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PubMed1998

Blood pressure and heart rate development in young spontaneously hypertensive rats.

The course of hypertension development in young spontaneously hypertensive rats (SHR) was studied by the measurement of changes in systolic blood pressure (BP), body weight, and heart rate (HR) at 2, 3, 4, and 6 wk of age. To achieve this, we compared inbreeding lines of SHR and Wistar-Kyoto rats (WKY) to determine if differences in BP, body weight, or HR were present among inbreeding lines of the same strain or between strains. The effect of these differences on the eventual level of BP was then assessed. We found that BP began to diverge between SHR and WKY at 4 wk of age. Significant differences in systolic BP (24 mmHg) between SHR inbreeding lines at 4 wk of age did not affect the BP at 8 wk (172 vs. 170 mmHg). Pulse pressure was significantly higher in SHR than in WKY at 4 wk of age. HR was elevated in SHR over age-matched WKY at 3 wk of age and positively correlated to the level of BP attained by individual animals at 6 wk (P = 0.037). Moreover, WKY inbreeding lines showing elevated HR developed higher BP (145 vs. 127 mmHg) at 10-12 and 20 wk of age. The prehypertensive tachycardia in SHR was investigated further and found to result from an increased intrinsic HR. Because HR at 3 wk is a genetic trait that can be partitioned into inbreeding lines, and inbreeding lines most expressive of this trait showed the highest eventual BP, we conclude that prehypertensive tachycardia may be an important first step during hypertension development in SHR. Moreover, early elevations in HR are highly predictive (r = 0.41) of hypertension occurrence in the animal population studied.

Age Factors↗
PubMed2005

Molecular polymorphism of strains within Paramecium septaurelia (Ciliophora, Oligohymenophorea).

RAPD-PCR fingerprinting and ARDRA riboprinting revealed polymorphism within P. septaurelia strains from Russia (4 strains from Lower Volga Basin), and one strain from USA, Florida. However, the first method showed the existence of four RAPD genotypes while the second revealed only two groups of strains with different band patterns. All studied strains had a high percentage of surviving hybrid clones in the inter-strain crosses, with little differentiation of strains within species. Intra-species differentiation of strains in RAPD band patterns may be connected with the degree of inbreeding for the studied species. Species of the P. aurelia complex can be arranged according to the degree of inbreeding characteristic for each, which is correlated with the degree of DNA polymorphism revealed by the RAPD method from extreme inbreeders (e.g. P. sexaurelia), moderate inbreeders (e.g. P. triaurelia) to weak inbreeders (e.g. P. pentaurelia). P. septaurelia of the P. aurelia complex should be included in the group of extreme inbreeder.

Animals↗
PubMed2001

Implications of mating patterns for conservation of the endangered plant Eriogonum ovalifolium var. vineum (Polygonaceae).

Mating patterns have direct application to conservation because of their influence on structuring genetic diversity within and among populations and on maintaining that diversity over time. We measured population and family outcrossing rates, biparental inbreeding, correlation of outcrossed paternity, and inbreeding coefficients in six populations from throughout the ecological range of the endangered plant Eriogonum ovalifolium var. vineum using naturally pollinated families. The taxon was primarily outcrossed: population outcrossing rates averaged 0.80 (SE 0.03) and family outcrossing rates averaged 0.88 (SE 0.03); neither rate varied among populations. Five population rates were significantly different from 1 while family rates differed from 1 in only one population. We found high correlated outcrossed paternity and evidence for biparental inbreeding in five populations each. As expected from the predominantly outcrossed mating system, levels of diversity were high and inbreeding coefficients among maternal individuals were low (averaging -0.05, SE 0.12). Differences between inbreeding coefficients of progeny (average 0.21, SE 0.06) and mothers indicated selection against homozygous offspring. These results indicate that it is important to maintain large populations to prevent increases in inbreeding and to maintain pollinator communities to facilitate outcrossing.

Journal Article↗
PubMed2006

Reduced heterozygosity depresses sperm quality in wild rabbits, Oryctolagus cuniculus.

