Where Does a Baby Develop in a Cow

Abstruse

Early pregnancy encompasses the period from germination of the zygote subsequently fertilization in the oviduct to the establishment of pregnancy and implantation of an elongated conceptus in the uterus. Important facets of early pregnancy in livestock include:
- The success of early pregnancy has a major influence on production and economic efficiency of livestock enterprises.
- The bulk of embryo loss occurs during the get-go two to three weeks of pregnancy in ruminants and showtime month in pigs.
- Nutrition, affliction, environment, and genetics are of import determinants of early pregnancy success.
- Genomic technology is expected to amend our understanding of the underlying complex biological processes involved in pregnancy and provide useful tools to decrease embryo mortality in livestock.
By increasing fertility, the efficiency and sustainability of livestock production enterprises can exist maximized.

Introduction

Early pregnancy in domestic livestock encompasses the period of development of the embryo in the oviduct later on fertilization of the oocyte(due south) past sperm, formation of a blastocyst in the uterus, and elongation of the conceptus (embryo/fetus and associated extraembryonic membranes) afterwards hatching of the blastocyst from the zona pellucida in the uterus. Conceptus elongation requires the uterus and is concomitant with pregnancy recognition signaling to maintain the corpus luteum (CL) and progesterone (P4) secretion besides every bit the onset of implantation for establishment of pregnancy. Uterine receptivity for conceptus elongation and implantation develops in response to P4 and is modified in response to products from the conceptus such as prostaglandins (PG) and interferons (IFN).

Fertility can be defined equally pregnancy rates to a single insemination. Based on that definition, fertility is loftier in sheep (85%) and pigs (90%), moderate in beef cattle (45%), and low in dairy cattle (35% or less in loftier-producing cattle) and humans (25%). Consequently, infertility and subfertility are major problems in domestic livestock besides equally in humans. The majority of embryonic bloodshed occurs after fertilization and during the starting time two to 3 weeks of pregnancy in cattle and month of pregnancy in pigs. Direct effects of embryonic mortality are reflected in reduced conception rates in cattle and reduced litter size in pigs and sheep. Of particular annotation, pregnancy rates have declined in dairy cattle as a result of increased early on embryonic bloodshed in association with pick for increased milk yield during the past 50 years (Diskin and Morris, 2008; Figure 1). New management tools are needed in livestock to decrease embryonic bloodshed and pregnancy loss, thereby increasing overall herd fertility, reproductive and productive longevity, and sustainability of livestock enterprises.

Figure 1.

Clan of milk yield in dairy cattle with girl pregnancy rate. Pick for greater milk production in United states of america dairy cattle has been very successful during the past l years; however, cow fertility has declined in spite of low heritabilities for reproductive traits. (Modified from the Dairy Cattle Reproduction Council.)

Master determinants of pregnancy success include nutrition, disease, environment, and genetics, and all of these are directly influenced by management strategies (Figure two). There is sufficient genetic variability within major breeds for fertility traits, and genetic option for dam fertility is likely a primal to long-term improvements in livestock fertility, particularly in cattle. In general, fertility traits are circuitous and polygenic. The advent of high-throughput DNA sequencing and genomic technologies is useful to identify genes responsible for improved embryo survival in ruminants too as uterine capacity for litter size in pigs. The incorporation of genetic technologies into livestock direction will undoubtedly increase the rate of genetic progress for fertility traits, thereby improving the economic and sustainability aspects of product enterprises (Schefers and Weigel, 2012). The objective of this review is to provide an overview of early on pregnancy, insights into the biology of early on embryonic mortality and potential solutions to early pregnancy loss with a particular focus on cattle.

Effigy 2.

Primary determinants of pregnancy success in livestock production enterprises.

Embryonic Development during Early Pregnancy

Zygote to blastocyst

Full general aspects of conceptus development, from fertilization to the time of hatching from the zona pellucida, are relatively similar in all mammals (Ostrup et al., 2011). Following fertilization in the oviduct (Figure 2), the zygote, surrounded by the zona pellucida, starts to split up, forming blastomeres. Inherited proteins and RNAs from the oocyte and sperm initially command embryo development. After undergoing genome activation, the zygote develops into a morula embryo. During the process of compaction, the outer cells of the morula adhere to each other and develop into the trophectoderm, whereas the inner cells get together at one pole of the embryo to form the inner prison cell mass resulting in a blastocyst. Blastocyst formation is generally initiated presently later entry into the uterus, which occurs around ii and 4 days after ovulation in the sow and moo-cow or sheep, respectively. The blastocyst then hatches from the zona pellucida on days eight to ix, thereby exposing the outer surface of trophectoderm of the conceptus directly to the uterine surround. All stages of zygote to blastocyst development tin can occur entirely in vitro after fertilization of oocytes with sperm; withal, the success rate is less in vitro, and the quality of the resulting blastocyst is less than in vivo, suggesting a major influence of the surround of the ovarian follicle, oviduct, and uterus on early embryonic development.

