جستجوی مقالات مرتبط با کلیدواژه « Zandi sheep » در نشریات گروه « علوم دام »

Identifying of genes with large effects on economically important traits, has been one of the important goal to sheep breeding. Over recent years, advances in DNA-based marker technology have made it possible to identify genomic regions or quantitative trait loci (QTLs) underlying complex traits, such as fleece traits, in sheep. The present study aimed to conduct a genome wide association studies (GWAS) based on gene-set enrichment analysis for identifying the loci associated with wool traits in native Zandi sheep using the 50K arrays.
A total of 300 Iranian Zandi sheep used in this study came from the Zandi sheep breeding station. Wool sampling coincided with the maximum wool growth prior to the shearing of wool. In order to facilitate sampling, sheep were restrained in a lateral position and true wool from the left mid-side site was cut from a 5×5 cm2 close to the skin using regular scissors. Each sample was separately packaged and labeled with ear tag number of the sheep. We measured and recorded four wool production traits: staple length (SL), mean fiber diameter (MFD), fiber diameter coefficient of variation (CVFD), and the proportion of fiber that are equal or more than 30 µm (PR), kemp percentage (KEMP%) and outer coat fiber (OCF) were measured. Genomic DNA extraction from sheep blood was performed by the applying a modified salting out protocol and genotyping of the Sheep SNPChip 50 K SNP Bead from Illumina Inc. The gene set analysis consists basically in three different steps: the assignment of SNPs to genes, the assignment of genes to functional categories, and finally the association analysis between each functional category and the phenotype of interest. Genome wide association study was performed with wool traits using GEMMA software. Using the biomaRt2 R package, the SNP were assigned to genes if they were within the genomic sequence of the gene or within a flanking region of 50 kb up- and downstream of the gene and bioinformatics analysis was implemented to identify the biological pathways performed in GO, KEEG, DAVID and PANTHER databases. The GO database designates biological descriptors to genes based on attributes of their encoded products and it is further partitioned into 3 components: biological process, molecular function, and cellular component. The KEGG pathway database contains metabolic and regulatory pathways, representing the actual knowledge on molecular interactions and reaction networks. Finally, a Fisher’s exact test was performed to test for overrepresentation of the significant genes for each gene-set. In the next step, a bioinformatics analysis was implemented to identify the biological pathways performed in GeneCards databases.
The result from genomic control showed weak population stratification with for woot traits among Zandi sheep population. We identified different sets of candidate genes related to wool traits including: CEP290, PRKCZ, TMTC3, RHPN2, TNFSF4, NLGN1, SPHKAP, PLCE1, FAT1 and PIK3R4 in Zandi sheep. Some of the found genes, are consistent with some of the previous studies related to reproductive traits. According to pathway analysis, 21 pathways from gene ontology and biological pathways were associated with the wool traits (P˂0.05).  Some of the genes were found are consistent with some prior studies and to be involved biological pathways related to hair follicle development, keratinocytes differentiation, synthesizes an enzyme of threonine kinases, development of epidermal and Wnt signaling pathway.
In total, this study supported previous results from GWAS of wool traits, also revealed additional regions in the sheep genome associated with these economically important traits. These findings could potentially be useful for genetic selection in the breeding programs and can be used to understand the genetic mechanism controlling this trait.

In this study (Co) variance components and genetic parameters for growth traits in Zandi Sheeps estimated by various animal models. The data used in this study, related to birth weight, weaning weight, 6 month weight, 9 month weight and yearling weight. The data collected during 1991-2011 by Nakhjir station in Tehran. (Co) variance components and genetic parameters were estimated by restricted maximum likelihood (REML). Environmental factors such as birth season, birth year, sex of lamb, birth type and mother's age at birth were significant on all traits and were fixed effects in model. The fit model by lowest AIC for birth weight, weaning weight, 6 month weight, 9 month weight and yearling weight selected 6, 2, 6, 4 and 4, respectively. Direct heritability was estimated for these traits results fitted models, 0.13±0.03, 0.17±0.03, 0.17±0.04, 0.07±0.03 and 0.18±0.06, respectively. Maternal heritability for birth weight, 6 month weight, 9 month weight and yearling weight were estimated 0.09±0.02, 0.04 ±0.02, 0.03±0.02 and 0.05±0.02, respectively. The selected models for these traits showed that maternal genetic effects, have important role in the occurrence of these traits. Estimated low heritability for these traits indicating that genetic improvement was slow for these traits and will be mostly affected by the herd management.

