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Parameters such as effective population size (Ne), runs of homozygosity (ROH), and inbreeding based on ROH (FROH) can give new insight into the level of genetic diversity for the population under selection. This research aimed to measure the extent of linkage disequilibrium (LD), effective population size (Ne), Haplotype Block Structure, and runs of homozygosity (ROHs) in several populations of cattle using SNP genotypes. In this study, that the average r2 decreased with the increasing distance of SNP pairs. A general decrease in Ne can be seen for all four populations, indicating a loss of genetic diversity. The Iranian Holstein had the lowest level of genomic inbreeding at an ROH of 1, 5, 10 Mb, while the French Holstein had the highest. The maximum number of ROH is seen at a distance of less than 1 Mb, and the lowest number of ROH is seen at a distance of 10 Mb. The number of ROH decreases with increasing distance due to the increased recombination rate. This is a concern as an increase in inbreeding leads to a reduction in the effective population size, which was also evident in the study populations.

Fatty acid metabolism in poultry has a major impact on production and disease resistance traits. According to the high rate of interactions between lipid metabolism and its regulating properties, a holistic approach is necessary. To study omics multilayers of adipose tissue and identification of genes and miRNAs involved in fat metabolism, storage and endocrine signaling pathways in two groups of broiler chickens with high and low abdominal fat, as well as high-throughput techniques, were used. The gene–miRNA interacting bipartite and metabolic-signaling networks were reconstructed using their interactions. In the analysis of microarray and RNA-Seq data, 1,835 genes were detected by comparing the identified genes with significant expression differences (p.adjust < 0.01, fold change ≥ 2 and ≤ −2). Then, by comparing between different data sets, 34 genes and 19 miRNAs were detected as common and main nodes. A literature mining approach was used, and seven genes were identified and added to the common gene set. Module finding revealed three important and functional modules, which were involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, biosynthesis of unsaturated fatty acids, Alzheimer’s disease metabolic pathway, adipocytokine, insulin, PI3K–Akt, mTOR, and AMPK signaling pathway. This approach revealed a new insight to better understand the biological processes associated with adipose tissue.

The Arabian horse, one of the world’s oldest breeds of any domesticated animal, is characterized by natural beauty, graceful movement, athletic endurance, and, as a result of its development in the arid Middle East, the ability to thrive in a hot, dry environment. Here we studied 378 Arabian horses from 12 countries using equine single nucleotide polymorphism (SNP) arrays and whole-genome re-sequencing to examine hypotheses about genomic diversity, population structure, and the relationship of the Arabian to other horse breeds. We identified a high degree of genetic variation and complex ancestry in Arabian horses from the Middle East region. Also, contrary to popular belief, we could detect no significant genomic contribution of the Arabian breed to the Thoroughbred racehorse, including Y chromosome ancestry. However, we found strong evidence for recent interbreeding of Thoroughbreds with Arabians used for flat-racing competitions. Genetic signatures suggestive of selective sweeps across the Arabian breed contain candidate genes for combating oxidative damage during exercise, and within the “Straight Egyptian” subgroup, for facial morphology. Overall, our data support an origin of the Arabian horse in the Middle East, no evidence for reduced global genetic diversity across the breed, and unique genetic adaptations for both physiology and conformation.

Background Fatty acid metabolism in animals has a major impact on production and disease resistance traits. According to the high rate of interactions between lipid metabolism and its regulating properties, a holistic approach is necessary. Methods To study multi-omics layers of adipose tissue and identification of genes involved in fat metabolism, storage and endocrine signaling pathways in two groups of broiler chickens with high and low abdominal fat, high-throughput screening (HTS) techniques were used. The Gene-miRNA interacting bipartite and metabolic-signaling networks were reconstructed using their interactions. Results In the analysis of microarray and RNA-Seq data, 1835 genes were detected by comparing the identified genes with significant expression differences. Then, by comparing, 34 genes and 19 miRNAs were detected as common and main nodes. The literature mining approach was used and 7 genes were identified and added to the common gene set. Module finding revealed three important and functional modules. The detected modules 1, 2, and 3 were involved in the PPAR signaling pathway, biosynthesis of unsaturated fatty acids, and Alzheimer's disease metabolic pathway, adipocytokine, insulin, PI3K-Akt, mTOR and AMPK signaling pathway. Conclusions This approach revealed a new insight for a better understanding of the biological processes associated with adipose tissue.

