Fertility In Dairy Cattle Research Articles

Assessment of Sensitivity and Profitability of an Intravaginal Sensor for Remote Calving Prediction in Dairy Cattle.

One critical point of dairy farm management is calving and neonatal first care. Timely calving assistance is associated with the reduction of calf mortality and postpartum uterine disease, and with improved fertility in dairy cattle. This study aimed to evaluate the performance and profitability of an intravaginal sensor for the prediction of stage II of labor in dairy farms, thus allowing proper calving assistance. Seventy-three late-gestating Italian Holstein cows were submitted to the insertion of an intravaginal device, equipped with light and temperature sensors, connected with a Central Unit for the commutation of a radio-signal into a cell phone alert. The remote calving alarm correctly identified the beginning of the expulsive phase of labor in 86.3% of the monitored cows. The mean interval from alarm to complete expulsion of the fetus was 71.56 ± 52.98 min, with a greater range in cows with dystocia (p = 0.012). The sensor worked correctly in both cold and warm weather conditions, and during day- or night-time. The intravaginal probe was well tolerated, as any cow showed lesions to the vaginal mucosa after calving. Using sex-sorted semen in heifers and beef bull semen in cows at their last lactation, the economic estimation performed through PrecisionTree™ software led to an income improvement of 119 € and 123 €/monitored delivery in primiparous and pluriparous cows, respectively. Remote calving alarm devices are key components of “precision farming” management and proven to improve animal welfare, to reduce calf losses and to increase farm incomes.

Nutritional Effects on Dairy Cattle Fertility

Dairy cow fertility has declined in recent decades, coincidental with large increases in milk production. The problem is often considered being nutritional and can be corrected through dietary adjustment. The interaction between nutrition and reproduction is poorly tuned, and study results are often contradictory. Nutrition is an important component of successful reproduction, but dietary change to improve pregnancy rates is complicated, and merely offering pastured cows a supplement is unlikely to result in large effects, say authors. The effect of energy balance, carbohydrate type, protein and fat on reproductive outcomes will be considered.

Ovarian cysts in cattle

Ovarian cysts (OC) are among the major factors affecting dairy cattle fertility due to their impacts on reproductive performance. Extension of the calving-calving interval and the costs of treatmentassociated with this pathology are the main sources of economic losses for the dairy industry. This study involved conducting an epidemiological survey relating to ovarian cysts in cows based on the observations of veterinary practitioners in Algeria. This survey was performed using a questionnaire distributed to 103 practicing veterinarians in different regions of Algeria. According to the responses, OC dominated all ovarian diseases, followed by smooth ovaries and ovarian adhesions. Ovarian tumours were encountered very rarely. In general, veterinarians considered any follicular structure greater than 20 mm in diameter and persisting for at least 10 days to be cystic. The aetiology was multifactorial, and the following were cited: alimentation, high milk production, puerperal pathologies (metritis, retained placenta), postpartum, age, and winter season. Anoestrus was often the most observed behaviour in cystic cows, accompanied by changes in the genital tract, namely the cervix and uterus. As a consequence, in most cases, OC was associated with a delay of first insemination and conception. The use of hormones, especially PGF2α and GnRH, to treat OC was the most widely used method in the field. Clinical recovery was obtained approximately 11-15 days after the beginning of treatment, though the risk of recurrence was appreciable. The majority of vets interviewed promoted the preventionof OC. They advised breeders to improve feeding and hygiene conditions, especially during calving. Medical prevention was based on the use of hormones (PGF2α and GnRH). Though the survey showed varying results, they were generally consistent with the literature.

