Genetic parameters for medullated fiber and its relationship with other productive traits in alpacas

The alpaca fiber diameter (FD) varies from 18 to 36 μm, being the finer fiber categories highly appreciated. However, the alpaca fiber presents some limitations in the textile industry due to the high incidence of fiber medullation and diameter variability, both reduces the comfort feeling of the garments. Decreasing or even removing medullation could be a possible selection objective in alpaca breeding programs for increasing economic value of the alpaca fiber. Therefore, the present work aimed to estimate genetic parameters regarding medullation traits, as well as the genetic correlations with other economical important traits, to be able to select the appropriate criteria to reduce or remove medullation on alpaca fiber and help to reduce the prickle factor in the garments. The data was collected from 2000 to 2017 and belonged to the Pacomarca experimental farm. There were 3698 medullation records corresponding to 1869 Huacaya and 414 Suri genetic types. The fiber samples were taken from the mid side, and were analyzed in an OFDA 100® device. The traits analyzed were percentage of medullation (PM), medullated fiber diameter (MFD), FD, standard deviation of FD, greasy fleece weight as fiber traits; density, crimp in Huacaya and lock structure in Suri, head conformation, leg coverage as morphological traits; weaning weight and age at first calving as secondary and functional traits. Genetic parameters were estimated via a multitrait restricted maximum likelihood. The heritabilities for PM and MFD were 0.225 and 0.237 in Huacaya genetic type and 0.664 and 0.237 in Suri genetic type, respectively; heritabilities for other traits were moderate for productive and morphological traits, and low to moderate for secondary and functional traits. The genetic correlations PM-FD and MFD-FD were high and favorable in both genetic types, between 0.531 and 0.975; the genetic correlation PM-MFD was 0.121 in Huacaya and 0.427 in Suri. The rest of genetic correlations with other traits were in general moderate and favorable. The repeatabilities were 0.556 and 0.668 for PM, and 0.322 and 0.293 for MFD in Huacaya and Suri genetic types, respectively. As a conclusion, PM was identified to be a good selection criterion, probably combined in an index with FD to reduce prickling factor.

Modulating birth weight heritability in mice

Expected genetic response is proportional to the heritability of the trait, and this parameter is considered inherent of a specific trait in a particular population. However, models assuming heterogeneity in residual variance lead to different estimates of heritability across combinations of systematic (environmental) effects. Modifying the residual variance of the birth weight by artificial selection was shown to be feasible in a divergent selection experiment in mice. The objectives of this work were to 1) estimate the evolution of the heritability of birth weight in mice in the mentioned experiment, and 2) estimate different heritability regarding systematic effects. Data came from eleven generations of a divergent selection experiment to modify the residual variability of birth weight in mice. A total of 15,431 birth weight records from 959 females and 1,641 litters in combination with 14,786 pedigree records were used. The model used for analysis included generation, litter size, sex, and parity number as systematic effects. Each record of birth weight was assigned to the mother of the pup in the model which assumes that the residual variance is heterogeneous and partially under genetic control. Differences in heritability between lines reached values of 0.06 in the last generations. Choosing the most extreme values of systematic effects, the birth weight heritability ranged from 0.04 to 0.22. From these results, the possibility of modulating the heritability for this trait could be explored in 1 of 2 ways: selecting to decrease the residual variability, or choosing the specific levels of the systematic effects.

Crossbreed genetic performance study in the eventing horse competition

Eventing is an equestrian discipline combining dressage, show jumping and cross-country exercises. The Spanish Sport Horse (SSH) was used in this study as an example to develop a method to ascertain the influence of parental breeds on particular performances by linking their parental genetic contribution with the individual phenotype value computing the optimal breed contribution for each trait evaluated in eventing. Data included 1220 eventing records from 210 SSH animals. The genetic contribution of six main founder populations were computed for each SSH: the Spanish Purebreed (SPB), Arab Horse (A), Thoroughbred (TB), Selle Français (SF), German breeds (G) and North(-west) European (N) breeds. For this analysis we used BLUP (best linear unbiased predictor) animal models for five defined traits and for the total score. The genetic contribution as linear and quadratic adjustment and the interaction between genetic contributions were included as covariates in the genetic model to separate the possible combining ability from the breeding values. The optimal breed genetic contribution for each trait was maximised by using a simplex method. The best combination for conformation was 51% SPB and 49% N, for cross-country aptitude 23% SPB and 77% N, for dressage 48% SF and 52% N, and for show jumping 64% A and 36% N. For cross-country the best performance was predicted using 100% N genetic contribution and for the total score of 24% SF and 76% N. The combination of two breeds (group of breeds) seemed to be the best option for most of the traits. Although the results should be interpreted with caution, the importance of this paper is that it can be considered as a starting point of the analysis. The methodology applied here performed nicely in searching for the best contribution of several breeds to find the best combination for particular interests and could, therefore, be useful for other species/populations.