Previous research on the equine major histocompatibility complex (MHC) demonstrated strong correlations between haplotypes defined by polymorphic intra-MHC microsatellites and haplotypes defined using classical serology. Here, we estimated MHC diversity in a sample of 124 Arabian horses from an endangered strain native to Iran (Persian Asil Arabians), using a validated 10-marker microsatellite panel. In a group of 66 horses related as parent-offspring pairs or half-sibling groups, we defined 51 MHC haplotypes, 49 of which were new. In 47 of the remaining 58 unrelated horses, we could assign one previously identified MHC haplotype, and by default, we gave provisional haplotype status to the remaining constellation of microsatellite alleles. In these horses, we found 21 haplotypes that we had previously defined and 31 provisional haplotypes, two of which had been identified in an earlier study. This gave a total of 78 new MHC haplotypes. The final 11 horses were MHC heterozygotes that we could not phase using information from any of the previously validated or provisional haplotypes. However, we could determine that these horses carried a total of 22 different undefined haplotypes. In the overall population sample, we detected three homozygous horses and one maternally inherited recombinant from 21 informative segregations. Virtually all of the horses tested were MHC heterozygotes, and most unrelated horses (98%) were heterozygous for rare microsatellite-defined haplotypes found less than three times in the sampled horses. This is evidence for a very high level of MHC haplotype variation in the Persian Asil Arabian horse.

The objectives of this study were to quantify the errors in economic values (EVs) for traits affected by cost or price thresholds when skewed or kurtotic distributions of varying degree are assumed to be normal and when data with a normal distribution is subject to censoring. EVs were estimated for a continuous trait with dichotomous economic implications because of a price premium or penalty arising from a threshold ranging between -4 and 4 standard deviations from the mean. In order to evaluate the impacts of skewness, positive and negative excess kurtosis, standard skew normal, Pearson and the raised cosine distributions were used, respectively. For the various evaluable levels of skewness and kurtosis, the results showed that EVs can be underestimated or overestimated by more than 100% when price determining thresholds fall within a range from the mean that might be expected in practice. Estimates of EVs were very sensitive to censoring or missing data. In contrast to practical genetic evaluation, economic evaluation is very sensitive to lack of normality and missing data. Although in some special situations, the presence of multiple thresholds may attenuate the combined effect of errors at each threshold point, in practical situations there is a tendency for a few key thresholds to dominate the EV, and there are many situations where errors could be compounded across multiple thresholds. In the development of breeding objectives for non-normal continuous traits influenced by value thresholds, it is necessary to select a transformation that will resolve problems of non-normality or consider alternative methods that are less sensitive to non-normality.

The aim of this study was to estimate genetic parameters for protein efficiency and its correlations with milk yield traits in lactating dairy cows. The data used were 2824 monthly records of 501 lactating Holstein cows located in 2 herds. Three methods were used to measure protein efficiency: Gross efficiency of crude protein (GECP) was calculated as protein yield in milk/CP intake. Crude protein balance (CPB) was measured as the difference of CP intake and protein excreted in milk. Residual protein intake (RPI) was calculated as the difference of actual and predicted CP intakes. Variance and covariance components were estimated using univariate and bivariate analyses of animal mixed models, respectively, using derivative free approach of restricted maximum likelihood algorithm. The estimated heritabilities for GECP, CPB and RPI were 0.07, 0.40 and 0.03, respectively. Repeatability estimates for GECP, CPB and RPI were 0.12, 0.40 and 0.32, respectively. Different measures of protein efficiency had low phenotypic correlations with the yield traits and dry matter intake, while noticeable genetic correlations were observed between different measures of protein efficiency and some of yield traits. It seems that protein efficiency could be improved by direct selection against CPB. Selection for milk fat and protein percentages is probably an effective way for indirect improvement of protein efficiency.