Heterologous beta-nerve growth factor (β-NGF) given at the LH surge enhances luteal function in dairy heifers

Genetic selection for high yield milk production has led to a decline in dairy cattle's reproductive performance over the last 40 years. Low progesterone (P4) plasma content following ovulation is associated with suboptimal fertility in dairy cattle. Several pieces of evidence indicate that the protein beta-nerve growth factor (β-NGF) that is present in the male seminal plasma exerts potent ovulatory and luteotrophic effects following systemic administration in camelids but also in other species. In this study, we determine whether systemic administration of purified llama β-NGF given at the induced preovulatory luteinizing hormone (LH) peak improves corpus luteum (CL) function in dairy heifers subjected to an estradiol (E2) / P4 estrus-synchronization protocol. To achieve this, we first determined plasma E2 and LH hormone profiles to establish the timing of the estradiol benzoate (EB)-induced LH peak in estrus-synchronized heifers. Then, we tested whether the administration of β-NGF given at the end of this peak affects the CL and its function by analyzing diameter, vascular area, and P4 output. Our results show that, with the estrus-synchronization protocol applied, plasma LH concentrations peaked (P < 0.01) 40-h and 16-h after removal of the bovine intravaginal device (DIB; containing 1.0 g of P4) plus cloprostenol injection and subsequent EB administration, respectively; after peaking, plasma LH concentrations remained stable for the next 8-h to then return to basal levels. Heifers synchronized with this protocol and receiving a dose of 1 mg of β-NGF at the end of the LH peak (ie, 48-h after DIB removal) did not show significant differences in CL diameter, but these exhibited a greater CL vascular area (P = 0.01) than the observed in vehicle-injected heifers. Furthermore, plasma P4 concentration in β-NGF-treated heifers was higher (P = 0.001) than those quantified in vehicle-injected heifers. These results support the use of β-NGF in estrus-synchronization protocols to improve the early luteal function in dairy heifers.

Ovarian cysts in cattle

Ovarian cysts (OC) are one of the major factors affecting the fertility of dairy cattle due to their negative effects on reproductive performances, causing great economic losses. They have been traditionally defined as anovulatory follicular structures with a diameter exceeding 20 or 25 mm, lasting at least 10 days on the ovary in the absence of a functional corpus luteum. However, in recent years, the development of ovarian ultrasound and hormonal assays, particularly progesterone (P4), have provided additional information, thus changing the definition of this disease. These methods were proposed as the most effective combination for the diagnosis of OC. Treatments are primarily based on the use of different hormones or hormonal associations. Particularly, the standard treatment is GnRH. PGF2α is very effective in the case of luteal cyst. However, treatment failures observed with commonly administered hormones require the use of second-line treatments. Therefore, the Ovsynch protocol and progestogen appear to be a possible alternative in OC treatment. In order to prevent OC formation and to reduce OC incidence, strategies should focus on reducing diseases and stress and optimizing food intake during dry-off and post-partum (PP) periods. Medical prevention has been proposed with the same substances commonly used in treatment (GnRH, PGF2α).

Gene Expression Profile of Oocytes Using Microarray and Single Nucleotide Polymorphisms of Stat3 and Odc1 Genes in Sperms Linked With Their Quality in Holstein-Friesian

Identification of molecular fingerprints of gametes quality could be used as a foundation for finding markers associated with fertility of dairy cattle. Therefore, the current investigation aimed to identify differential gene expression profile in oocytes collected from cyclic healthy heifers (n = 16) of Holstein breed with estimated breeding value of fertility. The animals were slaughtered at day 0 or day 12 of the oestrous cycle. The recovered oocytes from high-fertile animals (H-EBV-F >100; n=8) were compared with low-fertile group (L-EBV-F <100; n=8) using cDNA microarray. Additionally, SNPs were analysed for two candidate genes (STAT3 and ODC1) in relation with sperm quality traits. The results of this study clearly showed link of candidate genes with fertility and progesterone profile during oestrous cycle. For example, gene expression profile of STAT3 was increased in oocytes collected from H-EBV-F animals at day 0 and 12 of oestrous cycle. While ODC1 gene was up-regulated at day 12 and down-regulated at day 0 in H-EBV-F compared to L-EBV-F oocytes. Moreover, association study showed that SNP polymorphisms of STAT3 and ODC1 were linked (p < 0.05) with sperm quality traits. Therefore, it could be concluded that ODC1 and STAT3 could be considered candidate genes that are connected with Holstein cows fertility genetic merit of the associated with semen quality of sires.