Estimation of genetic parameters for reproductive traits in alpacas

One of the main deficiencies affecting animal breeding programs in Peruvian alpacas is the low reproductive performance leading to low number of animals available to select from, decreasing strongly the selection intensity. Some reproductive traits could be improved by artificial selection, but very few information about genetic parameters exists for these traits in this specie. The aim of this study was to estimate genetic parameters for six reproductive traits in alpacas both in Suri (SU) and Huacaya (HU) ecotypes, as well as their genetic relationship with fiber and morphological traits. Dataset belonging to Pacomarca experimental farm collected between 2000 and 2014 was used. Number of records for age at first service (AFS), age at first calving (AFC), copulation time (CT), pregnancy diagnosis (PD), gestation length (GL), and calving interval (CI) were, respectively, 1704, 854, 19,770, 5874, 4290 and 934. Pedigree consisted of 7742 animals. Regarding reproductive traits, model of analysis included additive and residual random effects for all traits, and also permanent environmental effect for CT, PD, GL and CI traits, with color and year of recording as fixed effects for all the reproductive traits and also age at mating and sex of calf for GL trait. Estimated heritabilities, respectively for HU and SU were 0.19 and 0.09 for AFS, 0.45 and 0.59 for AFC, 0.04 and 0.05 for CT, 0.07 and 0.05 for PD, 0.12 and 0.20 for GL, and 0.14 and 0.09 for CI. Genetic correlations between them ranged from -0.96 to 0.70. No important genetic correlations were found between reproductive traits and fiber or morphological traits in HU. However, some moderate favorable genetic correlations were found between reproductive and either fiber and morphological traits in SU. According to estimated genetic correlations, some reproductive traits might be included as additional selection criteria in HU.

Genetic control of the environmental variance for birth weight in seven generations of a divergent selection experiment in mice

Data from seven generations of a divergent selection experiment designed for environmental variability of birth weight were analysed to estimate genetic parameters and to explore signs of selection response. A total of 10 783 birth weight records from 638 females and 1127 litters in combination with 10 007 pedigree records were used. Each record of birth weight was assigned to the mother of the pup in a heteroscedastic model, and after seven generations of selection, evidence of success in the selection process was shown. A Bayesian analysis showed that success of the selection process started from the first generation for birth weight and from the second generation for its environmental variability. Genetic parameters were estimated across generations. However, only from the third generation onwards were the records useful to consider the results to be reliable. The results showed a consistent positive and low genetic correlation between the birth weight trait and its environmental variability, which could allow an independent selection process. This study has demonstrated that the genetic control of the birth weight environmental variability is possible in mice. Nevertheless, before the results are applied directly in farm animals, it would be worth confirming any other implications on other important traits, such as robustness, longevity and welfare.

Modelling genetic evaluation for dressage in Pura Raza Español horses with focus on the rider effect

The most popular use of the Pura Raza Español horse in sport is for dressage competitions. Tests on young sport horses were first established in 2004 in Spain to collect data for the genetic evaluation of this breed's suitability for dressage. The aim of this study was to compare eight different models to find out the most appropriate way to include the rider in the genetic evaluation of dressage. A progressive removal of systematic effects from model was also analysed. A total of 8867 performance records collected between 2004 and 2011 from 1234 horses aged between 4 and 6 years old were used. The final score in the dressage test was used as the performance trait. The pedigree matrix contained 8487 individuals. A BLUP animal model was applied using a Bayesian approach with TM software. The horse's age, gender, travelling time, training level, stud of birth and event were included as systematic effects in all the models. Apart from the animal and residual effects that were present in all models, different models were compared combining random effects such as the rider, match (i.e. rider-horse interaction) and permanent environmental effects. A cross-validation approach was used to evaluate the models' prediction ability. The best model included the permanent environmental, rider and match random effects. As far as systematic effects are concerned, the event or the stud of birth was essential effects needed to fit the data.

