جستجوی مقالات مرتبط با کلیدواژه « animal model » در نشریات گروه « علوم دام »

The present research aims to construct the latent variable of growth in Kermani sheep, and to evaluate the measurement model and genetic evaluation by applying pedigree and data information collected from 1993 to 2013 in the Breeding Station of Kermani sheep, Shahre Babak, Kerman Province. The records of body weights at birth (BWT), weaning (WWT), six months (SIXWT), nine months (NINEWT), and twelve months (YWT) of age were used to construct a growth latent variable. Fitting the measurement model considered for constructing the latent variable of growth was done by applying confirmatory factor analysis and was evaluated by using goodness of fit statistical measures including root mean square error of approximation (RMSEA), Tuker-Lewis index (TLI), and confirmatory fit index (CFI). The values of RMSEA, TLI, and CFI were obtained at 0.05, 0.99, and 0.99, respectively, implying the construct adequacy for assessing the latent variable of growth in Kermani sheep. An estimate of 0.34 was obtained for latent variable of growth. Positive estimates of genetic, phenotypic, and environmental correlations between the latent variable of growth and any of the investigated body weight traits were obtained. Furthermore, Spearman's rank correlations between estimated breeding values of the latent variable of growth with any of the investigated body weights were positive and high, implying the selection of superior animals for the latent variable of growth may result in the selection of superior animals for investigated body weights except for BWT.

The main aim of the present research was the genetic analysis of the first lactation milk yield trait and evaluation of the impact of selection for milk on the phenotype of age at first calving in Iranian dairy cows using quantile regression. Lactation milk records of 327190 first parity cows (progeny of 5260 sires and 235172 dams) in 637 herds (in 15 provinces) and calved between 2007 and 2015 were utilized. Genetic analysis was carried out with the use of an animal model. In the model, fixed effects of the province, herd, year and month of calving, covariates of lactation length, age at first calving, percentage of Holstein gene, as well as the random effect of the cow were included. The model was fitted on the data using the DMU package. Regression of age at first calving on predicted breeding value was fitted through a quantile regression model. The findings revealed that the heritability of lactation milk yield was equal to 0.276. Annual genetic gain in grade and Holstein purebred were found to be 17.352 (R2=0.913) and 23.398 (R2=0.962) Kg, respectively (P<0.0001). All estimated regression coefficients were negative in different percentiles of age at first calving and ranged between -0.0009 and -0.0344 (month per Kg) which indicates that the influence of genetic potential of cows for milk yield on different parts of calving age distribution is not the same.

In this study, the genetic parameters of body weight traits including body weights at birth, 7, 14, 21, 28 and 35 days were investigated in Japanese quail. For this aim, two Japanese white and wild quail populations and two types of pure and cross mating methods were used. The data were analysed with different animal models and restricted maximum likelihood (REML) procedures, using ASREML software. Six different animal models were implemented and were compared by likelihood ratio test. All models consisted of the direct additive genetic effect, but differed in combinations of maternal additive genetic, maternal environmental and covariance between direct and maternal additive genetic effects. Based on the results of Chi Square, the model including direct additive genetic, maternal additive genetic and environmental maternal effects was considered as the most appropriate model for genetic evaluation of birth weight. Based on this model, the direct heritability (h2a), maternal heritability (h2m), and the ratio of maternal environmental variance to phenotypic variance (c2) of birth weight were estimated 0.13±0.01, 0.48±0.01 and 0.06±0.01, respectively. For other body weight traits, a simple model that included the direct additive genetic effect was selected as the appropriate model. Direct heritability for body weight traits from 7 to 35 days was ranged from 0.29 to 0.39. The results of this study showed that maternal effects were significant only on birth weight of Japanese quails, and at older ages, the bird's genes play a major role to determine the weight traits