Evaluation of female fertility in dairy cattle enterprises – A review

&#x0D; &#x0D; &#x0D; The aim of this article was to review the state of fertility of female dairy cattle in South Africa and to compare it with international efforts at improving fertility. Fertility in dairy cows is defined as the ability to conceive from first insemination soon after calving and to carry the calf full term to calving. It is one of the main profit drivers in the dairy industry and is a complex trait that is influenced by the environment, genetics, and their interaction. Generally, there has been a decline in dairy cow fertility across breeds worldwide because of intense selection for milk yield, milk components, and body conformation traits. In addition, most fertility traits are negatively correlated to milk production traits. Milk production has been the focal point of selection programmes as it is linked directly to the profitability of the dairy enterprise. The low heritability of fertility traits is one of the factors that discouraged efforts to include fertility in genetic evaluations. However, owing to its economic importance, female fertility was later included in the breeding objectives for dairy cattle in several countries. Although most fertility traits are heritable to a low degree, some additive genetic variability can be exploited.&#x0D; &#x0D; &#x0D;

Concentration-Dependent Type 1 Interferon-Induced Regulation of MX1 and FABP3 in Bovine Endometrial Explants.

Simple SummaryLow fertility rates in high-yielding cows have been reported for many years. Due to its impact on animal welfare, this topic is relevant to the dairy industry, veterinary medicine, and consumers. This study was designed to apply a highly defined model to simulate complex mechanisms that occur in the inner layer of the uterus (endometrium) during pregnancy recognition. Samples were taken from animals with healthy uteri at the slaughterhouse and challenged in vitro. The endometrial gene expression of selected target genes differed according to the differing concentrations of the challenging admixtures. The findings indicated that the bovine embryonic pregnancy signal might compete with similar infection-associated signals for binding capacity at the receptor level, which might be relevant to pregnancy outcomes. In conclusion, an endometrial explant model was successfully applied to answer questions related to fertility in dairy cattle. According to the 3R principle (replacement, reduction, refinement), further studies could lead to new diagnostic and therapeutic strategies for tackling subfertility in dairy cows without the need for animal experiments.The inadequate maternal recognition of embryonic interferon τ (IFNτ) might explain subfertility in cattle. This study aimed at modeling the inducibility of type 1 interferon receptor subunits 1/2 (IFNAR1/2), mimicking competition between IFNτ and infection-associated interferon α (IFNα), and simulating type 1 interferon pathways in vitro. Endometrial explants (n = 728 from n = 26 healthy uteri) were collected at the abattoir, challenged with IFNτ and/or IFNα in different concentrations, and incubated for 24 h. Gene expression analysis confirmed the inducibility of IFNAR1/2 within this model, it being most prominent in IFNAR2 with 10 ng/mL IFNα (p = 0.001). The upregulation of interferon-induced GTP-binding protein (MX1, classical pathway) was higher in explants treated with 300 ng/mL compared to 10 ng/mL IFNτ (p < 0.0001), whereas the non‑classical candidate fatty acid binding protein 3 (FABP3) exhibited significant downregulation comparing 300 ng/mL to 10 ng/mL IFNτ. The comparison of explants challenged with IFNτ + IFNα indicated the competition of IFNτ and IFNα downstream of the regulatory factors. In conclusion, using this well-defined explant model, interactions between infection-associated signals and IFNτ were indicated. This model can be applied to verify these findings and to mimic and explore the embryo–maternal contact zone in more detail.

