations. Groups were defined using the 4-point VDS scale. Study groups included the following: non-endometritis (VDS=0; no/clear mucus; NEM group; n=168); mild endometritis, no treatment (VDS=1; mucus containing flecks of white/off-white pus; NTR group; n=30); and severe endometritis, treated with PGF2α (VDS≥2; discharge containing <50% pus; and VDS=3; discharge containing >50% pus, and fluid or uterine horn asymmetry; TEM group; n=31). Cows treated with PGF2α that did not recover (VDS≥1, n=5) received intrauterine procaine penicillin and streptomycin. Prevalence of clinical endometritis (VDS≥1) was 26.6%. The NTR group required significantly more artificial inseminations per pregnancy than NEM and TEM groups (2.8 ± 1.8 vs 2.0 ± 1.3, 1.9 ± 0.8, P<0.05). In survival analysis, the proportion of non-pregnant cows was higher in the NTR group compared to the NEM (P=0.012) and TEM (P=0.076) groups. In the TEM group, calving to first artificial insemination interval tended to be higher in cows treated 41 to 60 days postpartum than cows treated 29 to 40 days postpartum (97.2 ± 27.1 vs 74.4 ± 19.7, P=0.084). Our study suggests that cows with VDS=1 may require treatment to recover fertility. Diagnosis and treatment of clinical endometritis based on a VDS grading system may improve dairy herd reproductive performance.

Accuracy of fetal age estimates using transrectal ultrasonography for predicting calving dates in dairy cows in seasonally calving herds in New Zealand

AIM: To describe the accuracy of transrectal ultrasonography for predicting calving dates in dairy cows under typical New Zealand conditions and to assess potential risk factors for differences between predicted and actual calving dates.METHODS: Data were collected from 116 seasonally calving herds over 2 years in a retrospective single cohort study. Transrectal ultrasonography was undertaken by experienced veterinarians (n=12) to determine if cows were pregnant, and if so to estimate fetal age. Predicted calving date was calculated by adding 282 days to the estimated conception date. Accuracy was assessed using differences between predicted and actual calving dates for each animal. Potential risk factors for animals calving >10 days before or after their predicted calving date were assessed using multinomial logistic regression models.RESULTS: The study population comprised 83,104 cows over the 2 years of the study; 75,037 (90.3%) cows calved within 10 days of their predicted calving date, 3,683 (4.4%) calved >10 days earlier, and 4,384 (5.3%) >10 days later, than predicted. Risk factors for calving >10 days before or after the predicted calving date included having >1 artificial insemination (AI) before pregnancy diagnosis (p=0.03), where the cow’s most recent AI was <21 days before the end of the herd’s AI period (p<0.01), and where the diagnosis was made at the second or third herd-visit (p<0.01). The probability of calving being >10 days later than predicted also increased when the fetus was ≥13 weeks old at pregnancy diagnosis (p<0.01).CONCLUSIONS AND CLINICAL RELEVANCE: In this study, >90% of cows diagnosed pregnant by veterinarians using transrectal ultrasonography calved within 10 days of the predicted calving date. In herds where herd reproductive performance is high, it would be expected that more cows would conceive to their first AI, and potentially fewer cows would have AI close to the end of the herd’s AI period, which would increase diagnostic accuracy. Where herd managers rely on accurate predicted calving dates they should be informed about realistic expected accuracy. For greatest accuracy, a complete AI history should be made available to the person performing the pregnancy diagnoses and cows at most risk of having inaccurate predicted calving dates should be identified.

Recent Possibilities for Diagnosis and Treatment of Post Parturient Uterine Diseases in Dairy Cow

The successful genetic selection for higher milk production caused a dramatic decline in the reproductive performance of dairy cows all over the world during the last decades. Achievement of optimum herd reproductive performance (calving interval of 12 months or 13 months with the first calf born at 24 months of age) requires concentrated management activities especially during the first 100 days following calving. The following management activities are needed to pursue during the early postpartum period to reach or approach the optimal reproductive performance such as careful surveillance and assistance at calving, prevention of post parturient metabolic diseases, early diagnosis and treatment of post parturient uterine diseases, accurate detection of oestrus, correct timing of insemination, reducing the effect of heat stress and early pregnancy diagnosis. Among these main activities only early diagnosis and treatment of post parturient uterine diseases and their effects on reproductive performance are discussed. Clinical metritis and clinical endometritis (or recently used purulent vaginal discharge: PVD) can be accurately diagnosed in the field, however it is very important to remark that the presence of PVD alone is not sufficient to diagnose clinical endometritis because cervicitis and/or vaginitis can also cause PVD. Both diseases have detrimental effect on reproduction therefore it is important to diagnose as soon as possible and treat accordingly. Different treatment protocols that have changed in the recent years for those diseases, as well as recently performed therapies like ozone therapy or vaccination are also discussed. Although subclinical endometritis has also a detrimental effect on reproduction, it is complicated to diagnose in the field.

