inbreeding

近亲繁殖
  • 文章类型: Journal Article
    先天性畸形可影响近7%的犬新生儿。商品狗繁殖和近亲繁殖的增加用来保持每个品种的显著特征,畸形的出现变得越来越普遍,尤其是短头犬.原因是多种多样的,包括遗传,营养,医源性,和感染因素,通常很难建立因果关系。与畸形相关的高死亡率不仅来自于一些人与生活不相容的事实,而且还因为即使许多人接受手术治疗或矫正,它们需要特定的管理,监测,以及无限期的临床治疗。最常见的畸形,如唇腭裂,脑积水和房面积已经研究了很长时间,目前已知短头犬有更大的倾向,然而,对于其他不太常见的疾病,如腹裂和尿道下裂,只有少数病例报告。产仔先天缺陷的出现会给饲养员带来经济损失,主人和兽医的情感损失,并损害该人的福祉。出于这个原因,这篇评论文章的目的是收集有关特征的相关信息,诊断,以及小狗主要畸形的管理。兽医必须准备好诊断和治疗这些疾病,减少对动物和主人的负面影响。
    Congenital malformations can affect almost 7% of canine newborns. The increase of commercial dog breeding and inbreeding used to maintain the striking characteristics of each breed, the appearance of malformations has become increasingly common, especially in brachycephalic dogs. The causes are diverse, and include genetic, nutritional, iatrogenic, and infectious factors, often making it difficult to establish a cause-consequence relationship. The high mortality associated with malformations comes not only from the fact that some are incompatible with life, but also because even if many undergo surgical treatment or correction, they require specific management, monitoring, and clinical treatment for an indefinite period of time. The most common malformations such as cleft lip and palate, hydrocephalus and anasarca have been studied for a long time, and it is currently known that brachycephalic dogs have a greater predisposition, however, for other less common conditions as gastroschisis and hypospadias, there is only a few case reports. The appearance of congenital defects in a litter leads to financial losses for the breeder, emotional losses for the owner and the veterinarian and harms the well-being of that individual. For this reason, the aim of this review article is to gather relevant information on the characteristics, diagnosis, and management of the main malformations in puppies. It is essential that the veterinarian is prepared to diagnose and treat these conditions, reducing negative impacts on animals and owners.
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  • 文章类型: Journal Article
    许多牲畜物种对高维基因组信息的访问正在加速。这不仅得到了基因分型成本的持续降低,而且还得到了利用基因组信息创造更大投资回报的可用服务的扩展。个体动物的基因组信息有许多用途,包括(1)亲子关系验证和发现,(2)可追溯性,(3)核型分析,(4)性别决定,(5)报告和监测具有重大影响或先天性缺陷的突变,(6)更好地估计个体的近亲繁殖和个体之间的祖先,(7)交配建议,(8)确定品种组成,(9)实现精准管理,和(10)基因组评估;基因组评估利用全基因组基因型信息来提高预测动物(以及其后代)遗传价值的准确性。基因组数据也为研究提供了巨大的资源,尽管这项研究的结果是,如果成功,最终应该通过已经提到的十个应用程序之一来实现。描述了从样本采购到识别错误基因型的所有基因型的生成过程,以及在开发用于实际应用的定制基因分型面板时应考虑的步骤。
    Access to high-dimensional genomic information in many livestock species is accelerating. This has been greatly aided not only by continual reductions in genotyping costs but also an expansion in the services available that leverage genomic information to create a greater return-on-investment. Genomic information on individual animals has many uses including (1) parentage verification and discovery, (2) traceability, (3) karyotyping, (4) sex determination, (5) reporting and monitoring of mutations conferring major effects or congenital defects, (6) better estimating inbreeding of individuals and coancestry among individuals, (7) mating advice, (8) determining breed composition, (9) enabling precision management, and (10) genomic evaluations; genomic evaluations exploit genome-wide genotype information to improve the accuracy of predicting an animal\'s (and by extension its progeny\'s) genetic merit. Genomic data also provide a huge resource for research, albeit the outcome from this research, if successful, should eventually be realised through one of the ten applications already mentioned. The process for generating a genotype all the way from sample procurement to identifying erroneous genotypes is described, as are the steps that should be considered when developing a bespoke genotyping panel for practical application.