Lethal and semi-lethal mutations in Holstein calves in Uruguay

ABSTRACT: Genetic disorders in Holstein cattle are a health problem that has grown worldwide in recent years, compromising the sustainability of modern dairy production. In Uruguay, Holstein-based milk production is one of the most important sectors of the country’s economy, but high levels of inbreeding have decreased the breed’s fertility in recent decades. This study investigated the presence and diffusion of lethal and semi-lethal alleles causing embryo death, abortions, fetal malformations, and neonatal diseases in Holstein calves. Using the GeneSeek® Genomic Profiler™ Bovine 50K BeadChip, we genotyped 383 calves (1-30 days-old) from 27 farms located in the main dairy region of Uruguay. Results showed a high prevalence of farms (85%) and carrier calves (21%), including one or more of the following semi-lethal or lethal alleles: Syndactylism (4.18%), brachyspina (3.39%), cholesterol deficiency haplotype (2.61%), complex vertebral malformation (2.09%), bovine leukocyte adhesion deficiency (1.04%s), and Holstein haplotypes HH1 (4.44%), HH3 (3.13%), HH4 (1.04%), and HH5 (0.26%). Most of these alleles had not been recognized previously in Uruguay. We concluded that lethal and semi-lethal mutations are widespread in the Holstein breed in Uruguay. More studies are required to determine their impact on dairy cattle fertility.

Administration of acetylsalicylic acid after parturition in lactating dairy cows under certified organic management: Part I. Milk yield, milk components, activity patterns, fertility, and health

Parturition is a natural process that gradually progresses from one stage to the next. However, around 5% of dairy cows will experience dystocia, which is considered to be a painful and stressful event. Studies have reported positive effects on cow performance and welfare after treatment with nonsteroidal anti-inflammatory drugs during the first postpartum days. The objectives were to assess the effects of acetylsalicylic acid administration after calving on (1) milk yield and components, (2) daily activity patterns, (3) reproductive performance, and (4) health in lactating dairy cows under certified organic management. Cows from 3 organic herds were enrolled. Within 12 h after parturition, cows were blocked by parity and calving ease and randomly assigned to 2 treatments: (1) aspirin (ASP; n = 278), in which cows received 4 consecutive treatments every 12 h with acetylsalicylic acid (100 mg/kg; 2 boluses) or (2) placebo (PLC, n = 285), in which cows received 4 treatments every 12 h with gelatin capsules (2 capsules) filled with water. Daily milk yield for the first 30 d in milk (DIM) and monthly milk yield, fat, protein, and somatic cell count (SCC) data from the first 5 Dairy Herd Improvement Association tests were collected. Activity patterns were measured using activity data loggers in the first 7 DIM. Clinical disease events (60 DIM) and fertility data were collected from on-farm computer records. Statistical analysis was performed using the MIXED (milk yield, components, and activity), LIFETEST (fertility), and GLIMMIX (health) procedures of SAS (SAS Institute Inc., Cary, NC). Overall, ASP cows produced 1.82 kg/d more milk than PLC cows during the first 30 DIM. Interestingly, cows that experienced dystocia and received ASP produced 4.48 kg/d more milk compared with cows in the PLC group that experienced dystocia. Cows treated with ASP had lower somatic cell count during the first 5 Dairy Herd Improvement Association tests. There were no differences in daily lying time, lying bouts, and lying bout duration between the ASP and PLC groups. However, cows in the ASP group had 587,64 steps/d more compared with PLC cows. In addition, ASP cows tended to require fewer days (ASP = 113.76 ± 4.99 d; PLC = 125.36 ± 4.74 d) and needed fewer services (ASP = 1.86 ± 0.21 services; PLC = 2.19 ± 0.24 services) to become pregnant compared with PLC cows. There were no differences in clinical disease events between treatments. Results from this study suggest that treating cows with ASP after calving may help improve milk yields and udder health, increase activity, and enhance fertility in dairy cattle under certified organic management.

