Direct Additive Genetic Correlations Research Articles

Autosomal and Z-linked genetic evaluation for body weight in Mazandaran native chicken using different models for dosage compensation on the Z chromosome.

The objectives of this study were to assess the autosomal and sex-linked genetic inheritance of growth traits and identify the effective dosage compensation on the Z chromosome in Mazandaran native chickens. The data included body weights at hatching (BW0), 8 weeks (BW8) and 12 weeks (BW12) of age, related to the first 21 generations of selection, were collected from Mazandaran native chicken breeding centre. The fixed effects included sex of birds in two classes, hatch in five classes and generation in 21 classes. The inverse of the sex-linked additive genetic relationship matrix was constructed using nadiv package in R considering different models for dosage compensation on the Z chromosome. The setup inversed matrix was then supplied externally to WOMBAT using the GIN option. Twelve univariate animal models separating participation of autosomal additive genetic, sex-linked additive genetic and maternal effects (both genetic and permanent environment effects) with considering the five different dosage compensation methods for models with sex-linked effects were analysed by WOMBAT software. BW0 was not affected by sex-linked additive genetic effects. For BW8 and BW12 the model which included autosomal, sex-linked direct additive and maternal effects with no global dosage compensation for the Z chromosome was the most appropriate model. Autosomal heritability estimates were 0.05 ± 0.02, 0.10± 0.01 and 0.11 ± 0.01, for BW0, BW8 and BW12, respectively. For BW8 and BW12, sex-linked heritability estimates were 0.07 and 0.27, respectively. Spearman rank correlation coefficient between autosomal and sex-linked breeding values were 0.45 and 0.12 for BW8 and BW12, respectively. Spearman rank correlation coefficient between autosomal and sex-linked breeding values were 0.45 and 0.12 for BW8 and BW12, respectively. The autosomal direct additive genetic correlations between all traits were positive. The estimate of direct sex-linked additive genetic correlation between BW8 and BW12 was high (0.88). Also, maternal genetic correlations were 0.53, 0.54 and 0.91 between BW0-BW8, BW0-BW12 and BW8-BW12, respectively. Given the importance of Z-linked genes for BW8 and BW12, it is recommended that Z-linked effects be separated from autosomal effects in order to increase the accuracy of genetic evaluation of birds for these traits.

Estimation of genetic parameters for important traits using a multi-trait model in late-feathering Qingyuan partridge hens in China.

Qingyuan partridge chicken is one of the most well-known Chinese indigenous yellow broilers. In breeding programmes, five traits are usually selected when the chickens are 105 days old, namely body weight (BW), comb height (CH), shank length (SL), shank girth (SG) and feather maturity (FM). The objective of this study was to estimate the genetic parameters of these five traits, especially direct additive genetic correlations, to lay the foundation for balanced selection of Qingyuan partridge chickens. Approximately 9600 records were used for estimation. Variance components for these five traits were estimated using three multi-trait models incorporating different effects via Gibbs sampling. Based on model 1 in which the random effects included direct additive genetic effects and residuals, the estimated direct heritabilities for BW, CH, SL, SG and FM were 0.29 ± 0.04, 0.53 ± 0.04, 0.47 ± 0.04, 0.43 ± 0.05 and 0.18 ± 0.03, respectively. The direct genetic correlations ranged from -0.08 to 0.46. When additionally considering maternal additive genetic effects (model 2), the estimates of direct heritabilities and absolute values of direct additive genetic correlations were smaller. The heritabilities were 0.14 ± 0.04, 0.40 ± 0.02, 0.34 ± 0.05, 0.27 ± 0.05 and 0.12 ± 0.03 for BW, CH, SL, SG and FM, respectively. The direct additive genetic correlations ranged from -0.33 to 0.36. More specifically, the direct additive genetic correlations between BW and CH, SL, SG and FM were 0.19 ± 0.13, 0.15 ± 0.15, 0.36 ± 0.15 and - 0.33 ± 0.21, respectively. The genetic correlations of FM with SL, SG and CH were - 0.15 ± 0.15, -0.08 ± 0.17 and 0.18 ± 0.15, respectively. The direct genetic correlations between CH and SG and SL were - 0.02 ± 0.11 and - 0.20 ± 0.11, respectively, and that between SL and SG was 0.19 ± 0.11. The total heritabilities and maternal additive genetic correlations ranged from 0.16 to 0.44 and from -0.13 to 0.61, respectively. The third model also included the maternal permanent environmental effect for BW. The estimates of direct heritability, direct additive genetic correlation, total heritability and maternal additive genetic correlation were only slightly different from those based on the second model. Therefore, the maternal additive genetic effect has a large effect on the estimation of genetic parameters, and it is better to consider this effect in the genetic evaluation of these five traits. Relatively high direct and maternal additive genetic correlations for most trait pairs suggested that it is better to jointly evaluate these five traits in breeding programmes.