Being aware of the animals` food requirement, the amount of available forage in the rangeland and forage quality is necessary as the first step in successful management of animals and rangeland. Therefore, determining the weight of various animals` classes grazing in the rangeland and their conversion factor regarding country`s animal unit is an essential issue. In this research, to determine the weight of various classes of Zandi sheep grazing in the Lar National Park rangelands of Aroo region, three prevalent flocks of Zandi race were selected randomly and from each flock, 60 heads of animals including 20 heads of ewe ageing 3 years old, 20 heads of ewe aging 4 years old, 5 heads of ram aging 3 years old, 5 heads of ram aging 4 years old and 10 heads of lamb aging 3 months were signed and selected in two phases, one at the beginning of the season and the other at the end of season. Having utilized the mean weight of ewes aging 3 and 4 years, the weight of the sheep glazing in the studied region was estimated to be equal to 1.65±48.03 kg. Various kinds of forage being glazed by the sheep were identified and collected in this rangeland through two phases of flowering and seeding. The mean percentage of CP, ADF, DMD and ME in every kg of dry forage equaled to 11.56, 37.78, 56.88, 7.69 mega joule, respectively.

This research was conducted with the aim of estimation of environmental factors affecting survival and estimate the genetic parameters survival from 1 to the last recording date in Zandi sheep. The survival records of 9558 Zandi sheep from 273 rams and 2328 ewes collected by Animal Breeding Center of Iran during the 25 years (1987 to 2011) were used in the analysis. The effective factors on survival and culling risk were estimated by Survival and cmprsk package. Estimation of variance components was performed by using of exponential distribution for censored dates by the fitting of model with additive genetic effect (model 1) and joint additive genetic and maternal permanent environmental of effects (model 2) under Bayesian approach and Gibbs sampling. A total of 1000000 samples with a burn-in of 100000 and a sampling interval of 75 were generated to estimate the posterior distribution of variance components. The results showed that year, month, birth weight, type birth, sex (P<0.001) and dam age (p<0.01) had significant effect on survival trait. the direct heritability of survival trait using models 1 and 2 was 0.184( 0.136-0.264) and 0.162( 0.120-0.202), respectively. the proportion of permanent variance to phenotypic variance was  0.046( 0.063- 0.031). According to the results of this study, genetic improvement of survival trait in zandi lamb is possible by genetic selection and the culling risk reduction is effective via management of environmental factors.

Genomic data can lead us to how of breeds and populations forming and process of genetic occurrences effecting even infrequent cases of them at time passage. A very worthy instance to genetic resources preservation that itself is counted an important subject, and improvement of animal breeding plans, is genetic structure discovery of studying populations. For investigation about genetic structure homogeneity in Zandi breed sheep population located in Tehran Zandi sheep breeding station, discriminant analysis of principal components (DAPC) and in inside of this analysis, principal components analysis (PCA) were performed. For this purpose, 99 heads of sheep were bled and genotyped using Illumina SNP chip 50K. Discriminant analysis of principal component obviously showed the genetic structure of studying population and its members separation to two groups that it may be arising from DAPC high sensitiveness that is able to investigate variance homogeneity in animal populations. In DAPC, to evaluate the clusters optimized number using BIC, k=2 was shown as best result. Investigation of results to maintain the number of principal components for discriminant analysis, takes into account that the first 31 components is the optimized number of component for analysis next steps. Re the importance of within group variance contemplating and also populations genetic structure for important genomic analyses, became clear that DAPC in study of Zandi population genetic structure, because that contemplates of more principal component number and subsequently increasing of contemplated variance, is more effective than PCA.

Reproductive records of 5327 Zandi ewes were collected from a research flock at the Zandi sheep breeding from Varamin station during 1991-2011. Genetic parameters were estimated for main traits such as conception rate (CR), number of lambs born (NLB), number of lambs at weaning (NLW) and the composite traits including number of lambs born per ewe exposed, number of lambs weaned per ewe exposed, total litter weight at birth, total litter weight at weaning, total litter weight at birth per ewe exposed and total litter weight at weaning per ewe exposed. Year, age of ewe, breed of ewe on breeding were used as fixed effects. Direct and maternal genetic effects, permanent environmental effects of ewe and mate of ewe were considered as random effects in the model. The effect of environmental factors such as mating year and age of ewe at mating on all of reproductive traits were significant (P >0.01) exception CR, NLB¡NLB/EE, NLW NLW/EE, TLWB. Parametric and variance components were estimated by linear and threshold models. Estimates of heritability for animal genetic effects were mainly small and ranged from 0.0011 to 0.1 in linear model while the estimates resulting from thershold were ranged from 0.009 to 0.063. Estimates of heritability's for animal genetic and permanent environmental effects were low mainly due to the typical strong influence of environmental factors on reproductive traits. Estimates of repeatability's for animal permanent environmental effects were low to medium by linear analysis, and medium by threshold analysis.