Across-country genomic prediction of bull fertility in Jersey dairy cattle

The use of information across populations is an attractive approach to increase the accuracy of genomic predictions for numerically small breeds and traits that are time-consuming and difficult to measure, such as male fertility in cattle. This study was conducted to evaluate genomic prediction of Jersey bull fertility using an across-country reference population combining records from the United States and Australia. The data set consisted of 1,570 US Jersey bulls with sire conception rate (SCR) records, 603 Australian Jersey bulls with semen fertility value (SFV) records and SNP genotypes for roughly 90,000 loci. Both SCR and SFV are evaluations of service sire fertility based on cow field data, and both are intended as phenotypic evaluations because the estimates include genetic and nongenetic effects. Within- and across-country genomic predictions were evaluated using univariate and bivariate genomic best linear unbiased prediction models. Predictive ability was assessed in 5-fold cross-validation using the correlation between observed and predicted fertility values and mean squared error of prediction. Within-country genomic predictions exhibited predictive correlations of around 0.28 and 0.02 for the United States and Australia, respectively. The Australian Jersey population is genetically diverse and small in size, so careful selection of the reference population by including only closely related animals (e.g., excluding New Zealand bulls, which is a less-related population) increased the predictive correlations up to 0.20. Notably, the use of bivariate models fitting all US Jersey records and the optimized Australian population resulted in predictive correlations around of 0.24 for SFV values, which is a relative increase in predictive ability of 20%. Conversely, for predicting SCR values, the use of an across-country reference population did not outperform the standard approach using pure US Jersey reference data set. Our findings indicate that genomic prediction of male fertility in dairy cattle is feasible, and the use of an across-country reference population would be beneficial when local populations are small and genetically diverse.

Uterine infusion of bacteria alters the transcriptome of bovine oocytes.

Postpartum uterine infection reduces fertility in dairy cattle; however, the mechanisms of uterine infection‐mediated infertility are unknown. Paradoxically, infection‐induced infertility persists after the resolution of disease. Oocytes are a finite resource, which are present at various stages of development during uterine infection. It is likely that oocyte development is influenced by uterine infection‐induced changes to the follicular microenvironment. To better understand the impact of infection on oocyte quality we employed global transcriptomics of oocytes collected from heifers after receiving intrauterine infusion of pathogenic Escherichia coli and Trueperella pyogenes. We hypothesized that the oocyte transcriptome would be altered in response to intrauterine infection. A total of 452 differentially expressed genes were identified in oocytes collected from heifers 4 days after bacteria infusion compared to vehicle infusion, while 539 differentially expressed genes were identified in oocytes collected from heifers 60 days after bacteria infusion. Only 42 genes were differentially expressed in bacteria‐infused heifers at both Day 4 and Day 60. Interferon, HMGB1, ILK, IL‐6, and TGF‐beta signaling pathways were downregulated in oocytes collected at Day 4 from bacteria‐infused heifers, while interferon, ILK, and IL‐6 signaling were upregulated in oocytes collected at Day 60 from bacteria‐infused heifers. These data suggest that bacterial infusion alters the oocyte transcriptome differently at Day 4 and Day 60, suggesting different follicle stages are susceptible to damage. Characterizing the long‐term impacts of uterine infection on the oocyte transcriptome aids in our understanding of how infection causes infertility in dairy cattle.

Whole-genome homozygosity mapping reveals candidate regions affecting bull fertility in US Holstein cattle