Genetic parameters for birthweight environmental variability in mice

Data from a divergent experiment for birthweight (BrW) environmental variability were used to estimate genetic parameters for BrW trait and its environmental variability by fitting both homoscedastic (HO) and heteroscedastic (HE) models. A total of 5 475 records of BrW from animals born from inbred dams, and 7 140 pedigree records were used. The heritability of BrW using the model HO was 0.27, with the litter effect much more important, 0.43. The model HE provided a genetic correlation between the trait and its environmental variability that was very high and negative, -0.97, and a high value for the additive genetic variance for environmental variability, suggesting an artefact in the model. The residual skewness was found to be essentially null. A model considering the genetic correlation null was also fitted, and used to obtain the breeding values for the selection process. Moreover, the trait was considered as maternal resulting in similar estimates under the model HO, but more reasonable for the genetic correlation between the trait and its environmental variability of 0.48 with a value of 0.25 for the additive genetic variance regarding environmental variability under the model HE. This led to the conclusion that environmental variability of BrW in mice must be selected via dams. Estimated parameters in a reduced dataset without inbred animals did not substantially change this conclusion.

Pedigree analysis and inbreeding depression on growth traits in Brazilian Marchigiana and Bonsmara breeds

The study of population structure by pedigree analysis is useful to identify important circumstances that affect the genetic history of populations. The intensive use of a small number of superior individuals may reduce the genetic diversity of populations. This situation is very common for the beef cattle breeds. Therefore, the objectives of the present study were to analyze the pedigree and possible inbreeding depression on traits of economic interest in the Marchigiana and Bonsmara breeds and to test the inclusion of the individual inbreeding coefficient (F(i)) or individual increases in inbreeding coefficient (ΔF(i)) in the genetic evaluation model for the quantification of inbreeding depression. The complete pedigree file of the Marchigiana breed included 29,411 animals born between 1950 and 2003. For the Bonsmara breed, the pedigree file included 18,695 animals born between 1988 and 2006. Only animals with at least 2 equivalent generations of known pedigree were kept in the analyses of inbreeding effect on birth weight, weaning weight measured at about 205 d, and BW at 14 mo in the Marchigiana breed, and on birth weight, weaning weight, and scrotal circumference measured at 12 mo in the Bonsmara breed. The degree of pedigree knowledge was greater for Marchigiana than for Bonsmara animals. The average generation interval was 7.02 and 3.19 for the Marchigiana and Bonsmara breed, respectively. The average inbreeding coefficient was 1.33% for Marchigiana and 0.26% for Bonsmara. The number of ancestors explaining 50% of the gene pool and effective population size computed via individual increase in coancestry were 13 and 97.79 for Marchigiana and 41 and 54.57 for Bonsmara, respectively. These estimates indicate reduction in genetic variability in both breeds. Inbreeding depression was observed for most of the growth traits. The model including ΔF(i) can be considered more adequate to quantify inbreeding depression. The inclusion of F(i) or ΔF(i) in the genetic evaluation model may not result in better fit to the data. A genetic evaluation with simultaneous estimation of inbreeding depression can be performed in Marchigiana and Bonsmara breeds, providing additional information to producers and breeders.

Restricting inbreeding while maintaining selection response for weight gain in Mus musculus

An experiment with mice was designed to test the relative efficiency of three selection methods that help to minimize the rate of inbreeding during selection. A common house mice (Mus musculus) population was selected for 17 generations to increase the weight gain between 21 and 42 days. The population was split at random into three lines A, B and C where three selection methods were applied: individual selection and random mating, weighted selection with random mating and individual selection with minimum coancestry mating, respectively. There were three replicates for each line. Cumulated selection response was similar in the three lines, but there were differences in the level of inbreeding attained (in percentage): 31.24 (method A), 24.72 (method B) and 27.88 (method C). As consequence, lines B and C (weighted selection and minimum coancestry) showed a lower value of deterioration of fitness traits (the intrauterine mortality and the mortality at birth) than line A (random mating).

