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

Inbreeding is the increase in homozygosity of offspring resulted from mating between related animals or animals that have common ancestors. The main effect of inbreeding is decline in performance of inbred animals known as inbreeding depression. The magnitude of inbreeding depression is not the same across the various traits and population. Recent studies revealed that inbreeding depression also shows variation among founders within a population. Variability of inbreeding depression arises when distribution of deleterious recessive alleles among founders are not equal. Furthermore, the detrimental effects of inbreeding can be reduced if deleterious recessive alleles were removed (purged) by selection against homozygotes in earlier generations. Estimating the partial and ancestral inbreeding coefficients makes it possible to assess the balance of distribution of recessive alleles among founders and incidence of purging of deleterious alleles in population. The objective of this study was to estimate wright inbreeding, partial inbreeding, Ballou ancestral inbreeding and Kalinowski ancestral inbreeding coefficients in the breeding flock of Karakul sheep. In this study the pedigree file of the breeding flock of Karakul sheep containing 7477 pedigree records collected during 1989-2014 was used to estimate wright inbreeding, partial inbreeding and ancestral inbreeding coefficients of animals. Pedigree completeness index was calculated to evaluate the quality of pedigree. Animals that born in the last 4 years of the pedigree with pedigree completeness index of greater than 0.6 was considered as a reference population to decomposition of the inbreeding to partial inbreeding arises from founders. Ballou ancestral inbreeding of all animals was estimated. Also, inbreeding coefficients of animals were decomposed to the New and Kalinowski ancestral inbreeding. The mean of wright inbreeding coefficients of animals in all population and reference population were 0.85 and 1.36, respectively. A total of 108 of 280 founder animals (38%) have a positive contribution to the inbreeding of the reference population. Mean and standard deviation of the partial inbreeding coefficients of these 108 animals were 5.19 and 7.37%, respectively. The 10 and 25 founders contributing the most to inbreeding explained a large part of the inbreeding of the reference population (i.e., 42 and 66%, respectively). Mean Ballou ancestral inbreeding of the whole and reference population were 1.17 and 2.12, respectively. Most of the animals in the population have positive Ballou ancestral inbreeding. Kalinowski ancestral inbreeding of animals was low and its mean was 0.07% in the population. Ancestral inbreeding in this population was in accordance with Ballou definition of ancestral inbreeding. Correlation of wright inbreeding coefficient with Ballou ancestral inbreeding, Kalinowski ancestral inbreeding and New inbreeding coefficients was 0.1, 0.37 and 0.99, respectively. Based on the results of this study, Ballou ancestral inbreeding coefficients of animals in this flock has increasing trend which can lead to purging of deleterious alleles in this population. Therefore, for assessing the incidence of purging of deleterious alleles in this population, estimating of the effects of ancestral inbreeding on reproductive and production traits are suggested. Also, the estimated partial inbreeding coefficients of animals can be used to determine the contribution of each founder to observed inbreeding depression. On the other hand, estimated partial inbreeding coefficients can help to detect founders that carry the deleterious alleles. Then, these information could be used in mating programs so that new born lambs have a less partial inbreeding arises from carrier animals or those animals which have greater contribution to inbreeding depression.

In order to evaluate the impact of the prediction Incomplete pedigree breeding value and genetic trends of Karakul sheep pelt, from real data collected at the Sarakhs of karakul sheep breeding station during the years 1995 to 2015 were used. Studied trait was: degree of Pelt that birth weight as auxiliary variables in the statistical model was used. For every trait, data from 21 years of selection and mating was saved in separate files. And the file of pedigree, sire’s number by 25% (from zero to one hundred percent) was removed randomly and data files for each trait in a state of complete and incomplete pedigree (removed 25, 50, 75 and 100% Number of Sires) under the animal model was used. Genetic trends of the pelt through regression of average breeding value on Birth year estimate that has to remove different percentages Numbers sire (0, 25, 50, 75 and 100 percent) from pedigree to were as follows: 0.0420 ± 0.0061, 0.0161 ± 0.0056, -0.0472 ± 0.031, 0.0161± 0.0056 and 0.0161 ± 0.0056. And heritability were, respectively: 0.74 ± 1.76, 0.72 ± 1.65, 0.71 ± 1.49, 0.73 ± 1.38 and 0.76 ± 1.25. The overall defect in pedigree by increasing percentage of elimination the number of sire, direct heritability reduced to 75% removal sire's number, then place the increase of heritability was the pelt as well as genetic trend by increasing the removal rate Sire Number fell.

Introduction Lamb production is the largest part of income in sheep industry. Therefore, the mortality rate of lambs is a key factor in profit of the sheep breeding. Mortality rate of lambs (or Lamb mortality rate) in different breeds of sheep under different climatic conditions is varying from 15% to 50% and an average of 9% to 20% has been reported. Survival rate is a combination trait that is influenced by various factors such as management, weather condition, and behavior of dam and lamb, as well as genetic effects. Quantification of non-genetic effects on mortality rate can be useful in controlling lamb survival rate and increasing profitability of sheep breeding. Therefore, identification of genetic and environmental factors affecting the productive capacity of indigenous breeds in different area is the main priority that should be considered in breeding programmes. Therefore, the objective of this study was to estimate genetic and environmental factors of growth traits and mortality in Karakul lambs. To estimate the genetic and environmental parameters of Karakul lambs before weaning growth and mortality records of 4929 lambs from 207 rams and 1856 ewes at Sarakhs Karakul sheep breeding station, from 1994 to 2009 were used.
Materials and Methods The data were used in this study included a total of 4929 record of lamb birth weight, 1 and 3 months of age, average daily gain from birth to weaning (growth traits before weaning) and mortality rate of lambs from birth to 1, 2, 4, 8 and 14 weeks (mortality rate of lambs before weaning). Data were collected during the years 1994 to 2010 in karakul breeding station in Sarakhs. The data were edited and pedigree file and data file were prepared. Uni-variate animal model was used to estimate the genetic parameters as following: where is the vector of record, b is the vector of fixed effects (year, sex, type of birth, age of dam), a is the vector of direct additive genetic effects, m the vector of maternal additive genetic effects, X, Z1 and Z2 are the matrix of coefficients (0 and 1) that relate b, a and m to records and e is the vector of residuals. Analysis of each trait was performed considering the significant factors in the model including sex, birth-type, birth-year, dam-age and ewe weight at birth. In the analysis of maternal effect model for growth traits and Cox regression for mortality traits were used. Cox Regression in SPSS software was also used to calculating the survival function. (Co) variance components were estimated by Restricted Maximum Likelihood (REML) with uni-variate animal model. The genetic, phenotypic and environmental trends were estimated as regression of average breeding values on year of birth, regression of average phenotypic values on year of birth and, difference between genetic and phenotypic trends, respectively.
Results and discussion The results showed that year of birth had a significant effect on all traits (P

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.