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Heat stress is especially harmful for bovine ovarian follicle development and oocyte competence. In this study, we assessed the effects of heat shock on oocyte maturation in oocytes collected during the cold (February-March; n = 114) or warm (May-June; n = 116) periods of the year. In both cases, cumulus-oocyte complexes were matured under control (38 °C) and heat shock conditions (41.5 °C, 18-21 h of maturation). For each oocyte, nuclear stage, cortical granule distribution and steroidogenic activity of cumulus cells were evaluated. Based on the odds ratio, heat-shocked oocytes were 26.83 times more likely to show an anomalous metaphase II morphology. When matured under heat shock conditions, oocytes obtained in both seasons were similarly affected in terms of nuclear maturation, whereas a seasonal effect was observed on cytoplasmic maturation. For oocytes collected during the cold season, the likelihood to show an anomalous maturation was 25.96 times higher when exposed to the heat treatment than when matured under control conditions. By contrast, oocytes collected during the warm season matured under control or heat shock did not show significant risk of showing an anomalous cytoplasmic maturation. Our findings indicate an increased rate of premature oocytes in response to heat shock as well as a higher tolerance to this stress of oocytes harvested in the warm season compared with those collected in the colder period., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This study was designed to determine the effects of twinning on the subsequent reproductive performance and productive lifespan of high milk-producing dairy cows. The data analyzed were taken from complete reproductive records for 4861 Holstein Friesian cows comprising a commercial herd, including data for 12 587 calving events from April 1, 2001 to March 31, 2012. The twinning rate was 5.6%, and 9.6% of the cows delivered twins at least once during their life. Conception rates before Days 90, 120, and 300 postpartum were 20.8%, 36.9%, and 74.5%, and 34.2%, 51.8%, and 85.0% for cows delivering twins and singletons, respectively. Cox regression analysis revealed that twinning reduced the chances of conception before Day 90 by a factor of 0.76. Also, the median calving to conception interval was significantly longer for cows calving twins (134 ± 4.5 days) than for cows delivering singletons (108 ± 0.8 days; P < 0.001). Moreover, in cows in which conception was successful, the risk of abortion was higher for cows that calved twins than for those calving singletons (13.7% vs. 10.3%, respectively; P = 0.01). Culling rates before Days 90, 120, and 300 postpartum were 15.6%, 16.1%, and 28.6%, and 7.6%, 8.7%, and 15.9% for cows calving twins and singletons, respectively. Cox regression analysis of the factors affecting the culling rate before Day 300 postpartum revealed a 1.41 times greater hazard ratio of culling for cows calving twins than cows calving singletons. Further, mean productive lifespan was almost 300 days shorter for primiparous twinners (N = 48, 602 ± 493 days) than for nontwinners (N = 2592; 899 ± 581 days; P < 0.01), and 200 days shorter for secundiparous twinners (N = 126, 914 ± 429 days) than for nontwinners undergoing at least two lactations (N = 1936, 1101 ± 522 days; P < 0.01). Kaplan-Meier survival curves for productive lifespan differed between primiparous twinners and non-twinners (P < 0.001), and between secundiparous twinners and nontwinners having at least two lactations (P = 0.017). Differences in culling patterns for twinners and nontwinners were not restricted to the subsequent lactation but continued as long as 800 days after first calving, strongly suggesting long-term negative effects of twinning. As an economic implication of our findings, we suggest that twin embryo reduction at the moment of pregnancy diagnosis could be a profitable strategy to cut twinning rates and abolish their detrimental effects on subsequent reproductive performance and productive lifespan., (Copyright © 2012 Elsevier Inc. All rights reserved.)

