جستجوی مقالات مرتبط با کلیدواژه « وراثت پذیری » در نشریات گروه « علوم دام »

The aim of the present study was to investigate effect of additive genetic on egg weight, yolk weight and yolk fatty acid content and estimation of heritability for these traits. In this research, 150 white Japanese quails (50 males and 100 females) were used as the base population (without any pedigree information). In the F2 generation, 100 female quails were randomly selected at the fifth week of age and transferred to laying cages. The traits included egg weight, yolk weight and yolk fatty acid contents. (Co) Variance components and genetic parameters were estimated using multiple animal models by Wombat software. The estimated heritability for egg weight and yolk weight were 0.45 and 0.38, respectively. These estimates for yolk fatty acids ranged from 0.27 (Palmitoleic acid) to 0.45 (Palmetic acid). Genetic correlations between egg weight and yolk fatty acids were low, ranging from 0.01 (between egg weight and Linoleic acid) to 0.10 (between egg weight and Stearic acid). The higher genetic correlations were between yolk weight and yolk fatty acids, varying from 0.10 (between yolk weight and Linoleic acid) to 0.51 (between yolk weight and Stearic acid). The results showed that selection for increasing the yolk weight could lead to producing eggs with more contents of yolk fatty acids.

By aggregating the previous studies, the present study aimed to perform a meta-analysis to estimate the weighted average of the genetic parameters of fiber length, fiber diameter and percentage yield of fiber in cashmere goats to increase the accuracy of estimations. The data of 14 related published papers between 1989 and 2021 were used. A model with random effects was used to estimate the genetic parameters, standard error and 95% confidence range of traits by using Metafor package in R environment. The weighted average of heritability estimates for length, diameter and percentage yield were 0.24 ± 0.047, 0.42 ± 0.053 and 0.60 ± 0.103, respectively. The obtained results indicated that the studied traits have high heritability estimates and therefore the direct genetic selection can lead to the improvement of the performance of these traits. The highest estimate of genetic and phenotypic correlations were obtained between the percentage yield and the fiber length as 0.84 and 0.54, respectively. The lowest genetic and phenotypic correlations were obtained between the percentage yield and the fiber diameter as 0.38 and 0.35, respectively. Sharp reductions in the standard errors of the heritability estimates due to aggregating the results and increasing the sample size, improve accuracy of the corresponding estimates. The genetic parameters estimated in the present study may be used for developing the breeding programs to improve the fiber traits in Cashmere goats. Therefore, the results of meta-analysis study can improve the breeding programs, especially in breeds with insufficient records.

Estimates of genetic and environmental parameters of different component traits related to growth are needed to develop a proper selection program. The Kleiber ratio (KR) is defined as average daily gain as a proportion of metabolic body weight. Most studies conducted in KR ignored the effect of sex-linked chromosomes and assumed that direct genetic effects were influenced by autosomal chromosomes. Therefore, the purpose of this study was to estimate (Co)variance components of both autosomal and sex-Linked chromosomes for KR in Markhoz goat.

In the present study, the data were collected from 1992 to 2014 at Markhoz goat breeding station in Kurdistan province, Iran. The traits were kleiber ratio from birth to weaning (KR1), kleiber ratio from weaning to six months of age (KR2), kleiber ratio from weaning to six months of age (KR2), kleiber ratio from six to nine months of age (KR3) and kleiber ratio from nine to twelve months of age (KR4). The GLM procedure of the SAS software was used to determine significant fixed effects. The model accounting for fixed effects included year, sex, birth type and age of doe. In addition, random effects included direct additive genetic effects of autosomal chromosomes, direct additive genetic effects of sex-linked, maternal genetic effects, maternal permanent environmental effects and residual effects. (Co)variance components and genetic parameters were estimated using six different single-trait analysis via Average Information algorithm of Restricted Maximum Likelihood method using WOMBAT software. Akaike’s Information Criterion (AIC) test was applied to select the most apropariate model for each trait.

The most suitable model for KR1, KR2, KR3 and KR4 traits were the sixth, first, fourth and first models, respectively. Based on the best models, the estimated direct autosomal heritabilities were 0.410, 0.019, 0.172 and 0.020 for KR1, KR2, KR3 and KR4, respectively. The estimated sex-linked direct heritabilities were 0.008, 0.021, 0.049 and 0.023 for KR1, KR2, KR3 and KR4, respectively. The maternal heritability for KR1 and KR3 were 0.106 and 0.057, respectively. The maternal permanent environmental effect of 0.064 was estimatedfor KR1. The autosomal, sex-chromosome and phenotypic correlations between traits were ranged from -0.518 to 0.901, -0.943 to 0.652 and -0.001 to 0.312, respectively.

The results of this study showed that a considerable ratio of the phenotypic variance is explained by sex-linked chromosome effects. Therefore, including the sex-linked chromosome effect in the model may lead to a more precise estimates of direct autosomal heritability.

Improving the performance of economic traits of domestic livestock by means of sounds breeding programs could elaborate meeting the protein demands of the human world population. The water buffalo, also called the domestic water, bears up substantial value in terms of milk and meat production. Khuzestani buffalo, the subspecies of domestic Asian water buffalo (Bubalus bubalis) has become a strategic animal species in Khuzestan province, Iran, due to its ability to adapt to adverse environmental conditions, low quality feed sources dependency and high quality products. Archaeological and ancient records show little evidence regarding the expansion of the Khuzestani buffalo. Many people in the region depend on this species for their livelihoods than on any other domestic animal. In this regards, the buffalo lactation could have crucial role in farmers' economy. In general, having knowledge of lactation curve, may shed some lights on management and farm-based operation of milk production system. The lactation curve is a graphical representation tool that reflects the effect of couple of numbers of different factors on milk production during lactation; therefore, it is useful in making better management decisions. In other words, it could summarize the pattern of milk production, biological and economic efficiency of the animal. Several models have been suggested to describe the lactation curves. In this study, in order to estimate the association between different fitted lactation curves and their comparisons on Khuzestani buffalo, six nonlinear mathematical models (Wood, Wilmink, inverse polynomial, Complex logarithm, Ali and Schaefer and Digestra) were used.