Estimation of effective population size from the rate of coancestry in pedigreed populations

We introduce a simple method to estimate effective population size from increase in coancestry (Δc(jk)) for all pairs of individuals j and k in a reference subpopulation. An increase in pairwise coancestry for any pair of individuals j and k can be defined assuming that a hypothetical mating between them would give an individual with an inbreeding coefficient equal to c(jk), where c(jk) is the coancestry coefficient between the individuals j and k. The equivalent measure to discrete generations value (g(jk)) corresponding to the individual jk can be computed by averaging discrete equivalents generations of its parents (g(j) and g(k)). The mean increase in coancestry for all pairs of individuals in a reference subpopulation can be used to estimate a realized effective population size based on coancestries that would provide information on the effective size of a population under random mating. Performance of the new parameter was tested on simulated and empirical (horse) populations with different mating strategies and population structures. The routines needed to compute the introduced parameters have been included in a new version of the program ENDOG.

Assessment of inbreeding depression in a Guzerat dairy herd: effects of individual increase in inbreeding coefficients on production and reproduction

Influences of inbreeding on daily milk yield (DMY), age at first calving (AFC), and calving intervals (CI) were determined on a highly inbred zebu dairy subpopulation of the Guzerat breed. Variance components were estimated using animal models in single-trait analyses. Two approaches were employed to estimate inbreeding depression: using individual increase in inbreeding coefficients or using inbreeding coefficients as possible covariates included in the statistical models. The pedigree file included 9,915 animals, of which 9,055 were inbred, with an average inbreeding coefficient of 15.2%. The maximum inbreeding coefficient observed was 49.45%, and the average inbreeding for the females still in the herd during the analysis was 26.42%. Heritability estimates were 0.27 for DMY and 0.38 for AFC. The genetic variance ratio estimated with the random regression model for CI ranged around 0.10. Increased inbreeding caused poorer performance in DMY, AFC, and CI. However, some of the cows with the highest milk yield were among the highly inbred animals in this subpopulation. Individual increase in inbreeding used as a covariate in the statistical models accounted for inbreeding depression while avoiding overestimation that may result when fitting inbreeding coefficients.

Analysis of the existence of major genes affecting alpaca fiber traits

The aim of this study was to determine the presence of major genes for fiber diameter (FD), SD of FD (SDFD), CV of FD, and comfort factor (CF) in Huacaya (HU) and Suri (SU) Peruvian alpaca breeds. Bayesian segregation analyses with relaxed transmission probabilities were performed using 1,906 and 6,592 available records for SU and HU breeds. Evidence for the presence of major genes was statistically supported when the 95% posterior density did not include zero. Significant major genes were found associated with decreased FD, SDFD, CV values, and increased CF values. Additive effects of the major genes were 4.18 and 4.23 μm for FD, 1.67 and 1.61 μm for SDFD, 3.32 and 3.76% for CV, and 15.03 and 14.90% for CF in HU and SU breeds, respectively. Dominance effects were -1.98 and -2.03 μm for FD, -0.88 and -1.11 μm for SDFD, -1.37 and -2.17% for CV, and 13.0 and 11.8% for CF in HU and SU breeds, respectively. Major gene variance was larger than the polygenic variance for all traits. Major gene allelic frequencies for FD, SDFD, and CV ranged from 0.81 to 0.86 for HU breed and from 0.70 to 0.77 for the SU breed and were 0.24 and 0.36, respectively, for CF. It can be concluded that a major gene affecting these traits could be segregating. Then, molecular identification and monitoring of animals carrying favorable genes throughout the worldwide alpaca population would allow for a quick genetic improvement.

