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H Simianer

Publications and source records attributed to H Simianer.

12 recordsLinked to original sources
PubMed2007

Modeling the growth of the Goettingen minipig.

The Goettingen minipig developed at the University of Goettingen, Germany, is a special breed for medical research. As a laboratory animal it has to be as small and light as possible to facilitate handling during experiments. For achieving the breeding goal of small body size in the future, the growth pattern of the minipig was studied. This study deals with the analysis of minipig BW by modeling growth with linear and nonlinear functions and comparing the growth of the minipigs with that of normal, fattening pigs. Data were provided by Ellegaard Goettingen minipigs, Denmark, where 2 subpopulations of the Goettingen basis population are housed. In total 189,725 BW recordings of 33,704 animals collected from birth (d 0) to 700 d of age were analyzed. Seven nonlinear growth functions and 4 polynomial functions were applied. The growth models were compared by using the Akaike's information criterion (AIC). Regarding the whole growth curve, linear polynomials of third and fourth order of fit had the smallest AIC values, indicating the best fit for the minipig BW data. Among the nonlinear functions, the logistic model had the greatest AIC value. A comparison with fattening pigs showed that the minipigs have a nearly linear BW development in the time period from birth to 160 d. Fattening pigs have very low weight gains in their first 7 wk in relation to a specific end weight. After 7 wk, fattening pigs have increased growth, resulting in a growth curve that is more sigmoid than the growth curve of the minipig. Based on these results, further studies can be conducted to analyze the growth with random regression models and to estimate variance components for optimizing the strategies in minipig breeding.

Aging↗
PubMed2006

Epistatic kinship a new measure of genetic diversity for short-term phylogenetic structures--theoretical investigations.

The epistatic kinship describes the probability that chromosomal segments of length x in Morgan are identical by descent. It is an extension from the single locus consideration of the kinship coefficient to chromosomal segments. The parameter reflects the number of meioses separating individuals or populations. Hence it is suggested as a measure to quantify the genetic distance of subpopulations that have been separated only few generations ago. Algorithms for the epistatic kinship and the extension of the rules to set up the rectangular relationship matrix are presented. The properties of the epistatic kinship based on pedigree information were investigated theoretically. Pedigree data are often missing for small livestock populations. Therefore, an approach to estimate epistatic kinship based on molecular marker data are suggested. For the epistatic kinship based on marker information haplotypes are relevant. An easy and fast method that derives haplotypes and the respective frequencies without pedigree information was derived based on sampled full-sib pairs. Different parameters of the sampling scheme were tested in a simulation study. The power of the method decreases with increasing segment length and with increasing number of segments genotyped. Further, it is shown that the efficiency of the approach is influenced by the number of animals genotyped and the polymorphism of the markers. It is discussed that the suggested method has a considerable potential to allow a phylogenetic differentiation between close populations, where small sample size can be balanced by the number, the length, and the degree of polymorphism of the chromosome segments considered.

Algorithms↗
PubMed2006

Use of repeated measures analysis for evaluation of genetic background of dairy cattle behavior in automatic milking systems.

Milking frequencies measured at official test days were used with repeated measurement analysis to reveal the environmental and genetic impact on the milking frequency of cows in automatic milking systems. Repeated measurements were 3 test-day observations per cow within days in milk (DIM) classes, with 1,216 cows in DIM class 1 (d 0 to 99), from 1,112 cows in DIM class 2 (d 100 to 199), and from 1,004 cows in DIM class 3 (d 200 to 299) kept in 15 farms. Selection criteria for models analyzing repeated measurements were Akaike and Schwarz Bayesian values, which favored the autoregressive [AR(1)] covariance structure over the compound symmetry model. Results from the AR(1) model indicated a significant impact of fixed herd and parity effects. Milking frequencies decreased with increasing parities and were greatest for first-parity cows. High daily milk yield was associated with higher milking frequencies. Heritabilities for milking frequency were 0.16, 0.19, and 0.22 in DIM classes 1, 2, and 3, respectively, from the AR(1) model. Higher heritabilities in the later stage of lactation were due to a substantial reduction of the residual variance. Genetic correlations between test-day milk yield and daily milking frequency were in the range of 0.46 to 0.57 for all DIM classes and between milking frequency and somatic cell score were near zero. For verification of results, milking frequencies of the same cows obtained from herd management programs were averaged within DIM classes. Heritabilities were slightly above the values from the AR(1) model. In conclusion, heritabilities for milking frequency in automatic milking systems are moderate enough to incorporate this behavioral trait in a combined breeding goal. The inevitable improvement of labor efficiency in dairy cattle farming demands such cows going easily and voluntarily in automatic milking systems.