The objective of this study was to evaluate different animal models in different genomic scenarios to estimate the breeding values and to detect genotype × environment (G × E) interaction. Genomic data were simulated to reflect variations in number of QTL (100 and 500) and linkage disequilibrium (low and high) using 10K SNP panel for 30 chromosomes. On this genome, the trait simulated in three different environments with heritabilities 0.10, 0.25 and 0.50, respectively. In the next phase, low (0.47) and high (0.83) genetic correlations were assigned between third environment (h2=0.50) with first (h2=0.10) and second (h2=0.25) environments. The results indicated that the accuracy of genomic prediction increased with increasing the heritability, linkage disequilibrium and the genetic correlation between the traits. Comparing to single trait animal model, multiple trait animal model increased accuracy of genomic prediction. Accuracies of genomic predictions were generally high when the genomic breeding values of third environment were estimated using information of their relatives in the second environment, and the highest accuracy (0.422) obtained from the scenario with high linkage disequilibrium and low QTL. Also, accuracies of genomic prediction increased with increasing percentage of animals from 25 to 75. Generally, the level of LD, type of animals in training set, number of phenotypic records in validation set and genetic correlation across environments play important roles if G × E interaction exists. In conclusion, considering the G × E interaction contributes to understanding variations of quantitative trait and increasing accuracy of genomic prediction.

This study was performed to compare different models for estimation of direct and maternal heritability and also for obtaining of genetic trend for body weight traits in Kurdi sheep of North Khorasan. The records of body weight in birth (BW, 7345 records), 3-month (3W, 5905 records), 6-month (6W ,5294 records), 9-month (9W, 3800 records) and 12-month (12W, 3863 records) weight that collected during 1990 to 2013 by Sheep Breeding Station of Shirvan were used. Estimation of genetic parameters for different traits by using of six animal models was carried out by ThrGibbsf90 software. The most suitable model for each trait was determined based on Deviance Information Criterion (DIC). The estimates of direct heritability for BW, 3W, 6W, 9W and 12W traits were 0.172± 0.0007, .0.257± 0.0007, 0.351± 0.0006, 0.120± 0.0007 and 0.131± 0.0009, respectively. In this study, the material genetic effect was significant for BW, 3W and 6W traits (P

A total of 37300 records of egg weight (EW) and 1540 records of egg quality traits, namely, albumen weight (AW), yolk weight (YW), egg shell weight (ESW), egg shell strength (ESS), egg shell thickness (EST) and haugh unit (HU) of Mazandaran native hens were used to estimate genetic and phenotypic parameters. Egg weight data collected during 1991 to 2006 and egg quality traits were measured in 3 consecutive days on 769 hens. Data were analyzed with restricted maximum likelihood procedure by using multiple-trait animal model. Estimates of heritabilities were 0.471, 0.747, 0.334, 0.595, 0.218, 0.465 and 0.536 for EW, AW, YW, ESW, ESS, EST and HU, respectively. The genetic correlation between HU and AW was positive and low (0.11), whereas it was negative and low with other egg quality traits. The EW had a positive and high genetic correlation with AW (0.95) and moderate with YW (0.45) and EST (0.39). The range of genetic correlations among all other traits varied from 0.04 (between AW and ESS) to 0.81 (between EST and ESS). These estimates for phenotypic correlations ranged from -0.13 (between YW and HU) to 0.95 (between EW and YW). These results indicated that selection based on EW may increase YW, AW and egg shell quality.

The main objective of this research was genetic evaluation of dairy cows in Tehran province for 305-d milk production trait based upon 1- first lactation records (scenario one, S1) and 2- first and second lactation records (scenario two, S2). A total of 206,013 records (126,600 first lactation records and 79,413 first and second lactation records) belonging to 126,600 head (representing 2,876 sires and 89,368 dams) in 260 herds was used. The cows calved between 1983 and 2011. Total number of animals in the pedigree file was 218,844 head. DMU software was utilised for estimation variance components (REML) and for prediction breeding value (BLUP). Genetic trends for scenarios 1 and 2 were 16.6 kg (SE=2.42 kg) and 14.9 kg (SE=2.42 kg) per year, respectively and non-significance difference was found between them. Heritability of the trait was 0.281 and 0.247 for these scenarios, respectively. Based on the type of used records, mean accuracy selection of the daughters (0.67 for S1 and 0.69 for S2) were significantly (P<0.0001) different from each other. The findings of the present study revealed that more or less similar genetic trend as well as selection accuracy could be obtained as the genetic evaluation of the cows is undertaken through the scenarios, suggesting that first lactation record could be used to decrease generation interval, and as a consequence, to increase annual genetic gain.

