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1.
用随机回归模型估计SD-Ⅱ系猪体重的遗传和表型协方差函数 总被引：1，自引：0，他引：1
用6个世代的686头SD-Ⅱ系猪的生长记录估计作为经度数据的体重的遗传和表型协方差函数。配合将年龄的勒让德多项式作为自变量的随机回归模型，用平均信息约束最大似然（AIREML）法估计回归系数间的协方差，从而得到加性遗传和永久环境协方差函数的系数。结果表明，协方差函数可以反映出体重在连续的年龄尺度上的遗传和表型变异。当多项式的配合阶数k=3，即降阶配合时，便可充分描述SD-Ⅱ系猪体重的生长变化。降价配合涉及的参数较少，同时可以缓和协方差估值间的差异。 相似文献
2.
考力代羊生长性状的协方差函数估计 总被引：1，自引：0，他引：1
试验旨在模拟考力代羊生长过程中的遗传和表型变异,为其选种提供一定的依据.用1 269只考力代羊的3 332个生长发育记录,配合自变量为年龄的勒让德多项式的随机回归模型(RRM),其中个体加性遗传效应配合5阶,母体永久环境效应配合2~5阶,对数约束最大似然值和信息标准用来检测最佳配合阶数.用平均信息约束最大似然(AIREML)法来估计体重的遗传、环境和表型协方差函数,结果表明,母体永久环境效应配合4阶时,协方差图更符合考力代羊的生长变化情况,涉及的参数也较少,且羔羊在6月龄前后表现出较大的遗传和表型变异.这些结果提示随机回归模型在有限的数据下能够充分描述考力代羊体重在连续时间轴上的增长变化情况. 相似文献
3.
利用第一泌乳期5700个测定日奶量数据，使用DFREML(3．1)估计了测定日产奶量的方差协方差。得出方差一协方差函数矩阵，发现勒让德多项式的协方差函数最佳配合阶数是9，误差方差回归阶数是5。第一泌乳期加性遗传协方差除泌乳初期约40～60天内测定日产奶量协方差较大外，其它日产奶量的协方差均接近x轴。 相似文献
4.
《中国草食动物科学》2020,(3)
用多性状动物模型估计考力代羊体重的遗传参数,从而获得较准确的遗传参数估值。使用1 269只考力代羊的生长发育记录3 332个,用多性状动物模型,分不考虑误差间协方差和考虑误差间协方差两种情况估计考力代羊生长性状的遗传参数。结果表明:不考虑误差间协方差时,直接遗传力估值依次为0.28、0.79、0.77、0.64和0.65;考虑误差间协方差时,则为0.28、0.33、0.30、0.23和0.21。遗传和表型相关在两种情况下都有相同的特点,月龄相差越大,相关越小。说明当不考虑误差间协方差时,分析结果遗传力被过高地估计。 相似文献
5.
1鸡配合饲料的搅拌搅拌是生产配合饲料不可缺少的一环。各种配合饲料原料必须按配方比例计算出每罐应加入的重量并且准确称重,绝对不能用大致估计的方法来估计每种原料的重量。通常按照操作程序和质量要求进行搅拌,时间长了耗电多,增加成本;时间短了搅 相似文献
6.
动物双列杂交试验中所用亲本品种的纯合性常相差很大，所以各遗传组的性状间误差协方差矩阵常不同。本文根据线性模型技术，提出了分析双列杂交试验的新方法，可处理多性状、多环境单元，给出了任一遗传组的综合杂种优势、遗传经济价值和生产力等参数的最优线性无偏估计和置信区间。 相似文献
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在估计奶牛育种值的ＢＬＵＰ法中，综合多方面的信息对育种值作最佳预测，其关键是确定权衡项解的方差协方差矩阵。本文介绍协方差矩阵的求法。１奶牛育种值估计线性模型当利用多种信息，由个体及其亲属的表型值估计育种值时，需要一个ｂｉ来权衡每一个表型值，使估计的精确度达到最高，因此，有线性模型：ＡｄＩ＝ΣｂｉＰｊ＋ｅ１这里，ＡｄＩ为个体直接加性效应ｂｉ为回归系数Ｐｊ为具有亲缘关系的个体表型记录ｅ为剩余项回归系数ｂ的最小二乘方程是：Ｖｂ＝ＲＨＳ其中，Ｖ是个体及其亲属的方差协方差矩阵；ｂ为回归系数向量；ＲＨＳ… 相似文献
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EPD是在BLUP理论的基础上对种用动物遗传值估计的一种参数。EPD值是估计育种值的一半，它是一个容易理解和应用的种畜遗传传递力的值，能很直观地反映种畜价值在其后代中的体现。EPD主要是用在同一品种中2个不同个体间直接遗传效应的比较，从而预测在同一平均遗传值水平上种用动物未来子女的性能差异。EPD适用于动物的出生、发育、母性性状、屠宰性状以及其它特征性状的估计。EPD广泛应用于肉用种公牛价值的评定。对肉牛重要经济性状EPD估计后，以出版物和（或）计算机网络的方式发布，肉牛生产者根据自己的不同需要选用种牛或精液。作者对EPD的估计原理与应用作较为详细的论述。 相似文献
11.