The data used in this study, consisted of 103760 test day records of milk yield of 14280 buffalu in the first parity that collected by the Agricultural Jihad Center of Khuzestan province during 1993 to 2020. The Microsoft Excel was used to edit the data. Animals with unknown birth and calving dates were removed. Those fixed effects that had significant effects on the coefficients of lactation curve (P < 5%) were included in the final model. The lactation curve parameters were estimated using the nonlinear regression procedure (NLIN) of SAS software version 9.4 on test day records. Evaluation of goodness of fit was based on the coefficient of determination (R2), root mean square error (RMSE) and Akaike information criterion (AIC). The (Co) variance components were estimated by multi-trait animal model using restricted maximum likelihood method run in WOMBAT software.

Descriptive statistics of milk production of Khuzestani buffaloes based on 103760 records from different areas shown that the average milk production was 8.048 kg, standard deviation was 3.047 and coefficient of variation was 37.87 as well. Wood's mathematical model provided the best fit of the lactation curve due to the highest value for the R2 and lower values for RMSE and AIC compared to the other models and it obtained as 0.88. The a, b and c parameter values of Wood’s model were estimated 6.91, 0.057 and 0.00083, respectively. The results showed that the wood model was able to estimate the time of peak milk yield more accurately than the other models. The peak milk yield of Khuzestani buffaloes (8.30 kg/d) appeared on average in the tenth week (day 69) after calving. The heritability of lactation curve traits for initial yield (a), upward slope of the curve (b) and downward slope of the curve (c) were obtained 0.57, 0.27 and 0.48, respectively. In this study, the persistency(s) value for typical lactations were lactation curve were estimated 7.49. The genetic correlations among lactation curve parameters ranged from -0.55 (upward slope of the curve and initial yield) to 0.138 (upward and downward slope of the curve), whereas the phenotypic correlations ranged from -0.35 (Between initial yield and the upward slope of the curve) to +0.196 (b and c). The solutions of mixed model equations revealed that Buffalo with IDs 3436, 3410, 3360, 2868, 24, and 3174 had the highest breeding value for coefficient a. In other hand, buffalo 3438, 3409, 3418, 3361, 3282, and 3169 showed the highest breeding value in the coefficient b. Finally, the buffaloes that obtained the highest hereditary value in different coefficients of lactation curve were introduced as the superior buffaloes. By knowing the best buffaloes in terms of breeding value for parameters a and b, it is possible to select buffaloes to be parent for next generation. In general, evaluating lactation curve equations using nonlinear models and multi-trait analysis is an effective step in identifying buffaloes with high genetic potential to improve and increase milk production efficiency. The results of the present study showed that among the six mathematical models studied, Wood's incomplete gamma function had more viability for fitting the lactation curve of Khuzestani buffalo. The effect of calving season was not significant on lactation parameters while year of calving had a significant effect. Negative and moderate genetic correlations between initial production parameters (a) and upward slope (b) of the lactation curve indicate that keeping on with higher initial production level will have a lower rate of increase until peak production. In the present study, multivariate analysis led to the relationship of all coefficients of the lactation curve with each other and as a result more realistic parameters were estimated for them. It is suggested that in future studies, a computer-aided economic production system be designed and the economic coefficients related to the parameters of the lactation curve be estimated for integration into the selection index. Also, in order to improve the performance of Khuzestani buffalo, it is recommended to study the genomic relationship of milk production curve parameters.

The longevity of cows is crucial to the profitability of a dairy farm, and the culling of cows as a result of major health disorders is a significant risk that threatens production systems today. The possibility of taking diseases into account in the selection of dairy cows depends on the economic importance of the diseases. Mastitis and metritis are common diseases among dairy cows that are considered as risk factors for culling cows. The onset of these disorders can be attributed to factors such as environmental and managerial factors, but there is also evidence of a genetic component to each. Many genes are associated with resistance or susceptibility to mastitis and metritis in cattle, and their alleles have been reported. Subclinical mastitis seems to be one of the most important and damaging diseases threatening dairy cattle herds along with reproductive diseases, lameness and possibly some other common diseases such as Para-tuberculosis. Obviously, reducing production costs supports the profitability of dairy farms. By studying the relationship between the incidence rate and health disorders, in order to minimize the deaths due to health disorders, more emphasis has been placed on the health management of cows. The direct and adverse effects of mammary gland disorders (mastitis and nipple injury) on culling are well documented, while there are differences of results on the correlation between reproductive disorders and culling. Contradictory results may be due to differences in the purpose of the study, population, or the methods used. Many factors such as age, breed, production level, and calving season can play a role in the incidence of diseases.

The purpose of this study is to report the prevalence of clinical mastitis and metritis, moreover to investigate environmental and genetic factors affecting these diseases, to estimate the heritability of disease traits and to measure the correlation between disease and production traits in a Holstein cattle herd. Due to the fact that health records are not recorded in the country's farms in a regular and uniform manner, conducting this research is an experiment to collect this type of information so that in the future models can be provided for all Holstein cows in Iran to consider disease relating traits.

Data of 5052 milk yield from 1796 Holstein-Frisian cows has been gathered that had parturition from 2005 to 2009. In this study, using the 305-day milk production variables, parity, year of calving, the frequency of occurrence of clinical mastitis and metritis in cattle diseases using SAS software, using logistic procedure is estimated. The cows have been studied for all the diseases that occurred in all milking period. In logistic regression analysis, the effect of 305 days of milk and other factors in the occurrence of the disorder was investigated as a binary model. The effect of the lactation period in which the disorder was created was included in all analyzes and the fixed effects included milk for 305 days, calving period, calving year and calving season.Log [p. (1-p)] = b0 + b1 * milk305 + b2 * parity + b3 * calveyear + b4 * calve seasonA coefficient of b1 is assigned for the risk factor of milk production, a coefficient of b2 is assigned for the parturition, a coefficient of b3 is assigned for the factor of calving year and a coefficient of b4 is assigned for the factor of calving season. b0 is the logistic regression estimate if there is no predictor other than the response variable in the model. For each estimate of regression coefficients, the probability level, standard error and 95% confidence interval are also calculated. For a particular disease b1, b2, b3 and b4 are regression coefficients. Estimated genetic parameter in this research was heritability of diseases traits that has been done with ASReml software.