Analysis of (co) variance components and estimation of breeding value of growth and production traits in Dahlem Red chicken using pedigree relationship in an animal model.

Variance and covariance components of growth and production traits were analyzed employing REML animal model to assess the Dahlem Red (PD-3) chicken population for direct additive genetic, maternal effects and to estimate the estimated breeding value (EBV), genetic parameters, genetic trends and rate of inbreeding (ΔF) utilizing seven generation’s data. The generation and hatch had significant (P≤0.01) effect on the body weight at 0 day (BW0), 2 (BW2), 4 (BW4) and 6 weeks (BW6) and shank length at six weeks of age (SL6). The average least squares means (LSM) for BW6 and SL6 were 273.93±0.62 g and 53.97±0.05 mm, respectively. All the production traits were significantly (P≤0.01) influenced by generation and hatch. The average LSM for age at sexual maturity (ASM), egg production up to 40 weeks (EP40) and egg mass up to 40 weeks (EM40) were 168.82±0.25 d, 72.60±0.41 eggs and 4.21±0.07 kg, respectively. Model 5 with additive direct, maternal genetic, maternal permanent environmental and residual variance components was the best for BW0, BW2 and BW4 based on the AIC values obtained in WOMBAT. Model 4 was the best model for BW6, SL6, ASM, EP40 and EM40 with additive direct, maternal permanent environmental and residual variance components. Maternal effects were higher during early age, decreased with age, and remained present until 20 weeks of age. The heritability (h2) estimates were low to moderate in magnitude for all the growth traits and ranged from 0.02±0.03 to 0.19±0.03. The maternal heritability was high at hatch (0.35±0.06), decreased gradually until 4th week (0.02±0.01) and ceased afterwards. The heritabilities of EP40 (0.11±0.03) and EM40 (0.12±0.04) were low. The direct additive genetic correlations (ra) between BW2, BW4, BW6 and SL6 were high and positive (P≤ 0.05). The additive genetic and maternal permanent environmental correlation between EP40 and EM40 were high and positive (P≤ 0.05). The EBV of EM40 was significant (P≤ 0.05) with 0.48 kg/generation in PD-3 chicken at the end of the seventh generation. The EBV of EP40 showed an increasing trend with a genetic gain of 1.87 eggs per generation. The average inbreeding coefficient of the population was 0.019 and average ΔF was 0.007 over the last seven generations of selection. The EBV trends for primary and associated traits showed linear trends in the desired direction and negligible inbreeding.

Multi trait genetic evaluation of growth traits in Nellore sheep raised on pasture in semi-arid regions of India using Bayesian approach