When close relatives are forced to reproduce, the resulting offspring inherit above average homozygosity and reduced fitness. Biologists now recognize inbreeding depression in the wild, a phenomenon that will probably increase as natural populations become depleted and fragmented. Inbreeding depression is most commonly expressed as compromised fertility and embryogenesis, but actual mechanisms remain poorly understood, especially for wild populations. Here, we examine how reduced heterozygosity influences spermatozoal and gonadal traits in wild rabbits (Oryctolagus cuniculus) sampled across the United Kingdom. By using a suite of 29 microsatellite markers (analyzed to confirm representation of individual heterozygosity across our sample), we found a significant negative relationship between heterozygosity and the production of normal sperm; the relationship was significant both between (n = 12) and within (n = 91 [total males], 42 [island], 49 [mainland]) populations. Reduced heterozygosity was also associated with decreased testis size across males (n = 112), but no relationship was seen at the population level, suggesting environmental confounds. Our results show, for a wild mammal, that inbreeding is associated with decreased sperm quality, confirming suggestions of links between inbreeding and elevated sperm abnormalities in rare felids . These findings could explain why inbreeding depression so frequently arises via compromised fertility and embryogenesis .

Animals↗
PubMed2001

Effects of bottlenecks on quantitative genetic variation in the butterfly Bicyclus anynana.

The effects of a single population bottleneck of differing severity on heritability and additive genetic variance was investigated experimentally using a butterfly. An outbred laboratory stock was used to found replicate lines with one pair, three pairs and 10 pairs of adults, as well as control lines with approximately 75 effective pairs. Heritability and additive genetic variance of eight wing pattern characters and wing size were estimated using parent-offspring covariances in the base population and in all daughter lines. Individual morphological characters and principal components of the nine characters showed a consistent pattern of treatment effects in which average heritability and additive genetic variance was lower in one pair and three pair lines than in 10 pair and control lines. Observed losses in heritability and additive genetic variance were significantly greater than predicted by the neutral additive model when calculated with coefficients of inbreeding estimated from demographic parameters alone. However, use of molecular markers revealed substantially more inbreeding, generated by increased variance in family size and background selection. Conservative interpretation of a statistical analysis incorporating this previously undetected inbreeding led to the conclusion that the response to inbreeding of the morphological traits studied showed no significant departure from the neutral additive model. This result is consistent with the evidence for minimal directional dominance for these traits. In contrast, egg hatching rate in the same experimental lines showed strong inbreeding depression, increased phenotypic variance and rapid response to selection, highly indicative of an increase in additive genetic variance due to dominance variance conversion.

Analysis of Variance↗
PubMed2006

Among- and within-population variation in outcrossing rate of a mixed-mating freshwater snail.

Mixed-mating animals self-fertilize a proportion of their offspring. Outcrossing rate may covary with the ecological and historical factors affecting the population. Theory predicts that outcrossing is favored when inbreeding depression is high and when individual heterozygosity is important. Self-fertilization is predicted to be favored when costs of male function, or mate finding are high, for example, when empty patches are colonized by few individuals. In this study, we assessed primary (after hatching) and secondary (after juvenile mortality) outcrossing rates of two mixed-mating snail populations. Our purpose was to assess the variation in mating-system parameters and estimate significance of inbreeding depression for secondary outcrossing rate (the realized outcrossing rate of parents that produce the next generation). Secondary outcrossing rate was higher than the primary outcrossing rate in one of the two populations, suggesting considerable inbreeding depression. In the other study population, secondary outcrossing rates were found to increase when initially low, or decrease when initially high, depending on the family. Moderate outcrossing rates were found to be more stable. Parental inbreeding coefficients were close to zero in both populations. Outcrossing rate was much more variable among families in the population with the lower average outcrossing rate, suggesting that individuals differed considerably in their mating system. Our results add to recent studies suggesting that populations of mixed-mating animals may differ in their mating system parameters and expression of inbreeding depression.

Animals↗
PubMed2005

Estimation of heritability for Tying-up syndrome in the Thoroughbred racehorse by Gibbs sampling.