K. Meyer 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2005,122(2):73-85
Estimates of covariance functions and genetic parameters were obtained for growth of Angus cattle from birth to 820 days of age. Data comprised 84 533 records on 20 731 animals in 43 herds, with a high proportion of animals with 4 or more weights recorded. Changes in weights were modelled through random regression on orthogonal polynomials of age at recording. A total of 11 combinations of quadratic, cubic, quartic and quintic polynomials to model direct and maternal genetic effects and permanent environmental effects were considered. Results showed good agreement for all models at ages with many records, but differed at the highest ages and at very early ages with few weights available. Cubic polynomials appeared to be most problematic. The order of polynomial fit for permanent environmental effects of the animal dominated estimates of phenotypic variances and mean squares for residual errors. A model fitting a quartic polynomial for these effects and quadratic polynomials for the other random effects, appeared to be the best compromise between detailedness of the model which could be supported by the data, plausibility of results, and fit, measured as mean square error. 相似文献
12.
Baldi F Alencar MM Albuquerque LG 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2010,127(6):433-441
The objective of this work was to estimate covariance functions using random regression models on B-splines functions of animal age, for weights from birth to adult age in Canchim cattle. Data comprised 49,011 records on 2435 females. The model of analysis included fixed effects of contemporary groups, age of dam as quadratic covariable and the population mean trend taken into account by a cubic regression on orthogonal polynomials of animal age. Residual variances were modelled through a step function with four classes. The direct and maternal additive genetic effects, and animal and maternal permanent environmental effects were included as random effects in the model. A total of seventeen analyses, considering linear, quadratic and cubic B-splines functions and up to seven knots, were carried out. B-spline functions of the same order were considered for all random effects. Random regression models on B-splines functions were compared to a random regression model on Legendre polynomials and with a multitrait model. Results from different models of analyses were compared using the REML form of the Akaike Information criterion and Schwarz' Bayesian Information criterion. In addition, the variance components and genetic parameters estimated for each random regression model were also used as criteria to choose the most adequate model to describe the covariance structure of the data. A model fitting quadratic B-splines, with four knots or three segments for direct additive genetic effect and animal permanent environmental effect and two knots for maternal additive genetic effect and maternal permanent environmental effect, was the most adequate to describe the covariance structure of the data. Random regression models using B-spline functions as base functions fitted the data better than Legendre polynomials, especially at mature ages, but higher number of parameters need to be estimated with B-splines functions. 相似文献
13.
The objective of this study was to model the variances and covariances of total sperm cells per ejaculate (TSC) over the reproductive lifetime of AI boars. Data from boars (n = 834) selected for AI were provided by Smithfield Premium Genetics. The total numbers of records and animals were 19,629 and 1,736, respectively. Parameters were estimated for TSC by age of boar classification with a random regression model using the Simplex method and DxMRR procedures. The model included breed, collector, and year-season as fixed effects. Random effects were additive genetic, permanent environmental effect of boar, and residual. Observations were removed when the number of data at a given age of boar classification was < 10 records. Preliminary evaluations showed the best fit with fifth-order polynomials, indicating that the best model would have fifth-order fixed regression and fifth-order random regressions for animal and permanent environmental effects. Random regression models were fitted to evaluate all combinations of first- through seventh-order polynomial covariance functions. Goodness of fit for the models was tested using Akaike's Information Criterion and the Schwarz Criterion. The maximum log likelihood value was observed for sixth-, fifth-, and seventh-order polynomials for fixed, additive genetic, and permanent environmental effects, respectively. However, the best fit as determined by Akaike's Information Criterion and the Schwarz Criterion was by fitting sixth-, fourth-, and seventh-order polynomials; and fourth-, second-, and seventh-order polynomials for fixed, additive genetic, and permanent environmental effects, respectively. Heritability estimates for TSC ranged from 0.27 to 0.48 across age of boar classifications. In addition, heritability for TSC tended to increase with age of boar classification. 相似文献
14.