Multiple paternal origins of domestic cattle revealed by Y-specific interspersed multilocus microsatellites

In this study, we show how Y-specific interspersed multilocus microsatellites, which are loci that yield several amplified bands differing in size from the same male individual and PCR reaction, are a powerful source of information for tracing the history of cattle. Our results confirm the existence of three main groups of sires, which are separated by evolutionary time and clearly predate domestication. These three groups are consistent with the haplogroups previously identified by Götherström et al. (2005) using five Y-specific segregating sites: Y1 and Y2 in taurine (Bos taurus) cattle and Y3 in zebu (Bos indicus) cattle. The zebu cattle cluster clearly originates from a domestication process that was geographically and temporally separated from that of taurine clusters. Our analyses further suggest that: (i) introgression of wild sire genetic material into domesticated herds may have a significant role in the formation of modern cattle, including the formation of the Y1 haplogroup; (ii) a putative domestication event in Africa probably included local Y2-like wild sires; (iii) the West African zebu cattle Y-chromosome may have partially originated from an ancient introgression of humped cattle into Africa; and (iv) the high genetic similarity among Asian zebu sires is consistent with a single domestication process.

Genealogical analyses in open populations: the case of three Arab-derived Spanish horse breeds

This research assesses the genetic composition of three Arab-derived Spanish horse breeds as an example to highlight the major shortcomings related to genealogical analyses in open populations and to propose approaches useful to deal with this task. The studbooks of three Spanish Arab (SA)-derived horse breeds, Spanish Anglo-Arab (dAA), Hispano-Arab (dHA) and Spanish Sport Horse (dSSH) and those of their parental breeds SA, Spanish Purebred (SPB) and Thoroughbred (TB), totalling 211 754 individuals, were available. The genealogies of the dAA, dHA and dSSH were analysed not only using the corresponding studbook (breed exclusive dataset) but also including the genealogies of the founders from parental breeds (completed dataset). Coancestry analyses revealed that the present SA-derived populations share more genes with the Arab than with the other parental breeds. Effective population size was computed by accounting for migration rates to obtain an equivalent closed-population effective size ((eq)N(e)) of 39.2 for the dAA, 56.3 for dHA and 114.1 for dSSH. The essayed methodologies were useful for characterising populations involving migration. The consequences of the management of the analysed breeds are discussed. The results emphasize the need to include the complete genealogies of the individuals to attain reliable genealogical parameters.

Inbreeding depression on female fertility and calving ease in Spanish dairy cattle

Inbreeding depression on female fertility and calving ease in Spanish dairy cattle was studied by the traditional inbreeding coefficient (F) and an alternative measurement indicating the inbreeding rate (DeltaF) for each animal. Data included records from 49,497 and 62,134 cows for fertility and calving ease, respectively. Both inbreeding measurements were included separately in the routine genetic evaluation models for number of insemination to conception (sequential threshold animal model) and calving ease (sire-maternal grandsire threshold model). The F was included in the model as a categorical effect, whereas DeltaF was included as a linear covariate. Inbred cows showed impaired fertility and tended to have more difficult calvings than low or noninbred cows. Pregnancy rate decreased by 1.68% on average for cows with F from 6.25 to 12.5%. This amount of inbreeding, however, did not seem to increase dystocia incidence. Inbreeding depression was larger for F greater than 12.5%. Cows with F greater than 25% had lower pregnancy rate and higher dystocia rate (-6.37 and 1.67%, respectively) than low or noninbred cows. The DeltaF had a significant effect on female fertility. A DeltaF = 0.01, corresponding to an inbreeding coefficient of 5.62% for the average equivalent generations in the data used (5.68), lowered pregnancy rate by 1.5%. However, the posterior estimate for the effect of DeltaF on calving ease was not significantly different from zero. Although similar patterns were found with both F and DeltaF, the latter detected a lowered pregnancy rate at an equivalent F, probably because it may consider the known depth of the pedigree. The inbreeding rate might be an alternative choice to measure inbreeding depression.