A stochastic bio-economic model has been used to determine the effects of new reproductive technologies over a 15-year period. A strategy of using conventional artificial insemination (AI) or embryo transfer (ET) using two sex-controlled embryos at different conception rates (CRs) and herd sizes resulted in a 24 state model. The genetic means of AI population increased over the years, and the genetic means of milk production for all of the embryo strategies were greater than those of AI. In addition, the genetic means of milk yield using different embryo-based scenarios in the expanding herds were greater than those for the fixed herds. The net profit of using sexed ET in the expanding herds was greater (P < 0.05) than that of fixed size herds. In general, there was a roughly consistent trend in net profit per cow for sexed ET strategies in the expanding herds over the years, but there was an increasing trend in net profit per cow for sexed ET strategies in the fixed herds over the years. Medium to high CRs for ET and the use of sex-controlled embryo systems, especially for induction of twin births to produce dairy replacements, will be critical elements of a system that produces significant numbers of female calves. The greater number of female calves produced in the sex-controlled scenarios allows the farmer to select animals with the best genetic potential as dairy replacement heifers; therefore, the rate of genetic gain increased in the dairy herd. Results of sensitivity analyses showed that a significant decrease in the production costs and increase in the ET performance are essential for embryo-based technologies to be profitable.

The objective of this study was to develop a method for calculating economic values of clinical mastitis (CM) and somatic cell score (SCS) for inclusion in a dairy cattle breeding goal in the context of a country where farm production and economic data are scarce. In order to calculate the costs and derive economic values for SCS, a new model, 'milk collection method', has been developed and was compared with the Meijering model with individual and average SCS distributions. For the population, estimated economic values using the milk collection method were 1.3 and 2.4 times higher than those of Meijering method with average and individual SCS, respectively. The milk collection method needs no assumptions about normality of the distribution of SCS and because of a lack of normality in Iranian data for SCS, the Meijering method resulted in economic values that were biased downwards. Failing to account for the fact that milk price penalties for SCS are applied at milk collection rather than individual cow level resulted in a further large downward bias in the economic value of SCS. When the distribution of data is unknown or difficult to approximate or when a transformation to normality is not straightforward, the milk collection method would be preferable. Inclusion of SCS and CM in the breeding goal for Iranian dairy cattle is justified based on these results. The model to calculate mastitis costs proposed here could be used to estimate economic values for CM in other developing countries where farm production and economic data are generally poor.

A stochastic bio-economic model was used to determine the effects of applying artificial insemination (AI) with conventional or sexed semen at different conception rates and herd sizes on the genetic progress of productive trait and net profit over a 15-year period. The genetic means of the cattle population was predicted to increase over the years and the rate of genetic progress in the population program using sexed semen was significantly greater than the rate of progress in the population using conventional semen. The theoretical genetic gain was greater than the realized genetic gain for milk yield for all the AI scenarios. In addition, the genetic means for milk yield in the expanding herds were greater than in the fixed sized herds. The trend in net profit generated by using AI strategies with conventional semen over the time horizon was greater when herds were expanding (P < 0.01). The trend in net profit for fixed sized herds was generally negative, however, expanding herds experienced positive net profits over the years. Also, the net profit of using AI strategies with sexed semen was greater when dairy herds were expanding. On the other hand, the net profit of using AI with sexed semen was greater than that of AI with conventional semen at the end of the time horizon. The results of sensitivity analyses indicated that a 20% increase or decrease in milk sales income and feed costs have significantly modified the net profit of AI strategies using either sexed or conventional semen.

A Weibull proportional hazards model was applied to evaluate the effects of 18 linear type traits on the functional length of productive life in Holstein cattle of Iran. Culling data and classification scores on 44,179 cows with first calving from 1996 to 2004 were used. The data included up to 55% of censored records. Length of productive life was defined as the number of days from first calving until last test day or censoring. The significance of each type trait was tested by a likelihood ratio test comparing the full model (with one particular type trait) with reduced models (without any of the type traits). Analyses were performed for each type trait one at a time which included as a covariate in the model. The strongest relationship between length of productive life and type traits were found for fore udder attachment, udder depth, udder cleft angularity and loin strength. Body traits except angularity had minimal effect on functional longevity. Some traits such as udder depth, rear legs side view and foot angle showed an intermediate optimum with respect to longevity and extreme scores of these traits increased risk of involuntary culling. Results of the present study showed that improvement of conformation traits, which is more associated with functional longevity, is a useful way to increase functional length of productive life.