Tying-up is a condition that primarily affects the muscles of horses. In this study, the heritability of the Tying-up syndrome in the Thoroughbred racehorse was estimated by Bayesian analysis with Gibbs sampling based on the threshold model for binary traits. The data used were the clinical data in racehorses diagnosed by veterinarians of the Racehorse Clinics of Japan Racing Association from 2000 to 2003. The health status of the Tying-up was treated as a binary trait. In the genetic analysis, the effect of changing the amount of the pedigree or inbreeding information on the estimation of heritability was investigated, too. The heritability estimates with non-zero probability in the posterior densities were approximately 0.16-0.18 in minimum, suggesting that the heritability of the Tying-up is not zero at least. The posterior density distributions of the heritability estimates were generally more pointed and sharp with using inbreeding coefficients than without using it, suggesting that more stable estimations were obtained when inbreeding coefficients were used. Among the different amounts of pedigree and inbreeding information, the heritabilities obtained with three or four generations of pedigree using inbreeding coefficients seems to be preferable, i.e. heritability of 0.42 or 0.43 for Tying-up.

Animals↗
PubMed2001

Quantitative genetics of autogamous F2.

General quantitative genetic properties are derived for the F2 originating from self-fertilisation of hybrid (F1) individuals. These results extend and generalize previous restricted knowledge about this F2. New equations are found for all genotype frequencies, allele frequencies, inbreeding coefficient, genic (additive-genetic) and dominance variances, broadsense and narrowsense heritabilities, and selection potential. The bulk mean is generally lower, and the genotypic variance is generally higher, than those of the F1 and the allogamous F2. Genic and dominance variances for the selfed F2 are very different to the classical counterparts. Their relationships with inbreeding have been investigated, and they are more elaborate than previously considered. The level of inbreeding is constant irrespective of parental combinations, which is different to the inbreeding of an allogamous F2. Selection potential is generally high, and selection advance generally exceeds bulk inbreeding depression. If selection is assisted by dispersion, the autogamous F2 may obtain greater genetic advance than its allogamous counterpart for the same selection pressure. Under conditions of spatially separated F2, swarms, natural selection may be enhanced by selfing.

Alleles↗
PubMed1985

Development of a semi-inbred line of Landrace pigs. I. Breeding performance and immunogenetic characteristics.

During 15 years of inbreeding of pigs (Canadian Landrace) a semi-inbred line has been developed. The inbreeding coefficient (FX) is 0.84, which theoretically corresponds to between 8-9 generations of brother/sister matings. At the highest inbreeding level (0.84) the mean number of newborn piglets in the litter was 7.2 (5 litters, n = 36) including 5 stillborn (13.8%). The mean birth weight of the litter was 8.56 kg (5 litters, n = 31) the mean piglet birth weight was 1.23 kg and at the age of 21 days the mean weight of a litter was 33.24 kg with a mean piglet weight of 5.44 kg. During inbreeding, immunogenetic alloantigenic systems were investigated. Of 15 known erythrocyte systems, alleles of loci J, K, and of the most polymorphic system E, segregated. As to other immunogenetic systems (histocompatibility, leucocyte and allotypes) 2 SLA haplotypes (major histocompatibility complex) and 2 alleles of the SLC leucocyte system segregated. Allotransplants of the skin in SLA compatible siblings survived for a mean of 50.7 days (n = 77) compared with 10.8 days (n = 29) in non-inbred siblings. Tests of blastic transformation activated by T and B lymphocyte mitogens revealed a normal cell-mediated immune response. After immunization with some cell membrane alloantigens a normal humoral response was also recorded. All tested animals were halothane-resistant and tolerated a 10-min exposure to 5% without developing malignant hyperthermia. Depression due to inbreeding was manifested by a reduced reproductive ability (smaller number of piglets, frequent incidence of gonadal hypoplasia, diminution or loss of libido).

Animals↗
PubMed2003

Expected increases in genetic merit from using optimized contributions in two livestock populations of beef cattle and sheep.