This study addresses potential management risk factors affecting the incidence of twin pregnancies in high-producing dairy cows. Special attention was paid to the estrus synchronization protocol used before the AI resulting in pregnancy. Possible factors affecting the twin pregnancy rate were analyzed through binary logistic regression procedures on 2015 pregnant cows from July 2010 to July 2011. Twin pregnancy was recorded in 361 of the 2015 pregnancy diagnoses made (17.9%). Twin pregnancy rates differed among herds (P < 0.001) and ranged from 12.4% to 23.9%. Based on the odds ratios, the risk of twin pregnancy was reduced by factors of 0.65 or 0.71 when AI was performed during the warm season or an increasing photoperiod, respectively and increased by a factor of 1.11 for each unit increase in lactation number; by factors of 4.57 or 6.33 in cows that received a progesterone-releasing intravaginal device (PRID) plus 500 or 750 IU of equine chorionic gonadotropin (eCG) 28 days before the pregnancy AI, respectively; by a factor of 2.39 in cows with an ovarian cyst diagnosed in the 14 days prior to AI and treated with prostaglandins (PG); by factors of 1.94 or 3.91 in cows that received two PG doses during the 14 days prior to AI or cows that following failed PRID treatment had received PG started over the 28 days prior to AI, respectively; and by a factor of 2.58 in cows that had previously delivered twins compared to cows delivering singletons. Our results indicate that cow factors, such as lactation number and previous twining, as well as environmental factors, such as photoperiod and season and management related to synchronization protocols affect significantly the incidence of twin pregnancies., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Embryo reduction may prevent the negative effects of twinning in dairy cattle; however, the technique may carry an additional risk of pregnancy loss. The aim of this study was to evaluate the effect on pregnancy maintenance of embryo reduction by manual amnion rupture in unilateral and bilateral twin pregnant cows. A secondary objective was to examine the dynamics of endocrine factors following the treatment. On Day 35-41 of gestation 55 cows bearing two live twin embryos (28 bilateral, 27 unilateral) were randomly assigned to a twin reduction group (n = 27; cows fitted with a progesterone releasing intra-vaginal device for 21 days after manual amnion rupture) or control group (n = 28; untreated cows). Pregnancy loss before Day 90 was recorded in nine control and eleven twin reduction cows (32.1% vs 40.7%, respectively, p = 0.508). Logistic regression models indicated that laterality was the only variable significantly affecting pregnancy loss. The pregnancy loss risk was 8.7 times higher for unilateral than for bilateral twin pregnancies (59.3% vs 14.3%, respectively, P < 0.001) yet was similar in the unilateral control and unilateral twin reduction cows (62.3% vs 53.8%, respectively, P = 0.581). In contrast, four of 14 cows with bilateral twin pregnancies undergoing twin reduction lost their pregnancies while no losses were recorded in control cows with bilateral pregnancies (P = 0.049). A rise in plasma progesterone concentration was detected on the day following treatment in the twin reduction group and concentrations remained high within the first week of treatment. Plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations fell between Day 35-41 and Day 42-48, regardless of treatment. Our findings indicate that embryo reduction by manual amnion rupture did not carry an additional risk of pregnancy loss for unilateral twin pregnancies, whereas it increased the risk of pregnancy failure in bilateral twin pregnancies. However, benefits of preventing cows from delivering twins might also be considered when assessing the success of embryo reduction in bilateral twin pregnancies., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Considering the high temperatures that the tropical climate provides to most of Brazil and the effects of thermal stress on reproductive processes, the objective of the present study was to analyze, in the warmer months of 2016, conception rates of Nelore bovine embryos in Acre state. For this purpose, oocytes were aspirated (ultrasound-guided follicular aspiration), matured, fertilized with Nelore bull semen, cultured for 6 days, and then the embryos were transferred to crossbred recipients. Pregnancy diagnosis was performed 30 and 60 days after embryo transfer. Meteorological data were obtained at www.inmet.gov.br to generate temperature-humidity index (THI). The data from the conception rates and periods of the year were submitted to the chi-square test at 5% probability to verify independence. Regression analysis was used to verify the relationship between THI and gestation rate. There was a strong relationship between conception rates and THI values, verified by an increase in conception rates as THI values were reduced and a decrease when THI reached the highest value. Our findings demonstrated a negative effect of heat stress in conception rates of crossbred cows in northern Brazil.

