Effects of deep-horn AI on fertilization and embryo production in superovulated cows and heifers

Review: Postpartum reproductive disease and fertility in dairy cows

This paper reviews recent data and concepts on metritis, purulent vaginal discharge (PVD), and endometritis in dairy cows and the ways in which these diseases affect reproductive performance. Metritis is characterized by fetid discharge from the uterus, with or without fever. Purulent vaginal discharge describes exudate that is >50% pus that may be attributable to uterine infection or cervicitis. Endometritis is inflammation of the uterus diagnosed by endometrial cytology with a proportion of neutrophils (typically ≥5%) that is associated with impaired fertility. Metritis and PVD are associated with uterine bacterial dysbiosis: changes in the microbiota to lesser diversity and greater abundance of pathogens, especially Gram-negative anaerobic bacteria, and Trueperella pyogenes in the case of PVD. Metritis is justifiably treated with approved antibiotics but criteria for more selective treatment without loss of performance are emerging. Purulent vaginal discharge is not synonymous with clinical endometritis, and greater precision in terminology is warranted. PVD is likely under-diagnosed and represents an opportunity for improved management in many herds. Endometritis seems in many cases to reflect persistent, dysregulated inflammation, for which the inciting cause is unclear. Postpartum uterine infection and inflammation have harmful effects on oocytes, embryo development, and the endometrium for at least three months, even if the disease is apparently resolved. Emerging concepts of the resolution and regulation of inflammation are promising for the improvement of prevention and therapy of endometritis.

The first week following insemination is the period of major pregnancy failure in pasture-grazed dairy cows

A 60% pregnancy success for inseminations is targeted to optimize production efficiency for dairy cows within a seasonal, pasture-grazed system. Routine measures of pregnancy success are widely available but are limited, in practice, to a gestation stage beyond the first 28 d. Although some historical data exist on embryonic mortality before this stage, productivity of dairy systems and genetics of the cows have advanced significantly in recent decades. Accordingly, the aim was to construct an updated estimate of pregnancy success at key developmental stages during the first 70 d after insemination. Blood samples were collected for progesterone concentrations on d 0 and 7. A temporal series of 4 groups spanning fertilization through d 70 were conducted on 4 seasonal, pasture-grazed dairy farms (n = 1,467 cows) during the first 21 d of the seasonal breeding period. Morphological examination was undertaken on embryos collected on d 7 (group E7) and 15 (group E15), and pregnancy was diagnosed via ultrasonography on approximately d 28 and 35 (group E35) as well as d 70 (group E70). Fertilization, embryo, and fetal evaluation for viability established a pregnancy success pattern. Additionally, cow and on-farm risk factor variables associated with pregnancy success were evaluated. We estimated pregnancy success rates of 70.9%, 59.1%, 63.8%, 62.3%, and 56.7% at d 7, 15, 28, 35, and 70, respectively. Fertilization failure (15.8%) and embryonic arrest before the morula stage (10.3%) were the major developmental events contributing to first-week pregnancy failures. Embryo elongation failure of 7% contributed to pregnancy failure during the second week. The risk factors for pregnancy success that were related to the cows included interval between calving and insemination, and d-7 plasma progesterone concentrations, whereas insemination sire was associated with pregnancy outcome. Most pregnancy failure occurs during the first week among seasonal-calving pasture-grazed dairy cows.

Up-regulation of endometrial oxytocin receptor is associated with the timing of luteolysis in heifers with two and three follicular waves†

Initiation of luteolysis in ruminants is variable due to ill-defined mechanisms. Cycles of two follicular waves are shorter and have earlier luteolysis than three-wave cycles. This study validated a cytobrush technique for evaluating dynamics of endometrial gene expression and associated changes in mRNA with timing of luteolysis, based on circulating progesterone and ultrasound-determined changes in blood flow and volume of corpus luteum (CL). On day 8 (ovulation = day 0), Holstein heifers were randomized into two groups: cytobrush group (n = 9) had an endometrial sample collected every 48 h from day 8 until end of luteolysis (CL blood flow ≤ 20%) and control group was sampled only once either before (day 12; n = 4) or at the end of luteolysis (n = 5). Concentrations of progesterone, CL blood flow, CL volume, and the frequency of two and three-wave cycles were similar between groups. Endometrial mRNA for progesterone receptors and estradiol receptors 1 and 2 was greater on day 8 and decreased thereafter similarly in two and three-wave cycles. Oxytocin receptor mRNA increased earlier in two vs three-wave cycles (day 14 vs 18), and the increase was associated with the onset of luteolysis. In conclusion, the cytobrush technique allowed in vivo collection of multiple endometrial samples during the estrous cycle. Endometrial mRNA expression of steroid receptors did not explain the variability in timing of onset of luteolysis in heifers while the later onset of luteolysis in three-wave cycles was associated with later up-regulation of oxytocin receptor mRNA.