Abstract The main aim of this study is to estimate genetic parameters and (co) variance components for body weights at various ages in Nellore sheep born during the period from 1993 to 2016 (23 years). A total of 4822 lambs with pedigree descended from 144 sires and 1299 dams were included in this study. Bayesian analysis using Gibbs sampler multi trait animal model with and without maternal effects was studied. Traits included in this study were birth weight (BW), weaning weight (WW), six months body weight (6MW), nine months body weight (9 MW), Yearling weight (YW). Year-season of birth and sex of lamb (contemporary groups) were considered as fixed effects with ewe weight at lambing as a covariate. Estimates of direct heritability estimates for birth weight, WW, 6MW, 9MW and YW based on best model were 0.17, 0.28, 0.27, 26 and 0.23, respectively and the corresponding maternal heritability estimates were 0.12, 0.14, 0.14, 0.12 and 0.13, respectively. The direct-maternal genetic covariance was negative for all the studied traits. Strong and positive estimates of direct additive genetic correlations were observed in growth traits and they ranged from 0.16 to 0.83, whereas the direct-maternal genetic correlations were negative for all the traits and these estimates ranged from ˗0.89 to ˗0.08. Moderate estimates of heritability for the growth traits obtained in this study suggested the presence of better genetic variability and the possibility for genetic improvement of Nellore sheep through selection. Maternal genetic effects were significant in all the traits. Hence, it is recommended to incorporate these effects in the genetic analysis by including it as a genetic or environmental effect or both. The environmental variance obtained in the study suggested that the growth performance of Nellore sheep may be enhanced by improving the feeding and management aspects. Correlations among traits and effects should be considered while implementing breed improvement program.

Genetic appraisal of growth traits in Iranian native Ghezel sheep using random regression models

This research was carried out to estimate the genetic parameters of the body weight traits of the Ghezel sheep using three different random regression models. The used data were 39,288 test-day records collected from 13,378 animals at Ghezel Sheep Breeding Station in Miandoab, West Azerbaijan Province, Iran from 1994 to 2012. Fixed effects in models included type of birth (single, twin) and year of birth (1994-2012). The weight as a function of age in the days of weighting was considered as the fixed regression of orthogonal polynomial. The random effects of the basic model were direct genetic and direct permanent environment. Maternal genetic and maternal permanent environment effects were added to it respectively. In the basic model, increasing the order of fit for the fixed regression, direct genetic and direct permanent environment effects, increased the accuracy of the model. Adding the maternal permanent environmental effect to the model and increasing the order of fit increased the accuracy of the model. However, adding the maternal additive genetic effect to the model and increasing the order of fit for this effect, decreased the model accuracy. Direct heritability for birth weight and weight at 90, 180, 270, and 360 days of age were: 0.30, 0.22, 0.39, 0.38, and 0.55, respectively. These heritability estimates reduced after birth and reached the lowest amount for body weight at 20 days of age; however, after that, they increased as the age increased (this increase was not uniform and had some fluctuations). The direct additive genetic correlations between the traits of weight at 90 days of age and the weight at 180 days of age was the highest (0.955) and between the birth weight and 180 days of age was the lowest (0.072). These correlations between adjacent age groups were closer than the remote age groups. The value of the direct genetic, direct permanent environment, maternal permanent environment, and the phenotypic variances for birth weight was the lowest and increased by increasing of the age (maximum was for weight of 360th day of age).

The application of recursive multivariate model for genetic evaluation of early growth traits in Raeini Chasmere goat: A comparison with standard multivariate model