This study was conducted to introduce a method based on using digital image processing to estimate the weight of new born lambs of Zandi sheep. Data was collected from 115 new born lambs reared in the Zandi sheep breeding centre of Khojir, Tehran. Primarily, all lambs were weighted, and at the same time, several photos were taken from the side view of each lamb using a digital camera from a fixed imaging distance. Then, the features related to the lateral area of lambs were extracted from digital images using image processing tools (IPT) of MATLAB software. Afterwards, a suitable artificial neural network was designed to estimate the lamb's weight based on the features was extracted from digital images. The neural network was trained with the precision of 96.94 % to estimate the lamb's weight. In the test phase, there was a correlation equal to 90.11 percent between the actual weight of lambs and weights estimated by the artificial neural network (p

Modeling of breeding programs is useful to predict and compare the results before a strategy is implemented.
In order to compare of the genetic trend of growth traits and inbreeding in Zandi sheep with real condition, a simulation program was designed.
To design the simulating program, the R software of 2.13.0 version was used. Management parameters and average of traits in rural sheep production system for Zandi breed were used as input of the model. Economic values estimated for Zandi breed were used in selection index equations.
The results of a 15-year selection by the simulation method indicated that in the Zandi rural sheep production system, genetic improvement was positive for the traits under study. The accumulative genetic gain after 15 years for BW0, BW3, BW6 and BW9 were estimated to be 0.504, 3.008, 4.433 and 5.509 Kg respectively. The genetic trend of BW0, BW3, BW6 and BW9 were estimated to be 34.08 ±0.0007, 218.12±0.0057, 326.03 ±0.0086 and 395.20 ±0.0097 g per year respectively. The inbreeding coefficient average after 15 years was 1.411% and the aggregate genotype after 15 years of selection based on multi-traits index was 249883.7 Rls.
The genetic simulation results showed that with genetic evaluation by the convenient methods and selection intensity, it can be expected that the performance average due to genetic improvement in Iranian breeds is more changed compared with the current report is published.

In this study, (co) variance components, genetic and phenotyping parameters for body weight traits at different ages of Zandi sheep breed were estimated. Birth weight, weaning weight, 6-month weight, 9-month weight and yearling weight were studied. The data were collected during 1991-2011 by Nakhjir breeding station in Tehran. (Co) variance components were estimated by Bayesian statistical method based on Gibbs sampling technique. Environmental factors of birth year, sex of lamb, birth type and mother's age were significant on all traits. Appropriate fitted models (based on lowest residual variance) for birth weight, weaning weight, 6-month weight, 9-month weight and yearling weight were found to be models 5, 5, 2, 1 and 1, respectively. Direct heritability was found to be 0.15±0.01, 0.26±0.003, 0.21±0.002, 0.25±0.003 and 0.26±0.001 for the traits, respectively. Maternal heritability of birth weight and weaning weight were 0.11±0.01 and 0.06 ±0.001, respectively. The results revealed that growth traits are more influenced by mother’s genetic factors in the early of age. With increasing the age of lamb and decreasing dependency to the mother, the significance of maternal effect reduced. Low to moderate heritability of the traits indicate that selection for these traits will result in a low to moderate genetic improvement.

In this research, 6517 records, collected by Khojir sheep Breeding Station (Tehran, Iran), during 1991 to 2011 were used to estimate genetic parameters of lamb survival in Zandi sheep. Genetic parameters were estimated using 16 different models of animal model, sire and threshold models using REML procedures. The AIC criterion was used to evaluate the models. The effects in the most suitable animal model were included direct additive genetic, maternal additive genetic and permanent environmental effects. The effects in the most suitable sire model were included sire additive genetic effects and maternal common litter effects. The effects in the most suitable threshold model were included only sire additive genetic effect. The estimated heritability of lamb survival based on animal, sire, and threshold models were 0.09 ± 0.001 and 0.13 ± 0.02, and 0.19 ± 0.06, respectively.