Pregnancy losses in cattle: potential for improvement.

For heifers, beef and moderate-yielding dairy cows, it appears that the fertilisation rate generally lies between 90% and 100%. For high-producing dairy cows, there is a less substantive body of literature, but it would appear that the fertilisation rate is somewhat lower and possibly more variable. In cattle, the major component of embryo loss occurs in the first 16 days following breeding (Day 0), with emerging evidence of greater losses before Day 8 in high-producing dairy cows. In cattle, late embryo mortality causes serious economic losses because it is often recognised too late to rebreed females. Systemic concentrations of progesterone during both the cycle preceding and following insemination affect embryo survival, with evidence of either excessive or insufficient concentrations being negatively associated with survival rate. The application of direct progesterone supplementation or treatments to increase endogenous output of progesterone to increase embryo survival cannot be recommended at this time. Energy balance and dry matter intake during the first 4 weeks after calving are critically important in determining pregnancies per AI when cows are inseminated at 70-100 days after calving. Level of concentrate supplementation of cows at pasture during the breeding period has minimal effects on conception rates, although sudden reductions in dietary intake should be avoided. For all systems of milk production, more balanced breeding strategies with greater emphasis on fertility and feed intake and/or energy must be developed. There is genetic variability within the Holstein breed for fertility traits, which can be exploited. Genomic technology will not only provide scientists with an improved understanding of the underlying biological processes involved in fertilisation and the establishment of pregnancy, but also, in the future, could identify genes responsible for improved embryo survival. Such information could be incorporated into breeding objectives in order to increase the rate of genetic progress for embryo survival. In addition, there is a range of easily adoptable management factors, under producer control, that can either directly increase embryo survival or ameliorate the consequences of low embryo survival rates. The correction of minor deficits in several areas can have a substantial cumulative positive effect on herd reproductive performance.

Subclinical ketosis in post-partum dairy cows fed a predominantly pasture-based diet: defining cut-points for diagnosis using concentrations of beta-hydroxybutyrate in blood and determining prevalence

AIMS: Firstly, to define, in dairy cows in the first 5 weeks post-calving fed a predominantly pasture-based diet, cut-points of concentrations of beta-hydroxybutyrate (BHBA) in blood, above which there were associations with purulent vaginal discharge (PVD), reduced pregnancy rates (PR) and decreased milk production, in order to better define subclinical ketosis (SCK) in such cattle; and secondly, to determine the prevalence, incidence and risk factors for SCK.METHODS: An observational field study was conducted in 565 cows from 15 spring-calving and predominantly pasture-fed dairy herds in two regions of New Zealand during the 2010– 2011 dairy season. Within each herd, a cohort of randomly selected cows (approximately 40 per herd) was blood sampled to determine concentrations of BHBA on six occasions at weekly intervals starting within 5 days of calving. The key outcome variables were the presence/absence of PVD at 5 weeks post-calving, PR after 6 weeks (6-week PR) and after the completion of the breeding season (final PR), and mean daily milk solids production.RESULTS: Two cut-points for defining SCK were identified: firstly concentration of BHBA in blood ≥1.2 mmol/L within 5 days post-calving, which was associated with an increased diagnosis of PVD (24 vs. 8%); and secondly concentration of BHBA in blood ≥1.2 mmol/L at any stage within 5 weeks post-calving, which was associated with decreased 6-week PR (78 vs. 85%). The mean herd-level incidence of SCK within 5 weeks post-calving was 68 (min 12; max 100)% and large variations existed between herds in peak prevalence of SCK and the interval post-calving at which such peaks occurred. Cows >8 years of age and cows losing body condition were at increased risk of SCK within 5 weeks of calving.CONCLUSIONS: Cows with concentration of BHBA in blood ≥1.2 mmol/L in early lactation had a higher risk of PVD and lower 6-week PR. Cow and herd-level prevalence of SCK varied widely in early lactation.CLINICAL RELEVANCE: Subclinical ketosis is common and is significantly associated with reproductive performance in mainly pasture-fed New Zealand dairy cattle. Controlling SCK may therefore result in improvements in herd reproductive performance. However considerable variation exists among herds in the incidence of SCK and in the timing of peak prevalence which means that herd-specific monitoring programmes are required to define herd SCK status accurately.

