Estimation of additive and non-additive genetic parameters for reproduction, growth and survival traits in crosses between the Moroccan D'man and Timahdite sheep breeds

Genetic breed differences, heterosis, recombination loss, and heritability for reproduction traits, lamb survival and growth traits to 90 days of age were estimated from crossing D'man and Timahdite Moroccan breeds. The crossbreeding parameters were fitted as covariates in the model of analysis. The REML method was used to estimate (co)variance components using an animal model. The first estimation of crossbreeding effects for Timahdite and D'man breeds shows that breed differences in litter traits are mainly of maternal genetic origin: +1.04 lambs, +1.88 kg, +0.60 lambs, and +2.23 kg in favour of D'man breed for litter size at lambing, litter weight at lambing, litter size at weaning, and litter weight at 90 days, respectively. The breed differences in lamb growth and survival are also of maternal genetic origin for the majority of traits studied, but in favour of the Timahdite breed: +3.48 kg, +45 g day⁻¹ and +0.19 lambs for weight at 90 days, for average daily gain between 30 and 90 days of age, and for lamb survival to 90 days, respectively. The D'man direct genetic effect was low and negative for survival and birth weight of lambs during the first month of life. All traits studied showed positive heterosis effects. Recombination loss effects were not significant. Therefore, crossbreeding of Timahdite with D'man breeds of sheep can result in an improved efficiency of production of saleable lambs. Heritability estimates were medium for litter size but low for the other reproduction traits. Direct heritabilities were low for body weights and lamb survival at 90 days and the corresponding maternal heritabilities showed, however, low to moderate estimates. For litter traits, the estimates of genetic and phenotypic correlations were positive and particularly high for genetic correlations.     

Identification of monozygous twins and microsatellite mutation rate in pigs from QTL linkage analysis data

In previous work, microsatellite markers have primarily been tools for genome studies. However, the use of marker data can be extended beyond its original intent to maximize the amount of information obtained. There have been few studies to determine the occurrence of monozygous (MZ) twins in pigs. The advent of DNA marker technology, and microsatellites in particular, allows MZ twins to be identified based on their genotype data. To determine if MZ twin births occur in pigs, genotypes for F2 individuals, n =525, from 65 Berkshire × Yorkshire families were examined. One pair of female twins was found to have matching genotype data (95% CI: 0–2.94 twins). This is a unique result since there have been no published reports to date of twin pigs that survived until birth. Additionally, three dinucleotide microsatellite mutations were found after screening 134 565 meioses of 125 loci spanning the entire genome and the X chromosome. The average mutation rate for the population, n =570, was 2.23 × 10^–5 (95% CI: 6.17 × 10^–6–6.51 × 10^–5). A mutation rate similar to this was published earlier for dinucleotide repeat microsatellite mutations in swine.     

Generalized marker regression and interval QTL mapping methods for binary traits in half-sib family designs

A Generalized Marker Regression Mapping (GMR) approach was developed for mapping Quantitative Trait Loci (QTL) affecting binary polygenic traits in a single-family half-sib design. The GMR is based on threshold-liability model theory and regression of offspring phenotype on expected marker genotypes at flanking marker loci. Using simulation, statistical power and bias of QTL mapping for binary traits by GMR was compared with full QTL interval mapping based on a threshold model (GIM) and with a linear marker regression mapping method (LMR). Empirical significance threshold values, power and estimates of QTL location and effect were identical for GIM and GMR when QTL mapping was restricted to within the marker interval. These results show that the theory of the marker regression method for QTL mapping is also applicable to binary traits and possibly for traits with other non-normal distributions. The linear and threshold models based on marker regression (LMR and GMR) also resulted in similar estimates and power for large progeny group sizes, indicating that LMR can be used for binary data for balanced designs with large families, as this method is computationally simpler than GMR. GMR may have a greater potential than LMR for QTL mapping for binary traits in complex situations such as QTL mapping with complex pedigrees, random models and models with interactions.     