Embryo Transfer as an Option to Improve Fertility in Repeat Breeder Dairy Cows

Repeat breeding is a serious reproductive disorder in dairy cattle. The causes of repeat breeding are multifactorial and there are two main mechanisms: failure of fertilisation or early embryo death, mainly due to poor quality of oocytes and an inadequate uterine environment. Many methods have been used to increase the pregnancy rate for repeat breeder cows, such as intrauterine infusion of antibacterial agents or antibiotics, hormonal treatments for oestrus synchronisation and induction of ovulation, and progesterone supplementation or induction of accessory corpus luteum; however, the results were inconsistent between studies. Embryo transfer (ET) has the capability to minimalise the effects of poor oocyte quality and unfavourable uterine environments on early embryo development during the first seven days after ovulation in repeat breeder cows, and several studies showed that ET significantly improved the pregnancy rate in this group of animals. Thus, ET can be considered an option to increase the conception rate in repeat breeder dairy cows.

Factors affecting embryo production in superovulated Bos taurus cattle

Despite a long history of bovine superovulation research, significant commercial applications did not start until the early 1970s. For some 20 years thereafter, superovulation represented the primary tool for the production of cattle embryos. In the early 1990s, commercial invitro production (IVP) was initiated in cattle. Although ovum pick-up and IVP are now commercially practiced on a wide scale, superovulation and embryo recovery by flushing remain a widespread and very effective approach to the production of cattle embryos. This review covers both the history and the effects of multiple factors on superovulation in Bos taurus cattle. There are three general protocols for suitable pre-FSH programming of donors so that gonadotrophin-responsive follicles are available. Superovulation protocols vary widely based on the FSH source, the diluent used, the number and timing of FSH injections and the timing and utilisation of various prostaglandins, controlled internal progesterone releasing devices, gonadotrophin-releasing hormone, and other means of controlling follicular development and ovulation. The number of oocytes that can be stimulated to grow and ovulate within any given donor can be estimated by either ultrasound-guided sonography or by measuring concentrations of anti-Müllerian hormone in the blood. Animal-related factors that can influence the efficacy of superovulation include cattle breed, age, parity, genetics, lactational status and reproductive history. In addition, nutrition, stress, season, climate, weather and several semen factors are discussed.

Symposium review: Mechanisms of disruption of fertility by infectious diseases of the reproductive tract

Diseases of postpartum dairy cows impair reproductive processes, resulting in prolonged anestrus, reduced conception, and increased pregnancy attrition, regardless of whether the initial disease precedes insemination (even by many weeks), occurs close to insemination, or follows fertilization. Bacteria and their products activate pattern recognition receptors that respond to pathogen-associated molecular patterns (PAMP). These receptors include toll-like receptors (TLR), nucleotide-binding oligomerization domain (NOD)-like receptors and others, and their activation culminates in upregulation of proinflammatory cytokines such as IL-1β, IL-18, and tumor necrosis factor-α. These may have direct effects on the uterus and conceptus. Importantly, however, these inflammatory mediators, as well as the bacterial products, make their way to the ovary via the general circulation (even from distant sites) or possibly by using the countercurrent vascular mechanism that normally transports endometrial prostaglandin to the ipsilateral ovary. Endotoxin reaches concentrations in follicular fluid that exceed those found in the circulation or even in the infected uterus. Ovarian follicular cells also express TLR and can respond directly to bacterial products including endotoxin, impairing their function. Inflammation is accompanied by increased oxidative stress. The process of oocyte development from activation of primordial oocytes to potential ovulation spans 4 mo. Competence by an oocyte encompasses the ability to undergo not only fertilization but also a complex cytoplasmic maturation that lays the foundation for completion of meiosis at the appropriate time, the transition to mitosis in the zygote, and further development of the conceptus. Oocyte maturation relies on intimate association between cumulus cells and the oocyte, characterized by gap junctions through which molecules of various sizes pass. Signaling also occurs in the oocyte-to-cumulus cell direction. Because both granulosa and theca interna cells are capable of responding to inflammatory mediators, with observed alterations in some functions, it seems likely that disturbed ovarian follicular function may contribute to failure of oocytes to become fully competent, even if the insult occurs well before ovulation. Therefore, interruption of normal fertility by uterine infections may be mediated at the level of the uterine environment but the effect on the ovary and oocyte is likely to be even more important.