Altered lymphocyte homeostasis after oral prion infection in mouse

Transmissible spongiform encephalopathies (TSEs) or prion diseases develop as central nervous system (CNS) disorders characterized by extremely long incubation periods. Although TSEs do not go along with inflammatory infiltrates and/or antibody production against the prion protein (PrP(Sc)), the immune system plays an important role in pathogenesis as long as different lymphoid organs (Peyer's patches, lymph nodes and spleen) may facilitate the accumulation and further spread of prions after peripheral exposure. In this work we investigated the changes in lymphoid and dendritic cell (DC) populations as well as the implications of different cytokines during disease progression after experimental oral inoculation of prions in a transgenic mouse model. At different days post-inoculation (dpi), T and B lymphocytes and DC populations from lymphoid organs, blood and brain were analyzed by flow cytometry and immunohistochemistry. Besides time related variations in lymphoid cell numbers due to the aging of the animals significant changes related with the infection were found in mesenteric lymph nodes, peripheral blood leukocytes (PBLs) as well as in spleen, affecting the CD4/CD8 ratio. In contrast, little or no variation was detected in Peyer's Patches or in thymus either associated with aging or the infection status. At individual time points significant differences between infected and control mice were seen in the CD8, CD4 and DC populations, with less evidence of differences in the B cell compartment. Finally, a pro-inflammatory phenotype occurred at early times in the spleen, where the levels of lymphotoxin-beta mRNA were found augmented with respect to controls. Altogether, these results suggest that normal regulation of lymphocyte populations becomes altered along the progression of a prion infection.

Genetic relationships among calving ease, calving interval, birth weight, and weaning weight in the Asturiana de los Valles beef cattle breed1

The aim of this paper was to estimate direct and maternal genetic parameters for calving ease (CE), birth weight (BrW), weaning weight (WW), and calving interval (CI) to assess the possibility of including this information in beef cattle improvement programs. Field data, including a total of 59,813 animals (1,390 sires and 1,147 maternal grand sires) from the Asturiana de los Valles beef cattle breed, were analyzed with a multivariate linear model. Estimates of heritability for direct genetic effects (CED, CID, BrWD, and WWD) were 0.191 +/- 0.019, 0.121 +/- 0.013, 0.390 +/- 0.030, and 0.453 +/- 0.035, respectively, whereas those for maternal genetic effects (CEM, BrWM, and WWM) were 0.140 +/- 0.015, 0.208 +/- 0.020, and 0.138 +/- 0.022, respectively. Genetic correlations between direct or maternal genetic effects across traits were, in general, positive and moderate to low. However, genetic correlation for the pair CED-BrWD was positive and high (0.604 +/- 0.064). Genetic correlations between the direct and maternal genetic effects within a trait were negative and moderate (-0.219 +/- 0.097 for CE, -0.337 +/- 0.080 for BrW, and -0.440 +/- 0.102 for WW). Genetic correlations for CED-BrWM and CED-WWM were -0.121 +/- 0.090 and -0.097 +/- 0.113, respectively. The genetic correlation for CEM-CID was unfavorable (0.485 +/- 0.078), and those for CEM-BrWD (-0.094 +/- 0.079) and CEM-WWD (-0.125 +/- 0.082) were low and negative. The genetic correlation between CID and WWM was favorable (-0.148 +/- 0.106). Overall, the data presented here support the hypothesis that maternal effects for CE and BrW are not the same and that the genetic relationships between CI and maternal effects for WW in beef cattle follow a similar pattern to that reported between CI and milk yield in dairy cattle. Moreover, the need to include direct and maternal breeding values in beef cattle selection programs is suggested.

Pedigree information reveals moderate to high levels of inbreeding and a weak population structure in the endangered Catalonian donkey breed

The Catalonian donkey is one of the most endangered donkey breeds in the world. At present, five main subpopulations exist: AFRAC, which consists of many genetically connected Catalonian localities; Berga, which consists of a single herd located also in Catalunya but under private management; and three minor non-Catalonian subpopulations (Huesca, Sevilla and Toledo). In this study, we analysed the pedigree information of the Catalonian donkey herdbook to assess the genetic diversity and population structure of the breed. We found that the Catalonian donkey has suffered an important loss of genetic diversity and moderate to high increases of inbreeding because of the abuse of a few individuals in matings. This scenario is mainly characterized by the fact that both the effective number of founders and ancestors for the whole population was 70.6 and 27, respectively, while the equivalent number of founders was 146.5 and the number of ancestors explaining overall genetic variability was 93. In addition, only 14% of animals born between the 1960s and 1970s were significantly represented in the pedigree. Our results also show that subpopulations where breeders exchanged reproductive individuals had low levels of inbreeding and average relatedness. One subpopulation, Berga, was reproductively isolated and showed high levels of inbreeding (F = 7.22%), with average relatedness (AR = 6.61%) playing an important role in increasing the values of these coefficients in the whole pedigree. Using genealogical F-statistics we have found little evidence of population structuring (F(ST) = 0.0083) with major genetic differences among non-Catalonian subpopulations.

