R.L. Quaas

Quantitative trait loci for hip dysplasia in a crossbreed canine pedigree

Canine hip dysplasia is a common developmental inherited trait characterized by hip laxity, subluxation or incongruity of the femoral head and acetabulum in affected hips. The inheritance pattern is complex and the mutations contributing to trait expression are unknown. In the study reported here, 240 microsatellite markers distributed in 38 autosomes and the X chromosome were genotyped on 152 dogs from three generations of a crossbred pedigree based on trait-free Greyhound and dysplastic Labrador Retriever founders. Interval mapping was undertaken to map the QTL underlying the quantitative dysplastic traits of maximum passive hip laxity (the distraction index), the dorsolateral subluxation score, and the Norberg angle. Permutation testing was used to derive the chromosome-wide level of significance at p < 0.05 for each QTL. Chromosomes 4, 9, 10, 11 (p < 0.01), 16, 20, 22, 25, 29 (p < 0.01), 30, 35, and 37 harbor putative QTL for one or more traits. Successful detection of QTL was due to the crossbreed pedigree, multiple-trait measurements, control of environmental background, and marked advancement in canine mapping tools.

Avaliação do crescimento de bovinos jovens da raça Tabapuã, por meio de análises de funções de covariâncias

Restricted maximum likelihood (REML) estimates of additive and residual variances and covariances for birth weight and adjusted weights at 120, 205, 240, 365, 420 e 550 days of age were used to estimate growth covariance functions (CFs) of Tabapua beef calves. Data were observed on 41,415 animals born from 1975 to 1997 and raised under pasture conditions. Estimation of CFs is a very useful tool to analyze beef cattle growth. It was possible to estimate covariance between any pair of ages and the analyses of eigenfunctions associated with the eigenvalues of coefficients matrix of CFs showed that the growth curves of Tabapua calves could be easily changed by selection. Weaning stress, compensatory growth and selection of animals in the final period caused changes on (co)variance trajectories. Therefore only CFs of more complex order were able to estimate values near to REML estimates. However, high order Legendre polynomials drew sharp waves on variances trajectories at the period edges, witch does not have a coherently biological reason.

Categorical Trait Sire Evaluation by Best Linear Unbiased Prediction of Future Progeny Category Frequencies

SUMMARY This paper addresses the problem of the evaluation of the genetic merit of sires for a trait measured by assignment to discrete categories. A model for categorical data assumes that the probability of assignment to a particular category is a random variable. The best linear unbiased predictor of the category frequencies of future progeny is obtained. This procedure is compared to one in which values are assigned to the categories and used as observations. A numerical example is given. 1. Introductioll A common problem facing animal breeders is the prediction of the future performance of animals or their progeny from observations on their past performance. This may be formulated in terms of predicting the realized values of random variables. Henderson (1963) described a predictor which in the class of linear unbiased predictors minimizes the mean squared error of prediction. This predictor called the Best Linear Unbiased Predictor (BLUP) has provided a powerful and widely used tool for the genetic evaluation of animals for traits measured on a continuous scale. Traits which are measured by assignment to discrete categories have posed a special problem. The approach usually adopted has been to assign a value to each category and to use the assigned values as observations (Schaeffer and Wilton 1976; Berger and Freeman 1978). This is analogous to the approach of Grizzle Starmer and Koch (1969) for fixed effect analysis. The assignment of meaningful values to categories is not trivial when the categories are truly discrete and not based at least conceptually on an underlying continuous variable. We avoid the assignment of values completely. BLUP procedures are adapted to predict the frequency of future progeny in each category. An additional advantage is that the predictions of frequencies are easily interpreted. The impetus for this work is a need for the improved evaluation for calving difficulty scores. The procedure is also applicable to other categorically scored traits.