Conceptus elongation, pregnancy recognition signaling, and implantation

Establishment of pregnancy in domestic ruminants (i.e., sheep, cattle, and goats) begins at the conceptus stage and includes pregnancy recognition signaling, implantation, and placentation. The hatched blastocyst slowly grows into a tubular or ovoid grade and is then termed a conceptus (Figure iii). The hatched ungulate blastocyst does not invasively implant into the endometrium as in rodents and humans. Rather, it remains in the uterine lumen for an extended period of time, where information technology undergoes a phase of rapid trophectoderm growth and development, termed elongation. Elongation of the conceptus is initiated on days 11–12 in the squealer, days 12–xiii in sheep, and days 13–14 in cattle and is concomitant with pregnancy recognition and implantation (Bazer et al., 2011). Maternal recognition of pregnancy is the physiological procedure whereby the conceptus signals its presence to the maternal system and prolongs the lifespan of the ovarian CL (Bazer et al., 1991). Pregnancy recognition signaling occurs on day 12 in pigs, days 13–14 in sheep, and days 16–17 in cattle. Conceptus elongation involves exponential increases in length and weight of the trophectoderm and onset of extraembryonic membrane differentiation, including gastrulation of the embryo for formation of the yolk sac and allantois that are vital for embryonic survival and formation of a functional placenta. Common stages of implantation include: 1) hatching from zona pellucida; 2) pre-contact and orientation of the blastocyst with uterine luminal epithelium (LE); iii) apposition between conceptus trophectoderm and uterine LE; and 4) adhesion of conceptus trophectoderm to uterine LE (Spencer et al., 2008). These stages of implantation are common to all mammals, including those that implant into the endometrial stroma such every bit rodents and humans. The accessibility to and prolonged nature of the first stages of implantation in domestic animals makes them an attractive model for scientific studies.

Figure 3.

Early on pregnancy events in cattle. This schematic summarizes the relative changes in embryo/blastocyst/conceptus development after fertilization in relation to position in the female person reproductive tract and circulating concentrations of ovarian steroid hormones. Fertilization occurs in the oviduct, and the morula stage embryo enters the uterus on mean solar day 4. The blastocyst is formed past twenty-four hour period 7, and it hatches from the zona pellucida by day 9. The blastocyst develops from a spherical to a tubular course by day 13 so elongates to a filamentous conceptus betwixt days 14 and 19. Elongation of the conceptus marks the get-go of implantation, which involves apposition and transient attachment (days xiii to 18) and business firm adhesion past solar day nineteen and is concomitant with synthesis and secretions of prostaglandins (PG) and interferon tau (IFNT) by the trophectoderm. E2 = estrogen; P4 = progesterone.

A pig blastocyst (photo credit: Wikipedia).

Pig. Pig blastocysts undergo a morphological transition to big spheres of 10- to 15-mm diameter and and so tubular (xv past 50 mm) and filamentous (l mm by 100 to 200 mm) forms between days 10 and 12 of pregnancy to achieve a last length of 800 to 1,000 mm (eight to 10 cm) betwixt days 12 and 15 of pregnancy. During this peri-implantation catamenia of rapid elongation, the trophectoderm produces significant amounts of estrogen (E2), as well equally interferons g (IFNG) and delta (IFND). Estrogen is the major indicate for maternal recognition of pregnancy in the pig. Bazer and Thatcher (Bazer and Thatcher, 1977) proposed the endocrine-exocrine theory of pregnancy recognition in pigs in which conceptus estrogen alters the secretion pattern of luteolytic endometrial prostaglandin F2 α (PGF _2α). In non-significant pigs, PGF_2α secretion is endocrine during the mid- to-belatedly stages of the estrous cycle and enters the uterine venous drainage. In pregnant pigs, PGF_2α secretion is shifted and becomes exocrine into the uterine lumen, thereby keeping it from reaching CL on the ovaries. The precise cellular and molecular mechanisms underlying pregnancy recognition signaling in pigs are not known. In addition to its antiluteolytic actions, conceptus estrogen acts on the endometrium to alter expression of genes implicated in uterine receptivity and conceptus elongation (Johnson et al., 2009).

Ruminants. Sheep blastocysts develop from spherical on day 10 (0.iv mm diameter) to tubular and filamentous conceptuses between days 12 (ane mm past 33 mm), xiv (one mm past 68 mm) and 15 (ane mm past 150 to 190 mm) of pregnancy with extraembryonic membranes extending into the contralateral uterine horn between days xvi and 20 of pregnancy. In cattle, the hatched blastocyst forms an ovoid conceptus between days 12 to fourteen and is almost 2 mm in length on 24-hour interval 13. By day 14, the growing conceptus is almost vi mm. The elongating bovine conceptus reaches a length of near 60 mm (half dozen cm) by day 16 and is 20 cm or more past twenty-four hour period 19. Indeed, the bovine blastocyst/conceptus doubles in length every twenty-four hour period between days 9 and 16 with a significant increase (∼10-fold) in growth betwixt days 12 and 15 (Berg et al., 2010). Elongation of the conceptus is associated with the production of increasing amounts of interferon tau (IFNT) and PG in sheep and cattle.

Pregnancy recognition in sheep and cattle requires adequate IFNT secreted by the elongating conceptus. Conceptus IFNT acts in a paracrine manner on the endometrium to inhibit expression of the oxytocin receptor ( OXTR ) gene. As a result, the pregnant uterus does not produce luteolytic pulses of PGF_2α in response to oxytocin pulses released from the posterior pituitary gland and/or CL, thereby maintaining the ovarian corpus luteum and P4 production (Spencer and Bazer 1996). In addition to its antiluteolytic deportment, conceptus-derived IFNT and PG induces changes in the expression of many genes (IFNT-stimulated genes) that regulate uterine receptivity and conceptus elongation (Dorniak et al., 2013).