A note on ENDOG: a computer program for analysing pedigree information

The aim of this note is to describe the program ENDOG (v.3.0). The program handles pedigree information to conduct several demographic and genetic analyses including: (a) the individual inbreeding and average relatedness coefficients; (b) effective population size; (c) parameters characterizing the concentration of both gene and individuals origin such as the effective number of founders and ancestors, the effective number of founder herds; (d) F statistics and paired genetic distances for each subpopulation under study; (e) descriptors of the genetic importance of the herds in a population and (f) generation intervals. The program will help breeders and researchers to monitor the changes in genetic variability and population structure with limited costs of preparing datasets. The program, user's guide and example file can be down-loaded free of charge from the World Wide Web at http://www.ucm.es/ info/prodanim/Endog30.zip.

The origins of Iberian horses assessed via mitochondrial DNA

Despite a number of recent studies that have focused on the origin of domestic horses, genetic relationships between major geographical clusters still remain poorly understood. In this study we analyzed a 296 bp mtDNA fragment from the HVI region of 171 horses representing 11 native Iberian, Barb, and Exmoor breeds to assess the maternal phylogeography of Iberian horses. The mtDNA haplogroup with a CCG motif (nucleotide position 15,494 to 15,496) was the most frequent in Iberian and Barb breeds (0.42 and 0.57, respectively), regardless of geographic location or group of breeds. This finding supports the close genetic relationship between the ancestral mare populations of the Iberian Peninsula and Northern Africa. Phenotypic differences among the Northern and Southern Iberian groups of breeds are not explained by population subdivision based on maternal lineages. Our results also suggest that Northern Iberian ponies--which are phenotypically close to British ponies, especially Exmoor--are the result of an introgression rather than population replacement.

Testing the usefulness of the molecular coancestry information to assess genetic relationships in livestock using a set of Spanish sheep breeds1

Recent studies have proposed the use of molecular coancestry coefficients as a measure of genetic variability and as a useful tool for conservation purposes. Using simulated data, molecular coancestry has been shown to become constant very quickly after separation of populations, leading to population diversity remaining constant. However, the use of molecular coancestry information to study the genetic relationships between breeds has not yet been widely explored. Here we analyze the polymorphism of 14 microsatellites in 222 unrelated individuals belonging to seven native Spanish breeds to ascertain the usefulness of molecular coancestry-based methodologies in providing information on their genetic relationships. Average kinship distance (D(k)) and average molecular coancestry coefficients (f(ij)) were compared with well-known genetic distances, such as between-breed Reynolds' distance (D(R)), Nei's standard distance (D(s)), and shared allele distance (D(AS)). Kinship distance and f(ij) have moderate to low correlations with the other genetic distances, showing that they provide different information: both D(k) and f(ij) account for the allele frequencies in the founder population, whereas D(R), D(s), and D(AS) characterize the short-term evolution of the populations. Furthermore, D(k) and f(ij) were only moderately correlated (-0.500). The present study used field data to confirm previous research pointing out the ability of molecular coancestry coefficients to assess genetic differentiation of an ancestral origin. In this respect, molecular coancestry-based parameters may be used with classical genetic parameters to obtain information on population dynamics in livestock breeds. This study additionally presents reliable evidence on the history of these sheep breeds.

Genetic relationships and admixture among sheep breeds from Northern Spain assessed using microsatellites

Although many research papers have studied diversity and differentiation within livestock species, genetic relationships among neighboring populations remain poorly understood. Here we apply recent methodologies to analyze the polymorphism of 14 microsatellites in 238 unrelated individuals belonging to six sheep breeds from Northern Spain to ascertain their historical relationships and the relative genetic contributions existing between populations. Individual genotypes were analyzed to assess the existence of an underlying genetic structure. Long-term and recent migration rates were estimated to identify patterns of relative genetic contribution among breeds. The complete data set showed a strong population structure derived from both different ancestral origins and some geographical patterns of recent gene flow. Two of the analyzed breeds (Black-faced Latxa and Churra) had a marked genetic background, supporting the hypothesis that, regardless of their phenotypical similarities, they have different ancestral origins. Some of the more presumably related breeds had negative long-term admixture coefficients, showing that they diverged only recently. In addition, we show how methodologies for estimation of long-term gene flow and recent patterns of migration are complementary, providing information about migration rates on different timescales.