Selective genotyping with a main trait and a correlated trait

In some instances of quantitative trait loci (QTL) mapping, a correlated trait may be available for which measurement is less costly or more convenient than direct measurement of the trait of main interest. In this paper we consider ways of combining phenotyping for a main trait and a correlated trait to maximize power within the overall framework of a selective genotyping design. Four schemes are compared: (1) Selection for the main trait only (2) Selection for the correlated trait only (3) Two-stage selection (4) Three-stage selection. Optimum proportion selected for the two traits were obtained for the various schemes, and power parameters compared, according to the correlation r, between the two traits, and the proportion of the population, Q, phenotyped for the main trait. The schemes were compared under two sets of assumptions: (1) Total population size and proportion that can be phenotyped for the main trait are fixed, and (2) Total costs are fixed, with relative cost, c', of rearing and phenotyping for the correlated trait as compared to the main trait. Under (1), the multi-stage schemes are very advantageous when r is high, and Q is low. Under (2), the single-stage schemes were always superior to the multi-stage schemes; Scheme 1 being preferred when r²/c' < 1.0, and Scheme 2 when r²/c' > 1.0.     

Genetic diversity in Swiss cattle breeds

Introduction First attempts at establishing the genetic relationships among cattle populations relied on archeological evidence (Epstein 1971; Epstein and Mason 1984) and protein polymorphisms (Baker and Manwell 1980, 1991). Loftus et al. (1994) examined mitochondrial DNA to determine the divergence time between Bos taurus and Bos indicus. Today most studies on genetic diversity are based on microsatellite analysis (Litt and Luty 1989; Tautz 1989; Weber and May 1989). Microsatellites were used in, e.g. man (Bowcock et al. 1994), canids (Roy et al. 1994; Fredholm and Winter ø ; 1995) and sheep (Buchanan et al. 1994). Recent studies in cattle are also microsatellite based (e.g. Machugh et al. 1994; Ciampolini et al. 1995; Moazami -Goudarzi et al. 1997) and aim at facilitating the development of management programs for endangered breeds (FAO 1981). Our microsatellite-based investigation on the genetic diversity between and within Swiss cattle breeds included Original Swiss Brown, purebred Simmental, Holstein, Hérens and Evolènard. Previous studies in Swiss breeds made use of blood group systems (Reuse 1969), serum transferrin and hemoglobin (Krummen 1964), amylase (Buser 1970) and carboanhydrases (Kä ;stli et al. 1980). The Hérens breed is endemic to the canton of Wallis. The Evolènard, which are very few in numbers and restricted to a single valley in the canton of Wallis, are phenotypically very similar to the Hérens with the exception of the coat colour. In the Aosta valley (Italy) which borders the canton of Wallis these two breeds find their counterparts. The phenotype of the Aosta Chestnut fits the Hérens and the Aosta Black Pied fits the Evolènard. The Holstein breed replaced the Fribourg breed which was a colour variant of the purebred Simmental breed (Engeler et al. 1961) and is now extinct. The Original Swiss Brown and the purebred Simmental are endemic to Switzerland.     

Genetic diversity and assignment tests among seven French cattle breeds based on microsatellite DNA analysis

Genetic variability and relationships among six native French cattle breeds (Abondance, Tarentaise, Villard de Lans, Montbéliarde, Limousin, and Charolais) and one foreign breed (Holstein) were investigated using 23 microsatellite markers. These breeds were also compared with four Swiss breeds genotyped in a previously published study. Interestingly, the French alpine breeds have smaller population sizes but showed higher genetic variability than the larger Holstein breed. Neighbor-joining trees and PCA (principal components analysis) showed that alpine breeds tend to cluster together. Abondance and Tarentaise breeds were closely related, whereas the Holstein was highly differentiated from all breeds analyzed. Two different assignment tests for determining the breed of origin of individuals were compared: "direct" and "exclusion-simulation" approaches. The exclusion-simulation significance test correctly assigns fewer individuals than the direct approach but provides a confidence level (e.g., P < 0.01) for each individual being assigned. Accurate assignment with high statistical confidence is required for animal traceability. Unfortunately, the accuracy of assignment greatly decreases as the threshold level of confidence of assignment increases (e.g., from P < 0.05 to P < 0.001). Assignment accuracy also greatly declines as the level of population differentiation decreases below the level often found between related breeds (e.g., F(ST) < 0.1).     