Metritis incidence rate is lower than mastitis. The percentage of animals with mastitis and metritis in the herd was 3.11% and 1.67%, respectively. The average calving interval for metritis incidence was 167.3 days and 129.5 days for mastitis. Data analysis of correspondence of metritis and 305 milk yield, parity, the year and the season of calving showed none of the risk factors had relation with the occurrence of clinical mastitis. The heritability of clinical mastitis and metritis were estimated to be 0.27 and 0.23, respectively. We could not find a relationship between milk production and metritis. Can we consider the increase in milk production as a risk factor for disease occurrence? It is very difficult to prove and explain this relationship and there are many contradictions between the results of other studies. From the lack of a proven correlation between milk production and the occurrence of diseases, it can be concluded that if proper management and nutrition provided based on the biological needs of high-yielding cows, then cows with high milk production will not necessarily suffer from diseases in comparison with low-yielding cows.Genetic studies have shown a positive correlation between mastitis and milk production. Erb (1987) and Dehu and Martin (1984) concluded that high milk production could not be a risk factor for mastitis. A study of Ayrshire cows in Finland found that cows with higher milk production during the previous lactation period were at increased risk for mastitis (Grun et al. 1989 and Grun et al. 1990). There are few documented findings on the association between milk production and the incidence of disease. Of course, it should be borne in mind that "milk production" is not the only risk factor for the disease. Concerning diseases in Holstein dairy cattle it seems the occurrence of the disease can also be the result of breeding and nutrition conditions and management. However, identifying all relevant factors and determining their quality and relative importance is difficulty accessible. It is also not easy to estimate all possible interactions between production and disease traits, even with the efficiency of today's computer technology.

In dairy cattle genetic improvement programs, we suggest to record and estimate the breeding values for disease traits and consider them in multi-trait selections among elite sires. The estimated heritability of metritis was lower than clinical mastitis. Keywords: Holstein-Friesian cows, clinical mastitis, metritis, milk 305 days, heritability.

The ability of an animal to survive in the breeding period is called the survival trait. One of the most important features of survival analysis is unfinished (censored) observations. In other words, the event under study does not necessarily occur at the time of recording the observations. Thus, survival observations and data are generally incomplete, and events occur for some people but for others there is no observation for that event. In general, nonparametric regression methods (Kaplan-Meier estimator, Cox hazard ratio model) and parametric methods are used for this type of analysis more than other methods. Survival and longevity analysis is performed by linear, threshold and hazard ratio functions methods. Linear models are easier to use, but due to the nonlinearity of the survival trait, they are skewed, and the estimates of heritability with this method are low and close to zero. Threshold models are more accurate and obtain higher genetic estimates. In the analysis of hazard ratio method, the accuracy is higher than previous models due using the more information (use of censored data), but it is time consuming and its computational load is higher. Therefore, the aim of the present study was to estimate the genetic parameters and the effect of fixed factors on the survival of Makuie sheep lambs up to one and two years of age using the proportional hazard function under Weibull distribution.

In this study, 2332 records of Makuie lambs that collected between 1986 to 2010 in Makuie sheep breeding station, were used. In the first step, fixed factors affecting longevity (gender, type of birth, year of birth, month of birth, birth weight, weaning weight, weaning age and age of dam) Was investigated by LIFEREG procedure of SAS statistical software version 9.4 under Weibull distribution. Then significant effects were used in the survival analysis with the proportional hazard model. Survival up to one and two years of age were analyzed using the Weibull hazard model by SURVIVAL KIT software, version 6.12. SURVIVAL KIT software is able to provide components of genetic variance and can estimates breeding values for animals using mixed models. Survival from post-weaning to one year (for analysis up to one year of age) and two years (for analysis up to two years of age) were assessed by day.

In the analysis of survival from weaning to the one year of age, 38.12% of observations and in the study of survival up to the two years of age, 13.68% of the observations were censored. According to the study, the year of birth had a significant effect on the survival of lambs. The year of birth affects the amount of rainfall and ultimately the availability of food resources by affecting the pasture, and thus changes the quality and amount of nutrition. survival up to one year of age Lambs born in 2004 and for survival up to two years of age lambs born in 1994 had the lowest risk of elimination. Lambs born in 2010 had the highest risk of elimination. Scrutiny the effect of birth month on the survival of lambs, it was found that for survival up to one year of age, lambs born in April had a higher risk of elimination. However, for survival up to two years of age, lambs born in May had the highest risk of elimination and the amount of risk for May compared to March was 1.96. Lambs born in May reach autumn at a young age and during a period of rapid growth. Because the studied flock is kept semi-densely, access to feed for these lambs is reduced and they are removed from the flock due to their low weight and insufficient growth rate. Birth weight is one of the most important components affecting the survival rate and directly affects the elimination rate. Threshold weights have the highest elimination risk ratio and the weight of 3.5-4.7 kg has the lowest elimination risk ratio for survival up to one and two years of age. There is a curved relationship between elimination risk and birth weight, so with increasing birth weight to medium weight (3.5-4.5 kg), the risk ratio decreases and then increases. Mortality at low weights is due to the inability to control body temperature and high mortality at high birth weights is due to infertility. Weaning weight is an important factor influencing survival after weaning. Similar to birth weight, weaning weight has a curved relationship with survival. So that with increasing the weaning weight from 10 kg to 19 kg, the risk of elimination for survival to one and two years of age decreases from 1.8 to 0.97 and 0.93, respectively, and then with increasing the weaning weight, risk ratio reaches to 2.53 and 2.38, respectively. Lack of growth-induced production encourages the elimination of low-weight weaned lambs. So the elimination risk ratio is high at low weights. But as the weaning weight increases, the desire to keep it for later periods will be greater, and thus the removal pressure will be lower. The average weight of weaning in the herd is equal to 19.01 kg, the results also show that the lowest elimination risk ratio and consequently the highest survival for weaning weight is 18-20 kg. Therefore, in order to increase the survival and reduce the elimination risk ratio, management and corrective programs can be designed to select the optimal weaning weight. For survival up to one and two years of age, the risk of elimination for male lambs was higher than females. In the period between weaning until the age of one year, the elimination risk ratio for male lambs was 2.17 relation to females and for survival to the age of two years, the elimination risk ratio of males was 2.61 Compared to females. This difference in elimination rate can be attributed to sex-related factors, sex characteristics that may not have yet been discovered, systemic diseases, different management practices for males and females, and high elimination rate for males due to surplus fattening. There are three types of births in Makuie sheep (singles, twins and triplets). Lambs born with twins and triplets have lower birth weight and weaning weight than single lambs. Due to the above topics, low birth weight and low weaning weight, reduces the survival and, increase the risk of elimination. Another reason for the reduced survival of multiple births is the limitation in dam milk production, which can be due to poor maternal genetics or inadequate nutritional intake. Heritability of survival to one and two years of age for Makuie sheep lambs according to the censorship ratio of 38.12% and 13.68% (respectively) was 0.062 and 0.079, respectively.