Animal models are used to model the observations of animal performance that are genetically dependent.These models are considered as generalized linear mixed models and the genetic correlation structure of data is considered through random effects of breeding values. One goal of the mentioned models is to estimate variance components. In this research, an approximate Bayesian approach presented to estimate variance components in animal model and compared with the conventional Bayesian approach. A generated data set for hypothetical animal population with 1084 records was used. The observations are the animal's birth weight and the data includes dam ID, sire ID, sex and birth year. The effect of gender was considered as fixed effect and the effects of dam, animal and year of birth were used as random effect. Four different models were fitted by the conventional Bayesian approach and the appropriate model was selected by deviance information criteria. The approximate Bayesian approach was applied on it. Time consuming with a PC with configuration (Intel Core i7, 4GB, 2.7 GHz) was about 120 second for the conventional Bayesian approach and little than 10 second for the approximate Bayesian approach. Goodness of fit was computed by relative root mean squared error of prediction that was respectively 0.1568 and 0.1499 for conventional Bayesian and the approximate Bayesian approaches. T-test was used to illustrate lack of significant different to fit weight of animals between two approaches. The null hypothesis was accepted with p-value 0.98 that it shows mean of fitted animal weights for two approaches are equal.

The study was designed to investigate the relationship between growth trait and biometric traits in Baluchi sheep. This study was conducted to estimate the genetic and phenotypic biometric traits including daily gain (ADG) and height at withers (HW), height at back (HB), body length (BL), heart girth (HG), leg girth (LG) and testis girth (TG) in Baluchi sheep. Total data of 4542 records from six experimental herds of Jahad Organization Research Centre of Mashhad County were collected since 2001 to 2011. Data were analyzed using General Linear Model (GLM) of SAS. For the estimation of genetic parameters and genetic correlation between traits, animal model uni and multi-trait by restricted maximum likelihood (REML) of WOMBAT 32 (Meyer 2007) have been used. The mean heritability of ADG, BL, HG, HW, HB, TG and LG traits was estimated 0.13±0.01, 0.11±0.06, 0.21±0.07, 0.17±0.06, 0.32±0.1 and 0.2±0.06 respectively. The results of the current study showed that the TG trait has the highest heritability. The estimations shows genetic improvement will be predictable in biometric traits of Baluchi sheep. The genetic correlation between traits was positive, ranged between 0.15-0.97. Moreover, phenotypic correlation was positive and was estimated in range of 0.32 to 0.94.

In this study, 5608 records of Kordi sheep body weights collected during 21 years (1990 to 2010) in Sheep Breeding Station of Shirvan were used to estimate genetic, phenotypic and environmental trends. Best linear unbiased predictions (BLUP) of breeding values were obtained by derivative free restricted maximum likelihood (DFREML) using univariate animal model. Genetic, phenotypic and environmental trends were estimated by regression of average estimated breeding values, average phenotypic values and average difference between phenotypic and breeding values on birth year, respectively. Total genetic progress in 21 years for birth weight (BW), weaning weight (WW), body weight at 6 (6W), 9 (9W) and 12 months of age (12W) were 0.017, 0.890, 1.319, 0.727 and 1.199 kg, respectively. Genetic trends for BW, WW, 6W, 9W and 12W were 4.4±0.5, 64±2, 73±3, 71.56±4 and 98.4±5 gr per year, respectively. The phenotypic trends for BW, WW, 6W, 9W and 12W were 16±2, 328±13, 227±18, 295±23 and 405±28 gr per year, respectively. Estimates of trends were significant for all traits (P < 0.01).