Data collected on 2638 kids originated from 1305 dams and 197 sires during 1979 to 2012 in Raeini Cashmere goat breeding station located in Baft, Kerman province, south-eastern part of Iran, on body weights of 2638 Raeini Cashmere kids at birth (BW), at weaning (WW) and at six-month age (6 MW) were used to adopt a fully recursive multivariate model considering causal effects from BW on WW and on 6 MW and from WW on 6 MW. The adopted recursive multivariate model (RMM) was compared with a standard multivariate mixed model (SMM), in which causal relationships were ignored, in terms of deviance information criterion (DIC), predictive ability and the estimates of genetic and phenotypic parameters. Preliminary analyses revealed that the importance of direct additive genetic, maternal permanent environmental and temporary environmental effects for genetic evaluation of all the studied traits. Maternal additive genetic effects were only influencing on BW. Model comparisons via DIC revealed the plausibility of RMM over SMM; DIC value obtained by fitting RMM (-15,218.76) was lower than that of obtained under SMM (21,654.92). For BW, lower mean square of error (MSE) and higher Pearson's correlation coefficient between the observed and predicted values (r(y,y^)) were obtained under SMM but in the case of WW and 6 MW lower MSE and higher r(y,y^) were obtained under RMM. The causal effects of BW on WW and on 6 MW and that of WW on 6 MW were 1.94 kg, 2.48 kg and 1.03 kg, respectively. The estimates of direct heritability, maternal heritability (for BW) and ratio of permanent and / or temporary environmental variances to phenotypic variance were not significantly affected by model fitted (SMM and RMM). Direct additive genetic correlations of BW-WW and BW-6 MW were not statistically significant under SMM (95% HPD interval included zero) but the corresponding estimates under RMM were significant (99% HPD interval did not include zero) values of 0.28 and 0.84, respectively; implying that genes associated with BW also increase WW and 6 MW in Raeini Cashmere goat. Direct genetic correlation estimate for WW-6 MW were 0.88 (under SMM) and 0.29 (under RMM). Generally, RMMs perform better than SMMs and may provide a better explanation to biological relationships among the studied traits.

Genetic analysis of average daily gain in Baluchi sheep

The objective of the present study was to estimate genetic parameters and genetic trends for average daily gain (growth rate) and to investigate the genetic effect of body weight at different ages (birth (BW), weaning (WW), 6months (W6) and 9months (W9)) on growth rate of Baluchi sheep. Data were collected at the Abbasabad Baluchi Sheep Breeding Station (flock 2) from 1983 to 2009. Traits were average daily gain from birth to weaning (ADGa), from weaning to 6months of age (ADGb) and from weaning to 9months of age (ADGc). (Co) variance components and genetic parameters were estimated by univariate and multivariate animal models using Restricted Maximum Likelihood (REML) procedure. Genetic improvements over analyze were calculated as the differences between the means of estimated breeding values at the beginning and at the end of analyze. Genetic trends were obtained by regressing the means of predicted breeding values on year of birth for each trait. Direct heritability estimates were, correspondingly, 0.03, 0.11 and 0.05 for ADGa, ADGb and ADGc. Estimate of maternal heritability (m2) for ADGc was 0.11. Estimated value of maternal permanent environment variance as a proportion of phenotypic variance (c2) was 0.14 for ADGa. Negative genetic correlations were observed for BW-ADGb and BW-ADGc. Direct additive genetic correlations between traits ranged from −0.63 (BW-ADGc) to 0.91 (W9-ADGc). Phenotypic correlations ranged from −0.49 (BW-ADGb) to 0.88 (WW-ADGa). Maternal permanent environmental correlations ranged between 0.13 (W9-ADGa) to 0.99 (WW-ADGa). Genetic improvements were 0.033g, 0.36g and 0.31g for ADGa, ADGb and ADGc, respectively. Annual genetic gains (g/year) for ADGa, ADGb and ADGc, were 0.02, 0.03 and 0.04, respectively.

(Co)variance components and genetic parameters for growth rate and Kleiber ratio in fat-tailed Mehraban sheep

Abstract. The aim of the present study was to estimate (co)variance components and genetic parameters for average daily gain from birth to weaning (ADGa), weaning to 6 months (ADGb), weaning to 9 months (ADGc), 6 months to 9 months (ADGd) and corresponding Kleiber ratios (KRa, KRb, KRc and KRd) in Mehraban sheep. A derivative-free algorithm combined with a series of six univariate linear animal models was used to estimate phenotypic variance and its direct, maternal and residual components. In addition, bivariate analyses were done to estimate (co)variance components between traits. Estimates of direct heritability (h2) were 0.10, 0.11, 0.16, 0.09, 0.13, 0.13, 0.15 and 0.08 for ADGa, ADGb, ADGc, ADGd, KRa, KRb, KRc and KRd, respectively and indicate that in Mehraban sheep genes contribute very little to the variance of the growth rate and Kleiber ratio. Estimates of maternal heritability (m2) were 0.10, 0.08 and 0.05 for ADGa, KRa and KRb, respectively. Direct additive genetic correlations ranged from −0.32 (KRa-KRd) to 0.99 (ADGb-KRb) and phenotypic correlations ranged from −0.53 (ADGa- ADGd) to 0.99 (ADGa-KRa). Estimates of direct heritability and genetic correlations show that genetic improvement in efficiency of feed utilization through selection programmes is possible, though it would generate a relatively slow genetic progress.