Carrying twins has been extensively described as an emerging principal non-infectious factor jeopardizing pregnancy maintenance and reducing the lifespan of dairy cows. The risk of pregnancy loss during the first trimester of gestation for cows carrying twins may be from three to seven times higher than for cows carrying singletons. Longer calving to conception intervals, higher culling rates and a shorter mean production lifespan of 200 days have been reported for cows delivering twins compared to cows delivering singletons. There is therefore a need accurately to detect twin embryos at the time of pregnancy diagnosis to follow twin pregnancies carefully or, alternatively, to remove one of the embryos. Therapeutic approaches for the problem of twin pregnancies include GnRH treatment or induced embryo reduction. With similar results, manual rupture of the amniotic vesicle or transvaginal ultrasound-guided aspiration of allanto-amniotic fluid have been proposed as methods of choice to perform twin reduction in cows on Day 28–41 of gestation. However, benefits and risks of induced twin reduction should be quantified. This report reviews various aspects concerning control of twin pregnancies and the practical implications at herd level. Special attention is paid to timing of spontaneous twin reduction. Prospects for induced embryo reduction are also discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Heat stress is a major problem for the health and productivity of livestock, including cattle. Since the 1950s, researchers have studied how high environmental temperature affects cattle fertility through both laboratory and field studies. When a cow's rectal or vaginal temperature goes above 39.1 °C, it is considered heat-stressed, which can harm its ability to reproduce. However, there is not enough information about temperatures in the uterus, oviducts, and ovarian follicles, especially in lactating dairy cows, to ensure current laboratory models are accurate. These data are crucial for understanding how heat stress impacts oocyte (egg) development and early embryo survival in cattle. Additionally, it is important to improve live animal stress models to correctly identify when cows are truly experiencing heat stress, shown by signs like increased panting, body temperature, and heart rate, rather than just assuming they are stressed based on exposure to a high temperature–humidity index. Improving these models will make them more reliable and help identify cattle that can better tolerate heat. Rectal and vaginal temperatures are utilised in both in vivo and in vitro models to study the effects of heat stress on oocyte competence and embryo viability in cattle. However, uterine temperature increases by only 0.5 °C in heat-stressed cows, significantly lower than simulated increases in in vitro models. Temperature variations within oviducts and ovarian follicles during heat stress are poorly understood or unavailable, and evidence is lacking that oocytes and pre-implantation embryos experience mild (40 °C) or severe (41 °C) heat stress inside the ovarian follicle and the oviduct and uterus, respectively. Gathering detailed temperature data from the reproductive tract and follicles is crucial to accurately assess oocyte competence and embryo viability under realistic heat stress conditions. Potential harm from heat stress on oocytes and embryos may result from reduced nutrient availability (e.g., diminished blood flow to the reproductive tract) or other unidentified mechanisms affecting tissue function rather than direct thermal effects. Refining in vivo stress models in cattle is essential to accurately identify animals truly experiencing heat stress, rather than assuming heat stress exposure as done in most studies. This will improve model reliability and aid in the selection of heat-tolerant animals. [ABSTRACT FROM AUTHOR]

Simple Summary: Pregnancy loss at any developmental stage affects the reproductive efficiency of cattle both at the individual and herd levels. In dairy cows, negative effects on milk production along with the increased antibiotic usage associated with pregnancy loss can have dramatic consequences on herd economy. Pregnancy loss during late embryonic and early fetal development can affect up to 20% of animals within a dairy cattle herd, so regular screening and pregnancy maintenance protocols are mandatory as it is important to identify animals at risk of losing their pregnancy after its diagnosis. In this review, we describe possible noninfectious causes of pregnancy loss during this late embryonic/early fetal stage. In cattle, initial pregnancy diagnosis takes place during the late embryonic/early fetal stage of gestation. From this point onward, pregnancy loss may occur in up to one fifth of pregnancies before the initial pregnancy diagnosis is confirmed. This means the early identification of risk factors is a key part of pregnancy diagnosis and herd management. The various factors responsible for pregnancy losses are classified into infectious and noninfectious. Among the noninfectious causes, several dam-related (circumstances of the individual pregnancy or milk production) and herd-related factors causing stress have been well established. In this review, we summarize the impacts of these noninfectious factors and predict associated risks of pregnancy loss. [ABSTRACT FROM AUTHOR]