BackgroundAchieving rapid genetic progress while maintaining adequate genetic diversity is one of the main challenges facing the dairy industry. The increase in inbreeding can be used to monitor the loss of genetic diversity. Inbreeding tends to increase the proportion of homozygous loci, some of which cause homozygosity of recessive alleles that results in reduced performance. This phenomenon is known as inbreeding depression and tends to be most prominent on fitness-related traits, such as male fertility. Traditionally, inbreeding has been monitored using pedigree information, or more recently, genomic data. Alternatively, it can be quantified using runs of homozygosity (ROH), i.e., contiguous lengths of homozygous genotypes observed in an individual’s chromosome.ResultsThe objective of this study was to evaluate the association between ROH and sire conception rate. ROH were evaluated using 268 k genetic markers in 11,790 US Holstein bulls. Interestingly, either the sum, mean, or maximum length of ROH were negatively associated with bull fertility. The association analysis between ROH and sire fertility was performed comparing 300 high-fertility vs. 300 low-fertility bulls. Both the average and sum of ROH length were higher in the low-fertility group. The enrichment of ROH regions in bulls with low fertility was assessed using a Fisher’s exact test. Nine regions were significantly enriched in low-fertility compared to high-fertility bulls. Notably, these regions harbor genes that are closely related to sperm biology and male fertility, including genes exclusively or highly expressed in testis.ConclusionsThe results of this study can help not only to manage inbreeding in genomic selection programs by designing custom mating schemes, but also to better understand the mechanisms underlying male fertility in dairy cattle.

Gene mapping and genomic prediction of bull fertility using sex chromosome markers

Service sire has been recognized as an important factor affecting dairy herd fertility. Our group has reported promising results on gene mapping and genomic prediction of dairy bull fertility using autosomal SNP markers. Little is known, however, about the genetic contribution of sex chromosomes, which are enriched in genes related to sexual development and reproduction. As such, the main goal of this study was to investigate the effect of SNP markers on X and Y chromosomes (BTAX and BTAY, respectively) on sire conception rate (SCR) in US Holstein bulls. The analysis included a total of 5,014 bulls with SCR records and genotypes for roughly 291k SNP located on the autosomes, 1.5k SNP located on the pseudoautosomal region (PAR), 13.7k BTAX-specific SNP, and 24 BTAY-specific SNP. We first performed genomic scans of the sex chromosomes, and then we evaluated the genomic prediction of SCR including BTAX SNP markers in the predictive models. Two markers located on PAR and 3 markers located on the X-specific region showed significant associations with sire fertility. Interestingly, these regions harbor genes, such as FAM9B, TBL1X, and PIH1D3, that are directly implicated in testosterone concentration, spermatogenesis, and sperm motility. On the other hand, BTAY showed very low genetic variability, and none of the segregating markers were associated with SCR. Notably, model predictive ability was largely improved by including BTAX markers. Indeed, the combination of autosomal with BTAX SNP delivered predictive correlations around 0.343, representing an increase in accuracy of about 7.5% compared with the standard whole autosomal genome approach. Overall, this study provides evidence of the importance of both PAR and X-specific regions in male fertility in dairy cattle. These findings may help to improve conception rates in dairy herds through accurate genome-guided decisions on bull fertility.

Early and Late Embryonic Loss of Smallholder Synchronized Dairy Cows Within Ethiopia

This study was carried out on 53 cows selected from smallholder dairy farmers in the Ejerie, Adea Berga and Metarobi western Shoa of Oromia in Ethiopia. All of the cows were investigated in October and November, 2015 for their cyclicity, pregnancy and mainly for early embryonic mortality determination. Milk samples were collected from the 53 of synchronized lactating cows involved in the estrus synchronization programme at the time of AI (day 0). Out of lactating cows, 33 exhibited true heat but due heat detection error, only 26 lactating cows were inseminated in day AI (Artificial Insemination). After it was confirmed that 20 lactating cows were pregnant, then they were continued for further progesterone profiling starting from day 18 to 45 day of post AI at interval of 3 days for determination of early embryonic loss based on progesterone concentration. The milk sample was analyzed by Hormonost Farmer Test. Results of the study indicated that about 60% of lactating cows maintain pregnancy until 45-day post AI whereas 15%, 15% and 10% of early pregnant lactating cow’s loss their embryo at 21^st to 24^th days, 27^th to 30^th days and 33^rd day of post AI, respectively. The average progesterone concentration for pregnant cows was 24.46 ng/ml at day 21 to day 45 post AI. Based on finding of this result monitoring and evaluating reproductive traits with progesterone profiling is recommended to improve the fertility of dairy cattle. Finally, embryonic loss detection may serve as a basis for improvement of fertility of dairy cows mean while it will help for designing appropriate breeding management of dairy cattle.