Genetic Analysis of Growth Traits in Polled Nellore Cattle Raised on Pasture in Tropical Region Using Bayesian Approaches

Components of (co)variance and genetic parameters were estimated for adjusted weights at ages 120 (W120), 240 (W240), 365 (W365) and 450 (W450) days of Polled Nellore cattle raised on pasture and born between 1987 and 2010. Analyses were performed using an animal model, considering fixed effects: herd-year-season of birth and calf sex as contemporary groups and the age of cow as a covariate. Gibbs Samplers were used to estimate (co)variance components, genetic parameters and additive genetic effects, which accounted for great proportion of total variation in these traits. High direct heritability estimates for the growth traits were revealed and presented mean 0.43, 0.61, 0.72 and 0.67 for W120, W240, W365 and W450, respectively. Maternal heritabilities were 0.07 and 0.08 for W120 and W240, respectively. Direct additive genetic correlations between the weight at 120, 240, 365 and 450 days old were strong and positive. These estimates ranged from 0.68 to 0.98. Direct-maternal genetic correlations were negative for W120 and W240. The estimates ranged from −0.31 to −0.54. Estimates of maternal heritability ranged from 0.056 to 0.092 for W120 and from 0.064 to 0.096 for W240. This study showed that genetic progress is possible for the growth traits we studied, which is a novel and favorable indicator for an upcoming and promising Polled Zebu breed in Tropical regions. Maternal effects influenced the performance of weight at 120 and 240 days old. These effects should be taken into account in genetic analyses of growth traits by fitting them as a genetic or a permanent environmental effect, or even both. In general, due to a medium-high estimate of environmental (co)variance components, management and feeding conditions for Polled Nellore raised at pasture in tropical regions of Brazil needs improvement and growth performance can be enhanced.

Effects of selection for blood serum IGF-I concentration on reproductive performance of female Angus beef cattle1,2

Reproductive performance of animals affects lifetime productivity. However, improvement of reproductive traits via direct selection is generally slow due to low heritability. Therefore, identification of indicator traits for reproductive performance may enhance genetic response. Previous studies showed that serum IGF-I concentration is a candidate indicator for growth and reproductive traits. The objective of our study was to estimate the variances or covariances of IGF-I concentration with reproductive traits. Data were collected from a divergent selection experiment for serum IGF-I concentration at the Eastern Agricultural Research Station owned by The Ohio State University. The study included a total of 2,662 calves in the 1989 to 2005 calf crops. Variance or covariance components were estimated for direct and maternal genetic effects, maternal environment effects, environment effects, and phenotypic effects using an animal model in a multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML, Boldman et al., 1995) computer program. Direct additive genetic correlations suggest that selection for greater IGF-I concentration (heritability = 0.50 ± 0.07) could lead to increased conception rate (heritability = 0.11 ± 0.06, r = 0.32, P < 0.001) and calving rate (heritability = 0.13 ± 0.06, r = 0.43, P < 0.001) and decreased age at first calving in heifers (heritability = 0.35 ± 0.20, r = -0.40, P < 0.001).