The expected benefits from optimized selection in real livestock populations were evaluated by applying dynamic selection algorithms to two livestock populations of sheep (Meatlinc) and beef cattle (Aberdeen Angus). In addition, the effects of introducing BLUP evaluations on the population structure, genetic gain, and inbreeding were investigated. The use of BLUP-EBV accelerated the rates of gain in the Meatlinc, but the effects of BLUP evaluations on Aberdeen Angus are not as evident. Although steady increases in the average coefficient of inbreeding (F) were observed, the inbreeding rates (deltaF) before and after the introduction of BLUP evaluations were not significantly different. The observed deltaF in the last generation was 1.0% for Meatlinc and 0.2% for Aberdeen Angus. The application of the dynamic selection algorithms for maximizing genetic gain at a fixed deltaF led to important expected increases in the rate of genetic gain (deltaG). When deltaF was restricted to the value observed in both populations, increments per year in deltaG of 4.6 (i.e., 17%) index units for Meatlinc and 3.5 (i.e., 30%) index units for Aberdeen Angus were found in comparison to the deltaG expected from conventional truncation BLUP selection. More relaxed constraints on deltaF allowed even higher expected increases in deltaG in both populations. This study demonstrates that the optimization tools constitute a potentially highly effective way of managing gain and inbreeding under a broad range of schemes in terms of scale and inbreeding level. No losses in genetic gain were associated with the use of dynamic optimization selection when schemes were compared at the same deltaF.

Algorithms↗
PubMed2001

Using multiple objective programming in a dairy cow breeding program.

Multiple-objective programming was used to examine the effects various objectives had on the optimal portfolio of sires chosen for a given breeding problem in a Jersey cow dairy herd. It was assumed that the dairy producer had the following three objectives in the breeding decision: to maximize Net Merit, to minimize inbreeding, and to minimize total expenditure on semen. Integer programming models of these three single objectives were estimated to provide the ideal and anti-ideal values for use in several multiple-objective programming models. The integer multiple-objective models examined the interactions and costs of tradeoffs between the three single objectives in a model framework designed to minimize the maximum deviations from the single-objective optima. A model with equal weights on each objective resulted in a decrease of 3% in average inbreeding but also reduced average Net Merit by $170 from the single-objective optima. A second model, where the weight on Net Merit was twice that of inbreeding and semen cost, decreased Net Merit by $100 and reduced inbreeding by 2% from the single objective optima. The results of the multiple-objective programming models show that reducing the inbreeding coefficient for a group of sires purchased will decrease the Net Merit. However, the results generated also demonstrate that the weights placed on each objective by the dairy producer substantially affect the optimal levels of each objective within the multiple-objective model.

Algorithms↗
PubMed2002

Producer breeding objectives and optimal sire selection.

Information from an online survey of dairy producers was used to determine how important producers perceived three different objectives in the breeding problem. The objectives were: maximizing expected net merit of the progeny, minimizing the expected progeny inbreeding coefficient, and minimizing semen expenditure. Producers were asked to rank the three objectives and then to weight the importance of each objective relative to the others. This information was then used to determine weights to be used in a multiple-objective integer program designed to select individual mates for a herd of 76 Jersey cows with known genetic background and cow net merit. The results of the multiple-objective models show that rank and relative importance of producer objectives can affect the portfolio of sires selected. Producers whose primary objective was to maximize expected net merit had a range of average expected progeny net merit of $306 to $310, but the level of expected progeny inbreeding was from 6.99 to 10.45%, with a semen cost per conception of $35 to $41. For producers who selected minimizing progeny inbreeding as the primary goal in their breeding programs, the range of inbreeding was from 6.11 to 6.60%, with lower net merit range of $274 to $301 and semen expenditure of $30 to $37 per conception. One producer selected minimizing semen cost as the primary objective. For that producer's portfolio, the semen cost was $27 per conception and net merit was $288, with a progeny inbreeding coefficient of 10.68%. The results of this research suggest that producer information and goals have a substantial impact on the portfolio of sires selected by that producer to attain these goals.

Animals↗
PubMedDate not supplied

[Analysis of the population structure of the Black Forest Draught Horse].