Analysis of relationship between viability of cows, herd turnover rate, and milk production efficiency (system and algorithm modeling)

A model with a simple algorithm is presented to analyze the efficiency of milk production, taking into consideration the viability and productivity of cows, dairy herd turnover rate, and main economic indicators. Principle propositions of a general approach are set forth without any complicated mathematical formulas and equations. The impact of viability on herd profitability and reproductive performance has been analyzed with the actual data on culled Holstein Black-and-White and Holmogorskaya cows. Reducing the culling rate in first lactations should be recognized as a major breeding criterion for extending the average productive lifespan of cows.

Effects of subcutaneously injected Ca Cu EDTA on concentrations of Cu in liver, milk production and reproductive performance in New Zealand dairy cows

AIMS: To determine the effect of dose and frequency of injection of Cu as Ca Cu EDTA on concentrations of Cu in liver, and the effect of a single 200 mg treatment on milk production and reproductive performance in New Zealand dairy cows.METHODS: Four groups of dairy cows (n=18 per group) on three farms were injected with 100 or 200 mg Cu S/C once, or three times at 6-weekly intervals, commencing 6−8 weeks into lactation. Concentrations of Cu in liver were determined to 119 days after treatment. Cows at peak lactation on one farm were treated with 200 mg of Cu S/C, or received no treatment (n=92 per group). Milk production was determined 11 days before and 24 hours following treatment. In seven dairy herds from throughout New Zealand cows were injected S/C with 200 mg Cu 10 days prior to mating start date (MSD) or received no treatment. Oestrus detection and artificial inseminations were carried out for ≥24 days from MSD. Pregnancy diagnosis was performed at 12 weeks following MSD. The percentage of cows inseminated in the 21 days after MSD (21-day submission rate; n=2,022) and cows pregnant after 21 or 28 days (21- and 28-day pregnancy rates; n=2520) was determined.RESULTS: Injecting with 200 mg Cu once or 6-weekly increased concentrations of Cu in liver compared with 100 mg (p<0.05). Injection of 200 mg Cu decreased total milk yield (p=0.006) and protein production (p<0.001) in the 24−36 hours after treatment. Compared with Control cows, 200 mg Cu 10 days before MSD reduced 21-day submission (78 vs. 75%; p=0.04) and 21-day pregnancy rates (47 vs. 43%; p=0.03). For 28-day pregnancy rates there was a farm by treatment interaction (p=0.02), with a negative effect observed on some, but not other, farms.CONCLUSIONS: Injection of 200 mg Cu raised concentrations of Cu in liver for >42 days. A negative impact on milk yield and composition occurred immediately following injection. Injection 10 days prior to mating had a negative effect on submission and pregnancy rates. Further study is required to determine a safe treatment to mating interval and the mechanism by which adverse impacts occur.CLINICAL REVELENCE: Although 200 mg of Cu as Ca Cu EDTA is an effective supplement and generally well tolerated, determining the necessity for, and giving specific thought to the timing of, parenteral Cu supplementation is imperative to avoid negative impacts on herd production and reproductive performance.

Use of herd management programmes to improve the reproductive performance of dairy cattle

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.

An individual reproduction model sensitive to milk yield and body condition in Holstein dairy cows

To simulate the consequences of management in dairy herds, the use of individual-based herd models is very useful and has become common. Reproduction is a key driver of milk production and herd dynamics, whose influence has been magnified by the decrease in reproductive performance over the last decades. Moreover, feeding management influences milk yield (MY) and body reserves, which in turn influence reproductive performance. Therefore, our objective was to build an up-to-date animal reproduction model sensitive to both MY and body condition score (BCS). A dynamic and stochastic individual reproduction model was built mainly from data of a single recent long-term experiment. This model covers the whole reproductive process and is composed of a succession of discrete stochastic events, mainly calving, ovulations, conception and embryonic loss. Each reproductive step is sensitive to MY or BCS levels or changes. The model takes into account recent evolutions of reproductive performance, particularly concerning calving-to-first ovulation interval, cyclicity (normal cycle length, prevalence of prolonged luteal phase), oestrus expression and pregnancy (conception, early and late embryonic loss). A sensitivity analysis of the model to MY and BCS at calving was performed. The simulated performance was compared with observed data from the database used to build the model and from the bibliography to validate the model. Despite comprising a whole series of reproductive steps, the model made it possible to simulate realistic global reproduction outputs. It was able to well simulate the overall reproductive performance observed in farms in terms of both success rate (recalving rate) and reproduction delays (calving interval). This model has the purpose to be integrated in herd simulation models to usefully test the impact of management strategies on herd reproductive performance, and thus on calving patterns and culling rates.