By K. Meyer 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》1999,116(3):181-205
Annual weights of cows from 19 to 119 months of age in two herds were analysed fitting a random regression model, regressing on orthogonal polynomials of age in months. Estimates of covariances between random regression coefficients were obtained by restricted maximum likelihood, and the resulting estimates of covariance functions were used to construct covariance matrices for all ages in the data. Analyses were carried out fitting regression coefficients corresponding to overall animal effects only and fitting regressions for animals' additive genetic and permanent, environmental effects. Different definitions of fixed effects subclasses were examined. Models were compared using likelihood ratio tests and estimated standard deviations for the ages in the data. Cubic regressions were sufficient to model both population trajectories and individual growth curves. Random regression coefficients were highly correlated, so that estimation forcing their covariance matrices to have reduced rank (2 or 3) did not reduce likelihoods significantly, allowing parsimonious modelling. Results showed that records were clearly not repeated measurements of a single trait with constant variances. As cows grew up to about 5 years of age, variances. As cows grew up to about 5 years of age, variances increased. Estimates of genetic correlations between 3-year-old and older cows were close to unity in one herd but more erratic in the other. For both herds, genetic correlations between weights on 2-year-old cows and older animals were clearly less than unity. 相似文献
15.
Rates of gain and feed efficiency are important traits in most breeding programs for growing farm animals. The rate of gain (GAIN) is usually expressed over a certain age period and feed efficiency is often expressed as residual feed intake (RFI), defined as observed feed intake (FI) minus expected feed intake based on live weight (WGT) and GAIN. However, the basic traits recorded are always WGT and FI and other traits are derived from these basic records. The aim of this study was to develop a procedure for simultaneous analysis of the basic records and then derive linear traits related to feed efficiency without retorting to any approximation. A bivariate longitudinal random regression model was employed on 13,791 individual longitudinal records of WGT and FI from 2,827 bulls of six different beef breeds tested for their own performance in the period from 7 to 13 mo of age. Genetic and permanent environmental covariance functions for curves of WGT and FI were estimated using Gibbs sampling. Genetic and permanent covariance functions for curves of GAIN were estimated from the first derivative of the function for WGT and finally the covariance functions were extended to curves for RFI, based on the conditional distribution of FI given WGT and GAIN. Furthermore, the covariance functions were extended to include GAIN and RFI defined over different periods of the performance test. These periods included the whole test period as normally used when predicting breeding values for GAIN and RFI for beef bulls. Based on the presented method, breeding values and genetic parameters for derived traits such as GAIN and RFI defined longitudinally or integrated over (parts of) of the test period can be obtained from a joint analysis of the basic records. The resulting covariance functions for WGT, FI, GAIN, and RFI are usually singular but the method presented here does not suffer from the estimation problems associated with defining these traits individually before the genetic analysis. All the results are thus estimated simultaneously, and the set of parameters is consistent. 相似文献
16.
Molina A Menéndez-Buxadera A Valera M Serradilla JM 《Journal of animal science》2007,85(11):2830-2839
A total of 88,727 individual BW records of Spanish Merino lambs, obtained from 30,214 animals between 2 and 92 d of age, were analyzed using a random regression model (RRM). These animals were progeny of 546 rams and 15,586 ewes raised in 30 flocks, between 1992 and 2002, with a total of 45,941 animals in the pedigree. The contemporary groups (animals of the same flock, year, and season, with 452 levels), the lambing number (11 levels), the combination sex of lambs with type of litter (4 levels), and a fixed regression coefficient of age on BW were included as fixed effects. A total of 7 RRM were compared, and the best fit was obtained for a model of order 3 for the direct and maternal genetic effects and for the individual permanent environmental effect. For the maternal permanent environmental effect the best model had an order 2. The residual variance was assumed to be heterogeneous with 10 age classes; the covariance between both genetic effects was included. According to the results of the selected RRM, the heritability for both genetic effects (h(a)2 and h(m)2) increased with age, with estimates of 0.123 to 0.186 for h(a)2 and of 0.059 to 0.108 for h(m)2. The correlations between direct and genetic maternal effects were -0.619 to -0.387 during the first 45 d of age and decreased as age increased, until reaching values from -0.366 to -0.275 between 45 to 75 d of age. Important changes in ranking of the animals were found based on the breeding value estimation with the current method and with the random regression procedure. The use of RRM to analyze the genetic trajectory of growth in this population of Merino sheep is highly recommended. 相似文献
17.