Contents: The objective of this study was to determine whether fluid drainage from the subordinate follicles by ovum pickup procedures prevents the risk of twin pregnancy without reducing the fertility of the cow. Lactating dairy cows with at least two follicles over 12 mm diameter located one on each ovary and selected from synchronized groups for fixed‐time insemination were assigned to a Control (n = 49) or Drainage (n = 49) group. The largest follicle was considered as the dominant follicle. Draining of all subordinate follicles (≥10 mm) was performed in the Drainage group. All drained follicles developed as a corpus luteum 7 days later. In the Control cows, the presence of two corpora lutea (55.1%) was lower (p = .003) than those in the Drainage cows (87.8%), whereas the incidence of twin pregnancies was 50% and 0% for the Control and Drainage groups, respectively (p < .001). Draining did not affect the pregnancy rate. These results indicate that puncture and drainage of the subordinate follicles at insemination may eliminate the risk of twin pregnancies and reduce the risk of subsequent pregnancy loss by increasing the incidence of additional corpora lutea. [ABSTRACT FROM AUTHOR]

Simple Summary: The impact of heat stress on reproduction is complex and multifactorial and is compounded by growing challenges due to climate change. Both animal welfare and fertility are vulnerable parameters easily affected by heat stress. Heat stress leads to a marked decrease in the developmental competence of oocytes and the fertilizing capacity of spermatozoa, leading to a declining reproduction rate and losses for the cattle industry. There is an urgent need to find viable methods of alleviating the effects of global warming on animal welfare and fertility and, accordingly, guard the reproductivity, productivity, and profitability of cattle farms. In recent decades, the adverse effects of global warming on all living beings have been unanimously recognized across the world. A high environmental temperature that increases the respiration and rectal temperature of cattle is called heat stress (HS), and it can affect both male and female reproductive functions. For successful reproduction and fertilization, mature and healthy oocytes are crucial; however, HS reduces the developmental competence of oocytes, which compromises reproduction. HS disturbs the hormonal balance that plays a crucial role in successful reproduction, particularly in reducing the luteinizing hormone and progesterone levels, which leads to severe problems such as poor follicle development with a poor-quality oocyte and problems related to maturity, silent estrus, abnormal or weak embryo development, and pregnancy loss, resulting in a declining reproduction rate and losses for the cattle industry. Lactating cattle are particularly susceptible to HS and, hence, their reproduction rate is substantially reduced. Additionally, bulls are also affected by HS; during summer, semen quality and sperm motility decline, leading to compromised reproduction. In summer, the conception rate is reduced by 20–30% worldwide. Although various techniques, such as the provision of water sprinklers, shade, and air conditioning, are used during summer, these methods are insufficient to recover the normal reproduction rate and, therefore, special attention is needed to improve reproductive efficiency and minimize the detrimental effect of HS on cattle during summer. The application of advanced reproductive technologies such as the production of embryos in vitro, cryopreservation during the hot season, embryo transfer, and timed artificial insemination may minimize the detrimental effects of HS on livestock reproduction and recover the losses in the cattle industry. [ABSTRACT FROM AUTHOR]

A photoperiod is the time duration when animals are exposed to light in an entire day. An exposure of 16 hours or more is considered a long-day photoperiod and 8 hours of light is a short-day photoperiod. Exposure to light prevents the secretion of melatonin from the pineal gland. Melatonin can influence the release of several hormones, including prolactin, cortisol, kisspeptin, GnRH and others. Eventually, it can also affect the reproductive performance of the animal. Though cattle are not a seasonal breeder, photoperiod has an indirect role in the onset of puberty, pregnancy and parturition. It can also promote the growth rate of the heifers and enhance their reproductive capabilities, which are very much desired by the producers. Therefore, photoperiod can be used as an effective and non-invasive tool in the reproductive management of cattle. [ABSTRACT FROM AUTHOR]