我国6个绵(山)羊群体遗传分化的微卫星分析

为进一步了解我国绵(山)羊群体的品种特性及其遗传分化,本文利用微卫星标记对我国6个绵(山)羊群体遗传分化进行了分析。采用中心产区典型群随机抽样方法用聚丙烯酰胺凝胶电泳检测乌珠穆沁羊7个微卫星位点,并引用同实验室小尾寒羊、滩羊、湖羊、同羊、长江三角洲白山羊(参照群体)的相关资料进行群体遗传分化水平分析。研究表明:7个微卫星位点在乌珠穆沁羊、小尾寒羊、滩羊、湖羊、同羊、山羊这6个品种中均存在遗传多态性,各座位等位基因均较丰富。根据标准遗传距离、DA遗传距离以及模糊相容关系进行聚类分析,湖羊与同羊首先聚为一类,乌珠穆沁羊和小尾寒羊聚为一类,然后与滩羊聚为一类,5个绵羊品种最后与山羊相聚。     

山羊品种遗传多样性的分析

利用6个微卫星标记对中西部7个山羊品种(陕南白山羊、陕北白绒山羊、西农萨能羊、关中奶山羊、太行山羊、黄淮山羊、伏牛山羊)共计322个个体进行了遗传多样性检测,并根据Nei氏遗传距离进行了聚类分析。结果表明:6个微卫星标记在这7个品种中存在高度多态性;陕北白绒山羊的遗传变异程度最大,平均杂合度和平均多态信息含量分别为:0.8401和0.8244;而关中奶山羊的遗传变异程度相对较小,平均杂合度和平均多态信息含量分别为:0.7990和0.7784。UPGMA聚类分析表明,黄淮山羊和伏牛山羊聚为一类,陕南白山羊,太行山羊,陕北白绒山羊依次加入,西农萨能羊和关中奶山羊作为一类最后加入。     

Genetic diversity of Indian native cattle breeds as analysed with 20 microsatellite loci

The aim of the present study was to assess the genetic variation and establish the relationship amongst the three Indian zebu cattle breeds using 20 bovine‐specific microsatellite markers. A total of 136 unrelated DNA samples from Sahiwal (SC), Hariana (HC) and Deoni (DC) breeds of cattle were genotyped to estimate within and between breed genetic diversity indices. The estimated mean allelic diversity was 5.2, 6.5 and 5.9 in SC, HC and DC, respectively, with a total of 167 alleles. The average observed and expected heterozygosity for the population varied from 0.42 (SC) to 0.59 (DC), and from 0.61 (SC) to 0.70 (DC), respectively. Low values of genetic variability estimates were observed in SC when compared with DC and HC, indicating some loss of variability because of its relatively small population size. From global F‐statistics a significant deficit of heterozygotes of 24.2% (p < 0.05) was observed for each one of the analysed breeds whereas the total population had a 32.8% (p < 0.05) deficit of heterozygotes. The F_ST estimates demonstrated that approximately 88.7% of the total genetic variation was because of the genetic differentiation within each breed. Pair‐wise breed differentiation, Nei's standard and D_A genetic distance estimates revealed relatively close genetic similarity between HC and DC in comparison with SC. In the UPGMA‐based phylogenetic tree constructed from the genetic distances, HC and DC were grouped together in one cluster and SC in the other. The estimated time of divergence suggested a separation time of approximately 776 years between DC and HC, and a comparatively longer period (1296 years) between DC and SC.     