F. Baldi L.G. Albuquerque M.M. Alencar 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2010,127(4):289-299
The objective of this work was to estimate covariance functions for direct and maternal genetic effects, animal and maternal permanent environmental effects, and subsequently, to derive relevant genetic parameters for growth traits in Canchim cattle. Data comprised 49 011 weight records on 2435 females from birth to adult age. The model of analysis included fixed effects of contemporary groups (year and month of birth and at weighing) and age of dam as quadratic covariable. Mean trends were taken into account by a cubic regression on orthogonal polynomials of animal age. Residual variances were allowed to vary and were modelled by a step function with 1, 4 or 11 classes based on animal’s age. The model fitting four classes of residual variances was the best. A total of 12 random regression models from second to seventh order were used to model direct and maternal genetic effects, animal and maternal permanent environmental effects. The model with direct and maternal genetic effects, animal and maternal permanent environmental effects fitted by quadric, cubic, quintic and linear Legendre polynomials, respectively, was the most adequate to describe the covariance structure of the data. Estimates of direct and maternal heritability obtained by multi‐trait (seven traits) and random regression models were very similar. Selection for higher weight at any age, especially after weaning, will produce an increase in mature cow weight. The possibility to modify the growth curve in Canchim cattle to obtain animals with rapid growth at early ages and moderate to low mature cow weight is limited. 相似文献
18.
Genetic analysis of the rates of conception using a longitudinal threshold model with random regression in dairy crossbreeding within a tropical environment 
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下载免费PDF全文 Sayan Buaban Keigo Kuchida Mitsuyoshi Suzuki Yutaka Masuda Wuttigrai Boonkum Monchai Duangjinda 《Animal Science Journal》2016,87(8):961-971
This study was designed to: (i) estimate genetic parameters and breeding values for conception rates (CR) using the repeatability threshold model (RP‐THM) and random regression threshold models (RR‐THM); and (ii) compare covariance functions for modeling the additive genetic (AG) and permanent environmental (PE) effects in the RR‐THM. The CR was defined as the outcome of an insemination. A data set of 130 592 first‐lactation insemination records of 55 789 Thai dairy cows, calving between 1996 and 2011, was used in the analyses. All models included fixed effects of year × month of insemination, breed × day in milk to insemination class and age at calving. The random effects consisted of herd × year interaction, service sire, PE, AG and residual. Variance components were estimated using a Bayesian method via Gibbs sampling. Heritability estimates of CR ranged from 0.032 to 0.067, 0.037 to 0.165 and 0.045 to 0.218 for RR‐THM with the second, third and fourth‐order of Legendre polynomials, respectively. The heritability estimated from RP‐THM was 0.056. Model comparisons based on goodness of fit, predictive abilities, predicted service results of animal, and pattern of genetic parameter estimates, indicated that the model which fit the desired outcome of insemination was the RR‐THM with two regression coefficients. 相似文献
19.
R.C. Sesana A.B. Bignardi R.R.A. Borquis L. El Faro F. Baldi L.G. Albuquerque H. Tonhati 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2010,127(5):369-376
The objective of this work was to estimate covariance functions for additive genetic and permanent environmental effects and, subsequently, to obtain genetic parameters for buffalo’s test‐day milk production using random regression models on Legendre polynomials (LPs). A total of 17 935 test‐day milk yield (TDMY) from 1433 first lactations of Murrah buffaloes, calving from 1985 to 2005 and belonging to 12 herds located in São Paulo state, Brazil, were analysed. Contemporary groups (CGs) were defined by herd, year and month of milk test. Residual variances were modelled through variance functions, from second to fourth order and also by a step function with 1, 4, 6, 22 and 42 classes. The model of analyses included the fixed effect of CGs, number of milking, age of cow at calving as a covariable (linear and quadratic) and the mean trend of the population. As random effects were included the additive genetic and permanent environmental effects. The additive genetic and permanent environmental random effects were modelled by LP of days in milk from quadratic to seventh degree polynomial functions. The model with additive genetic and animal permanent environmental effects adjusted by quintic and sixth order LP, respectively, and residual variance modelled through a step function with six classes was the most adequate model to describe the covariance structure of the data. Heritability estimates decreased from 0.44 (first week) to 0.18 (fourth week). Unexpected negative genetic correlation estimates were obtained between TDMY records at first weeks with records from middle to the end of lactation, being the values varied from ?0.07 (second with eighth week) to ?0.34 (1st with 42nd week). TDMY heritability estimates were moderate in the course of the lactation, suggesting that this trait could be applied as selection criteria in milking buffaloes. 相似文献