The negative effects of heat stress on dairy cattle's fertility have been extensively studied, but the relevant knowledge for beef cattle is rather limited. The aims of this study were to investigate the effects of HS during in vitro maturation on the developmental potential of oocytes derived from Limousine and Holstein cows and to estimate the effect of the differential gene expression of important genes in oocytes, cumulus cells and blastocysts in the growth competence between the breeds. In seven replicates, cumulus oocyte complexes from Holstein and Limousine cows were matured for 24 hr at 39°C (controls C; Hol_39, Lim_39) or at 41°C from hour 2 to hour 8 of IVM (treated T; Hol_41, Lim_41), fertilized, and presumptive zygotes were cultured for 9 days at 39°C. Cleavage and embryo formation rates were evaluated 48 hr post‐insemination and on days 7, 8 and 9, respectively. From all groups, subsets of cumulus cells, oocytes and blastocysts were analysed for the relative expression of genes related to metabolism, stress, apoptosis and placentation. No difference was detected in cleavage rate or in blastocyst formation rate among the control groups. In both breeds, heat stress reduced blastocyst yield, but at all days the suppression was higher in Limousines. In Holsteins, altered gene expression was detected in cumulus cells (G6PD, GLUT1) and blastocysts (PLAC8), while in Limousines, differences were found in oocytes (G6PD, HSP90AA1), in cumulus cells (CPT1B, HSP90AA1, SOD2) and blastocysts (DNMT, HSP90AA1, SOD2). It appears that Holstein COCs are more tolerant than Limousine COCs, possibly due to compulsory, production driven selection. [ABSTRACT FROM AUTHOR]

Freemartinism, a disorder of sex development (DSD), is an important problem in cattle breeding. The aim of this paper was to describe a new case of freemartinism in cattle, diagnosed by cytogenetic and molecular techniques. 13-months old Holstein-Freisian heifer was subjected to clinical and genetic examination due to abnormal external genitalia. Physical examination revealed short distance between anus and comissura labiorum dorsalis, presence of prominent tuft of hair in comissura labiorum ventralis, shortened vagina and hypoplastic uterus. Blood, skin and hair samples were collected for further genetic analyses. Levels of estradiol and progesterone were determined by a commercial radioimmunoassay. Analysis of cytogenetic preparations from lymphocytes culture has revealed two cell lines - 60,XX and 60,XY, whereas in preparations from fibroblasts culture only one cell line - 60,XX was found. Molecular analysis of the Y-specific gene (SRY), has confirmed presence of Y chromosome in blood samples and no SRY sequence was found in skin samples. Based on these results the case was classified as a freemartin. Concentrations of estradiol and progesterone were lower than in healthy heifers, which is common finding in freemartins, and were as high as 7.08pg/ml and < 0.2ng/ml, respectively. It is assumed that application of different approaches (cytogenetic, molecular and endocrinological), allows a detailed description of freemartin cases in cattle. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of twin pregnancy, fetal laterality, the number of corpora lutea (CL) and cavitary CL on pregnancy losses in Holstein-Friesian cows with a positive pregnancy diagnosis based on ultrasonography between days 29–42 after AI. Pregnancy was confirmed by transrectal palpation between days 57–70 after AI and at the time of drying-off as well. Twin pregnancy rate was 8.4% at the time of the early pregnancy examination. Pregnancy loss did not differ between singleton- and twin-carrying animals either between days 57–70 of gestation or at drying-off. More losses occurred in singletons between days 29–42 and 57–70 in cows with cavitary than in cows with noncavitary CL (12.1% vs. 3.6%; P < 0.05) and in cows with double CL than in cows with single CL (7.3% vs. 3.6% %; P < 0.05). Between days 57–70 of gestation and drying-off this difference was still significant (20.7% vs. 3.7%; P < 0.001), while it was non-significant between cows with one CL (5.7%) vs. double CL (3.7%). Cavity occurrence was not affected by hormone therapy prior to AI (either PGF2α or OvSynch; 4.4% vs. 5.4%, respectively); however, the number of CL was reduced by the treatments (11.6 vs. 19.6%; P < 0.0005). In twin pregnancies there was no difference in the pregnancy losses between bilateral and unilateral pregnancies at any time point. The length of gestation was 278.2 ± 10.5 (singleton) and 267.4 ± 31.2 (twin) days, respectively (P < 0.01). The stillbirth ratio was higher in twin carriers than in singleton carriers (19.5% vs. 5.3%; P < 0.001). [ABSTRACT FROM AUTHOR]