Genetic parameters for direct and maternal effects on growth traits of sheep

Abstract. The aim of the present study was to estimate (co)variance components and corresponding genetic parameters for birth weight (BW), weaning weight (WW), 6-month weight (W6), 9-month weight (W9), average daily gain from birth to weaning (WWDG), average daily gain from weaning to 6 months (W6DG) and average daily gain from 6 months to 9 months (W9DG) for a nucleus flock of Iranian Makooei sheep. Genetic parameters were estimated by REML procedure fitting six animal models including various combinations of maternal effects. The Akaike information criterion (AIC) was used to determine the most appropriate model. Estimates of direct heritability (h2) ranged from 0.13 (W6DG) to 0.32 (BW). Maternal effects were found to be important in the growth performance of the Makooei sheep, indicating the necessity of including maternal effects in the model to obtain accurate estimates of direct heritability. Estimates of maternal heritability (m2) ranged from 0.05 (W6) to 0.16 (WWDG) and the estimates of proportion of maternal permanent environmental variance to phenotypic variance (c2) were in the range between 0.05 (BW) and 0.10 (W6). Direct additive genetic correlations were positive in all cases and ranged from 0.00 (BW/W9DG) to 0.99 (WW/WWDG). Phenotypic correlations showed a broad range from −0.27 (WW/W9DG) to 0.99 (WW/WWDG). Estimates of genetic parameters showed that genetic improvement through selection programs is possible. WW would be a suitable selection criterion since it has acceptable direct heritability and relatively high genetic correlation with other traits.

Estimation of genetic parameters for fleece traits in yearling Inner Mongolia Cashmere goats

The objective of this study was to determine the genetic parameters and variance components of the economically important fleece traits staple fineness (SF), staple length (SL), fiber diameter (FD) and fiber length (FL) in yearling Inner Mongolia Cashmere goats (IMWC). Data collected in 2008–2011 from 5 Arbas Cashmere goat flocks were analyzed. Fixed effects were determined using a generalized linear model with least square means. Variance components and genetic parameters were determined using the restricted maximum likelihood method. By ignoring or including maternal additive genetic effects and maternal permanent environment effects, and considering whether direct additive genetic and maternal additive genetic effects were correlated or not, six different single-trait animal models were obtained. A log likelihood ratio test was conducted to choose the most appropriate model. Then, genetic correlations among fleece traits were obtained using the average information restricted maximum likelihood method with multi-trait models. Year of production and herd had highly significant influences on all fleece traits (P<0.01). Sex had highly significant influences on all fleece traits (P<0.01) except SF. Dam ages had a significant effect on FD (P<0.05), but was not related to other three traits. Type of birth had no significant effect on the fleece traits in this study (P>0.05). The log likelihood ratio test indicated that neither maternal additive genetic effects nor maternal permanent environment effects had a significant influence on the traits examined in this study. Direct additive heritabilities (hd2) were 0.27, 0.28, 0.34 and 0.17 for SF, SL, FD and FL, respectively, which is moderate to low. Direct additive genetic correlations were negative (−0.40) between SL and SF, but were positive (0.45) between SF and FD. Genetic correlations among the other traits were low, ranging from −0.17 to 0.12. The purpose of this study was to determine the genetics parameters of fleece traits to help improve the genetics of the Inner Mongolia Cashmere goats (IMWC).

English

&nbsp; Genetic parameters and (co)variance components were estimated by restricted maximum likelihood (REML) procedure, using animal models of kind 1, 2, 3, 4, 5 and 6, for body weight in birth, three, six, nine and 12 months of age in a Kurdish sheep flock. Direct and maternal breeding values were estimated using the best linear unbiased prediction (BLUP) by DF-REML software. The data used in the present study was obtained from one research flock of Kurdistan Kurdish sheep, including 2476 animals, during the period of 1993 to 2003 (11 years). The log L estimated for all of the six models of this study showed that model 6 was the most appropriate for the analysis of data. Direct heritability values for the traits of this study based on the model 6 (best model) were 0.161, 0.233, 0.260, 0.091, and 0.122, for body weight in birth, three, six, nine and 12 months of age, respectively. Furthermore, maternal heritability (m2) based on the model were 0.238, 0.023, 0.014, 0.005, 0.004, for body weight in birth, three, six, nine and 12 months of age, respectively. Correlation between direct and maternal additive genetic values for body weight in birth, three, six, nine and 12 months of age were 0.0351, 0.5911, 0.7427, 0.7968 and 0.5735, respectively. Direct additive genetic correlations between birth weight and body weight performance at later ages were positive and relatively high, ranging from 0.31 to 0.67, and they were positive and high between weaning and later weights and six month with yearling weight, ranging from 0.54 to 0.79. &nbsp; Key words:&nbsp;Genetic parameters, (co)variance components, body weights, Kurdish sheep.