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  • 文章类型: Journal Article
    The advent of genomic selection paved the way for an unprecedented acceleration in genetic progress. The increased ability to select superior individuals has been coupled with a drastic reduction in the generation interval for most dairy populations, representing both an opportunity and a challenge. Homozygosity is now rapidly accumulating in dairy populations. Currently, inbreeding depression is managed mostly by culling at the farm level and by controlling the overall accumulation of homozygosity at the population level. A better understanding of how homozygosity and recessive load are related will guarantee continued genetic improvement while curtailing the accumulation of harmful recessives and maintaining enough genetic variability to ensure the possibility of selection in the face of changing environmental conditions. In this review, we present a snapshot of the current dairy selection structure as it relates to response to selection and accumulation of homozygosity, briefly outline the main approaches currently used to manage inbreeding and overall variability, and present some approaches that can be used in the short term to control accumulation of harmful recessives while maintaining sustained selection pressure.
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  • 文章类型: Congress
    近亲繁殖抑郁症在牲畜中日益受到关注,因为它会对动物健康产生不利影响,健康,和生产水平。基因组信息可用于更有效地捕获孟德尔采样中的方差,从而能够更准确地估计近亲繁殖,但仍需取得进一步进展。为羊群管理目的的近亲繁殖的计算在很大程度上仍然仅使用谱系信息,尽管以这种方式计算的近交系数已被证明不如基因组近交测量准确。纯合基因型的连续延伸,所谓的纯合性运行,已被证明在基因组水平上提供了比基于通过常规谱系信息甚至基因组关系矩阵计算的近交系数的常规措施更好的自合性估计。为了在种群水平上改善和有针对性地管理基因组近交,在配偶选择程序中整合基因组信息的方法的发展可能为减少奶牛群近亲繁殖的有害影响提供更精确的工具。此外,更好地了解近亲繁殖的基因组结构并将这些知识纳入育种计划可以显着改善当前的实践。在高度选择的乳品群体中,存在保持感兴趣的性状的高水平遗传进展,同时管理纯合性并维持可接受的杂合性水平的机会,应该更仔细地检查奶牛群体和乳品行业的持续可持续性。包括近亲繁殖的精确基因组测量,例如纯合性的运行,近亲繁殖,和交配程序,可以提供前进的道路。在这篇研讨会综述文章中,我们描述了近亲繁殖的传统方法,以及使用基因组信息更精确地测量纯合性的最新进展。近交纯合性对表型的影响,有害纯合性单倍型的鉴定和作图,用基因组数据管理近亲繁殖,并讨论了需要进一步研究的领域。
    Inbreeding depression is a growing concern in livestock because it can detrimentally affect animal fitness, health, and production levels. Genomic information can be used to more effectively capture variance in Mendelian sampling, thereby enabling more accurate estimation of inbreeding, but further progress is still required. The calculation of inbreeding for herd management purposes is largely still done using pedigree information only, although inbreeding coefficients calculated in this manner have been shown to be less accurate than genomic inbreeding measures. Continuous stretches of homozygous genotypes, so called runs of homozygosity, have been shown to provide a better estimate of autozygosity at the genomic level than conventional measures based on inbreeding coefficients calculated through conventional pedigree information or even genomic relationship matrices. For improved and targeted management of genomic inbreeding at the population level, the development of methods that incorporate genomic information in mate selection programs may provide a more precise tool for reducing the detrimental effects of inbreeding in dairy herds. Additionally, a better understanding of the genomic architecture of inbreeding and incorporating that knowledge into breeding programs could significantly refine current practices. Opportunities to maintain high levels of genetic progress in traits of interest while managing homozygosity and sustaining acceptable levels of heterozygosity in highly selected dairy populations exist and should be examined more closely for continued sustainability of both the dairy cattle population as well as the dairy industry. The inclusion of precise genomic measures of inbreeding, such as runs of homozygosity, inbreeding, and mating programs, may provide a path forward. In this symposium review article, we describe traditional measures of inbreeding and the recent developments made toward more precise measures of homozygosity using genomic information. The effects of homozygosity resulting from inbreeding on phenotypes, the identification and mapping of detrimental homozygosity haplotypes, management of inbreeding with genomic data, and areas in need of further research are discussed.