Extent and Timing of Early Pregnancy Loss in Pigs and Cattle

Pig

Although fertility is rather loftier in pigs, conceptus loss significantly limits litter size and has a negative economical event on the swine industry (Town et al., 2005). Fertilization rate is mostly loftier (90 to 100%), whereas the rate of prenatal mortality is 30 to 40% on average in pigs. The largest loss (20 to thirty%) occurs during the outset month of gestation. Later on oocyte fertilization, a twenty to 45% reduction in litter size occurs before parturition, with the majority of this loss (20 to thirty%) during the peri-implantation period betwixt gestation days 12 and 30; an additional x to fifteen% of conceptuses are lost during mid- to late gestation. The underlying mechanisms and processes involved in pregnancy loss are not well understood in pigs just likely involve insufficient conceptus elongation, early on embryonic decease, and inadequate vascular growth in the endometrium and perhaps conceptus.

Flickr/auntiep/

Cattle

In cattle, fertilization rate is 90% with an boilerplate calving rate of about 55%, indicating an embryonic-fetal mortality of about 35% (Diskin et al., 2006). Further, 70 to 80% of total embryonic loss occurs during the commencement three weeks after insemination, especially between days 7 and 16. Embryo bloodshed is greater in not-lactating cows than heifers, and early on pregnancy loss is even greater in lactating dairy cattle and can approach lxx%. Infertility and subfertility are also major cost factors in the cattle embryo transfer (ET) industry. Mean survival charge per unit to calving following transfer of in vivo-derived embryos from superovulated donors is only 43% with a range from 31 to sixty%, whereas the hateful survival charge per unit afterwards transfer of in vitro-produced embryos is less and ranges from 30 to 40%.

The reproductive status of Usa Holstein and Jersey cattle betwixt 1996 and 2006 was recently evaluated (Norman et al., 2009). During that 10-year menses, conception rate (CR), defined every bit the probability of a successful outcome of private convenance services, declined past iii and 4% for all services in Holsteins and Jerseys, respectively. By 2006, overall CR was only 30% in Holsteins and 35% in Jerseys. Conception rate failures and early pregnancy loss in both heifers and lactating cows can be attributed to the absence of a feasible embryo due to issues with oocyte quality (generally in lactating cows) and fertilization success and inability of the uterus to support blastocyst growth and conceptus elongation (Hansen, 2007). There are a large number of published estimates of fertilization rate in heifers and in moderate-yielding dairy cows (Diskin and Morris, 2008). If semen of known high fertility is used in artificial insemination (AI), fertilization rates are mostly high (ninety to 100%). Overall, there appears to be little differences in lactating and non-lactating dairy cattle in ambient or absurd-season conditions (Sartori et al., 2002). Fertilization rate is similar in high- and moderate-producing cows and unlikely to be affected by whether cows are on pasture or high-input total mixed ration diets. At that place is some evidence that the pattern of early on embryo death in the modern high-producing moo-cow may exist different to that observed in heifers and lower-producing dairy cows. Embryos recovered on day 6 to 7 mail-mating were of greater quality from heifers compared with lactating cows. Further, lactating cows have greater pregnancy rates after ET compared with AI. Thus, early embryo loss appears to be greater in the high-producing dairy cow, and a greater proportion of the embryos die earlier day 7 post-obit insemination. Nonetheless, embryo loss in all cattle peaks between days 7 and sixteen mail-mating during the period in which the uterus must develop receptivity in response to ovarian P4 to support conceptus growth and implantation. Although a myriad of gene expression profiling studies have been conducted in dairy and beef cattle, we all the same do not actually understand the critical gene networks and biological pathways that underpin the physiological processes that command maternal fertility (i.e., estrous behavior, hypothalamic-pituitary role, ovarian function, oogenesis, oviductal and uterine role, and conceptus elongation.)

Uterine Receptivity and Conceptus Elongation in Ruminants

Uterine receptivity tin be defined as a physiological country of the uterus when conceptus growth and implantation for institution of pregnancy is possible. Progesterone from the ovary stimulates and maintains endometrial functions necessary for conceptus growth, implantation, placentation, and development to term. In cattle, P4 concentrations clearly affect embryonic survival during early pregnancy (Diskin and Morris, 2008; Lonergan, 2011). Progesterone predominantly exerts an indirect upshot on the conceptus via the endometrium to regulate blastocyst growth and conceptus elongation. Similar to the human, endometria of both circadian and pregnant sheep and cattle express genes implicated in uterine receptivity (Bauersachs and Wolf, 2012; Dorniak et al., 2013; Ulbrich et al., 2013). The absence of a sufficiently developed conceptus to signal pregnancy recognition results in those genes being "turned off" as luteolysis ensues, P4 concentrations decline, and the animal returns to oestrus for another opportunity to mate.

Currently, the biological pathways that make up one's mind physiological processes that control maternal fertility in dairy and beef cattle are not well understood (photograph credit: Flickr/37177488@N06/).