In this research to estimate of genetic parameters and inbreeding effect for birth weight (BW) and lamb survival(LS) in Balouchi lambs, we used of 12040 records, which collected by the center of Sheep Breeding Station of (Abbasabad), during the period 1989 to 2009. Genetic parameters estimated with use of 16 difference model, inclusive animal, and threshold and sire model with use of REML method. The most appropriate model was determinate based on log likelihood method. The suitable model for BW included direct additive genetic, maternal additive genetic, maternal permanent environmental and common litter effects. Also, suitable model for LS were included direct additive genetic and common litter effects. Direct heritability for BW was 0.05±0.01, and direct heritability for LS with animal, threshold model and sire model was 0.07±0.01, 0.16±0.08 and 0.31±0.1 respectively. It also genetic, environment and phenotypeic correlation between BW and LS was 0.12±0.01, 0.12±0.2 and 0.10±0.01 respectively, (p<0.05). The mean of inbreeding coefficients in population and inbreed animals were 0.60 and 31.2%, respectively. The estimates of inbreeding depression were -2.62 gr for BW and -0.08 percent for LS, respectively (p<0.05)..

The purpose of this study was to estimate genetic and phenotypic correlations between production, Body weight at birth (BWT), Weaning weight (WWT), 6 month weight (BWT6M) and yearling weight (BWT12M) and ewe reproduction traits including total number of lamb’s born (NLB/EL) and weaned (NLW/EL) and total weight of lambs born (TLBW/EJ) and weaned per ewes joined (TLWW/EJ) of Shal sheep born from 1998 to 2009 at Agricultural Jahad Organization. Data were related to 6221 lambs descending from 180 rams and 4060 ewes. Bivariate analysis for estimate the genetic covariance was conducted. Direct additive genetic correlations between body weights at different ages, were positive and moderate to high (ranged from 0.56 to 0.88) and phenotypic correlation between these traits were estimated positive, but with lower than respected genetic correlations. Direct additive genetic correlations between body weight at different ages and TLWW­/EJ were positive and high (ranged from 0.76 to 0.91) and phenotypic correlations between them were positive however they were less than genetic correlations. Direct additive genetic correlations between body weight at different ages with NLB/EL and NLW/EL were positive and moderate to high (ranged from 0.44 to 0.89) and phenotypic correlations between them were also positive but lower. The results of this study indicated that direct selection for body weight at early stage of life, can improve ewe composite reproduction traits.

Genetic resources in any country are valuable materials which needed to be conserved for a sustainable agriculture. An animal phenotype is generally affected by genetic and environmental factors. To increase mean performance in a population under consideration not only environmental conditions, but also genetic potential of the animals should be improved. Although, environmental improvement could increase the level of animals’ production in a more rapid way, it is not a permanent and non-cumulative progress. In any breeding schemes prediction breeding value of the candidate animals is needed to be obtained with a high precision and accuracy for making a remarkable genetic gain for the traits over the time. The main objective of the present research was to study accuracy of predicted breeding value for body weight at eighth week of age in indigenous chickens of Khorasan Razavi province. A set of 47,000 body weight (at the age of eight weeks) records belonging to 47,000 head of male and female chicks (progeny of 753 sires and 5,154 dams) collected during seven generations (2006-2012) was used. The data were obtained in Khorasan Razavi native chicken breeding center. An animal model was applied for analyzing the records. In the model, contemporary group of generation*hatch*sex (GHS) as a fixed effect, weight at birth as a covariable, as well as direct and maternal additive genetic random effects were taken into account. In an initial analysis using SAS software, all fixed and covariate factors included in the model were detected to be significant for the trait. All additive genetic relationships among the animals in the pedigree file (47,880 animals) were accounted for. Variance and covariance components of direct and maternal additive genetic effects were estimated through restricted maximum likelihood (REML) method. Breeding value of the animals was obtained by best linear unbiased prediction (BLUP). Selection accuracy was then calculated based on prediction error variance (PEV). The model was fitted to the data using DMU package. Post analysis of breeding values (genetic trend estimation and statistical comparison of groups using student’s t test) was also undertaken using SPSS software. Average and standard deviation of body weight at the age of eight weeks were 607.93 g. and 127.347 g., respectively. As expected, males (668.98 g.) were generally heavier than females (549.86 g.) chickens. Additive and maternal genetic variance components were 3183.9253 and 350.8929, respectively. Based on genetic covariance (-363.8555) the correlation between direct and maternal genetic effects was revealed to be -0.3442. Direct and maternal heritability for the trait were found to be 0.4387 and 0.0483, respectively. Mean direct and maternal breeding values were 76.65 g. and -7.91 g., respectively. The corresponding figures for the direct and maternal accuracies were 0.741 and 0.427, respectively. Genetic trends for direct and maternal breeding value were 26.951 g. (SE=1.344 g.) and -2.252 g. (SE=0.199 g.), respectively and statistically significant (P