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  • 文章类型: Journal Article
    Dispersal is ubiquitous throughout the tree of life: factors selecting for dispersal include kin competition, inbreeding avoidance and spatiotemporal variation in resources or habitat suitability. These factors differ in whether they promote male and female dispersal equally strongly, and often selection on dispersal of one sex depends on how much the other disperses. For example, for inbreeding avoidance it can be sufficient that one sex disperses away from the natal site. Attempts to understand sex-specific dispersal evolution have created a rich body of theoretical literature, which we review here. We highlight an interesting gap between empirical and theoretical literature. The former associates different patterns of sex-biased dispersal with mating systems, such as female-biased dispersal in monogamous birds and male-biased dispersal in polygynous mammals. The predominant explanation is traceable back to Greenwood\'s () ideas of how successful philopatric or dispersing individuals are at gaining mates or the resources required to attract them. Theory, however, has developed surprisingly independently of these ideas: models typically track how immigration and emigration change relatedness patterns and alter competition for limiting resources. The limiting resources are often considered sexually distinct, with breeding sites and fertilizable females limiting reproductive success for females and males, respectively. We show that the link between mating system and sex-biased dispersal is far from resolved: there are studies showing that mating systems matter, but the oft-stated association between polygyny and male-biased dispersal is not a straightforward theoretical expectation. Here, an important understudied factor is the extent to which movement is interpretable as an extension of mate-searching (e.g. are matings possible en route or do they only happen after settling in new habitat - or can females perhaps move with stored sperm). We also point out other new directions for bridging the gap between empirical and theoretical studies: there is a need to build Greenwood\'s influential yet verbal explanation into formal models, which also includes the possibility that an individual benefits from mobility as it leads to fitness gains in more than one final breeding location (a possibility not present in models with a very rigid deme structure). The order of life-cycle events is likewise important, as this impacts whether a departing individual leaves behind important resources for its female or male kin, or perhaps both, in the case of partially overlapping resource use.
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  • 文章类型: Journal Article
    Traditionally, pedigree-based relationship coefficients have been used to manage the inbreeding and degree of inbreeding depression that exists within a population. The widespread incorporation of genomic information in dairy cattle genetic evaluations allows for the opportunity to develop and implement methods to manage populations at the genomic level. As a result, the realized proportion of the genome that 2 individuals share can be more accurately estimated instead of using pedigree information to estimate the expected proportion of shared alleles. Furthermore, genomic information allows genome-wide relationship or inbreeding estimates to be augmented to characterize relationships for specific regions of the genome. Region-specific stretches can be used to more effectively manage areas of low genetic diversity or areas that, when homozygous, result in reduced performance across economically important traits. The use of region-specific metrics should allow breeders to more precisely manage the trade-off between the genetic value of the progeny and undesirable side effects associated with inbreeding. Methods tailored toward more effectively identifying regions affected by inbreeding and their associated use to manage the genome at the herd level, however, still need to be developed. We have reviewed topics related to inbreeding, measures of relatedness, genetic diversity and methods to manage populations at the genomic level, and we discuss future challenges related to managing populations through implementing genomic methods at the herd and population levels.
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  • 文章类型: Case Reports
    Usher syndrome is defined by the association of a progressive or non-progressive congenital sensorineural hearing loss with variable severity and a gradually blinding pigmentary retinopathy. Von Recklinghausen neurofibromatosis or Neurofibromatosis type 1 is the major clinically form of neurofibromatosis which occurs in approximately 90% of cases. Both types of disease are genetic in origin with very low prevalence. The probability of co-occurrence of these diseases in a single individual is exceptional. Inbreeding, as well as all genetic diseases, increases quite significantly the probability of their occurrence. Consanguineous marriages are still widespread in Maghreb and in some regions of the western African. This observation reports an exceptional case of this association in a 40-year-old man of Mauritanian origin born from a consanguineous union.