It is clear that secretions from the endometrial epithelia, especially the glands, are required for establishment of uterine receptivity (Grayness et al., 2001; Spencer et al., 2008). The recurrent early pregnancy loss observed in uterine gland knockout (UGKO) sheep established the importance of uterine epithelial-derived secretions for back up of conceptus elongation and implantation. Endometrial secretions govern elongation of the conceptus via effects on trophectoderm by stimulating cell proliferation and migration or mediating zipper and adhesion to the endometrial LE (Spencer et al., 2008; Bazer et al., 2010). They are derived primarily from transport and (or) synthesis and secretion of substances by the endometrial LE and glandular epithelia (GE). Although not completely defined in any species, the uterine lumen contains a complex and rather undefined mixture of proteins, lipids, amino acids, sugars, ions, and other components. The effect of the P4-induced changes in the cyclic and pregnant uterus of ruminants is to modify or "customize" the intrauterine milieu, such as an increase in select amino acids, glucose, cytokines, and growth factors, for back up of blastocyst growth into an ovoid conceptus and elongation to form a filamentous conceptus (Forde and Lonergan, 2012; Dorniak et al., 2013).

Bachelor evidence in ruminants supports the idea that factors from the conceptus (eastward.thousand., IFNT and PG) also every bit the endometrium itself (e.g., PG) further stimulate a number of P4-induced genes in the uterine epithelia (meet Effigy 3; Dorniak et al., 2013). The genes and functions regulated by these hormones and factors in the endometrial epithelia elicit specific changes in the intrauterine histotrophic milieu necessary for conceptus elongation. Transcriptomic and candidate gene studies have established changes in the endometrium that occur during the estrous cycle and early pregnancy, in response to ovarian P4, and in response to conceptus-derived IFNT and PG. However, we yet exercise non understand which genes and biological pathways are disquisitional for uterine receptivity and conceptus elongation in domestic animals. That knowledge is important to formulate methods to subtract early embryonic mortality and thus increase early pregnancy success (Ulbrich et al., 2013).

USDA

Challenges to Early on Pregnancy Success

Multiple factors impact early pregnancy success in all livestock, including nutrition, disease, environment, and genetics (Effigy 2).

Nutrition

Post-obit parturition, the nutrient demands of the dairy moo-cow increment dramatically as height lactation yield is approached and typically exceed dietary intake, resulting in a state of negative energy balance (NEB; Chagas et al., 2007). During this period, torso reserves are mobilized to meet the combined demands of maintenance and lactation. Over the by three decades, intensive genetic pick for milk yield has increased the divergence between feed intake potential and milk yield potential. As a result, dairy cows accept a greater predisposition for mobilizing trunk reserves and for Bill. There is evidence that reproductive performance has been decreasing in high-producing dairy cows, particularly when animals are under severe Nib (meet review by (Diskin et al., 2006). A greater number of ovulatory estrous cycles preceding insemination are beneficial for subsequent CR, and there is bear witness from a number of studies of an association between the Nib during the first iii to 4 weeks of lactation and the timing of the first mail-partum ovulation. Consequently, information technology is desirable that dairy cows resume ovulation in the first 4 weeks after calving. Thus, information technology is important to maximize feed intake and minimize NEB in the immediate post-calving menstruation to sustain high embryo survival rates.

Disease

Disease in dairy cattle and other livestock has substantial effects on early embryonic bloodshed. In dairy cattle, fertility is decreased in lactating cows experiencing mastitis, retained placenta, metritis or uterine infection, milk fever, displaced abomasum, and/or clinical lameness (Chebel et al., 2004). In practice, dairy cows with one or more diseases feel the greatest early on embryonic mortality and difficulty re-breeding. 1 of the nigh prevalent diseases is uterine metritis, which is observed in up to 40% of dairy cows within a week of parturition (Sheldon et al., 2009; LeBlanc, 2012). Maximal herd rates for obvious clinical disease of 36 and 50% have been reported in big surveys and 18.5 to 21% of animals have metritis with signs of systemic illness such as pyrexia. Subsequently, 15 to 20% of cattle have clinical disease that persists across three weeks mail partum (endometritis), and most xxx% take chronic inflammation of the uterus without clinical signs of uterine disease (subclinical endometritis). Generally, worse postpartum Pecker is associated with more astringent or prolonged uterine inflammation. Negative energy balance likely contributes to immune dysfunction that in plough is a major component of reproductive tract inflammatory disease. The outcome of disease is a failure in embryo survival afterward breeding due to defects in oocyte quality, fertilization and early embryogenesis every bit well as a uterine environment that is not conducive to sperm or embryo survival.

Environment

Early pregnancy tin be compromised when cattle are subjected to environmental stressors (Hansen, 2007). For instance, heat stress before and immediately after breeding can also substantially increment early pregnancy loss, likely due to compromised oocyte quality and thus evolution of the early on embryo. Indeed ET improved fertility when cows were subfertile (east.one thousand., during heat stress or in echo breeder cows; Block et al., 2010). Notwithstanding, transfer of embryos produced in vivo or in vitro did not increase fertility of lactating dairy cows when pregnancy rates to AI were not compromised. The effect of heat stress on fertilization is the field of study of another review in this issue by Dr. Peter J. Hansen.