Gene contributions of foreign populations as well as coefficients of inbreeding and relationship were evaluated in 699 Black Forest Draught horses of Baden-Württemberg actually registered in the year 2002. Based on nearly complete 5-generation-pedigrees and after taking into account the remaining incompleteness, the mean coefficient of inbreeding for the total population was 6.5%. The recently by incrossing with different breeds newly established lines of stallions showed significantly lower mean coefficients of inbreeding. High rates of inbreeding of about 1.6% in the last five generations could also be faced by incrossing stallions of foreign coldblooded populations what resulted in a decrease of inbreeding in the last generation. In the total population the mean degree of relationship was 16%. The mean degree of relationships within lines of stallions was between 18.3 and 26.8%. The coefficients of relationships between lines of stallions varied between 5.1 and 16.6%. Especially, the newly established lines of stallions showed a lower mean degree of relationships to the other different lines of stallions. The proportion of purebred Black Forest Draught horses in the total population was nearly 70%. Assuming that most animals of unknown origin were purebred, the proportion of purebred Black Forest Draught horses reached about 90%. Austrian Noric, Swiss Freiberg and South German Coldblood stallions were the most important contributors to the Black Forest Draught horse population.

Animals↗
PubMed2005

[Effect of population size of performance test on short-term selection result of sire line].

The effects of the population size,boar to sow ratio,and the number of pigs tested per litter on the selection response and its coefficient of variation, inbreeding coefficient of sire line selection were studied. Pig populations of 100 to 500 sows were simulated with Monte Carlo method,and the ratios of boar to sow were 1:10 and 1:20. The number of pigs tested per litter were 2 and 4 composed equally of boars and gilts. The traits selected were average daily gain after weaning (ADG) and backfat thickness (BF) at 100 kg live weight. Breeding pigs were selected according to multiple-trait BLUP,and economic weight of BF was set as 2.5 times of that of ADG. After five generation selection, the results showed that the more the number of sows of the breeding population, the higher the cumulative selection response at 5th generation, and the slower the coefficient of inbreeding increment per generation, the smaller the coefficient of variation of the cumulative selection response at 5th generation. Increasing the number of pigs tested per litter and/or the boar to sow ratio increased the cumulative selection response at 5th generation, inbreeding coefficient increment per generation, and the coefficient of variation of the cumulative selection response at 5th generation. The cumulative selection response got higher and the increment of inbreeding coefficient slowed down significantly when the number of sows in the breeding population increased from 100 to 300,and the ratio of boar to sow and the number of pigs tested per litter were fixed. When the sow number of breeding population was increased from 300 to 400 above,the cumulative selection response only increased slightly,and the coefficient of inbreeding continued to decrease but at a diminished rate. In conclusion, for the short-term selection of sire line, it is recommended that the breeding population should be composed of 400 or above sows, 4 pigs tested per litter,and the ratio of boar to sow should be maintained at 1:20.

Adipose Tissue↗
PubMed1977

On consanguineous marriages and the genetic load.

It has been reported that studies of the genetic consequences of inbreeding should adopt a different strategy in populations having a relatively old inbreeding history and where inbreeding levels have varied over time. This contention is tested with a series of 39,495 single-birth records from Bombay, India, collected in a World Health Organization survey on congenital malformations. Our analysis reveals that: 1. the incidence of major malformations is significantly higher among the inbred offspring (1.34%) as compared to that among non-inbred ones (0,81%)--a finding at variance with a previous study in the same area; 2. the inbreeding effect on perinatal mortality (stillbirths and mortality during the first few days of life) is also found to be significant. In view of the above findings, the genetic load as disclosed by inbreeding is computed for perinatal mortality, major malformations and pooling these together. A + B, the measure of the number of lethal equivalents per gamete, is found to be at variance with other reports. Such variability can be ascribed to non-genetic factors. Supporting evidence collected from Brazil and Malaysia in the same survey is also presented.

Brazil↗
PubMed1987

Genetic heterogeneity of prematurity and intrauterine growth retardation: clues from the Old Order Amish.