Analysis of Variance↗
PubMed2005

Conservation programmes for African cattle: design, cost and benefits.

Information on costs and benefits of conservation programmes for cattle is scarce in the literature and mainly available for Europe. This study aims at simulating cost of and benefits from different kinds of conservation programmes designed for indigenous African cattle. The programmes include installation of a herdbook and activities to promote the breed (HB), in situ conservation with a sire rotation scheme (IS), cryoconservation of semen (CC) and CC combined with in situ conservation (IC). The results indicate that cost of the analysed conservation programmes was generally higher than those reported in the literature for comparable schemes. If cost per effective population size conserved is considered, programmes analysed in this study do not appear to be more expensive. The proposed rotation scheme in IS can be applied to many different production systems and prove to be effective with regard to low increase in kinship. Reduction in extinction probability is found to be higher for conservation programmes that strongly involve farmers and give them part of the responsibility for the breeding population. IC was most efficient with regard to cost per effective population size conserved. However, if cost per reduction in endangerment is considered as criterion for the efficiency of a programme, IS, HB and CC are superior to IC. These findings suggest that decisions on conservation programmes should be based on multiple criteria, and not just on cost per effective population size.

Africa↗
PubMed2005

Using expected allele number as objective function to design between and within breed conservation of farm animal biodiversity.

Conservation of genetic diversity in farm animal species can be achieved by preventing extinction of breeds and by reducing genetic drift within breeds. It is suggested to use the expected number of alleles segregating in the species after a given time period as objective function in the design of conservation strategies. A formal approach is presented to predict this quantity based on marker information, accounting for extinction probability of breeds and effective population size within breeds as the major component of genetic drift. Based on this model, relative efficiency of different strategies of diversity conservation can be quantified. Formulas are given to derive the marginal expected number of alleles with respect to genetic drift within population and extinction probability, respectively. The suggested approach is illustrated with an example of 13 European cattle breeds. With the assumed parameters, drift is shown to be the major force leading to loss of alleles, and different breeds are prioritized for activities to reduce risk of extinction and for measures to reduce genetic drift, respectively. Although different aspects of the model need to be further refined, the suggested methodology provides a general and flexible tool to derive the optimum conservation strategy in various scenarios.

Alleles↗
PubMed2005

Genetic parameters of claw and foot disorders estimated with logistic models.

The primary aim of this study was to estimate heritabilities for different types of claw and foot disorders and the genetic relationship of disorders with milk yield and selected conformation traits by applying logistic models in Holstein dairy cattle. The study included data from 5634 Holstein cows kept on large-scale dairy farms in Eastern Germany. Dichotomous response variables were the presence or absence of the disorder in 2003. Cows that were present in herds for <6 wk in 2003 were excluded from the analysis. Incidences, disregarding repeated measurements, for digital dermatitis (DD), sole ulceration (SU), wall disorder (WD), and interdigital hyperplasia (IH) in rear legs were 13.2, 16.1, 9.6, and 6.3%, respectively. The herd effect was highly significant for all disorders. Incidences increased with increasing parities for SU and WD, but were highest among heifers for DD. High milk yield at the first 2 test d after calving was associated with a greater risk for claw and foot disorders in the same lactation. Estimates of heritability were 0.073 for DD, 0.086 for SU, 0.104 for WD, and 0.115 for IH. Genetically, health problems appear to occur in clusters (i.e., a cow showing one disease has an increased genetic risk of showing another claw disease). This phenomenon was also observed between claw and foot disorders and the somatic cell score. Genetic correlations between milk yield in early lactation and disorders were 0.240 for DD, 0.057 for SU, 0.270 for WD, and 0.336 for IH, indicating a physiological antagonism. Correlations between breeding values for claw and foot disorders of bulls and official breeding values for functional type traits were mostly favorable. Routine recording of claw data will offer a new chance to improve claw health within the population as was elaborated by different scenarios applying selection index procedures.

Animals↗
PubMed2000

Sex ratio distortion in bovine sperm correlates to recombination in the pseudoautosomal region.

A total of 2122 single sperm from 35 bulls belonging to six different paternal half-sib groups were analysed with respect to two markers in the bovine pseudoautosomal region (PAR) and sex-specific loci on the X and Y chromosomes, respectively. A segregation ratio significantly different from 1:1 was observed in a test over all families, with a higher proportion of X-bearing gametes (53.5%). The analysis of recombination conducted separately for X- and Y-bearing sperm showed that X-bearing sperm cells possess highly significant individual and between-family variability in recombination rate, whereas Y-bearing sperm show linkage homogeneity. To test whether the two phenomena are related, different logistic regression models were fitted to the data. The results show that sex ratio significantly correlates with changes in recombination rate among X-bearing but not among Y-bearing sperm. Different hypotheses to explain these observations are discussed.