Repeatability and heritability of lactational occurrence of reproductive disorders in dairy cows

Abstract The repeatability and heritability of reproductive disorders were estimated using data from 28 277 Finnish Ayrshire cows. A four-trait linear model including effects of community-year, calving age and month, birth year of the sire, and random sire was used. The number of sires was 339. Variance components were estimated using a method of restricted maximum likelihood. The disease traits were analyzed also with a categorical model including the same effects except that community and year were included as two separate factors. Variance components were estimated with the method of marginal maximum likelihood. Genetic relationships between sires were included in both models. The phenotypic correlation between the first and second lactation was defined as a repeatability of the trait. The lactational incidence risk of reproductive disorders was 0.16 in the first lactation and 0.15 in the second. The risk of ovulatory disorder (anestrus and subestrus, 41%; cyst, 46%; other infertility, 13%) and metritis (early, 63%; late, 37%) were 0.13 and 0.04 in the first lactation and 0.13 and 0.03 in the second lactation, respectively. Average milk production was 4956 (6095 as 3.5% fat corrected milk (FCM)) kg in the first and 5547 (6805 as 3.5% FCM) kg in the second lactation. Estimates of heritabilities in the first lactation were 0.03 and 0.04 (0.03 and 0.02 in the second lactation) for ovulatory disorder and for metritis, respectively. Genetic correlations between the first and the second lactation recordings were 0.60 for ovulatory disorder, −0.58 for metritis and 0.94 for milk yield. Repeatabilities between subsequent lactations were 0.33 for ovulatory disorder, 0.24 for metritis, and 0.67 for milk yield. In the first lactation, the genetic relationship between milk yield and ovulatory disorder and between milk yield and metritis were large and unfavorable. Also in the second lactation, the genetic correlation between milk yield and ovulatory disorder was large, but the correlation between milk yield and metritis was zero.

Trajetória de crescimento e efeito da idade da vaca nos modelos de regressão aleatória de bovinos jovens da raça Tabapuã

This study was undertaken to establish the best way of considering the fixed effects in random regression models for genetic evaluations. The use of polynomial functions to describe growth curves and age-of-dam effects was evaluated by analyzing body weight of 41,415 young Tabapua beef cattle, born from 1975 to 1997 and raised under pasture conditions. Age-of-dam and sex effects showed significant influence on body weights of animals younger than 2-year-old. Age-of-dam effect on weights of offspring showed to be dependent on age of animals. High goodness of fit (R2>0.98) were reached using age of dam at weighing day (i.e., sum of age of dam at birth plus age of animal at weighing day) with at least second degree polynomials and growth curves fitted to each sex separately with at least third degree polynomials.

21 QTL Mapping Using Crossbreed Pedigrees: Strategies for Canine Hip Dysplasia

Canine hip dysplasia (CHD) is a common inherited trait in dogs and the secondary debilitating hip osteoarthritis (OA) results in pain, lameness, and physical disability. Because CHD is a complex trait, the genotype of a dog cannot be judged from its phenotype. Furthermore, dysplastic dogs also have abnormalities in other joints (Olsewski et al. 1983; Kealy et al. 1992, 1997, 2000; Farquhar et al. 1997; Morgan et al. 1999), indicating that the primary defect is systemic, rather than restricted to the hip. We developed an informative crossbreed pedigree for mapping the quantitative trait loci (QTL) contributing to CHD expression. In the context of this unique pedigree, we review here recent advances in CHD and our first attempts in defining the molecular genetic basis of this common complex disease trait, although the trigger event for CHD remains elusive. The dysplastic dog presents itself as an important natural large animal model of a complex human trait. BREED PREVALENCE Hip dysplasia occurs in any pure or mixed breed dog but more commonly affects large breed dogs (Hedhammar et al. 1974; Leighton et al. 1977; Cardinet et al. 1983; Willis 1989; Kaneene et al. 1997; Breur et al. 2002). Breed prevalence, as estimated by the Orthopedic Foundation for Animals (OFA), varies from 1% to 75% (http://www.offa.org/hipstatbreed.html). Phenotype Traditional Mature dogs are positioned in dorsal recumbency with the hips extended, and a ventrodorsal radiograph is taken (Fig. 1). In North America, radiographs are scored based on the degree of subluxation and secondary OA according to...