جستجوی مقالات مرتبط با کلیدواژه « وراثت پذیری » در نشریات گروه « محیط زیست »

The longevity in dairy cow is the duration of presence of an animal the herd from the date of first calving to the date culled. In present research, the aim is 1) to estimate the genetic parameters of the longevity trait of uncensored animals using random regression model and 2) to study longevity of daughters of sires in the population using the EBV of bulls based on 20 daughters and 3) to test the random regression model (RRM) for EBV prediction of Animals with censored data. Genetic parameters of longevity and breeding value of bulls were estimated by ECHIDNA software using RRM with restricted maximum likelihood (REML) method. The file used for the genetic evaluation contained data on 18,120 daughters from 906 bulls. A number of 20 daughters that randomly selected from each sire to use for EBV prediction. In addition to the daughters used for genetic evaluation (18,120 cows), there were 285,064 daughters of the bulls in the main file. The bulls were grouped according to the Breeding value from high to low based on the area under the normal curve. Then, the mean of longevity of the daughters in each group who were not used the EBV prediction calculated. In a file 10 daughters were randomly selected of 20 daughters of each bull and their months of longevity divided by 2 and 3. These data were considered as censored in the data file. The permanent environmental effect and the additive genetic effect had the largest and smallest contribution to the total variance, respectively. The heritability of the trait was low (0.003-0.032) which is in agreement with results of other report. The difference of mean longevity between groups (LSD test) was significant (P˂0.01). Also, the increase of the mean of EBV of the groups, the mean of longevity of their daughters in the population increased. The correlation of EBV of animals with censored and uncensored data state were +0.815. In the split the low heritability of the longevity trait, using the sperm of superior bulls in terms of EBV of longevity can improve the longevity in the population. Also, it is possible to evaluate and select the bulls with a low progeny number and increase the mean of longevity in the population of Holstein dairy cows. Moreover, the EBV of longevity for young and producing animals can be predicted by RRM.

In this study, assessed genomic prediction accuracies based on different selection methods (phenotypic and estimated breeding value), evaluation procedures (GBLUP and ssGBLUP),training population (TP) sizes, heritability (h2) levels, marker densities and pedigree error (PE) rates in a simulated population. QMSim software was used to create a reference database of 1000 and number of animals was reduced to 200 (100 males and 100 females) during 95 generations to create LD and mutation-drift equilibrium. The heritability of the trait was 0.1, 0.3 and 0.5 and the marker density was simulated for three strategies of 1, 5 and 10 K. The proportions of errors substituted were 10%, 20% and 30%, respectively.The results of this study showed that, compared with phenotypic selection, the results revealed that the prediction accuracies obtained using GBLUP and ssGBLUP increased across heritability levels and TP sizes during EBV selection.With increasing reference population size and trait heritability, genomic prediction accuracy increased in all strategies.When errors were introduced into the pedigree dataset from 0 to 30%, the prediction accuracies were only minimally influenced across all scenarios.Our study suggests that the use of ssGBLUP, EBV sThe results of this study showed that, compared with phenotypic selection, the results revealed that the prediction accuracies obtained using GBLUP and ssGBLUP increased across heritability levels and TP sizes during EBV selection.With increasing reference population size and trait heritability, genomic prediction accuracy increased in all strategies.When errors were introduced into the pedigree dataset from 0 to 30%, the prediction accuracies were only minimally influenced across all scenarios.Our study suggests that the use of ssGBLUP, EBV selection, and high marker density could help improve genetic gainseven in the case of pedigree error in cattle.election, and high marker density could help improve genetic gainseven in the case of pedigree error in cattle.The results of this study showed that, compared with phenotypic selection, the results revealed that the prediction accuracies obtained using GBLUP and ssGBLUP increased across heritability levels and TP sizes during EBV selection.With increasing reference population size and trait heritability, genomic prediction accuracy increased in all strategies.When errors were introduced into the pedigree dataset from 0 to 30%, the prediction accuracies were only minimally influenced across all scenarios.Our study suggests that the use of ssGBLUP, EBV selection, and high marker density could help improve genetic gainseven in the case of pedigree error in cattle.