Since heritability was estimated at a low level, control of environmental factors and management will play an important role in improving the survival of Makuie lambs.

Quails are beneficial for their meat and eggs and have been the focus of poultry breeders in recent decades. Egg quality traits are usually divided into external (such as shell quality and egg weight) and internal (like yolk and albumen parameters) traits. Shell characteristics are important factors to determine egg quality. The breakage of quail eggs can be occurred in various processes such as collection, packaging, and transportation or in the setter and hatcher devices, and leads to serious economic problems for the breeders in the poultry industry. The size and weight of the quail egg are important factors in the marketability of this product. From an economic point of view, the yolk is the most valuable part of the egg. The yolk is a concentrated source of nutrients, as well as it has a significant effect on the weight of the chicken. The ratio of yolk to white in quail eggs has been reported to be 35 to 65, which is higher in comparison to laying hens. Egg quality can be affected by different factors such as genotype, breed, strain, age, management, nutrition, temperature, and illness. Although there have been many studies to determine the environmental factors on traits related to egg quality in quail, there are few studies to investigate the effect of genetic factors and different mating systems on the occurrence of these traits. Therefore, the present study was conducted to estimate genetic parameters of external and internal egg quality traits in wild and white strains of Japanese quails.

A total number of 570 laying quails were obtained from pure and cross-mating groups of wild and white Japanese quails. The base population was divided into four mating groups including two pure and two crossed mating groups (group 1: wild male × wild female; group 2: white male × wild female; group 3: wild male × white female, and group 4: white male × white female). The studied traits included external (egg weight, length, and width, shell weight and thickness, and egg shape index) and internal (yolk weight, albumen weight, yolk index, albumen index, and internal egg quality unit) egg quality traits. The effects of hatch and mating groups on traits related to egg quality were investigated. The means of traits related to external and internal egg quality were compared using the Duncan test. (Co)Variance components and genetic parameters of traits related to external and internal quality traits were estimated by multiple trait animal models and restricted maximum likelihood using ASREML software.

The effect of the hatch on egg weight, shell weight, and albumen weight was significant (P<0.05) and the eggs from the second and third hatches showed higher egg weight, shell weight, and albumen weight in comparison to the first hatch (P<0.05). The difference between mating groups was not significant (P>0.05) except for albumen and egg weights. The laying quails from the pure white mating group showed lower albumen and egg weights (P<0.05). The heritability estimates for traits related to external egg quality varied from 0.16 (egg shape index) to 0.39 (egg weight). These estimates for traits related to internal egg quality ranged from 0.10 (internal quality unit) to 0.31 (yolk weight). Genetic correlations were estimated from -0.33 (between egg length and egg shape index) to 0.71 (between egg length and width) for traits related to external egg quality, and from -0.37 (between yolk weight and yolk index) to 0.71 (between albumen weight and albumen height) for traits related to internal egg quality, respectively. Phenotypic correlations varied from -0.32 (between egg length and egg shape index) to 0.61 (between egg length and width) for traits related to external egg quality, and from 0.11 (between yolk index and albumen height) to 0.59 (between the internal quality unit and albumen height) for traits related to internal egg quality, respectively.

Heritability estimates for traits related to egg quality were moderate which indicates the significant effect of additive genes on the occurrence of these traits. Positive genetic correlations between egg weight and traits related to external egg quality, as well as appropriate genetic correlations between traits related to internal egg quality showed that selection based on some egg traits like egg weight and internal egg unit can effectively lead to the improvement of other egg quality traits.

This study aimed to estimate the genetic parameters of body weight traits in Markhoz goats, using B-spline random regression models. The data used in this study included 19549 records collected during 29 years (1992-2021) in Markhoz goat Breeding Research Station, located in Sanandaj, Iran. The model used to analyze data included fixed effects (year of birth, sex, type of birth and age of dam) and random effects including direct additive genetic, maternal additive genetic, permanent environmental and maternal permanent environmental assuming homogeneous and heterogeneous residual variance during the time. Akaike (BIC) and Bayesian (BIC) information criteria were used to compare the models and bspq.4.4.4.4 was selected as the best model. The direct heritability values for birth, 3-month, 6-month, 9-month and 12-month weights were estimated to be 0.14, 0.16, 0.08, 0.28 and 0.26, respectively. Genetic correlation between body weights at birth and 3-month, birth and 6-month, birth and 9-month, birth and 12-month, 3-month and 6-month, 3-month and 9-month, 3-month and 12-month, 6-months and 9-month and 9-month and 12-month were 0.22, 0.38, 0.21, 0.56, -0.26, 0.30, 0.62, 0.86 and 0.77, respectively. The highest phenotypic correlation was between the weight of 9-month and 12-month (0.82) and the lowest correlation was between birth weight and 3-month and 6-month (0.12). The results showed that the 9-month weight is a good criterion for selection in Markhoz goats.

Native fowl have become valuable genetic resources over the years due to their adaptation to harsh conditions in rural areas (Emamgholi et al 2009). Native fowl, despite their lower growth rate and lower egg production compared with broiler strains such as Ross and Cobb and layer strains such as Hy-Line and Lohman, perform much better in the rural system due to their good disease resistance and production under adverse nutritional and environmental conditions (Lakhi et al 2013). Breeding programs have a significant effect on improving the genetic structure of native fowl (Kiani manesh et al 2002). The purpose of this study was to combine the results of studies related to estimating genetic parameters for productive and reproductive traits in native fowl using meta-analysis method in order to improve the accuracy of estimations. In addition, the use of meta-analysis method eliminates the existing differences between studies by examining the heterogeneity between them (Field and Gillett 2010; Lortie et al 2013; Hooijmans et al 2014). Increasing the accuracy of estimates can consequently increase genetic improvement through selecting proper candidates to be parents of next generations. Higher performance will increase the courage of farmers to keep native fowl and therefore it help to keep the birds as a valuable genetic source for the future.