The records of growth traits of 2778 lambs of Sangsari sheep flock from Damghan research station (Semnan Province, Iran), collected during 1986–1998, were analyzed to estimate the variance components and heritabilities of some growth and gain traits, using a Derivative Free, Restricted Maximum Likelihood (DFREML) approach. The single and/or multiple trait animal models were employed to perform the mentioned task. Different models of DFREML run for univariate analysis and log likelihood ratio for different models were compared to locate the most appropriate model for the analysis of each trait. With univariate analysis, direct heritability estimates for birth weight, weaning weight, 6 months weight, 9 months weight, yearling weight, average daily gain from birth to weaning, average daily gain from birth to 6 months of age and average daily gain from weaning to 6 months of age were 0.33 ± 0.05, 0.17 ± 0.05, 0.49 ± 0.07, 0.08 ± 0.05, 0.10 ± 0.05, 0.03 ± 0.02, 0.17 ± 0.60 and 0.05 ± 0.30, respectively. Maternal heritability estimates were 0.65 for birth weight, 0.08 for weaning weight, 0.01 for average daily gain from birth to weaning and 0.11 for 6 months weight. The results of pair-wise and multivariate (five traits) analyses for heritability estimates are also reported, which are not very different from those mentioned above. The results of this study showed that maternal heritability was higher for pre-weaning than for post-weaning traits.

In this study, direct and maternal heritabilities were estimated for growth traits and carcass characteristics in Lori-Bakhtiari sheep. Data for birth weight (BW; n=5826), weaning weight (WW; n=5408), body weight at six months of age (6MW; n=4237), body weight at slaughter (SW; n=396), cold carcass weight (CCW; n=291), lean weight (LW; n=204), bone weight (WB; n=291), fat weight (WF; n=204) and fat-tail weight (FTW; n=396) were used to estimate the heritabilities. The data for first three traits had been collected during seventeen years, 1990 to 2006, while for other traits had been collected during six years, 2000 to 2006. Genetic parameters including both direct and maternal genetic effects were estimated using multivariate animal models, and a Derivative Free Restricted Maximum Likelihood (DFREML) approach. The direct heritability for BW, WW, 6MW, SW, CCW, LW, WB, WF and FTW were 0.30 ? 0.03, 0.13 ? 0.03, 0.20 ? 0.03, 0.24 ? 0.06, 0.16 ? 0.06, 0.16 ? 0.06, 0.20 ? 0.11, 0.23 ? 0.11, and 0.27 ? 0.11, respectively. Maternal heritability estimates were 0.22, 0.17, 0.06, 0.10, 0.09, 0.15, 0.26, 0.06 and 0.07 for BW, WW, 6MW, SW, CCW, LW, WB, WF and FTW, respectively. Consequently, genetic progress is possible for growth traits and carcass composition by selection.

In this research, heterogeneity of variance components in cattle populations at climatical regions in the first three lactations was studied. The data set included the following: 161328 records of first, 123369 records of second and 81013 records of third lactations, which was collected by Animal Breeding Center of Iran from 1983 to 2004. Records of three lactations were divided in the base of Domarten method. Bartlett test for heterogeneity of variance components was significant among all subgroups. In order to decrease the heterogeneity of variance components, we used several data transformation methods including Logarithmic, Square root and Arc sin transformations. Logarithmic transformation decreased the heterogeneity of variance components in the three lactations and other methods had not effect for removing the heterogeneity in any group. Genetic parameters and heritability were estimated for three lactations by MATVEC program, using animal model. Results showed that the heritability estimates of milk yield were decreased from the first lactation to the third; also the heritability estimates of transformed data were slightly higher than the original data. Comparison between estimated parameters in single trait and two traits analysis, before and after data transformation, showed that there were not significant differences between derived results.

The somatotropic axis, the control system for growth hormone (GH) secretion and its endogenous factors involved in the regulation of metabolism and energy partitioning, has promising potentials for producing economically valuable traits in farm animals. Here we investigated single nucleotide polymorphisms (SNPs) of the genes of factors involved in the somatotropic axis for growth hormone (GH1), growth hormone receptor (GHR), ghrelin (GHRL), insulin-like growth factor 1 (IGF-I) and leptin (LEP), using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods in 452 individual Mehraban sheep. A nonradioactive method to allow SSCP detection was used for genomic DNA and PCR amplification of six fragments: exons 4 and 5 of GH1; exon 10 of GH receptor (GHR); exon 1 of ghrelin (GHRL); exon 1 of insulin-like growth factor-I (IGF-I), and exon 3 of leptin (LEP). Polymorphisms were detected in five of the six PCR products. Two electrophoretic patterns were detected for GH1 exon 4. Five conformational patterns were detected for GH1 exon 5 and LEP exon 3, and three for IGF-I exon 1. Only GHR and GHRL were monomorphic. Changes in protein structures due to variable SNPs were also analyzed. The results suggest that Mehraban sheep, a major breed that is important for the animal industry in Middle East countries, has high genetic variability, opening interesting prospects for future selection programs and preservation strategies.