Profitability in dairy herds depend on animal survival in the herd, which is provided by reducing involuntary culling and increasing the voluntary culling in the herd. The aim of this study was to investigate the non-genetic factors affecting longevity and to estimate the genetic parameters of longevity and somatic cell score in Iranian Holstein cows. For this purpose, the data of 277715 cattle that were collected by Animal Breeding Center of Iran during 2001 to 2018, were used. Longevity was defined as length of life (LL), lifetime number of days in milk (LDIM), lifetime milk yield (LMY), lifetime fat yield (LFY), and lifetime protein yield (LPY), and the effect of environmental factors on traits and risk of culling were determined using Survival kit and cmprsk statistical packages. Variance components of longevity traits were estimated based on exponential distribution and censored data along with somatic cell score trait using two-trait analysis by Gibbs sampling method. The results showed that the effect of herd, year and season of calving and calving age of cows was significant on all longevity traits (P <0.001). Cows with a high degree of dystocia had a higher culling risk than other cows and the culling risk was higher for cows born in the spring than in other seasons (except to the LL). The range of heritability for different longevity traits varied from 0.076 to 0.186 and the heritability of the somatic cell score was estimated to be 0.31. The results showed that genetic selection for somatic cell score and some longevity traits such as LPY can be effective in improving these traits, although due to the importance of environmental factors on longevity traits, these factors should also be considered. Genetic and residual correlation between somatic cell score with longevity traits were negative and the amount of genetic correlation between traits were higher than their residual correlation. Therefore, genetic selection for somatic cell score and considering it as a selection criterion in breeding programs can indirectly improve the longevity traits in Iranian Holstein cows. Increasing and improvement of longevity is not only economically important but also improves animal welfare.

The aim of this study was to analyze survival and its relationship with body weight and average daily gain traits in Japanese quail. For this purpose, Data base with 1854 Japanese quail survival records were used which collected during 4 generations from 1396 to 1398, by Khorasan Razavi Agricultural and Natural Resources Research and Education Center. The Survival and cmprsk statistical packages were employed to determine the non-genetic effects on survival and culling risk at different times, and variance components estimates of survival trait was performed by MCMCglmm package. Genetic parameters of traits were estimated using single and two-trait analyses via Gibbs sampling. The mean mortality of breeding period (0.206) and the average survival rate (0.793) were calculated. The estimated average heritabilities for survival in single and two-trait analyses were 0.216 and 0.153, respectively. The range of heritability of body weight in single trait analysis was estimated between 0.135 to 0.307) with a mean of 0.219 by two- trait analysis. In two-trait analysis, heritability of body weight trait ranged from 0.155 to 0.014. The highest genetic correlation was -0.3113 (between body weight and average daily gain) and the lowest genetic correlation was -0.0277 (between survival trait and average daily gain). The results showed that optimal management of environmental factors is effective in reducing the culling risk and genetic selection for survival trait can improve the genetic potential of survival.

The aim of this study was to estimate genetic parameters of humoral immune responses (antibody titers against sheep red blood cells (SRBC) and Newcastle Disease Virus (NDV)) and residual feed intake from 20 to 45 days of age in Japanese quail. For this purpose, a total of 2492 records of residual feed intake traits and 5238 records of immune traits were used. The analyses of Genetic parameters of traits were estimated through single and bivariate animal models via Gibbs sampling method. Heritability estimates of total antibody titer (AbT), titer of immunoglobulin Y (IgY), titer of immunoglobulin M (IgM) and titer of immunoglobulin F (IgF) against SRBC were 0.08, 0.14, 0.02 and 0.24, respectively, however, heritability of antibody titer against NDV was lower than estimated of SRBC antigen (h2= 0.05). heritability of RFI in different ages were in ranges of 0.04 to 0.07. genetic correlations estimate between total antibody and IgY were positive and high and was 0.92. The negative genetic correlations were related to IgM with RFI and genetic correlations estimates between RFI and other immunoglobulins (IgY, AbT, IgF) and NDV were positive. As a conclusion, selection for IgF due to its heritability (0.24) and negative genetic correlation (-0.23) with RFI, cause improve in RFI and reduce costs, related mainly to feeding and selecting of animals with phenotyping. On the other hand, due to moderate to high positive genetic correlations (0.34-0.80) were found between IgF and other immunoglobulins, selection of it didn’t lead to decline of humoral immune responses in quail.

In this regard, the objective of this research was to investigate the impact of temperature-humidity index (THI) as an environmental descriptor for heat stress on milk yield (MY) and fat percentage (FP) of Holstein dairy cattle in Mediterranean climate of Iran. The first lactation information between 2001 and 2016 from 42781 and 38829 cows with 348868 and 302851 records, for MY and FP were considered, respectively. The average of daily THI for 3 days before test date was used as an environmental factor which calculated using information of the nearest weather stations to each herd. (Co) variance components were estimated using Bayesian methodology via random regression model (RRM) for different combinations of THI and days in milk (DIM). As a function of DIM at the end of the lactation increases the heritability and decreases the heritability as a function of the THI with increasing THI.For both DIM and THI values, the genetic correlations gradually decline as the distance between values increases. It is evidence that different records along the different THI values like DIM are affected by different genes. In this regard, the estimated genetic correlations for FP were lower than corresponding correlations for MY. The overall idea of this research on heat stress indicates the need to model an additive genetic effect for heat tolerance of dairy cattle in Mediterranean climate of Iran and the genetic potential of the animal can play an important role in controlling the reduction in the production of herd milk in stressful weather conditions.