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Contents Temperature gradients in female reproductive tissues seem to influence the success of key processes such as ovulation and fertilization. The objective of this study was to investigate whether pre-ovulatory follicles are cooler than neighbouring uterine tissue and deep rectal temperatures in lactating dairy cows under heat stress conditions. Temperatures within the pre-ovulatory follicle, on the uterine adjacent surface and 20 cm deep within rectum, were measured using fine thermistor probes within 45 min after sunrise (dawn). Cows were selected from synchronized groups for fixed-time insemination during the warm period of the year. Five cows under direct sun radiation and 11 cows in the shade were included in the study. None of the cows in the sun area ovulated within 24 hr, whereas 10 of the 11 cows in the sun area ovulated. Four of the 10 ovulating cows became pregnant. In the ovulating cows, follicular temperatures were 0.74 and 1.54°C significantly cooler than uterine surface and rectal temperatures, respectively, whereas temperatures in the uterine area were 0.80°C significantly cooler than rectal temperatures. No significant differences among temperatures were found in non-ovulating cows. Follicular size was similar for ovulating and non-ovulating cows. Environmental temperatures in the shade area were 6.4°C significantly lower than those in the sun area. Results of this study indicate that pre-ovulatory follicles are cooler than neighbouring uterine tissue and deep rectal temperatures and those temperature gradients were not found in cows suffering ovulation failure. [ABSTRACT FROM AUTHOR]

Reproduction is among the physiological functions in mammals most susceptible to disruption by hyperthermia. Many of the effects of heat stress on function of the oocyte and embryo involve direct effects of elevated temperature (i.e. heat shock) on cellular function. Mammals limit the effects of heat shock by tightly regulating body temperature. This ability is genetically controlled: lines of domestic animals have been developed with superior ability to regulate body temperature during heat stress. Through experimentation in cattle, it is also evident that there is genetic variation in the resistance of cells to the deleterious effects of elevated temperature. Several breeds that were developed in hot climates, including Bos indicus (Brahman, Gir, Nelore and Sahiwal) and Bos taurus (Romosinuano and Senepol) are more resistant to the effects of elevated temperature on cellular function than breeds that evolved in cooler climates (Angus, Holstein and Jersey). Genetic differences are expressed in the preimplantation embryo by Day 4-5 of development (after embryonic genome activation). It is not clear whether genetic differences are expressed in cells in which transcription is repressed (oocytes >100 µm in diameter or embryos at stages before embryonic genome activation). The molecular basis for cellular thermotolerance has also not been established, although there is some suggestion for involvement of heat shock protein 90 and the insulin-like growth factor 1 system. Given the availability of genomic tools for genetic selection, identification of genes controlling cellular resistance to elevated temperature could be followed by progress in selection for those genes within the populations in which they exist. It could also be possible to introduce genes from thermotolerant breeds into thermally sensitive breeds. The ability to edit the genome makes it possible to design new genes that confer protection of cells from stresses like heat shock. [ABSTRACT FROM AUTHOR]

Contents Equine chorionic gonadotropin (e CG) is a member of the glycoprotein family of hormones along with LH, FSH and thyroid-stimulating hormone. In non-equid species, e CG shows high LH- and FSH-like activities and has a high affinity for both FSH and LH receptors in the ovaries. On the granulosa and thecal cells of the follicle, eCG has long-lasting LH- and FSH-like effects that stimulate oestradiol and progesterone secretion. Thus, eCG administration in dairy cattle results in fewer atretic follicles, the recruitment of more small follicles showing an elevated growth rate, the sustained growth of medium and large follicles and improved development of the dominant and pre-ovulatory follicle. In consequence, the quality of the ensuing CL is improved, and thereby progesterone secretion increased. Based on these characteristics, eCG treatment is utilized in veterinary medicine to control the reproductive activity of the cow by i) improving reproductive performance during early post-partum stages; ii) increasing ovulation and pregnancy rates in non-cyclic cows; iii) improving the conception rate in cows showing delayed ovulation; and finally, iv) eCG is currently included in protocols for fixed-time artificial insemination since after inducing the synchrony of ovulation using a progesterone-releasing device, eCG has beneficial effects on embryo development and survival. The above effects are not always observed in cyclic animals, but they are evident in animals in which LH secretion and ovarian activity are reduced or compromised, for instance, during the early post-partum period, under seasonal heat stress, in anoestrus animals or in animals with a low body condition score. [ABSTRACT FROM AUTHOR]