Growth hormone secretagogue receptor (GHSR), a G protein-coupled receptor that binds ghrelin, plays an important role in the central regulation of pituitary growth hormone secretion, food intake, and energy homeostasis. Ghrelin receptor (GHSR) modulates many physiological effects and therefore is a candidate gene for sheep production performance. Polymorphism of the GHSR gene was detected by PCR-SSCP and DNA sequencing methods in 463 individuals. Two different structures in protein and nine single nucleotide polymorphisms (SNPs) were identified. The evaluation of the associations between these SSCP patterns with carcass traits suggests a positive effect of genotype TT and B structure on carcass weight, and body length (P

Trait-by-trait and multiple trait bioeconomic modeling were used to derive farm-specific economic weights (EW) for a wide range of traits under different production and economic circumstances to define breeding objectives for Holstein dairy cattle in Iran. Production parameters and economic data were gathered on 10 dairy farms from March 2008 to February 2010. The EW (economic values multiplied by gene expressions, in US dollars per unit of trait per calf born from sires of self-replacing females in planning horizon of 20 yr) were estimated to be $0.15 per kilogram of milk yield; $1.36 per kilogram of fat yield; −$1.02 per kilogram of protein yield; $4.59 per month of longevity; −$1.22 per kilogram of mature cow weight; −$105.67 for combined somatic cell score and clinical mastitis; −$1.35 and −$0.28 for percentage direct and maternal calving difficulties, respectively; −$3.98 for percentage direct stillbirth; −$0.76 per day of age at first calving; −$0.72 per calving interval day; and $0.91 for percentage 56-d nonreturn rate on averages across investigated farms. The coefficient of variation of economic weights across the 10 farms was lowest for direct calving difficulty and highest for calving interval. The proposed Iranian selection index was compared with selection indices of major countries exporting semen to Iran. Average relative emphasis for production, durability, and health and reproduction, across all exporter countries, was 41, 37.5, and 21.5%, respectively, whereas the respective values were 50, 14, and 36% for the Iranian index. Significant differences in selection indices may potentially decrease the utility of importation of semen as a means of achieving sustainable genetic progress in Iran. Results obtained in this study provide important information about economic values of traits that can be used to improve the Iranian national progeny testing program as well as importation rules for semen to Iran.

Calving records from the Animal Breeding Center of Iran, collected from January 1991 to December 2007 and comprising 1,163,594 Holstein calving events from 2,552 herds, were analyzed using a linear animal model, linear sire model, threshold animal model, and threshold sire model to estimate variance components, heritabilities, genetic correlations, and genetic trends for twinning rate in the first, second, and third parities. The overall twinning rate was 3.01%. Mean incidence of twins increased from first to fourth and later parities: 1.10, 3.20, 4.22, and 4.50%, respectively. For first-parity cows, a maximum frequency of twinning was observed from January through April (1.36%), and second- and third-parity cows showed peaks from July to September (at 3.35 and 4.55%, respectively). The phenotypic rate of twinning decreased from 1991 to 2007 for the first, second, and third parities. Sire predicted transmitting abilities were estimated using linear sire model and threshold sire model analyses. Sire transmitting abilities for twinning rate in the first, second, and third parities ranged from -0.30 to 0.42, -0.32 to 0.31, and -0.27 to 0.30, respectively. Heritability estimates of twinning rate for parities 1, 2, and 3 ranged from 1.66 to 10.6%, 1.35 to 9.0%, and 1.10 to 7.3%, respectively, using different models for analysis. Heritability estimates for twinning rate, obtained from the analysis of threshold models, were greater than the estimates of linear models. Solutions for age at calving for the first, second, and third parities demonstrated that cows older at calving were more likely to have twins. Genetic correlations for twinning rate between parities 2 and 3 were greater than correlations between parities 1 and 2 and between parities 1 and 3. There was a slightly increasing trend for twinning rate in parities 1, 2, and 3 over time with the analysis of linear animal and linear sire models, but the trend for twinning rate in parities 1, 2, and 3 with threshold animal model analysis was decreased over the years. There was a significant decreasing trend for twinning rate in parities 1 and 2 over time with the threshold sire model analysis, but the genetic trend for twinning rate in parity 3 with this model of analysis was significant and positive. In general, there were increasing genetic trends for twinning rate from parities 1 through 3 using different models of analysis.