Factors affecting actual weaning weight, preweaning average daily gain and relative growth rate in Asturiana de los Valles beef cattle breed

Abstract. In this paper we analyse the major environmental and genetic factors affecting actual weaning weight (WW), preweaning average daily gain (ADG) and relative growth rate (RGR) in a representative sample of field data of Asturiana de los Valles beef cattle breed. Major environmental factors affect preweaning growth performance of Asturiana de los Valles calves in the direction usually found in the literature. However RGR seems to be self-corrected for sex of calf and calving number. Heritabilities for the direct and maternal genetic effects were 0.67 and 0.29, 0.51 and 0.31 and 0.18 and 0.12 respectively for WW, ADG and RGR. The estimates of genetic parameters affecting RGR are more realistic than those estimated for the WW and ADG. Selection for RGR would lead to obtain higher growth rates and lower birth weights. RGR could be an interesting selection criterion in beef cattle improvement programs.

Vallecular cysts in newborns and young infants

Vallecular cyst is a rare cause of stridor and respiratory distress in infancy and has been associated with sudden airway obstruction resulting in death. In a retrospective review of eight cases over a 20-year period all infants developed symptoms during the first week of life. All had stridor and feeding difficulties and two required endotracheal intubation. Other common findings included signs of increased work of breathing and episodes of cyanosis. Failure to thrive was present in five patients diagnosed later than the first week of life. An abnormal or a hoarse cry was present in only two patients. Diagnosis in all cases was made by endoscopy. Where a VC is clinically suspected, it is important to stress the need to visualize the base of the tongue during any diagnostic endoscopic procedure. At endoscopy, a smooth localized mass arising from and distorting the lingual surface of the epiglottis was identified. Histologically, the cysts contained respiratory epithelium with mucous glands with an external lining of squamous epithelium. Treatment by cyst marsupialization is safe and definitive, in particular when performed by CO2 laser.

Comparison of two models for estimation of variance components in a sample of Spanish Holstein Friesians

SUMMARY

Two models for estimating genetic parameters in animal populations were compared. The cheapest, in terms of computing costs, was based on a sire model and the most expensive on an animal model. In order to check the accuracy of both methods they were applied to the best available sample of Spanish Friesian cattle. Milk production of each cow, as well as fat contents were simulated using prior estimates of genetic additive, permanent environment and residual variances, keeping the actual mating scheme, so that the simulation mimicked the actual population structure. Results, under the above premises, show no advantages of the more costly procedure over the cheaper one, suggesting that a sire model based estimating procedure for genetic parameters may be preferred when a small number of individuals, little pedigree information and highly disequilibrated distribution of effects characterize the data. ZUSAMMENFASSUNG: Vergleich zweier Methoden der Varianzkomponentenschätzung beim Spanischen Holstein Zwei Modelle zur Schätzung von genetischen Parametern wurden verglichen. Das im Hinblick auf die Rechenleistung günstigere Modell war ein Vatermodell, das aufwendigere Modell ein Tiermodell. Um die Genauigkeit der Modelle in der Praxis zu prüfen, wurden sie auf verfügbares Material der spanischen Holstein-Friesian Population angewendet. Sowohl die Milchleistung jeder Kuh als auch der Fettgehalt wurden simuliert mit Hilfe von Schät- zwerten der additiv-genetischen Varianz, der permanenten und der residuellen Umweltvarianz. Dabei wurde das tatsächliche Ungleichgewicht in der Population berücksichtigt. Unter den obengenannten Voraussetzungen zeigen die Ergebnisse keinen Vorteil der rechnerisch aufwendigeren Prozedur gegenäber der einfacheren. Die Schlußfolgerung lautet, daß das Vatermodell unter den Bedingungen der kleinen Tierzahlen, wenig Pedigree-Informationen und einer stark unbalan- cierten Verteilung der Tiere auf die einzelnen Effektklassen zu bevorzugen ist.