A Post-mortem Survey of Bovine Female Reproductive Tracts in the UK.

The aim of this study was to estimate the prevalence of macroscopic reproductive tract abnormalities in a sample of female cattle in the UK. To our knowledge, this type of post-mortem survey has not been conducted in the UK since the 1970s. Over the last 40 years significant changes have occurred with respect to management and genetics. Moreover, there have been changes in growth rates in beef animals, elevated milk yields and a decline in fertility in dairy cattle. It was hypothesised that differences may exist in the extent and type of lesions occurring compared with previous studies. Between May and July 2017, the reproductive tracts of cattle (Bos taurus) were examined post-mortem at an abattoir in the north west of England. All female cattle slaughtered on visit days were eligible. In total 680 tracts were examined, constituting 88% of those eligible. Macroscopic abnormalities were recorded using a standard format and definitions. The majority of cattle were a dairy breed (73%) with Holstein-Friesian accounting for over half of these. Median age at slaughter for dairy breeds was 5.1 years (range 1.7–13.8 years) and 3.9 years (0.92–16.8 years) for beef breeds. A total of 141 out of the 680 reproductive tracts examined exhibited at least one lesion, giving an overall prevalence of abnormalities of 20.7%, with 95% confidence interval (CI) 17.9–23.9%. This is double the last similar UK-based study carried out in the late 1970s. There were 20 different types of abnormality identified, with 207 individual lesions in 141 abnormal tracts. The ovary was the most common anatomical location displaying abnormalities, accounting for 70.2% of all abnormal tracts. Ovaro-bursal adhesions were the most common abnormality found at 5.3% (CI 3.9–7.2%) and half of these were classified as severe. The second most common lesion was follicular cystic ovarian disease at 4.6% (CI 3.2–6.4%), followed by anoestrus at 4.1% (CI 2.9–5.9%). Double the prevalence of macroscopic reproductive tract lesions is a concern. Greater use of post-mortem material for disease surveillance and further studies into risk factors, especially for the most prevalent lesions, is warranted.

155 Fertility of sexed semen in Holstein heifers and cows

Compared with conventional semen, use of sexed semen decreases the conception rate (CR); therefore, it is important to address the factors that lead to sperm damage. Recently, a novel sexed semen technology was developed for improving dairy cattle fertility (Betthauser et al. 2016 J. Dairy Sci. 99 (E-Suppl. 1), 534). However, there are few reports about the fertility of this novel sexed semen in dairy cattle in Japan. The objective of this study was to compare the CR of traditional sorting semen (S1: flow cytometry/cell sorting) and the novel sexed semen (S2: SexcelTM, ABS Global Inc.) in Holstein heifers and cows in Japan. The CR for the first insemination was obtained from 391 Holstein cows and 148 heifers (10.7-17.8 months old) from 14 dairy farms in Hokkaido from June 2017 to April 2019. Semen used for AI was collected from six bulls and packaged into 0.25-mL straws and frozen. Cows inseminated with conventional frozen semen (S3: unsexed semen in 0.5-mL straws) were used as controls. Calving data were collected from 123 cows and 69 heifers that had calved between January 2018 and May 2019. The diagnosis of pregnancy was confirmed using ultrasonography between 30 and 45 days after insemination. The CR and sex ratio were analysed using chi-square test. The average parity number was 1.9±1.1, and average days open was 84.9±20.4 days. The average interval between calving and the first service was 86.2±20.3 days. The average milk yield (at 305 days) was 12 195±1595 kg. All of the animals were inseminated after the onset of standing heat or removal of the tail chalk of natural heats and oestrus and ovulation synchronisation programmes on the farm. Conception rates of heifers of the first service of S1 (n=54) and S2 (n=94) were 68.5 and 70.2%, respectively. Conception rates of cows of the first service of S1 (n=32), S2 (n=173), and S3 (n=186) were 56.3, 57.8, and 53.8%, respectively. There were no significant differences in CR between these groups (P&amp;gt;0.4). The proportion of female calves produced using S1 (n=61) and S2 (n=57) was 91.8 and 93.0%, respectively, which was significantly more (P&amp;lt;0.01) compared with the 50.0% produced using S3 (n=74). There were no significant differences between S1 and S2 (P&amp;gt;0.8) in terms of the proportion of calves produced. The results of this study demonstrated that the traditional sorting and novel sexed semen (S1 and S2, respectively) did not differ in terms of the first-service CR and produced considerably more female calves than when the conventional semen (S3) was used. Furthermore, these findings indicate that the use of this novel sexed semen could achieve a sex ratio close to 90% female offspring.