Genetics

Genetic causes of embryonic mortality include chromosomal defects, individual genes, and genetic interactions as well as inbreeding (VanRaden and Miller, 2006). In dairy and beef breeds, major recessive defects affecting embryo-fetal survival have been detected due to founder effects. Recently, loftier-throughput single nucleotide polymorphism (SNP) genotyping and side by side-generation sequencing identified a deletion in the bovine FANCI gene that causes brachyspina syndrome, a rare recessive genetic defect in Holstein dairy cattle (Charlier et al., 2012). Despite the very low incidence of brachyspina syndrome (<1/100,000), carrier frequency is as high as 7.4% in the Holstein breed. In Bailiwick of jersey cattle, a newly identified lethal [nonsense mutation in CWC15 spliceosome-associated poly peptide homolog (Southward. cerevisiae)] was implicated in decreased reproductive efficiency due to embryonic lethality based on the absenteeism of homozygous recessive individuals and association with spontaneous abortions (Sonstegard et al., 2013). Although not well investigated, genetic causes may be responsible for early pregnancy loss due to insufficient conceptus elongation and production of pregnancy recognition signals in cattle likewise as pigs.

Potential Solutions to Early on Pregnancy Loss in Livestock

Potential solutions to early on pregnancy loss in livestock include direction changes to provide adequate nutrition, ameliorate and care for disease, and command or adjust the surround too as utilization of genomic technologies.

Pigs

Litter size involves several different interactive components including ovulation rate, embryonic viability, and uterine chapters (Bennett and Leymaster, 1990). In simulation models, the greatest increase in litter size was produced following combined selection for indices of ovulation rate and uterine chapters. Although current commercial pigs accept a relatively high ovulation rate (twenty to 25), litter size is express to only 12 to 13 feasible conceptuses (Town et al., 2005). Indeed, selection for greater ovulation rates produces simply modest increases in litter size due to crowding of embryos in utero during the immediate mail-implantation menses and a top of prenatal loss betwixt 24-hour interval xxx and 50 of gestation. Consequences are increased variability in postnatal growth performance. Farther, choice for increased litter size may result in more than depression-birthweight piglets, which also leads to postnatal operation issues in growth and health. The concept of uterine chapters as the ultimate constraint on litter size in swine has been widely studied. Available studies concluded that intrauterine crowding was a limiting factor for litter size when the number of embryos exceeded 14. Uterine capacity may become a limiting gene for fetal survival subsequently day 25 of gestation, particularly between days thirty to 40 of gestation. In essence, uterine capacity in pigs tin can be ultimately defined as the physical, biochemical, and genetic chapters of the uterus to back up a large number of embryos. Many of the embryos that are developmentally retarded may exist lost during early pregnancy. Given that early pregnancy loss occurs afterward conceptus elongation, another determinant of pregnancy loss may be defects in gastrulation and vascularization of the placenta and endometrium of the uterus, especially given that the pig has a true epitheliochorial placenta.

I potential nutriceutical arroyo to increasing litter size is through dietary manipulations, such as arginine supplementation, which may enhance uterine likewise every bit placental growth and function via vascular effects (Wu et al., 2013). Another potential arroyo to increasing litter size is through genetic selection. Indeed, decreased fetal losses during gestation offer the greatest opportunity to increase reproductive efficiency. Selection for increased litter size has been shown to exist effective in pigs (Johnson et al., 1999). Litter size is a relatively circuitous trait, determined by ovulation charge per unit and the proportion of ova resulting in offspring at term or, alternatively, past the number of potentially viable embryos and the capacity of the uterus. The advent and apply of genomic technologies should be useful to identify genes responsible for improved litter size and uterine chapters in pigs and permit producers to select for those traits without detrimental furnishings on other important production traits.

Cattle

Nutrition. It is important to maximize feed intake and minimize NEB in the immediate post-calving period to sustain high embryo survival rates in lactating dairy cattle as well as beef cattle and other livestock. Every bit reviewed by Santos et al. (2008), increasing the caloric density of the ration by feeding lipids has more often than not improved measures of cow reproduction; however, when milk yield and body weight losses were increased by fat supplementation, positive effects on reproduction were not e'er observed. Feeding fat has influenced reproduction by decreasing the interval to first postpartum ovulation in beef cows, increasing P4 concentrations during the luteal stage of the estrous cycle, and improving oocyte and embryo quality and developmental competence. Some fatty effects depend on the type of fat acrid (FA) fed (Hutchinson et al., 2012); the polyunsaturated FA of the n-6 and n-3 families seem to accept the most remarkable effects on reproductive responses of cattle. Thus, nutriceutical approaches to meliorate reproduction, immunity, and health may be useful as a direction tool to increment pregnancy success.

Progesterone. In that location is now good evidence linking circulating concentrations of P4 during the cycle immediately before insemination also every bit during the early luteal phase of the bike post-obit insemination with low CR and greater rates of early pregnancy loss (Diskin and Morris, 2008; Lonergan, 2011). Potential mechanisms by which low concentrations of P4 during the preceding estrous cycle might reduce fertilization and/or embryo survival rates include effects on oocyte quality or an alteration in oviductal and uterine surround. The more probable issue of depression concentrations of P4 in the wheel preceding oestrus on subsequent embryo survival is to outcome in pre-mature oocyte maturation, which afterwards compromises its ability to continue normal embryo development afterward its fertilization.

Simulation models have shown that combined selection for indices of ovulation rate and uterine chapters produces the greatest increment in grunter litter size (photo credit: iStockphoto.com/mikedabell).

three-D model of progesterone molecule (photo credit: Wikipedia).