The aims of this study were estimation of inbreeding coefficients and its effects on birth weight (BW), weaning weight (WW), 6 month weight (6MW), 9 month weight (9MW) and yearling weight (YW) of Zandi sheep. The pedigree data and records were of 6140 Zandi sheep, which were collected during 1991-2011 by Zandi sheep Breeding Center located in Tehran. 36.32 % of the animals were inbred. Mean inbreeding coefficient for the herd and inbred population was 1.22 and 3.61 percent, respectively. Inbreeding coefficient was increased by 0.02±0.01 percent per year (P<0.05). Effects of inbreeding on traits were estimated by restricted maximum likelihood method using 12 animal models. The most appropriate model for each trait was determined based on Akaike’s Information Criterion. The regression coefficients of inbreeding on BW, WW, 6MW, 9MW and YW were -3.49±4.87 (P>0.05), -42.20±20.18 (P<0.05), -60.35±25.12 (P<0.05), -40.70±24.80 (P>0.05) and -76.55±29.24 gr (P<0.01), respectively.

To investigate the effect of hormone therapy and 3 lambing in 2 years schedule on lambing performance of Zandi ewes in different ages, 149 ewes were randomly assigned to 7 groups as their ages (1 year old to 7 year old). In all group ewes were exposed to hormone therapy for 3 lambing periods by 8 months intervals. Hormone therapy comprised that all ewes were inserted progesterone sponges for 12 to 14 days before their own mating dates and administrated with 400 IU PMSG at sponge removal. All ewes were mated with rams naturally. There were significant differences among age groups as parturition mean, lambing rate, litter size, weaning rate, lamb born crop and lamb weaned crop (P<0.01), while the bareness of ewes and lamb mortality rate before weaning, were statistically equal in all groups. The results revealed that 5 year old and 6 year old ewes had the highest response to hormone therapy under a 3 times lambing in two years schedule and have a highest lamb production, whereas 1 year old and 7 year old ewes had a lowest performance.

This study was undertaken to estimate genetic parameters for total weight of weaned lambs per ewe joined (TWW/EJ) in first to 4th parities. Data were obtained from 1912 ewes collected during 17 years (1990-2006) by the Zandi sheep breeding station in the Khojir Tehran province. Analysis was carried out by Restricted Maximum Likelihood procedures using univariate and multivariate animal models. Heritability obtained for total weight of lamb weaned per ewe joined (TWW/EJ) in parity one through parity four as 0.065±0.04, 0.100± 0.06, 0.110±0.07 and 0.159±0.05, respectively. In the univariate analysis, two models including genetic additive effects and service sire effect were used. Results showed that effects mentioned above had a minor importance in phenotypic appearances of the studied trait. Random effect variances due to service sire for these traits were low. Additive genetic correlations of total weight of lamb weaned per ewe joined among different parities moderate to high and positive, ranging from 0.454 (between first and 4th parity) to 0.723 (between first and 2th parity). The corresponding estimations for phenotypic correlations ranged from 0.034 (between first and 3rd parity) to 0.414 (between first and 2rd parity). Considering high genetic correlations between first and subsequent parities, selection for increasing reproductive performance can be based on total weight of lambs weaned per ewe exposed at first parity.

To estimate variance components and genetic parameters of growth traits in Zandi sheep, 5542 records during years 2005 to 2011 of herds under research center in Qom were used. Estimates of variance components with derivative-free restricted maximum likelihood method (DFREML) and using the animal model was estimated through six models using WOMBAT software. Year of birth, season of birth, lamb sex and birth (singleton and twin) and the herd showed significant effects (P<0.05) in the studied traits. Therefore, it was implemented as a fixed effects model. The magnitude of likelihood logarithm was estimated for the six models for all the traits. To ensure, the constant (AIC) was also used and the best model for each trait was reported. Direct heritability of traits was estimated based on the values of 3, 3, 2, 2, 2, 2, respectively, for total average birth weight, birth weight, total weaning weight, weaning weight, weights of 12 and 24 months of lambs of ewe were found to be 0.18, 0.17, 0.29, 0.23, 0.18 and 0.1, respectively. Average value of phenotypic and genetic direct and maternal traits in each year were estimated using the best linear unbiased prediction (BLUP) estimates, and the genetic trends of the traits were looked at for over 6 years. The average direct genetic birth weight and total birth weight of lambs of ewes and average of total weight and weaning weights of 12 and 24 months using a single-single analysis were 1.33 ± 0.07, 2.28 ± 0.4, 6.68 ± 2.1, 8.57 ± 1.9, 98.54 ± 22.1 and 205.11 ± 25.8 g, respectively.