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  • 文章类型: Journal Article
    到1970年代,在德克萨斯州和路易斯安那州的南部边界,政府支持的根除运动将红狼减少到不到100个人的剩余种群。由于捕食者控制程序和与土狼的杂交,该地区的恢复工作被认为没有希望。美国鱼类和野生动物服务局(USFWS)从野外清除了最后剩下的红狼,并将其置于圈养繁殖计划中。1980年,USFWS宣布红狼在野外灭绝。1987年,USFWS,通过红狼恢复计划,将红狼重新引入北卡罗来纳州东北部。尽管恢复工作已经在野外建立了大约70-80只红狼的种群,与土狼杂交的问题,近亲繁殖,人类造成的死亡继续阻碍红狼的康复。我们探索这三个挑战,在每一个挑战中,我们说明了如何使用研究来解决与红狼-土狼互动相关的问题,近亲繁殖的影响,和人口对人为死亡率的反应。我们希望这说明了研究促进红狼恢复的实用性。
    By the 1970s, government-supported eradication campaigns reduced red wolves to a remnant population of less than 100 individuals on the southern border of Texas and Louisiana. Restoration efforts in the region were deemed unpromising because of predator-control programs and hybridization with coyotes. The U.S. Fish and Wildlife Service (USFWS) removed the last remaining red wolves from the wild and placed them in a captive-breeding program. In 1980, the USFWS declared red wolves extinct in the wild. During 1987, the USFWS, through the Red Wolf Recovery Program, reintroduced red wolves into northeastern North Carolina. Although restoration efforts have established a population of approximately 70-80 red wolves in the wild, issues of hybridization with coyotes, inbreeding, and human-caused mortality continue to hamper red wolf recovery. We explore these three challenges and, within each challenge, we illustrate how research can be used to resolve problems associated with red wolf-coyote interactions, effects of inbreeding, and demographic responses to human-caused mortality. We hope this illustrates the utility of research to advance restoration of red wolves.
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  • 文章类型: Journal Article
    Inbreeding, by virtue of its consequence on traits of interest, is a topic of major interest for geneticists and animal breeders. Based on meta-analysis conducted on 57 studies and seven livestock species considering a wide variety of selected traits, it was estimated that inbreeding depression corresponds to on average a decrease of 0.137 percent of the mean of a trait per 1 percent of inbreeding. The decrease was larger for production traits (reduction of 0.351%) than for other trait categories. For populations raised as purebreds, inbreeding depression may impact the economic income of breeders. There is a need for studies assessing the existence of an inbreeding purge phenomenon as well as the impact of inbreeding on adaptation capacities of livestock species. Promises brought by the development of dense genotyping as well as functional genomics will increase the capacities to improve our understanding and management of the phenomenon.
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  • 文章类型: Journal Article
    Environmental heat stress, present during warm seasons and warm episodes, severely impairs dairy cattle performance, particularly in warmer climates. It is widely viewed that warm climate breeds (Zebu and Sanga cattle) are adapted to the climate in which they evolved. Such adaptations might be exploited for increasing cattle productivity in warm climates and decrease the effect of warm periods in cooler climates. The literature was reviewed for presence of such adaptations. Evidence is clear for resistance to ticks and tick-transmitted diseases in Zebu and Sanga breeds as well as for a possible development of resistance to ticks in additional breeds. Development of resistance to ticks demands time; hence, it needs to be balanced with potential use of insecticides or vaccination. The presumption of higher sweating rates in Zebu-derived breeds, based upon morphological differences in sweat glands between breeds, has not been substantiated. Relatively few studies have examined hair coat characteristics and their responses to seasonal heat, particularly in temperate climate breeds. Recently, a gene for slick hair coat has been observed that improved heat tolerance when introduced into temperate climate breeds. No solid evidence exists that hair coat in these lines is lighter than in well-fed warm climate-adapted Holsteins. Warm climate breeds and their F1 crosses share as dominant characteristics lower maintenance requirements and milk yields, and limited response to improved feeding and management. These characteristics are not adaptations to a feed-limited environment but are constitutive and useful in serving survival when feed is scarce and seasonal and high temperatures prevail. The negative relationship between milk yield and fertility present in temperate climates breeds also prevails in Zebu cattle. Fertility impairment by warm conditions might be counteracted in advanced farming systems by extra corporeal early embryo culture. In general, adaptations found in warm climate cattle breeds did not increase heat dissipation capacity, but rather diminished climate-induced strain by decreasing milk production. The negative relationship between reproductive efficiency and milk yield, although relatively low, also appears in Zebu cattle. This association, coupled with limited feed intake, acting over millennia, probably created the selection pressure for a low milk production in these breeds.
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