The Importance of the Periconception Period: Immediate Effects in Cattle Breeding and in Assisted Reproduction Such as Artificial Insemination and Embryo Transfer

In livestock breeding, the successful outcome is largely depending on the "periconception environment" which, in a narrow sense, refers to the genital tract, where gametogenesis and embryogenesis occur. During these early stages of development, gametes and embryos are known to be particularly sensitive to alterations in their microenvironment. However, as the microenvironment somehow reflects what is going on in the external world, we must widen our definition of "periconception environment" and refer to all events taking place around the time of conception, including metabolic state and health and nutrition of the dam. In modern dairy cows that have to manage an optimal reproductive performance with continued growth and high milk yield, the periconception period is particularly challenging. The metabolic priority for growth and lactation is known to generate adverse conditions hampering optimal ovarian function, oocyte maturation, and development of embryo/fetus. In addition, by using artificial reproductive technologies (ARTs), gametes and/or embryos of livestock are exposed to unnatural conditions outside the male and female genital tract. Artificial insemination, the most widely used technique, is currently yielding pregnancy rates similar to natural mating, and calves produced by AI are equally viable after natural mating. In contrast, other ART, such as multiple ovulation and embryo transfer, have been reported to induce changes in gene expression and DNA methylation patterns with potential consequences for development.Finally, the "periconceptional" environment has been shown to not only influence the successful establishment of pregnancy but also the long-term health and productivity of the offspring. Hence, the optimization of management around the time of conception might open doors to improve animal production and product quality.

Exfoliative Endometrial Cytology in Embryo Donor Cows-Comparison of Sampling Localizations for the Diagnosis of Subclinical Endometritis

Subclinical endometritis has a major effect on the reproductive performance of dairy cows and also on the success of embryo collection. Thus it is important to minimize the number of false-negative diagnoses. In order to evaluate the question of whether or not a single cytobrush sample is representative of the whole endometrium, 53 German Holstein embryo donor cows in the northwest of Germany were examined via the cytobrush method at three different localizations of the uterus: the uterine body about 0.5 cm cranial of the cervical canal and both uterine horns about 1.5 cm cranial of the bifurcation. Although the mean percentage of polymorphonuclear neutrophils at the three locations is not significantly different (p = 0.64), the individual variations lead to the conclusion that more than one sample of the endometrium should be taken into account when diagnosing subclinical endometritis in embryo donor cows.

Effect of uterine size on fertility of lactating dairy cows

There are multiple reasons for reduced fertility in lactating dairy cows. We hypothesized that one cause of reduced fertility could be the overall size of the reproductive tract, particularly the uterus, given well-established uterine functions in many aspects of the reproductive process. Thus, the objectives of this study were to evaluate the variability in uterine size in primiparous and multiparous dairy cows and to analyze whether there was an association between uterine size and fertility, particularly within a given parity. Lactating Holstein dairy cows (n = 704) were synchronized to receive timed artificial insemination (TAI) on Day 81 ± 3 of lactation by using the Double-Ovsynch protocol (GnRH-7d-PGF-3d-GnRH-7d-GnRH-7d-PGF-56h-GnRH-16h-TAI). At the time of the last injection of PGF, uterine diameter was determined at the greater curvature using ultrasound, uterine length was determined by rectal palpation, and uterine volume was calculated from these two measurements. Blood samples were also taken to measure progesterone to assure synchronization of all cows used in the final analysis (n = 616; primiparous, n = 289; multiparous, n = 327). Primiparous cows had greater percentage pregnant/AI (P/AI) compared to multiparous cows (49.8% vs. 39.1% at 67 days of pregnancy diagnosis, P = 0.009). Diameter, length, and volume of the uterus were larger in multiparous than in primiparous cows (P < 0.001). For multiparous cows, uterine diameter and volume were smaller in cows that became pregnant compared to cows that were not pregnant to the TAI with a similar tendency observed in primiparous cows. Logistic regression and quartile analysis also showed that as uterine volume increased, there was decreased P/AI in either primiparous or multiparous cows. Thus, there is a negative association between uterine size and fertility in lactating dairy cows with a larger uterus associated with reduced fertility, particularly for multiparous cows.