In this meta-analysis study, previous studies in the field of estimating genetic parameters of productive and reproductive traits in Iranian native fowl were collected and used. These articles consisted of 33 articles which were published between years 2007 and 2016. Information used in current study included heritability, genetic and phenotypic correlations of productive and reproductive traits. These traits consisted of birth weight, weight at eight weeks of age, weight at twelve weeks of age, egg number, egg weight, age at sexual maturity and weight at sexual maturity. Cochran test and I2 criterion were used for testing heterogenty among used articles. The range of heterogeneity among studies could be from zero to 100 percent. Ranges of 0 to 25 percent, 25 to 50 percent, 50 to 75 percent and 75 to 100 percent indicate very low, low, moderate and high heterogeneity among studies, respectively. Fixed meta-analysis model is usually recommended for very low and low heterogeneity among studies and random meta-analysis model is normally used for moderate to high rates of heterogeneity among studies. Due to high heterogenty observed among studies in present study, random effects model meta-analysis was performed using Metacor package R software version 3,3,1 and Comprehensive Meta-Analysis (CMA) software version 3. The weighted average of the heritability, genetic and phenotypic correlations were calculated accordingly.

According to the results, the highest heritability among productive and reproductive traits was related to egg weight (0.42) and then weight at sexual maturity (0.41). The lowest heritability was related to egg number with a value of 0.20 and then birth weight with a value of 0.25. The highest positive genetic correlation between productive and reproductive traits was estimated between weight at eight and weight at twelve weeks of age (0.86) and then between weight at twelve weeks of age and weight at sexual maturity (0.64). The highest negative genetic correlation was related to the correlation between age at sexual maturity and egg number (-0.66), then egg number and egg weight (-0.19). Due to combing the results of individual studies using meta-analysis, the standard error of estimations for genetic parameters and consequently their 95% confidence interval were significantly reduced compared to individual studies (Bayssa et al 2021). This reduction indicates an increase in the accuracy of the estimates due to aggregating the results of individual studies (Field and Gillett 2010). A comparison between the results of independent studies and the results of meta-analysis shows a significant reduction in estimated standard errors for heritability and genetic and phenotype correlations in the meta-analysis method. For example, the amount of estimated standard error related to heritability of weight at twelve weeks of age in the meta-analysis was calculated to be 0.0009, while the range of reported standard error in the articles for the heritability of this trait was from 0.05 to 0.08. For weight at eight weeks of age the amount of standard error of heritability in the meta-analysis was estimated to be 0.0009, but the range reported for standard error of heritability for this trait in the articles was zero to 0.06. Similar reduction in the amount of estimated standard error were observed for reproductive traits. For example for egg number, the amount of error in the meta-analysis was estimated to be 0.0013, but the range reported in the articles was 0.01 to 0.13. The amount of estimated standard error related to egg weight in the meta-analysis was calculated to be 0.0009, while the range reported in the studied articles was from 0.004 to 0.07. This decreasing trend was similarly observed for other studied traits, which is due to the aggregation of the results obtained from independent studies.

The results of this study showed that the use of meta-analysis method by aggregating the results of individual studies, will increase the accuracy of genetic parameters of productive and reproductive traits in native fowls through increasing the sample size and reducing estimated standard errors. Therefore, by taking into consideration that Iranian native fowl are economically important animals and considerable demands for their products in the country, using genetic parameters obtained from this study with higher accuracy can play an effective role in the successful design of breeding programs for native fowls and promote genetic improvement in native fowl in Iran.

Genetic differences in expression of traits between sexes can be applied for developing efficient genetic evaluation of animals. The aim of the present study was to investigate the existence of sexual dimorphism (SD) in birth weight (BW), weaning weight (WW) and six months weight (6MW) and also correspondingly the genetic analysis of SD in male and female Kermani lambs applying pedigree information and records, collected from 1993 to 2013 in Breeding Station of Kermani sheep,. The SD values, defined as mean body weight of male lambs to mean body weight of female lambs were 1.04, 1.09 and 1.13 for BW, WW and 6MW, respectively. Six bivariate animal models, contained different combinations of direct additive genetic, maternal additive genetic and maternal permanent environmental effects, were used for genetic analysis of SD. Each body weight traits were considered as distinct traits in male and females. The considered bivariate animal models was evaluated via Bayesian Information Criterion (BIC). Direct heritability estimates for BW, WW and 6MW in male lambs were 0.11, 0.35 and 0.32, respectively. The corresponding estimates in female lambs were 0.10, 0.36 and 0.23, respectively. Cross-sex genetic correlations for BW, WW and 6MW were 0.92, 0.93, and 1.00, respectively. High and positive genetic correlations indicated that the studied traits in male and female lambs are control by common genes. Due to high and positive cross-sex genetic correlations for the studied body weight traits it may be concluded that selection in male lambs would result in a positive correlated response in females.

The aim of this research was to investigate the immune system responses against sheep red blood cells (SRBC) and Newcastle disease virus (NDV) in two sexes of both wild and Italian speckled quails. To compare phenotypic differences of two sexes for humoral immune responses a one-way analysis was applied, and a simple animal model using the MCMCglmm package of R software was used for genetic analysis, assuming variance components between the two sexes are different. Phenotypic comparison between males and females did not show a significant difference in any of the strains. In both strains, heritability of humoral immunity in males was higher than females. Results indicated that heritability of IgT in males (0.187), and IgY in females (0.177) were higher than other estimates in wild strain. The highest heritability was related to the NDV, which was estimated to be 0.214 and 0.268 in males and females, respectively. Therefore, genetic selection for IgN can be expected to improve the performance of the birds’ humoral immune system. Likewise, according to the higher estimates of immune responses in males, genetic selection of humoral immune responses for IgN, leads to higher genetic progression.