Cattle are monotocous species and cow usually deliver one calf per birth. The present report has the aim to notify the birth occurrence of quadruplets of a Nelore cow: first time in scientific literature for this breed. The report presents negative and positive consequences of event. [ABSTRACT FROM AUTHOR]

Simple Summary: The Holstein cows are among the most thermosensitive farm animals. In this breed, during the heat stress periods, fertility is seriously compromised due to induced alterations of the endocrine status, reduced fertilizing capacity of the oocyte and increased embryo deaths. To combat the deleterious effects of stress, cells synthesize a series of specific molecules that are mainly involved in cellular protection against the heat insult, called heat shock proteins (HSPs). Here, we examined the effects of supplementing HSP70 in in vitro matured bovine oocytes under thermoneutral or heat stress conditions, and we assessed its efficacy on in vitro embryo yield and quality; the latter was determined on the basis of the expression of various genes related to important cellular functions. It was manifested that HSP70 addition into the in vitro maturation medium restores the developmental competence of heat stressed oocytes and improves the quality of the in vitro produced embryos. Heat shock protein 70 (HSP70) is a chaperon that stabilizes unfolded or partially folded proteins, preventing inappropriate inter- and intramolecular interactions. Here, we examined the developmental competence of in vitro matured oocytes exposed to heat stress with or without HSP70. Bovine oocytes were matured for 24 h at 39 °C without (group C39) or with HSP70 (group H39) and at 41 °C for the first 6 h, followed by 16 h at 39 °C with (group H41) or without HSP70 (group C41). After insemination, zygotes were cultured for 9 days at 39 °C. Cleavage and embryo yield were assessed 48 h post insemination and on days 7, 8, 9, respectively. Gene expression was assessed by RT-PCR in oocytes, cumulus cells and blastocysts. In C41, blastocysts formation rate was lower than in C39 and on day 9 it was lower than in H41. In oocytes, HSP70 enhanced the expression of three HSP genes regardless of incubation temperature. HSP70 at 39 °C led to tight coordination of gene expression in oocytes and blastocysts, but not in cumulus cells. Our results imply that HSP70, by preventing apoptosis, supporting signal transduction, and increasing antioxidant protection of the embryo, protects heat stressed maturing bovine oocyte and restores its developmental competence. [ABSTRACT FROM AUTHOR]

Simple Summary: This review summarizes the clinical background, possibilities, and limitations of twin pregnancy diagnosis in cattle, with a special emphasis on pregnancy loss aspects. Due to the fact that reproductive performance is strongly affected by twin pregnancy, clinical veterinarians should become familiar with the correct diagnosis of this phenomenon. Thus, each herd must plan a herd-specific management practice to detect twin pregnancies. A highly accurate diagnostic tool is required to detect such pregnancies, already during the first month of gestation. This commentary review focuses on the diagnostic possibilities and limitations on the field. Twin pregnancies are an economically unwanted phenomenon in dairy cattle, not only because they increase pregnancy losses, but also because antibiotics usage and culling rate of the dam are also dramatically increased due to them, furthermore animal welfare issues are also affected through them. In cattle, under field conditions using an early pregnancy determination tool, the first accurate diagnosis from the pregnancy status is available from around day 28, although further confirmations of pregnancy are required. Twin pregnancy diagnosis is available either by rectal palpation or ultrasonography. The measurement of pregnancy specific proteins are also available to determine gestation, but there is still a long way to go to properly identify twin pregnancies. In this commentary, we compared our own results with the literature data in this field with a special emphasis on the clinical practices. [ABSTRACT FROM AUTHOR]