Although Quercus brantii Lindl. has shown suitable genetic variation in Iran, which is required for a sustainable forest ecosystem, but during the last decade, it came across some difficulties which are considered as oak decline. This research investigated seedling characteristics of four plant populations of the Quercus brantii species to assess genetic potentials of the populations to base a cornerstone for complimentary studies. Seeds were collected on ten single trees for each of plant population located in Kurdistan, Lorestan, Ilam, and Fars provinces in Iran. Seeds were sown in pots at greenhouse conditions to produce at least 30 single progeny seedlings from each population with three replications were studied. Vegetative characteristics such as plant height, leaf length, leaf width, and plant vigor were studied on the single plants. Data were analyzed based on a double nested statistical model, and then the data were analyzed on each population separately. Results indicated significant differences between the studied populations based on seedling height and plant vigor. Plant within population, showing possible differences between the single trees within the populations, was also significant for seedling height, leaf length and leaf width. In population based analysis, the populations showed different behaviors, so as there was not significant effects between single plants in Kurdistan population for plant height and leaf traits; whereas, in Lorestan and Ilam populations significant effects for the mentioned traits were observed. Although the populations showed different characteristics at seedling stage, but it is sought that there are still enough genetic variability and the high heritability that might be used in future breeding projects.

In this study, performance and pedigree records of the native fowls of Fars province collected by Breeding Center during 1990-2004 were analyzed. A pedigree file collected on 30855 female and male birds was used to calculate the inbreeding coefficients. Heritability and Genetic and phenotypic correlations between recorded traits including body weight at 12 weeks (BW12), egg number (EN), egg weight (EW) and age sexual maturity (ASM) were estimated by multivariate animal model procedure by restricted maximum likelihood using ASREML software. On the other hand, The Inbreeding coefficient has been considered as a covariate to estimate its effects on traits. Results showed that inbreeding has not significant effects on recorded traits. The average of inbreeding coefficient for all birds were 0.002%, ranged from 0 to 14.8%. In this population, 14% of the birds were inbred, and average inbreeding coefficient for inbred birds was 0.019%. Estimated heritabilities were 0.53, 0.47, 0.57 and 0.22 for body weight at 12 weeks (BW12), age of sexual maturity (ASM), egg weight (EW) and egg number (EN), respectively. Due to relatively high heritability and low inbreeding coefficient of productive and reproductive traits, it is possible to achieve more progress in these traits using appropriate genetic selection.

In this study, total number of 4817, 1913, 1515, 6249, 1871, 1532, 1208 records of birth weight, weight of 3 and 12 month age, cashmere weight, total number of lambs born, total number of lambs weaned and lambing interval in Raienian cashmere goat were used. These records were collected in Baft station from 1989 to 2006. The animal model was used for genetic evaluation and estimation of genetic and phenotypic correlations for these traits. Heritability above was estimated 0.24, 0.07, 0.20, 0.17, 0.06, 0.08 and 0.03, respectively on the basis of the best model for each trait. Genetic correlation between birth weight and12 month weight, birth weight and cashmere weight, 3month weight and total number of lambs weaned, 3month weight and total number of lambs born, 12 month weight and cashmere weight, 12month weight and total number of lambs born, 12 month weight and total number of lams weaned, 12month weight and lambing interval, lambing interval and total number of lambs born, lambing interval and total number of lambs weaned, was estimated 0.27, 0.072, 0.02, -0.16, 0.28, 0.10, -0.27, -0.12, 0.30 and 0.42, respectively and phenotypic correlation was estimated 0.23, 0.056, 0.066, 0.07, 0.20, 0.01, -0.54, -0.43, 0.02 and 0.04 respectively, using Bivariate analaysis.

In this study، the genome consists of 3 chromosomes، each 100cM with different marker density (100 markers with 1cM space، 200 markers with 0. 5cM space، 1000 markers with 0. 1cM space and 2000 markers with 0. 05cM space) and 30 random distributed QTL were simulated. After 50 generations of random mating in a finite population (Ne=100) to create sufficient linkage disequilibrium، population size were expanded by 1000 (500 males and 500 females). This structure was conserved until generation 58. Two heritability (h2=0. 1 and h2=0. 5) were considered. Individuals of generation 51 and 52 have phenotype records and then used to estimate marker effects. Accuracy of genomic estimated breeding value (GEBV) was calculated for individuals of generations 51-58. Results of first trial showed that accuracy of GEBV will increase by increasing in marker density for high heritability traits، but it increase to some extent (markers with 0. 1cM space) for low heritability traits and it decrease by more dense markers. Results in second trial which used half of individuals of generation 51 and 52 for marker effect estimation، showed that accuracy of GEBV will decrease by decreasing in number of individual. In both trials، accuracy of GEBV for high heritability traits was higher than low heritability traits in same marker density. Finally، results of this study showed that accuracy of GEBV will decease by passing generations after generations used for marker effect estimation