Meta-analysis of genetic parameters for growth traits in Iranian sheep was performed by aggregating the reported genetic parameters of growth traits (birth weight, weaning weight, six months weight, nine months weight and yearling weight) in 80 papers published between 1996 and 2020. The studied parameters consisted of heritability values as well as genetic and phenotypic correlations between growth traits at different ages. Data analysis was performed in Comprehensive Meta-Analysis (Version2) software package using random effects model. The weighted average of heritability for growth traits was estimated in the range of 0.196 (birth weight) to 0.226 (yearling weight) and the weighted averages of genetic and phenotypic correlations were in the range of 0.318-0.915 and 0.221-0.769, respectively. Comparison of 95% confidence interval for genetic parameters obtained from meta-analyses with those mentioned in articles showed that aggregation of the results of different studies had significantly reduced the confidence interval ranges. Moreover, comparison of standard error of parameters in meta-analyses with those in different studies showed that the aggregation of results and subsequent increase in sample size reduced the standard errors of the genetic parameters. Therefore, comparing the results of meta-analysis in this study with the estimated parameters in individual studies showed that aggregation of results decreased the standard error and increased the accuracy of estimated parameters. Consequently, the results of meta-analysis studies can be more reliable compared to the results of individual studies to be used in breeding programs.

Growth, defined as changes of body weight over time, is an economically important trait in sheep that directly determines meat production.Increase in live weight or dimension against age has been described as growth. Changes in live weight or dimension for a period of time are explained by the growth curves. Animal breeders are interested in the genotypic and phenotypic relationships during all phases of growth. Knowledge of genotypic and phenotypic relationships among live weights, degree of maturity and growth rate during all phases of growth is necessary to formulate breeding programs to improve lifetime efficiency.  Growth models are mathematical functions which are applied for describing the growth pattern. Understanding, estimating, and capturing the defining characteristics of growth processes are key components of developmental research. The aim of the present study was to estimate the genetic parameters for growth traits in Zandi sheep, by determining the most appropriate animal models to be fitted. In addition, genetic, phenotypic and environmental correlations between traits were estimated.

The data used in this study were obtained from the Animal Breeding Center of Iran. The data were screened several times to remove the defective and out of range records. Growth curve parameters used in study were asymptomatic mature weight (A), Growth rate (B) and maturity rate (K). The procedure of SAS software was used for studying of fix effects. Based on body weight at different ages and using different initial values, each of the growth curve parameters was estimated using SAS software version 9.1 and NLIN procedure. Estimation of (co)variance components of growth curve parameters was conducted using Bayesian approach implemented in MTGSAM and Wombat software. The number of Gibbs sampling rounds used was 200,000 rounds.  Ten percent of these numbers (20,000 rounds) was burn-in. The convergence criterion for stopping repetitions in this analysis was also considered as 10 decimals (10-10). Sampling intervals of 200 and Gouss- Seidel 10000 repetitions were considered. In order to find the best model incorporating the constant and random effects affecting each of the parameters of the growth pattern, the following models, with and without regard to maternal effects including maternal additive genetic effects and permanent maternal environmental effects in the model (Meyer’s models) were tested.

 Environmental factors such as year of birth and sex of lamb showed significant influence on growth curve parameters (A, B and k) in Zandi sheep. Estimates of direct heritability is based on best models using REML and Bayesian methods for A, B and K were 0.064 and 0.14, 0.17and 0.16, 0.16and 0.18 respectively. Maternal heritability was in range of 0.006 - 0.08 and Proportion of environmental variance to phenotypic variance in range of 0.03 - 0.05 parameters growth curve. Among the growth curve parameters, only A and k have biological interpretation and therefore, relationship between them may provide necessary conclusions. Estimates of direct genetic correlation between growth curve parameters were 0.323, -0.429 and 0.803 between A-B, A-K and B-K, respectively. The positive and high genetic correlation between A and B parameters is evident as expected for common genetic and physiological mechanisms controlling these traits. Positive genetic correlation between these traits suggests that selection in one parameter of the growth curve would also improve the other parameter. Residual correlations between growth curve parameters varied form −0.296 (between A-K) to 0.732 (between B-K). Phenotypic correlations between growth curve parameters varied form −0.184 (between A-K) to 0.743 (between B-K). The phenotypic and genetic antagonism between A and k indicates that rapid reduction in growth rate after inflexion point results in lower mature weights. This finding would be helpful for improving selection by identifying the animal who reaches inflexion point earlier and attend higher mature weights later.

 Current genetic estimates for growth curve parameters in Zandi sheep could be applied in designing selection program in this breed. The low estimates of heritability for A, B and K parameters could be assigned to the high phenotypic variance arising from large environmental variation. This therefore implies that much of the improvement in these growth curve parameters could be obtained by improvement of environment rather than genetic selection. It is important to provide good environmental conditions along with optimal management strategies in the flock to achieve a desired shape of growth curve through changing the parameters of model.

Data used in this study related to growth traits in Lori sheep that were collected during 2001 - 2010 by Research Center for Agriculture and Natural Resources of Lorestan province. Growth traits were consist of different ags (brithy, 3 month, 6 month and 9 month). Avarage weight Lori sheep was in birth weight 3.49 kg and in 9 month weight 29.79 kg. The SAS statistical software was used to determine the effect of environmental factors and WOMBAT software was applied to estimate genetic parameters with 6 different models via animal model analysis one trait REML parameters. Environmental factors like birth year, sex, type of birth and age of mother on lambing time had significant effect on all traits (p<0.0001). Type of birth and sex had significant effect on all traits except the 9 month age (p<0.0001). The direct heritability using best chosen model for birth weight, weaning weight, 6 months weight, 9 months weight were respectively obtained as follows: 0.34, 0.01, 0.16 and 0.1 and mathernal heritability for these traits were estimated 0.16, 0.03, 0.05 and 0.06, respectively.