We studied differences in the role of genetic factors in prematurity and intrauterine growth retardation with the use of data on 312 Amish singleton live children ascertained from Amish records in Lancaster county, Pennsylvania, between 1969 and 1980. Birth and death certificates were obtained on all children, and inbreeding coefficients of child, mother, and father were computed by use of the path method of tracing common ancestors in a unique genealogic registry of Amish ancestors dating back to the 1700s. Multivariate analysis with linear and log linear models showed that a lower mean gestational age and a higher risk of prematurity (less than 37 weeks) and borderline maturity (37 to 38 weeks) were significantly associated with increased maternal inbreeding but not child or paternal inbreeding. On the other hand, a higher risk of intrauterine growth retardation (less than the tenth percentile in birth weight for gestational age) and mild intrauterine growth delay (tenth to twenty-fifth percentile) were associated with increased child inbreeding but not maternal or paternal inbreeding. The analysis suggests the presence of genetic heterogeneity in the etiology of prematurity and intrauterine growth retardation; while prematurity is mostly related to the maternal genotype, intrauterine growth retardation is related to the fetal genotype. The study reemphasizes the need for separating low birth weight into prematurity and intrauterine growth retardation in genetic and epidemiologic studies.

Consanguinity↗
PubMed1991

Intraspecific variation in population gene diversity and effective population size correlates with the mating system in plants.

Published data on allele frequencies at isozyme loci in inbreeding and outbreeding plant species were analyzed to examine intraspecific variation in gene diversity and effective population size (Ne). Compared with outbreeders, inbreeding species showed markedly greater variation among populations in average values of Nei's gene diversity statistic. Effective population size was estimated by assuming that the variation observed at isozyme loci is selectively neutral. Inbreeding species showed greater levels of variation in Ne than did outbreeders, although the upper range of Ne was similar in the two classes of species. The results suggest that there may be considerable genetic variation and potential for evolutionary change in some but not all populations of inbreeders. Moreover, these findings are important with respect to the conservation of genetic resources. In particular, that the amount of intraspecific variation in population genetic diversity and Ne differs between inbreeding and outbreeding species should be taken into account in sampling efforts designed to optimize the diversity of germplasm collections.

Journal Article↗
PubMedDate not supplied

Consanguinity in the Bishopric of Ourense (Galicia, Spain) from 1900 to 1979.

BACKGROUND: Knowledge of the levels of inbreeding in the human population is interesting because it is one of the characteristics that conditions its genetic structure and has important genetic-medical repercussions in the descendants of marriages between close relatives. Galicia (north-west Spain) is a region with very special geographic, historic and social characteristics that makes it particularly interesting for consanguinity studies. PRIMARY OBJECTIVE: The object of this investigation is the study of the levels of inbreeding and the structure of consanguinity in rural area of the Dioceses of Ourense (Galicia) during the period 1900-1979. SUBJECTS AND METHODS: In the study, data corresponding to 437 parishes, integrated in 80 municipalities of the rural area of the Dioceses of Ourense were analysed. In the period studied, of a total of 110 128 marriages, 9010 took place between biologically related individuals up to the level of second cousins. The rate of consanguinity and the average coefficient of inbreeding of the population, as well as the percentage of the different types of consanguineous marriages, were calculated. MAIN OUTCOMES AND RESULTS: The rate of consanguinity for the period 1900-1979 is 8.18% and the average coefficient of inbreeding is 3.0662 x 10(-3). The most frequent type of consanguineous marriage is between second cousins (4.00% of all marriages). There is a notably high frequency of marriages of multiple relationships (0.52%) and the frequency of uncle-niece or aunt-nephew marriages is 0.16%. The average value of the M22/M33 ratio is 0.66 and during the 80 years studied, with regard to the temporal variation of the average coefficient of inbreeding, the annual values followed a polynomial curve with an inflection point in 1921. CONCLUSIONS: The highest values of consanguinity detected in Galicia, for the same period, were registered in the Dioceses of Ourense and the high rate of uncle-niece or aunt-nephew marriages habitual in this region was confirmed. The latter is explained by the important incidence in the Galician population of the migration to America at the end of the 19th and beginning of the 20th century. However, when the relative frequency of this type of marriage with respect to the total number of consanguineous marriages is calculated, it has relatively low values due to the high proportion of marriages between second cousins and marriages of multiple relationships, the highest in Galicia for an equal period of time. The rate of marriages between first cousins is also the highest in Galicia, confirming a phenomenon that appears to be common in the rural areas of the northern area of the Iberian Peninsula.

Consanguinity↗