Supplementation of ascorbic acid to improve fertility in dairy cattle. Review

Ascorbic acid (vitamin C: VC) is an antioxidant that participates in the regulatory processes involved in the development of ovarian structures and fertility. However, supplementation of VC to dairy cattle to improve fertility has received little attention. However, reduced fertility in dairy cattle associated with high genetic merit for milk production and heat stress, which also diminish blood VC concentrations, suggest a potentially beneficial role for VC supplementation. The objectives of this review are to contribute to the current knowledge regarding the relationship between VC and fertility and to share many experiences that support the relevance of VC supplementation to improve dairy cattle reproductive performance.

The early gestation period and long returns to oestrus in cattle

The fertility of dairy cattle has declined over the last 30 years. As a push for higher milk production has taken place, consideration of the negative impact on fertility has not been sufficiently addressed. As a result, it has become even more important for veterinarians to have a good understanding of normal reproduction processes in cattle, so that every cow has the best opportunity to reproduce successfully. This article aims to explore the early gestation period in dairy cattle, and some of the mechanisms of prolonged returns to oestrus when pregnancy is not established.

Overlap between eQTL and QTL associated with production traits and fertility in dairy cattle

BackgroundIdentifying causative mutations or genes through which quantitative trait loci (QTL) act has proven very difficult. Using information such as gene expression may help to identify genes and mutations underlying QTL. Our objective was to identify regions associated both with production traits or fertility and with gene expression, in dairy cattle. We used three different approaches to discover QTL that are also expression QTL (eQTL): 1) estimate the correlation between local genomic estimated breeding values (GEBV) and gene expression, 2) investigate whether the 300 intervals explaining most genetic variance for a trait contain more eQTL than 300 randomly selected intervals, and 3) a colocalisation analysis. Phenotypes and genotypes up to sequence level of 35,775 dairy bulls and cows were used for QTL mapping, and gene expression and genotypes of 131 cows were used to identify eQTL.ResultsWith all three approaches, we identified some overlap between eQTL and QTL, though the majority of QTL in our dataset did not seem to be eQTL. The most significant associations between QTL and eQTL were found for intervals on chromosome 18, where local GEBV for all traits showed a strong association with the expression of the FUK and DDX19B. Intervals whose local GEBV for a trait correlated highly significantly with the expression of a nearby gene explained only a very small part of the genetic variance for that trait. It is likely that part of these correlations were due to linkage disequilibrium (LD) in the interval. While the 300 intervals explaining most genetic variance explained most of the GEBV variance, they contained only slightly more eQTL than 300 randomly selected intervals that explained a minimal portion of the GEBV variance. Furthermore, some variants showed a high colocalisation probability, but this was only the case for few variants.ConclusionsSeveral reasons may have contributed to the low level of overlap between QTL and eQTL detected in our study, including a lack of power in the eQTL study and long-range LD making it difficult to separate QTL and eQTL. Furthermore, it may be that eQTL explain only a small fraction of QTL.