 Arabi sheep population includes almost 55% of the local sheep population in Khuzestan province. Lamb mortality is a universal problem in sheep breeding that may be reached to 20-40% of total lambs born and could impact the genetic improvement, animal welfare and economic viability of sheep breeding, adversely. Research on improving survival of lambs is likely to have a higher pay-off than research on improving the number of lambs conceived. Lamb survival is a compound trait affected by many various factors related to climate, management, lamb and ewe behavior and genetic effects. Lamb survivability is controlled by genetics of the animal, contributed by direct genetic and maternal effects and also by environmental effects. There are disagreements among researchers about using a suitable model to analyze the survival traits, and each researcher has suggested the use of specific models. In general, the use of linear and threshold models has been suggested for survival trait analysis. Although survival has great economic importance, in the studies conducted on Iranian livestock, less attention has been paid to it. The aim of this study was to analyze the genetic parameters for the survival of Arabi lambs from birth to one year of age using linear and Weibull models.

 in this study, 5452 lamb survival records collected by the Jahad Agricultural Organization of Ahvaz from 1993 to 2005 were used. Traits included were cumulative survival from birth to the end of one year and on a monthly basis. In order to estimate genetic parameters using linear models, the Restricted Maximum Likelihood (REML) method was used in Wombat software based on a univariate analysis. The Weibull model and Matvec software were also used for estimating variance component and genetic parameters of Survival rate.

 Different models compared using the likelihood ratio test. For survival traits until 1, 4, 5, and 10 months, the model 4 was suitable, which include the direct additive genetic effect, maternal additive genetic effect and their covariance. In the case of until 2 months, the best model was the model 3, which include the direct and maternal additive genetic effects. For until 3, 8, 9, and 12 months, model 1 including direct additive genetic effect was selected. And for other traits Model 5 (direct additive genetic, maternal additive genetic, and maternal permanent environmental effects) was chosen as the best model. The direct heritability of survival rate estimated from different linear models was in the range of 0.025 to 0.061. In general, despite the high economic importance of survival in the breeds until one year of age, due to low estimates of the inheritance of these traits using linear models, it cannot be expected that genetic selection alone can make significant genetic progress. The genetic variance component among sires, heritability on the logarithmic scale, heritability on the original scale, and effective heritability obtained from Weibull sire model were increased to a peak point at 4 months. After that, a decline occurred until 5 months, and then a fluctuation was observed until 9 months. A limited increase was found in the 11 and 12 months. The heritability of sire model, in the logarithmic scale, had a low to medium range (0.13-0.25), and in the original scale had a medium to high range (0.39-0.75). The effective heritability was estimated in the medium range. Estimated values of the survival heritability using the Weibull model was greater than the value obtained from the linear animal model. Although heritability estimations for survival and mortality is low, it is possible that genetic progress may be enhanced by selecting lambs with higher breeding value for survival.

 Estimation of the genetic parameters for survival lambs from birth to one year of age using linear and Weibull models were low vs medium to high, respectively. Therefore, based on the results of linear models, response to  direct selection to improve the survival of lambs in this breed will be very slow, and more attention should be paid to improving non-genetic factors and indirect selection and outbreeding, but based on The results of Weibull models, it seems that the rate of response to genetic selection to improve survival trait is faster using these models compared to the linear models, suggest that lamb survival could be improved  through direct selection and could be included in the Arabi sheep selection  index.

The traits of economic importance such as body weight at different ages and growth rate in sheep are used as selection criteria in breeding programs. Growth can be defined either as an increase in the number of body cells or an increase in body weight and volume over a period of a lifetime. Animal growth curves can be described using various mathematical models. Growth curve components are heritable in different species. Therefore, the genetic potential of animals can be predicted for growth curve components. The best function describing the growth curve can vary depending on the breed and population under study. The aim of the present study was to investigate the ability of different nonlinear models to fit the growth curve of Moghani sheep and to estimate the genetic parameters of the growth curve characteristics in this breed.

In the current study, the data related to the body weights of Moghani sheep collected at the Moghani sheep breeding station in Jafarabad, Moghan, during the years 1989 – 2016 were used to investigate the growth curve and estimating the genetic parameters of the growth curve characteristics in this breed. Four nonlinear models including Brody, Logistic, Gompertz and von Bertalanffy were used to describe the growth curve of Moghani sheep. All models were fitted on the body weight records of animals at different ages using the NLIN procedure of SAS 9.0 software. The models used have three components including A (maturity weight), B (initial weight of animal) and K (maturity rate). Goodness-of-fit indices including coefficient of determination (R2), Root-Mean-Square Error (RMSE) and Akaike information criterion (AIC) were used to select the best model. After fitting the nonlinear models and selecting the best model, the components of the growth curve of individual animals were estimated using the best nonlinear model. Then, non-genetic factors affecting the growth curve components were investigated using the GLM procedure of SAS. Six univariate animal models that differed in terms of maternal permanent environmental effects and maternal genetic effect as well as covariance between direct and maternal genetic effects were used to analyze the traits. Also, three bivariate analyzes between growth curve components were performed to estimate the genetic correlation between traits.

According to our results, the logistic model with the lowest MSE and AIC and the highest R2 was the best model to describe the growth curve of Moghani sheep. The estimated values for the maturity weight (A), initial weight of animal (B) and maturity rate (K) by the logistic model were 40.328, 7.582 and 0.0270, respectively. The fixed effects of lamb sex, birth type, year and month of calving as well as dam age at calving had a significant effect on the components of the growth curve. Between the six fitted linear models, models number six, two and four were selected as the best models to analyze the components of maturity weight (A), initial weight of animal (B) and maturity rate (K), respectively. Direct heritability for maturity weight (A), initial weight of animal (B) and maturity rate (K) were estimated to 0.17, 0.08 and 0.19, respectively. Estimates of genetic correlation obtained from bivariate analysis between A-B, A-K and B-K were 0•06, 0•03 and −0•0003, respectively.

Among the four nonlinear models used, the logistic model had the best fit for the growth of Moghani sheep. According to the results of our study, the growth curve components of this breed had an acceptable heritability, so that these traits could be used in breeding programs to alter the growth curve and improve the growth pattern of animals in this breed.

