جستجوی مقالات مرتبط با کلیدواژه "maternal effect" در نشریات گروه "علوم دام"

Pedigree and weight trait records belonging to 13633 Baluchi lambs descendent from 308 ram and 3747 dam which were collected in North-east animal breeding center from years 1989 to 2021 were used. Six univariate animal models with fixed (birth year, month, type, sex of lamb and age of dam) and different random effects were fitted to data. Effects of non-genetic factors on weight traits were investigated by Proc GLM of SAS software, and to estimate the variance components the Wombat software was used. All fixed effects had significant effect on the studied traits (P<0.001). Model with additive autosomal, sex linked, and additive maternal random with covariance between direct additive genetic and maternal genetic effect had the lowest AIC and was used for genetic analysis. For birth, weaning, 6, 9 month and yearling weight respectively additive autosomal heritability were 0.16, 0.34, 0.41, 0.49 and 0.56, additive sex-linked heritability were 0.004, 0, 0, 0.007 and 0.005 and maternal heritability were 0.34, 0.38, 0.32, 0.32 and 0.36. Results showed that sex-linked genes possibly have negligible and close to zero additive genetic effects on body weights at initial ages and in comparison, more noticeable effects on body weights at higher ages. In general, it is recommended to use an animal model for genetic analysis of growth traits in sheep, which is able to separate the total genetic variance into three autosomal, sex-dependent and maternal components in order to be more effective in genetic selection.

Introduction Egg quality related traits are economically important in laying hens Egg quality is one of the important factors in the process of hatching. So, economical success of commercial and local flocks of hens depends on the quality of eggs produced. Increased egg quality results in higher marketability of the egg. Having eggs with higher quality is possible through improving nutrition, management and genetics. Understanding genetic structure of these traits with high accuracy will help us to design a desirable breeding program. Maternal effects can be caused by genetic or environmental differences between mothers or by the combination of the genetic and environmental differences. Advantages of Bayesian technique as a method of choice would be a promising method for providing high accurate genetic parameters estimations and having eggs with higher quality in next generations.
The purpose of current study was to estimate and compare variance components and heritability for egg quality traits in Khorasan Razavi native fowl using different animal models.
Materials and Methods The records for egg quality traits were collected from native fowl of Khorasan Razavi breeding center located in east north of Iran. In this experiment, 1000 eggs from 775 hens of 9th generation at the age of 28 to 29 weeks were collected and measured for internal and external traits. An electronic scale with an accuracy of 0.01 g was used to weigh the eggs (EW). The short and long lengths of each egg (SL and LL, respectively) were measured using Egg Form Coefficient Measuring Gauge. The eggs were broken using an Egg Shell Strength Tester to measure shell strength (SS). The height of yolk and albumen (YH and AH, respectively) were measured using a tripod micrometer (calibrated in mm) and a dial caliper to the nearest 0.01 mm was used to measure albumen and yolk diameters (AD and YD, respectively). Subsequently, yolk and albumen were carefully separated and yolk weight (YW) and albumen weight (AW) were measured. Shell weight (SW) was measured after 72 hours’ exposure to dry air. Shell thickness (ST) was measured with a Shell Thickness Meter (calibrated in mm) at the pointed end, equator and blunt end of shells and average values were used. These traits were evaluated by six different animal models through Bayesian method using Gibbs3f90 software. The most suitable model was determined by deviance information criterion (DIC) for each trait.
Results and Discussion The mean value of egg weight in this local breed was 49.66 gr. The mean value for specific gravity in present study was 1.089. Specific gravity is an important indicator to determine the quality of shell and the amount of shell to the other members. The mean values of shape index, shell strength, shell weight and shell thickness obtained in this study were 76.92, 4.24 kg/cm2, 5.19 g and 0.43 mm, respectively. The mean values of albumen weight, albumen height, yolk weight and yolk height were 28.11 g, 6.41 mm, 14.07 g, and 17.53 mm, respectively. For egg weight, specific gravity, egg length, shape index, yolk diameter and Haugh unit, a model consisted of maternal permanent environmental effects in addition to direct genetic effects was the most suitable. For egg width, shell strength, shell thickness, shell weight, yolk weight and yolk height, model including maternal genetic and permanent environmental effects in addition to direct genetic effects was the optimal model. For albumen index and albumen diameter, only direct genetic effects were affective. The estimates of direct heritability were from 0.08 (albumen height) to 0.28 (egg weight and shell weight) and maternal heritability ranged from 0.03(yolk index) to 0.13 (yolk height and albumen height). Observed differences in genetic and non-genetic parameters estimations determined by different models indicated that model choice is an important aspect for obtaining accurate estimates, which are going to be used when deciding on a breeding scheme. Generally, this study indicated that considering maternal effects in the models resulted in unbiased estimations of direct genetic variance and heritability for most of the studied traits.
Conclusion It can be concluded that all egg quality traits in Khorasan Razavi native fowl are influenced by maternal genetic and environmental effects. Therefore, including maternal effects in statistical models is essential for estimation of genetic parameters; the models included direct and maternal effects result in more accurate genetic parameters estimations for most of the studied traits.