Animals↗
PubMed1998

Fitting genetic mapping functions based on sperm typing: results for three chromosomal segments in cattle.

Genetic mapping functions translate the observed recombination rate between two loci into the corresponding map distance in Morgan units. Different mapping functions give different weights to multiple crossing over and therefore lead to different results. This points out that not every function is best suited to fit a data set. The data used in this study originated from 2214 sperm from 37 Norwegian bulls, which were genotyped for 11 markers. The optimal functions for the chromosomes 6, 23 and the sex chromosome of cattle were derived using the maximum likelihood method, the likelihood ratio test and empirical discriminant analysis. It became apparent that for each chromosome a different function fitted the data best. These were the function of Rao et al. (Human Heredity 1977, 27, 99-104) with p = 0.63 for chromosome 6, the function of Goldgar & Fain (American Journal of Human Genetics 1988, 43, 38-45) with C0 = 0.42, C1 = 0.47, C2 = 0.07 and C3 = 0.04 for chromosome 23 and the function of Felsenstein (Genetics 1979, 91, 769-75) with K = 0.23 for the sex chromosome. The well known functions of Haldane (Journal of Genetics 1919, 8, 299-309) and Kosambi (Annals of Eugenics 1944, 12, 172-5) were shown to be suboptimal in most cases. A function is said to be multilocus feasible if the evaluation of the probability of all possible recombination events does not lead to negative values. The optimal function for chromosome 23 turned out to be multilocus feasible, whereas the functions for chromosome 6 and the sex chromosome were not. The choice of the correct mapping function is shown to have a considerable impact in mapping studies, when double recombinations have to be taken into account. Since there is no unique best mapping function, it is argued that it might be useful to use a simple parametric mapping function (like the one of Felsenstein 1979) and to estimate the respective parameter specifically for a given data set.

Animals↗
PubMed1997

Evidence for individual and between-family variability of the recombination rate in cattle.

We have conducted a study based on single sperm typing in a family design to assess patterns of variability of the male recombination rate in cattle. 2214 sperm of 37 bulls were typed for 11 loci on bovine Chromosomes (Chrs) 6, 23, and the sex chromosomes. Statistically significant individual variability of the recombination rate was observed for one interval in the pseudoautosomal region (PAR) of the bovine sex chromosomes; one marker interval on bovine Chr 23 exhibited individual variability that was close to significance. Thirty-five of the bulls were members of six paternal halfsib groups, and highly significant variability between families was found for one interval in the PAR. This variability may be due to DNA sequence differences in the PAR or to a genetic control of the recombination activity in this region. It is demonstrated that differences in the recombination rate of the magnitude observed in the present study may have a considerable impact on the power of QTL mapping experiments as well as on the sustainability of marker-assisted selection strategies.

Animals↗
PubMed1993

Linkage between the loci for serum albumin and vitamin D binding protein (GC) in sheep.

Evidence for close genetic linkage between the loci for serum albumin (ALB) and vitamin D binding protein (GC) in sheep is presented. No recombinants were found in 28 informative offspring of a single ram family. The recombination frequency between the two loci was estimated to be in the range of 0 to 10%. No sign of linkage was observed between the ALB-GC complex and transferrin.

Animals↗
PubMed1991

Estimated genetic correlations between disease and yield traits in dairy cattle.

Data included observations on more than 200,000 first lactations of Norwegian cattle. Milk yield, fat and protein percentages, and observations on mastitis, ketosis, and presence of disease (binary coding of 0 or 1) were analyzed. Following Bayesian principles and applying the threshold concept, dispersion parameters for the binary traits (on the underlying scale) with continuous production traits were estimated. Heritabilities were .27, .34, and .43 for milk yield, fat percentage, and protein percentage, respectively. Heritabilities for the disease traits were .05 to .13 but may be inconsistent because of methodology problems with small sire by herd-year-season subclass size. Genetic correlations between milk yield and all three disease traits were above .5, indicating an undesirable relationship. Genetic correlations between ketosis and the content traits were -.38 to -.65; low component percentages were associated with high ketosis frequencies. Ignoring diseases in breeding programs may lead to undesirable correlated selection responses when selecting on milk yield.

Animals↗