Increasing concentrations of P4 subsequently ovulation enhanced conceptus elongation in beef heifers, dairy cows, and sheep, whereas smaller P4 concentrations in the early on luteal stage retarded embryonic development in sheep and cattle (Diskin and Morris, 2008; Spencer et al., 2008; Lonergan, 2011). However, supplementation of cattle with P4 during early pregnancy has equivocal effects to increase embryonic survival because peripheral concentrations of both P4 and estrogen are reduced in dairy cattle by increased metabolic clearance rate of the steroids related to liver blood menstruation. Farther, P4 supplementation is unlikely to rescue development of embryos with inherent genetic defects or in high-producing dairy cows (Wiltbank et al., 2011). Coating treatment of herds with P4, via a controlled intravaginal drug releasing device (CIDR), may exist problematic due to concerns with marketing their milk and meat. Thus, the solution may be to optimize office of the corpus luteum via novel genetic or physiological strategies.

Genomics. Comeback of functional traits using conventional approaches of quantitative genetics is difficult because many production traits are circuitous (polygenic) with low heritability (Weigel, 2006). However, information technology is articulate that genetic variability exists within livestock for of import fertility traits as well every bit resistance to body condition loss, heat stress, and disease. Importantly, contempo developments in molecular genetics and genotyping platforms and our agreement of breeding and reproduction offer a unique opportunity to identify loci and genomic rearrangements associated with fertility and other production traits in livestock (Garrick et al., 2012). In case, testing of AI sires has significantly reduced the frequency of heterozygous sires and of homozygous recessive embryos and tin can be used to eliminate them as a cause of fertility losses. Notwithstanding, recessive lethal defects will probable continue to arise in livestock, particularly due to inbreeding and founder effects due to widespread use of individual males as well as females due to the employ of ET. Although most of the known homozygous recessive alleles identified are associated with mid- to belatedly embryonic bloodshed, it is tempting to speculate that early embryonic mortality in cattle every bit well as in pigs and other mammals could exist attributed to other embryonic lethals that may segregate in livestock and significantly compromise fertility.

Selection for uterine chapters for pregnancy. Although direction practices can improve pregnancy rates to the mid-20s, maternal fertility is a lowly heritable polygenic trait that can only be chop-chop improved by genomic pick, particularly given the being of significant genetic variation for fertility (see Veerkamp and Beerda, 2007). Natural variation in early pregnancy rates are observed in cattle independent of nutritional, environmental, disease, and other management factors and may be useful to ascertain genes and pathways important for uterine receptivity and essential for early pregnancy loss and success. McMillan and Donnison (1999) summarized an interesting approach for experimentally identifying high- and low-fertility heifers based on early pregnancy success using serial transfer of in vitro-produced embryos. Of notation, those investigators suggested that a failure in the mechanism involved in conceptus elongation and maternal recognition of pregnancy was a major cause of early pregnancy loss in low-fertility heifers. Accordingly, the selected loftier-fertility heifers would have a uterus that was superior in the ability to support growth and development of the conceptus. Other ruminant models to empathize uterine receptivity and early pregnancy loss include: a) the UGKO ewe (Gray et al., 2002); b) heifers versus cows (Berg et al., 2010); c) non-lactating versus lactating cows (Cerri et al., 2012); d) avant-garde versus delayed post-ovulatory ascension in P4 (Forde and Lonergan, 2012); and due east) recessive lethal mutations that manifest during early pregnancy (Charlier et al., 2012). A systems biology approach is necessary to empathize the multifactorial phenomenon of early pregnancy loss and provide a basis for new strategies to improve pregnancy outcomes, fertility, and reproductive efficiency in livestock.

Conclusions

Knowledge gained from functional genomics studies is expected to translate into novel genomic selection approaches to complement management practices aimed at improving the productivity and sustainability of livestock production enterprises (Schefers and Weigel, 2012). Reducing the considerable economic losses associated with poor reproductive performance in livestock requires the simultaneous development of genomic tools to enable the selection of dams and sires with superior fertility and appropriate sire selection for daughter fertility equally well as a sustained educational effort to increase the adoption of genetic management practices that improve reproductive performance, thereby increasing industry profitability. Further, the information gained from studies in livestock can be potentially translated into noesis to improve the success rates of assisted reproductive technologies used to treat subfertility and infertility in women, particularly since pregnancy loss is the most common complication of human gestation.

Thomas East. Spencer is Professor and Baxter Endowed Chair in Beef Cattle Research in the Section of Animal Sciences at Washington State Academy. His enquiry focuses on the improving fertility by studying evolution and function of the uterus, role of endometrial glands in uterine function, and cellular and molecular aspects of conceptus-endometrial interactions. His research program uses a broad multifariousness of animal models including sheep, beef cattle, dairy cattle, and laboratory rodents. Spencer has published more than than 250 peer-reviewed journal articles on various aspects of reproduction biology and has given more than 75 lectures to academic and industry audiences.

Literature Cited

Bauersachs

Wolf

East.

2012

Transcriptome analyses of bovine, porcine and equine endometrium during the pre-implantation phase

Anim. Reprod. Sci.

134

–

Bazer

F.West.

Spencer

T.Eastward.

Johnson

M.A.

Burghardt

R.C.

2011

Uterine receptivity to implantation of blastocysts in mammals

Front. Biosci.

745

–

767

Bazer

F.W.

Thatcher

Westward.Westward.

1977

Theory of maternal recognition of pregnancy in swine based on estrogen controlled endocrine versus exocrine secretion of prostaglandin F2alpha past the uterine endometrium

Prostaglandins

xiv

397

–

400

Bazer

F.W.