Inroduction: Inbreeding is defined as the probability that two alleles at any locus are identical by descent and occur when related individuals are mated to each other. The initial consequence of inbreeding is inbreeding depression reducing the performance of growth, production, health, fertility, and survival traits. This concern has become more serious in animal breeding nowadays, in which selection responses are maximized using animal model best linear unbiased predictors (BLUP) of breeding value. The use of these breeding values alone may result in more closely related selection candidates preferred for selection, with increased levels of inbreeding since they share most of their familial information. The unavoidable mating of related animals in closed populations leads to accumulation of inbreeding and decreased genetic diversity. Inbreeding has deleterious effect on additive genetic variance as well as on phenotypic values. Heterozygosity and allelic diversities can be lost from small, closed, selected populations at a rapid rate. The rates of inbreeding must be limited to maintain diversity at an acceptable level so that genetic variation will ensure that future animals can respond to changes in environment. Inbreeding depression has been found in a large proportion of species examined. Lori sheep breed is mainly raised in Lorestan Province in Iran. This study was conducted to identify pedigrees and inbreeding depression on growth traits in Lori sheep population from 2001 to 2010. The rate of inbreeding needs to be limited to maintain diversity at an acceptable level so that genetic variation will ensure that future animals can respond to changes in the environment and to selection. Without genetic variation, animals cannot adapt to these changes. For this study pedigree information and body weight at different ages (birth weight, weaning weight, 6-month weight, and 9-month weight) of 6440 lambs from 273 rams and 1955 ewes during the years 2001 to 2010 from Lorestan Agricultural and Natural Resources Research Center were used. The pedigree corrections were done by the Excel program and the estimation of inbreeding coefficients was done by pedigree software. To study the pedigree, Pedigree, program, or estimate inbreeding coefficient, CFC program, and for calculate the amount of inbreeding citizenship traits, wombat software were used. In total population the number of inbred animals were 2126 (33%) of the herd. The average total population inbreeding coefficient and average inbreeding coefficient inbred of population were 0.69% and 2.24%, respectively. Annual changes in inbreeding coefficient was 0.21, which was statistically significant (p

In this research 5633 records, which collected by Khojir Sheep Breeding Station of Tehran, during the 1994 to 2011 were used for estimate of (co)variance component and evaluation of inbreeding effects on birth weight (BW) and pre weaning mortality (PMW) in Zandi lamb. Genetic parameters were estimated using REML procedures. AIC criterion test were used to choose the most suitable model. The most suitable animal model for BW included direct additive genetic, maternal additive genetic, maternal permanent environmental and common litter effects, and suitable model for PMW were included direct additive genetic, maternal additive genetic and common litter effects. Also suitable threshold model was included sire additive genetic effects and litter effects, but the most appropriate sire model only including sire additive genetic effect. Direct and maternal heritability for BW was 0.11 and 0.08, respectively. Also, logit heritability and heritability obtained from threshold, animal and sire models were 0.14, 0.20 and 0.18, respectively. Genetic, environmental and phenotypic correlation between BW and PMW was -0.27, -0.23 and -0.28, respectively (p<0.05). The 27 percent of all animals in population were inbred. The mean of inbreeding coefficients in population and inbreed animals were 3.5 and 0.9 percent, respectively. The estimates of inbreeding depression were -3.5 g for BW and 0.1 percent for mortality, respectively (p<0.05).