Genetic diversity and differentiation of five Cuban cattle breeds using 30 microsatellite loci

Conservation and improvement strategies in farm animals should be based on a combination of genetic and phenotypic characteristics. Genotype data from 30 microsatellites were used to assess the genetic diversity and relationships among five Cuban cattle breeds (Siboney de Cuba, Criollo Cubano, Cebú Cubano, Mambí de Cuba and Taíno de Cuba). All microsatellite markers were highly polymorphic in all the breeds. The expected heterozygosity ranged from 0.67 ± 0.02 in the Taíno de Cuba breed to 0.75 ± 0.02 in the Mambí de Cuba breed, and the observed heterozygosity ranged from 0.66 ± 0.03 in the Cebú Cubano breed to 0.73 ± 0.02 in the Siboney de Cuba breed. The genetic differentiation between the breeds was significant (p < 0.01) based on the infinitesimal model (F_ST). The exact test for Hardy‐Weinberg equilibrium within breeds showed a significant deviation in each breed (p < 0.0003) for one or more loci. The genetic distance and structure analysis showed that a significant amount of genetic variation is maintained in the local cattle population and that all breeds studied could be considered genetically distinct. The Siboney de Cuba and Mambí de Cuba breeds seem to be the most genetically related among the studied five breeds.     

漳州斗鸡群体遗传多样性研究

漳州斗鸡为中国斗鸡种的名品,由于长期缺乏有效的保种措施,已面临退化和血缘混杂的危险.为摸清现存漳州斗鸡的遗传结构,我们选用30个微卫星位点,结合聚丙烯酰胺凝胶电泳进行遗传多样性分析,结果表明,共检测到135个等位基因,平均达4.633个,基因杂合度为0.953,非常高,说明该品种的遗传一致性很差,平均多态信息含量为0.586,说明漳州斗鸡微卫星位点多态性丰富,变异程度高,也解释了漳州斗鸡体型外貌多样,生产性能不均的群体遗传特性.漳州斗鸡的保护已刻不容缓.     

利用微卫星标记对四个绵羊品种遗传多样性的初步研究

采用3个微卫星标记，对4个中国地方绵羊品种进行遗传多样性检测。利用POPGENE软件分析了受试羊等位基因频率、等位基因数、有效等位基因数、遗传杂合度。     

Genetic diversity and relationships among three Southern African Nguni cattle populations

Tropical Animal Health and Production - The Nguni cattle breed has distinct populations that are adapted to the different ecological zones of Southern Africa. This study was carried out to assess...     

西藏部分山羊群体线粒体DNA D-loop区遗传多样性及系统进化分析

为了探究西藏不同山羊群体的遗传多样性和亲缘关系,提取4个山羊群体DNA,扩增其mtDNA D-loop区,并测序。结果显示:西藏山羊群体mtDNA D-loop区长度在1 200～1 212 bp,各群体山羊D-loop区富含A、T碱基,共发现106个多态位点,分离出21个单倍型。西藏山羊群体单倍型多样性(Hd)和核苷酸多样性(Pi)分别为0.085 7～1.000 0,0.007 04～0.019 14,4个群体山羊碱基突变率高,表明西藏山羊的遗传多样性非常丰富。核苷酸歧义度、NJ系统进化树表明西藏山羊群体间有共同母系血源,部分支系母系起源于镰刀型角野山羊(Capra aegagrus)和捻角山羊(Capra falconeri),同时存在其他的母系起源,支持山羊品种内的多起源说。     

丝羽乌骨鸡群体遗传结构的微卫星标记分析

用9对微卫星引物对170只丝羽乌骨鸡的基因组DNA进行扩增,结果表明,9个微卫星标记在该品系中都表现出了丰富的多态性,所有扩增结果都能重复.微卫星标记平均每个座位检测到4.56个等位基因(3-7个).9对微卫星引物平均多态信息含量为0.6072,标记平均杂合度为0.7423.本研究的结果可以为进一步利用微卫星进行丝羽乌骨鸡种质特性等研究提供一定的参考.     