Transcervical collection of bovine embryos up to Day 21: an 8-year overview

Transcervical embryo collection is used routinely in the bovine species throughout the world to collect Day 6 to Day 9 embryos (early embryos) for genetic selection. For research purposes, however, the collection of embryos at later stages of pregnancy, i.e., Days 12 to 21 (late embryos), is needed. So far, for the recovery of late embryos, females are euthanized and embryo collection is performed after recovery of the genital tract. To reduce the number of animals used and still provide valuable material for embryo research, we have therefore developed a transcervical technique to collect late embryos. The objective of this study was to compare embryo recovery results at early and late stages within our laboratory. Altogether, 232 cows were used for this study. One hundred forty-five flushes were performed to collect embryos from Days 6 to 9, and 251 flushes were performed to collect embryos from Days 12 to 21. For the early embryos, a classical three-way collection equipment was used. To collect the late embryos, the same equipment was used, but the extensible flexible catheter that goes inside the external rigid catheter was removed, so that larger embryos could be collected through the remaining larger hole (two-way collection). All females were submitted to ovum pick up to remove the dominant follicle and were subsequently superovulated with FSH. Luteolysis was induced 48 hours before artificial insemination. Two artificial inseminations were performed with frozen semen, 48 and 56 hours after PGF2α injection. Before embryo collection, cows were treated with an epidural injection of a local anesthetic drug. The presence of CL was checked, and they were counted by rectal palpation. For all collections, the cervix was prepared with the initial introduction of a dilator. Then, the catheter was introduced in one horn, and the cuff was inflated as low as possible. For the collection of late embryos, the flushing solution (30 mL) was injected slowly twice to suspend the embryos before flushing the horn with 500 mL, and the same operation was performed on the second horn. There was no significant difference in the number of embryos collected per flush in the early- and late-stage (758 embryos collected, 5.22 ± 6.02 per flush vs. 1238 embryos collected, 4.93 ± 5.07 per flush, respectively). The number of embryos collected per CL, however, was significantly lower in the early versus late group (0.39 ± 0.32% vs. 0.44 ± 0.34%, respectively). The late collection allowed the retrieval of full conceptuses (embryonic and extraembryonic tissues), even at very late stages such as Days 18 to 21. Careful collection is needed, however, so that conceptuses are not damaged or torn: the horn must be massaged gently and the flush should be ideally recovered in one single flow. This technique is a powerful tool to collect the late-stage embryos for research purposes. Because it is not traumatic, animals can be used again for the same procedure.

Use of a single injection of long-acting recombinant bovine FSH to superovulate Holstein heifers: a preliminary study

Our objective was to compare several experimental preparations of a single injection of long-acting recombinant bovine FSH (rbFSH; types A and B) to a porcine pituitary-derived FSH (Folltropin) to superovulate Holstein dairy heifers. Nonlactating, nonpregnant virgin Holstein heifers (n = 56) aged 12 to 15 months were randomly assigned to one of four superstimulatory treatments. Beginning at a random stage of the estrous cycle, all follicles greater than 5 mm were aspirated. Thirty-six hours later, heifers received an intravaginal P4 device and superstimulatory treatments were initiated. Treatments were (1) 300 mg of pituitary-derived FSH (Folltropin) administered in eight decreasing doses over a period of 3.5 days; (2) a single injection of 50 μg of A-rbFSH; (3) a single injection of 100 μg of A-rbFSH; and (4) a single injection of 50 μg of B-rbFSH. All heifers received 25 mg PGF2α at 48 and 72 hours after the insertion of P4 device. At 84 hours after insertion, P4 devices were removed, and ovulation was induced 24 hours later with hCG (2500 IU). Heifers were inseminated at 12 and 24 hours after hCG treatment. The number of ovulatory follicles was greatest for heifers treated with Folltropin and B50-rbFSH, least for heifers treated with A50-rbFSH, and was intermediate for heifers treated with A100-rbFSH (25.7 ± 3.2, 18.9 ± 3.2, 5.9 ± 0.9, and 16.6 ± 3.1, respectively; P < 0.001). The number of corpora lutea was greatest for heifers treated with Folltropin, B50-rbFSH, and A100-rbFSH, and least for heifers treated with A50-rbFSH (19.1 ± 2.4, 16.1 ± 3.0, 15.9 ± 2.9, and 2.6 ± 0.9, respectively; P < 0.001). The number of good-quality embryos differed among treatments and was greatest for heifers treated with B50-rbFSH, Folltropin, and A100-rbFSH and least for heifers treated with A50-rbFSH (7.6 ± 2.4, 6.5 ± 1.7, 4.3 ± 1.5, and 0.8 ± 0.5, respectively; P < 0.001). In conclusion, a single injection of a preparation of long-acting rbFSH (either 100 μg of A-rbFSH or 50 μg of B-rbFSH but not 50 μg of A-rbFSH) produced similar superovulatory responses resulting in the production of good-quality embryos when compared with a pituitary-derived FSH preparation administered twice daily for 4 days. More studies using different types of cattle and different doses of rbFSH are needed to confirm the findings reported in this preliminary study.