In order to estimate the genetic parameters and heritabilities of growth traits and Kleiber ratios in Moghani sheep, data collected in Jafarabad-e-Moghan station from 1994 to 2016 were used. Investigated traits including birth weight, average daily gains and Kleiber ratios during four time periods that is birth to 3 months, 3 t 6 months, 6 to 9 months and 9 to 12 months first analyzed by SAS 9.2 software to indicate the significant fixed effects, finally, 6 animal models running by Wombat software was used to estimate the genetic parameters and heritabilities. The heritability of birth weight (0.31), Average daily gain and Kleiber ratio from birth to 3 months and from 3 to 6 months (0.34, 0.36, 0.40 and 0.38 respectively) were medium to high. The maternal heritabilities and the ratios of maternal permanent environmental variance to the total variance were in the range of 0 to 4 percent and 0 to 2 percent respectively. The genetic trend for birth weight, Average daily gains and Kleiber ratios during four time periods were 0.13, 0.21, 0.27, -0.0000014, 0.01, 0.01, -0.0002 and 0.00004 respectively. These results indicated the relative efficiency of breeding programs for the average daily gains and Kleiber ratios during birth to 3 months and 3 to 6 months in Moghani sheep.

The estimate variance components with a satisfying accuracy of important economic traits such as reproductive traits is a prerequisite for designing breeding strategies. Genetic grouping was suggested in order to predict breeding values of phenotypic records in different years with high accuracy. As there is unknown information in the pedigree of Holstein dairy cows in Iran, genetic group animal models with unknown parents seem necessary. Therefore, the present study was conducted to estimate the genetic parameters, genetic trend and accuracy of estimated breeding values of some reproductive traits (i.e. calving to first service (CTFS), first service to conception (FSTC) and calving interval (CI)) in dairy cows with considering genetic grouping for animals with unknown parents.

Information on calving and insemination dates of the first three calving periods from 3361 herds of the Iranian Holstein, collected by the Animal Breeding Center of Iran during 1981 to 2013 was used. Animals with unknown parents were grouped based on the year of birth and sex and the traits were analyzed using two models, with (model 2) or without genetic grouping (model 1). The model with the lowest Bayesian information criterion (BIC) and the Akaic information criterion (AIC) is considered the best model. Spearman's rank correlation coefficient was used to change in animal rank by considering the genetic grouping. The accuracy of estimated breeding values and genetic trend of the traits was estimated using two models and was compared. Preparation of data for statistical and genetic analysis were carried out using R-software and ASReml software, respectively.

The amount of variance and the standard error of additive variance in model 2 was lower than model 1 and for the residual variance was conversely, but there was no significant difference between the values of the two models. Model 2 was selected the best model for all studied traits based on the goodness of fit criteria. Heritability of CI and CTFS using model 2 was estimated lower (non-significant) than model 1. The heritability value for all reproductive traits was estimated less than 0.05 by two models. The rank of males and females changed duo to genetic grouping. The accuracy of estimated breeding values (EBVs) for all studied traits in model 2 was significantly higher than model 1 (P <0.001). The genetic trend of all traits (exception of the FSTC in the first and third calving period) was positive by model 1 and 2, and the estimated values between the two models were different.

The results of the current study showed that using genetic grouping for reproductive traits analysis of Iranian Holstein cows and accurate prediction of genetic merit of animals seems necessary.

The egg quality is one of the most important economic factors for layers that are crucial for hatchability and marketing. Given the low number of egg quality traits records, one of the approaches in estimating phenotypic and genetic parameters is multi trait analysis. The aim of this study was to estimate the phenotypic and genetic parameters of west Azerbaijan native hens egg quality traits by multi-trait analysis. For this purpose, 2000 eggs of 14th and 15th generation of pedigree hens were purchased from west Azerbaijan native fowl breeding station and for measuring egg quality traits were transferred to laboratory. The genetic and phenotypic parameters of egg quality traits were estimated by multi-trait analysis using SAS and WOMBAT softwares. The generation-hatching time and storage duration in refrigerator had significant effect on egg quality traits. The mean of some egg quality traits were: egg weight 55.306 g±3.94, egg shape index 75.192±2.9, egg shell percentage 9.389 %±0.73, albumin percentage 60.160 %±2.49, yolk percentage 30.466%±2.35, yolk index 35.928±3.13 and yolk pH 6.442±0.13. The highest and the lowest coefficient of variance were calculated in air cell height and albumin pH, as 16.947 % and 1.366 %, respectively. The highest positive phenotypic correlation was observed between egg weight and egg volume (0.644), and the lowest one was observed between pH of albumen and yolk weight (0.004). The highest positive genetic correlation was observed between egg weight and egg shell surface area (0.999), the highest negative genetic correlation was observed between albumen percentage and yolk to albumen ratio (-0.994). The lowest positive genetic correlation was estimated between yolk index and yolk weight (0.002) and the lowest negative genetic correlation was evaluated between yolk index and dry matter of yolk (-0.005). The range of estimated heritability of studied egg quality traits were 0.212 (albumen percentage) and 0.015 (pH of albumen). Generally, the results indicated that the egg quality traits of Azarbaijan indigenous hens have relatively high phenotypic and genetic correlation, which in order to decreasing the cost of data recording, the number of recorded traits could be decreased. The heritabilities of egg quality traits were moderate to low that indicated the low progress with direct selection.

The aim of this study was to estimate the genetic parameters of lactation curve traits (milk yield at beginning of lactation, the rate to reach peak yield, a parameter related to maximum milk yield, the changes in curve shape after reaching maximum yield, peak time, peak milk, persistency) was fitted by Rook function and the inbreeding effect on these parameters for Holstein cows in Iran. For this purpose, the test-day milk yield records of the first three lactations that were collected by the Animal Breeding Center of Iran from 1983 to 2017, were used. The Rook function parameters were calculated for all animals and the peak time, peak milk and persistency were estimated from the curve parameters. The estimation of variance components and genetic parameters of traits were performed by single and two- trait analysis via Gibbs sampling method using of Gibbs3f90 software. The effect of inbreeding was negative on the most of the traits; especially those had a higher heritability and also decreased milk production persistency. The heritability range of the aforementioned traits varied from 0.0003 to 0.086 and the highest heritability was related to persistency trait (0.086) in second lactation and peak milk (0.067) in third lactation. In general, the parameters of the lactation curve had a low heritability, so genetic selection would not show favorable results and changes in environmental and management conditions could be more effective for improving these traits.