The assessment of genetic diversity within and among the eight subpopulations of Japanese Black cattle using 52 microsatellite markers

Japanese Black cattle are at risk for genetic homogeneity due to intensive use of a few sires. Therefore, assessment of the actual genetic diversity of this breed is important for future breeding plans. In the present study, we investigated the genetic diversity within and among eight subpopulations of Japanese Black cattle using 52 microsatellite markers. The parameters for genetic diversity of Japanese Black cattle were comparable to those of other cattle breeds, suggesting that the relatively high genetic diversity of the breed. However, upon comparison among the eight subpopulations, the Hyogo subpopulation showed markedly low genetic diversity. The results of the pairwise F_ST values, phylogenetic network and structure analysis indicated that the Hyogo population has remarkably high level of genetic differentiation from other populations, while Yamagata, Niigata, Hiroshima and Kagawa populations have low levels of genetic differentiation. Furthermore, multidimensional scaling plots indicated that individuals in some subpopulations were separated from individuals in the other subpopulations. We conclude that while the overall genetic diversity of Japanese Black cattle is still maintained at a relatively high level, that of a particular subpopulation is significantly reduced, and therefore the effective population size of the breed needs to be controlled by correct mating strategies.     

利用微卫星分子标记研究我国16份披碱草遗传多样性

利用微卫星(Microsatellite)分子标记对我国16份披碱草Elymus dahuricus进行遗传多样性研究。研究共筛选了38对引物,其中18对引物有扩增条带,占总数的47.4%,具有多态性并且扩增效果较好的引物有6对,占总数的15.8%。用筛选出的这6对引物对供试的16份材料进行微卫星分析,6对引物共检测出26个等位基因,平均每对引物所产生的平均等位基因数为4.3个位点;利用微卫星分子标记数据,对其居群遗传分化进行研究,结果表明:披碱草77.36%的遗传变异出现在居群内,因此,披碱草的遗传多样性主要存在于居群内;对16份披碱草进行聚类分析,构建了亲缘关系树状图,16份供试材料大致分为5类。     

Genetic differences among native and modern cattle breeds in Lithuania based on milk protein loci polymorphism

The intrabreed and interbreed genetic diversity of Lithuanian cattle breeds - two native, namely Lithuanian Light Grey and Lithuanian White-Backed and two modern, namely Lithuanian Red and Lithuanian Black and White was investigated by determination of genetic markers: 4 milk protein systems, Alpha(s1)-casein, Kappa-casein, Beta-casein and Beta-lactoglobulin, which are comprised of 12 different milk protein types. According to results, the B type of Alpha(s1)-casein was found as predominant in all four studied breeds. The most common A and B types of Kappa-casein were found at high frequency in all investigated cattle breeds. All investigated Lithuanian dairy cattle breeds had high frequency of Beta-lactoglobulin whey protein B types, with the highest frequency in Lithuanian Red breed, and the lowest in Lithuanian Light Grey. After investigation the diversity of alleles and genotypes of milk proteins in Lithuanian dairy cattle breeds was determined that, Lithuanian Red breed was distinguished private C allele and BC genotype of Beta-lactoglobulin and CC genotype of Alpha(s1)-casein. The interbreed genetic diversity was estimated by a principal component analysis (PCA). The first principal component (PC) explains 63.39% and the second principal component (PC) explains 33.67% of the genetics diversity between the breeds. Principal component analysis, suggests the hypothesis that native Lithuanian White Backed and Lithuanian Light Grey breeds still have traits tracing to old native populations.     

Genetic structure and diversity among sheep breeds in the United States: identification of the major gene pools

Understanding existing levels of genetic diversity of sheep breeds facilitates in situ and ex situ conservation activities. A comprehensive evaluation of US sheep breeds has not been previously performed; therefore, we evaluated the genetic diversity among and within 28 US sheep breeds. Both major and minor breeds were included in the analysis and consisted of 666 animals from 222 producers located in 38 states. The level of within-breed genetic diversity was variable and not dependent upon status of a breed as a major or minor breed. Bayesian cluster analysis indicated the breeds were grouped more by physiological differences (meat vs. wool production) rather than geographic origin. Results suggest several actionable items to improve in situ and ex situ conservation. The results clearly identify breeds in need of increased in situ and ex situ management (e.g., Hog Island and Karakul) and allow several suggestions for in situ management of flocks. Conversely, several of the breeds appear genetically similar and therefore require less emphasis on collecting germplasm samples for the gene bank. Commercially important breeds (e.g., Rambouillet and Suffolk) were found to have substantial variation, which should enable breeders to proceed, unencumbered by genetic diversity concerns, with selection strategies that maximize profit.