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

The objective of this study was to investigate genetic and phenotypic characteristics of body weight of Kordi lambs in different ages. Records of growth traits obtained from 5،144 lambs (progeny of 161 rams and 1،982 ewes) were used. The records of birth weight، BW (5،069 records)، 3-month weight، 3 (3،968 records)، 6- month weight، W6 (3،519 records)، 9-month weight، W9 (2،840 records) and 12-month weight، W12 (2،595 records) and collected between 1996 and 2013 in Kordi Breeding Station in Shirvan city of northern Khorasan province. Genetic parameters were estimated applying restricted maximum likelihood method fitting an animal model using WOMBAT program. Test of significance for the fixed effects was carried out using SAS 9. 2 software. The mean ± standard deviation of BW، W3، W6، W9 and W12 were 4. 38±0. 75، 23. 47±5. 77، 31. 99±6. 80، 35. 96±7. 06، and 43. 23±8. 44 kg، respectively. Direct heritability estimates of 0. 12±0. 02، 0. 36±0. 04، 0. 31±0. 03، 0. 21±0. 03، and 0. 19±0. 02 were obtained for the traits، respectively. The highest maternal heritability was estimated for BW (0. 15±0. 02)، and then reduced as the age of lambs increased. Estimates of direct genetic and phenotypic correlations among the studied traits varied from 0. 56 to 0. 97 and 0. 18 to 0. 81، respectively. Maternal genetic correlations among growth traits ranged between 0. 84 and 0. 99. According to the results of this study، W3 had the highest heritability and strong genetic correlation with other traits suggesting that it could be considered as a selection criterion for growth in this breed.

The objective of the present study was to estimate variance components and the heritability for economic traits in Yazd native fowl and evaluation of performed breeding programs based on genetic and phenotypic trends according to the most suitable model for each trait. For this purpose، the information of 9000 female and 9000 male birds collected during 2001 to 2008 were used. Variance components were estimated for body weight at 8 (BW8) and 12 (BW12) weeks of age، age at sexual maturity (ASM)، egg number (EN) and average egg weight at 28th، 30th and 32nd weeks (EW) using restricted maximum likelihood method and six animal models. The most suitable model was determined using likelihood ratio test for each trait. For BW8، BW12، ASM and EN، a model consisting of maternal permanent environmental effect in addition to direct genetic effect was the best. For egg weight، a model with maternal genetic and permanent environmental effects in addition to direct genetic effect was the optimal model. The estimates of direct heritability were from 0. 11 (EN) to 0. 17 (ASM). The results indicated that ignoring maternal effects in the models، overestimates the estimating of direct genetic variance and heritability for all traits. The genetic trends were calculated for BW8، BW12، ASM، EN and EW (2. 96 and 4. 86 g، -0. 02 day، 0. 02 egg number and 0. 01 g، respectively). Maternal genetic trend for EW (-0. 01) was significant (P<0. 001). The results indicated that performed breeding program during generations was favorable for BW8 and BW12