In this study, in order to multivariate analysis of genetic and phenotypic correlations of productive and reproductive traits in Iranian Holstein dairy cows, records of 64220 first lactation dairy cows were used. Data were collected from 749 herds during 1996 to 2009 by the Animal Breeding Center of Iran. The studied traits were productive (305 days milk yield, 305 days fat percentage, 305 days protein percentage and lactation length) and reproductive (dry days, age at first calving, calving interval and open days). Animals breeding values were predicted using a single trait animal model. A canonical correlation analysis using CANCORR procedure of SAS software was carried out to examine the relation between sets of productive and reproductive traits. Analysis indicated that first canonical correlation between first canonical variate pair for phenotypic and breeding values were 0.999 and 0.996, respectively (P<0.0001). Considering high and undesirable genetic correlation between sets of productive and reproductive traits, for long term profitability, designing selection programs based on a combination of these traits is recommendable.

In this research genetic trends for body weight traits of Shal lambs, including: birth weight (BW), weaning weight (WW), 6-month weight (6MW), 9-month weight (9MW) and yearling weight (YW) were studied over a 16-year period. Genetic parameters were estimated using restricted maximum likelihood (REML) method under animal model and breeding values of animals were predicted with Best Linear Unbiased Prediction (BLUP) methodology with single-trait and five-trait animal models. Genetic trends were estimated by regressing the mean of breeding values on year of birth. Direct heritability for BW, WW, 6MW, 9MW and YW were estimated 0.32, 0.47, 0.32, 0.41 and 0.28, respectively. Genetic trends for these traits from both single- and five-trait analyses were estimated (-3 and 4), (32 and 35), (-18 and 10), (27 and 28), (-3 and 11) g per year, respectively, and were non-significant (P>0.05). Also, genetic progress for these traits from both single- and five-trait analyses were calculated (1 and 118), (316 and 918), (404 and 438), (522 and 672) and (60 and 379) g in studied period, respectively. The highest genetic trend was for WW, which had the highest heritability. Despite relatively high heritability for all studied traits, insignificant genetic trends for these traits indicate an undesirable selection program in Shal sheep.

In this study, inbreeding coefficients and effect of inbreeding depression on growth traits were estimated using pedigree and body weight records of Karakul sheep kept (over a period of 24 years (1984-2008)) at the breeding station in Sarakhs, Razavi Khorasan, Iran. Inbreeding coefficients for all animals were estimated using Van Raden algorithm due to low pedigree completeness index. Inbreeding depressions on growth traits were estimated as the regression of body weight in different age, average daily gains in pre-weaning and post-weaning on animal and dam’s estimated inbreeding coefficients as co-variables. The mean of inbreeding for all animals, females and males were 1.59, 1.64 and 1.54 percent, respectively. Inbreeding depression per 1 percent increasing of individual inbreeding for birth, 3,6,9 and 12 month weight and average daily gains in pre-weaning and post-weaning was -0.005, -0.039, -0.117, -0.168, -0.17,-0.0004 and -0.0005 Kg, respectively. Inbreeding depression per 1 percent increasing of dam inbreeding for these traits was 0, -0.050, -0.014,-0.042, -0.055, -0.0006 and 0 kg, respectively. Estimated inbreeding coefficients for this breed showed high degree of close mating in this herd and due to the significant effect of inbreeding on some growth traits it is suggested that this breeding station should use a breeding plan to avoid mating of close relative animals and will use from assortative and compensatory mating.