Genetic and Phenotypic Parameter Estimates of Body Weight at Different Ages and Yearling Fleece Weight in Markhoz Goats

The objective of the present study was to estimate genetic parameters for economic traits in Markhoz goats. Data collected from 1993 to 2006 by the Markhoz goat Performance Testing Station in Sanandaj, Iran, were analyzed. The traits recorded as body weight performance at birth (BW), weaning (WW), six month (6MW), nine month (9MW), yearling (YW) and yearling fleece weight (YFW) were investigated. Least square analyses were used for estimation of environmental effects. Genetic parameters were estimated with single and multi trait analysis using restricted maximum likelihood (REML) procedures, under animal models. By ignoring or including maternal additive genetic effects and maternal permanent environmental effects, five different models were fitted for each trait. The effects of sex, type of birth, age of dam and year of birth on the all body weights were significant (p<0.01), but had no effects on YFW except year of birth. Age of kids had significant influences on WW and 6MW (p<0.01). A log likelihood ratio test was carried out for choosing the most suitable model for each trait. Total heritability estimates for YFW and growth traits varied from 0.16 for YFW and WW to 0.41 for YW. For all traits, maternal heritability was lower than direct heritability, ranging from 0.06 for BW to 0.01 for 6MW and 9MW. The magnitude of c 2 was more substantial for BW than the others, and relative importance was reduced from 0.12 for BW to 0.04 for 9MW. The direct additive genetic correlations estimates were positive and varied from 0.21 between BW-YW to 0.96 between WW-6MW. Direct additive genetic correlations between YFW and body weight traits were positive and ranged from 0.14 between BW-YFW to 0.67 between 6MW-YFW. For all traits, the corresponding estimates for phenotypic correlation were positive and lower than genetic correlations. The maternal additive genetic correlations between various traits were varied and ranged from -0.19 between 9MW-YFW to 0.96 between 6MW-9MW. The estimates of the maternal permanent environmental correlations between various traits were positive and ranged from 0.33 between WW-YFW to 0.93 between WW-6MW. Also, the environmental correlations between various traits ranged from 0.01 between BW-YFW and WW-YFW to 0.70 between 9MW-YW. Estimates of genetic parameters for various traits in this study confirm that selection should be applied on WW for genetic improvement in Markhoz goats.

Application of Random Regression Model to Estimate Genetic Parameters for Average Daily Gains in Lori-Bakhtiari Sheep Breed of Iran

A random regression model was applied to estimate (co) variances, heritabilities and additive genetic correlations among average daily gains. The data was a total of 10876 records belonging to 1828 lambs (progenies of 123 sires and 743 dams) born between 1995 and 2001 in a single large size flock of Lori-Bakhtiari sheep breed in Iran. In the model, fixed environmental effects of year-season of birth, sex, birth type, age of dam and random effects of direct and maternal additive genetic and permanent environment were included. Orthogonal polynomial regression (on the Legendre scale) of third order (cubic) was utilized to model the genetic and permanent environmental (co) variance structure throughout the growth trajectory. Direct and maternal heritability estimates of average daily gains ranged from 0.011 to 0.131 and 0.008 to 0.181, respectively in which pre-weaning average daily gain (0-3 in months) had the lowest direct and highest maternal heritability estimates among the other age groups. The highest and lowest positive direct additive genetic correlations were found to be 0.993 and 0.118 between ADG (0-9) and ADG (0-12) and between ADG (0-3) and ADG (0-12), respectively. The direct additive genetic correlations between adjacent age groups were more closely than between remote age groups.