Thatcher

Westward.W.

Hansen

P.J.

Mirando

M.A.

Ott

T.L.

Plante

1991

Physiological mechanisms of pregnancy recognition in ruminants

J. Reprod. Fertil. Suppl.

–

Bazer

F.W.

Spencer

T.E.

Johnson

Thou.A.

Burghardt

R.C.

Bayless

2010

Novel pathways for implantation and establishment and maintenance of pregnancy in mammals

Mol. Hum. Reprod.

xvi

135

–

152

Bennett

G.L.

Leymaster

K.A.

1990

Genetic implications of a simulation model of litter size in swine based on ovulation rate, potential embryonic viability and uterine capacity: I. Genetic theory

J. Anim. Sci.

969

–

979

Berg

D.K.

van Leeuwen

Beaumont

Berg

Pfeffer

P.L.

2010

Embryo loss in cattle between days vii and xvi of pregnancy

Theriogenology

250

–

260

Cake

Bonilla

Hansen

P.J.

2010

Efficacy of in vitro embryo transfer in lactating dairy cows using fresh or vitrified embryos produced in a novel embryo culture medium

J. Dairy Sci.

5234

–

5242

Cerri

R.L.

Thompson

I.M.

Kim

I.H.

Ealy

A.D.

Hansen

P.J.

Staples

C.R.

J.L.

Santos

J.E.

Thatcher

W.West.

2012

Effects of lactation and pregnancy on cistron expression of endometrium of Holstein cows at day 17 of the estrous cycle or pregnancy

J. Dairy Sci.

5657

–

5675

Chagas

L.M.

Bass

J.J.

Blache

Burke

C.R.

Kay

J.One thousand.

Lindsay

D.R.

Lucy

M.C.

Martin

G.B.

Meier

Rhodes

F.M.

Roche

J.R.

Thatcher

W.W.

Webb

2007

Invited review: New perspectives on the roles of diet and metabolic priorities in the subfertility of high-producing dairy cows

J. Dairy Sci.

ninety

4022

–

4032

Charlier

Agerholm

J.S.

Coppieters

Westward.

Karlskov-Mortensen

West.

de Jong

Fasquelle

Karim

Cirera

Cambisano

Ahariz

Due north.

Mullaart

Georges

Thousand.

Fredholm

Yard.

2012

A deletion in the bovine FANCI cistron compromises fertility past causing fetal expiry and brachyspina

PLoS One vii:e43085

Chebel

R.C.

Santos

J.E.

Reynolds

J.P.

Cerri

R.Fifty.

Juchem

S.O.

Overton

2004

Factors affecting conception rate after bogus insemination and pregnancy loss in lactating dairy cows

Anim. Reprod. Sci.

239

–

255

Diskin

M.G.

Morris

D.G.

2008

Embryonic and early foetal losses in cattle and other ruminants

Reprod. Domest. Anim.

(

Suppl 2

260

–

267

Diskin

1000.Chiliad.

Murphy

J.J.

Sreenan

J.M.

2006

Embryo survival in dairy cows managed nether pastoral conditions

Anim. Reprod. Sci.

297

–

311

Dorniak

Bazer

F.W.

Spencer

T.E.

2013

Physiology and Endocrinology Symposium: Biological role of interferon tau in endometrial function and conceptus elongation

J. Anim. Sci.

1627

–

1638

Forde

Lonergan

2012

Transcriptomic analysis of the bovine endometrium: What is required to establish uterine receptivity to implantation in cattle?

J. Reprod. Dev.

189

–

195

Garrick

D.J.

Baumgard

50.H.

Neibergs

H.Fifty.

2012

Invited review: Genomic analysis of information from physiological studies

J. Dairy Sci.

499

–

507

Gray

C.A.

Bartol

F.F.

Tarleton

B.J.

Wiley

A.A.

Johnson

G.A.

Bazer

F.Due west.

Spencer

T.E.

2001

Developmental biology of uterine glands

Biol. Reprod.

1311

–

1323

Gray

C.A.

Burghardt

R.C.

Johnson

G.A.

Bazer

F.West.

Spencer

T.E.

2002

Testify that absenteeism of endometrial gland secretions in uterine gland knockout ewes compromises conceptus survival and elongation

Reproduction

124

289

–

300

Hansen

P.J.

2007

Exploitation of genetic and physiological determinants of embryonic resistance to elevated temperature to better embryonic survival in dairy cattle during oestrus stress

Theriogenology

(

Suppl i

S242

–

S249

Hutchinson

I.A.

Hennessy

A.A.

Waters

S.M.

Dewhurst

R.J.

Evans

A.C.

Lonergan

Butler

S.T.

2012

Effect of supplementation with different fat sources on the mechanisms involved in reproductive performance in lactating dairy cattle

Theriogenology

–

Johnson

1000.A.

Bazer

F.W.

Burghardt

R.C.

Spencer

T.E.

Bayless

K.J.

2009

Conceptus-uterus interactions in pigs: Endometrial gene expression in response to estrogens and interferons from conceptuses

Soc. Reprod. Fertil. Suppl.

321

–

332

Johnson

R.Thousand.

Nielsen

K.K.

Casey

D.S.

1999

Responses in ovulation rate, embryonal survival, and litter traits in swine to 14 generations of selection to increase litter size

J. Anim. Sci.

541

–

557

LeBlanc

S.J.

2012

Interactions of metabolism, inflammation, and reproductive tract wellness in the postpartum period in dairy cattle

Reprod. Domest. Anim.

(

Suppl v

–

Lonergan

2011

Influence of progesterone on oocyte quality and embryo development in cows

Theriogenology

1594

–

1601

McMillan

Westward.H.

Donnison

1000.J.

1999

Understanding maternal contributions to fertility in recipient cattle: Development of herds with contrasting pregnancy rates

Anim. Reprod. Sci.

127

–

140

Norman

H.D.

Wright

J.R.

Hubbard

S.M.

Miller

R.H.

Hutchison

J.L.

2009

Reproductive status of Holstein and Jersey cows in the United states of america

J. Dairy Sci.

3517

–

3528

Ostrup

Eastward.

Hyttel

Ostrup

2011

Embryo-maternal communication: Signalling before and during placentation in cattle and pig

Reprod. Fertil. Dev.

964

–

975

Santos

J.E.

Bilby

T.R.

Thatcher

W.W.

Staples

C.R.

Silvestre

F.T.

2008

Long chain fatty acids of diet as factors influencing reproduction in cattle

Reprod. Domest. Anim.

(

Suppl ii

–

Sartori

Sartor-Bergfelt

Mertens

Southward.A.

Guenther

J.N.

Parrish

J.J.

Wiltbank

Thousand.C.

2002

Fertilization and early embryonic development in heifers and lactating cows in summertime and lactating and dry cows in winter

J. Dairy Sci.

(

2803

–

2812

Schefers

J.One thousand.

Weigel

Chiliad.A.

2012

Genomic option in dairy cattle: Integration of DNA testing into convenance programs

Anim. Front.

four

–

nine

Sheldon

I.M.

Cronin

Goetze

50.

Donofrio

One thousand.

Schuberth

H.J.

2009

Defining postpartum uterine affliction and the mechanisms of infection and immunity in the female reproductive tract in cattle

Biol. Reprod.

1025

–

1032

Sonstegard

T.S.

Cole

J.B.

VanRaden

P.M.

Van Tassell

C.P.

Null

D.J.

Schroeder

S.Thou.

Bickhart

McClure

1000.C.

2013

Identification of a nonsense mutation in CWC15 associated with decreased reproductive efficiency in Bailiwick of jersey cattle

PLoS ONE 8:e54872

Spencer

T.E.

Ott

T.L.

Bazer

F.W.

1996

tau-Interferon: pregnancy recognition signal in ruminants

Proc. Soc. Exp. Biol. Med.

213

(

215

–

229

Spencer

T.Eastward.

Sandra

Wolf

2008

Genes involved in conceptus-endometrial interactions in ruminants: Insights from reductionism and thoughts on holistic approaches

Reproduction

135

165

–

179

Town

South.C.

Patterson

J.Fifty.

Pereira

C.Z.

Gourley

Foxcroft

G.R.

2005

Embryonic and fetal development in a commercial dam-line genotype

Anim. Reprod. Sci.

301

–

316

Ulbrich

S.E.

Groebner

A.E.

Bauersachs

Due south.

2013

Transcriptional profiling to address molecular determinants of endometrial receptivity—lessons from studies in livestock species

Methods

108

–

115

VanRaden

P.Yard.

Miller

R.H.

2006

Effects of nonadditive genetic interactions, inbreeding, and recessive defects on embryo and fetal loss by seventy days

J. Dairy Sci.

2716

–

2721

Veerkamp

R.F.

Beerda

2007

Genetics and genomics to better fertility in high producing dairy cows

Theriogenology

(

Suppl 1

S266

–

S273

Weigel

M.A.

2006

Prospects for improving reproductive performance through genetic option

Anim. Reprod. Sci.

323

–

330

Wiltbank

Yard.C.

Souza

A.H.

Carvalho

P.D.

Bender

R.Westward.

Nascimento

A.B.

2011

Improving fertility to timed artificial insemination by manipulation of circulating progesterone concentrations in lactating dairy cattle

Reprod. Fertil. Dev.

238

–

243

Thou.

Bazer

F.W.

Satterfield

Thou.C.

Wang

Ten.

Johnson

G.A.

Burghardt

R.C.

Dai

Wang

2013

Impacts of arginine diet on embryonic and fetal development in mammals

Amino Acids.

(

241

–

256

This is an Open Access commodity distributed under the terms of the Creative Eatables Attribution Non-Commercial License (http://creativecommons.org/licenses/past-nc/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

parkerhimathat.blogspot.com

Source: https://academic.oup.com/af/article/3/4/48/4638665

Where Does a Baby Develop in a Cow

Abstruse

Introduction

Embryonic Development during Early Pregnancy

Zygote to blastocyst

Conceptus elongation, pregnancy recognition signaling, and implantation

Extent and Timing of Early Pregnancy Loss in Pigs and Cattle

Pig

Cattle

Uterine Receptivity and Conceptus Elongation in Ruminants

Challenges to Early on Pregnancy Success

Nutrition

Disease

Environment

Genetics

Potential Solutions to Early on Pregnancy Loss in Livestock

Pigs

Cattle

Conclusions

Literature Cited

0 Response to "Where Does a Baby Develop in a Cow"

Post a Comment

Iklan Atas Artikel

Iklan Tengah Artikel 1

Iklan Tengah Artikel 2

Iklan Bawah Artikel