Calving records of Holstein dairy cows from April 1998 to September 2006 comprising 16 herds with 104,572 calving events representing 4,045 twin births were used to evaluate reported twinning rate, calf sex ratio, stillbirth, and abortion rates in single and twin births. Overall, the reported twinning rate was 3.9%, and twinning increased with parity [1.1% for primiparous cows vs. 5.7% for cows in their fourth or greater lactation; odds ratio (OR) = 5.50]. Regardless of parity, the greatest twinning rate was observed when conception occurred in fall season from September to December (OR = 1.17). Calf stillbirth was greater after twin births, with 18.8% of twin calving events resulting in one or both calves as stillborn, compared with 4.0% for singleton births (OR = 7.58). Calf stillbirth for multiparous cows was 2.9% for single births and 18.0% for twin births (OR = 7.08), whereas for primiparous cows, stillbirth was 6.6% for singletons and 27.7% for twins (OR = 5.85). Calf sex ratios (male, M; female, F) were 52.4% M and 47.6% F for singleton calves and 28.2% MM, 48.9% MF, and 22.9% FF for twin calves. The mean abortion rate was 13.4%, with 13.8% for single births and 4.2% for twin births (OR = 1.22). Abortion rate for multiparous cows was 15.9% for single births and 4.0% for twin births (OR = 4.31), whereas for primiparous cows, abortion rate was 9.4% for single births and 5.4% for twin births (OR = 1.89). Although milk production, as a causative factor associated with twinning, increased in recent years, twinning rate decreased over the years.

The present study indicates an association between carcass traits and genetic polymorphism and changes in the protein structure of the growth hormone 1 (GH1) gene in Mehraban sheep. Polymorphism of the GH1 gene was detected by polymerase chain reaction–single strand conformation polymorphism (PCR–SSCP) and DNA sequencing methods in 463 individuals. Two different structures in the GH1 protein and six single nucleotide polymorphisms were identified. The association of these SSCP patterns and protein structures with carcass traits was analysed. The SSCP patterns were shown to be associated with carcass traits. Individuals with AB SSCP pattern and Type B protein structure had significantly higher fat-tail weight and volume (P < 0.05) than did those individuals with CC SSCP pattern and Type A protein structure. Moreover, CC SSCP pattern and Type A protein structure contributed to low concentration of blood triglycerides (P = 0.004). The results confirmed the importance of GH1 as a candidate gene for marker-assisted selection for carcass-trait variations in sheep.

Meat production is the most important goal of sheep breeders in Iran. Crossbreeding between rams from relatively heavier breeds with ewes from light breeds (terminal crossing) is common method for increasing meat production in many countries (Bunch et al., 2004; Guney, 1990; Macit et al., 2001). The objective of this study was to compare the growth and feed-lot performance of crossbred lambs, resulted from Shall, Moghani and Afshari (three heavy breeds) rams and Kordi (a light breed) ewes. The performance of pure Kordi lambs was also adopted as a comparison benchmark.

Improvement of herd life increases profitability due to lower replacement costs of heifers, higher proportion of mature cows that produce at their maximum potential and increased opportunity for voluntary culling. Functional productive life (PL) after adjustment for production is the ability of a cow to remain healthy and delay involuntary culling (Ducrocq et al 1988). Survival or failure time analysis has replaced linear model approaches for routine genetic evaluation of dairy cattle in several countries (Sewalem et. al. 2003). It allows proper treatment of censored data, inclusion of time-dependent covariates and skewed or non normal distribution of data. Approximate estimates of the heritability of longevity traits typically range from 0.05 to 0.10 and 0.15 to 0.20 using linear models and survival analysis, respectively (Vollema et al. 2000 and Caraviello et. al. 2004). The objective of this study was to apply survival analysis methodology for assessing the most important factor influencing PL, estimation of genetic parameters of productive life and genetic evaluation in Iranian Holstein dairy cattle.

The goal of a breeding programme is to select animals that will be more profitable or efficient than their parents. Two main methods have been developed to allow selection on the breeding objective. The first method is use of selection index that combines individual trait breeding values with economic weights to provide a single measure on which to select animals. The second method measures the breeding objective (e.g. net profit or lifetime profit) directly and provides genetic evaluations for this measure (Visscher and Goddard, 1995). The profitability of a dairy cow is dependent on both outputs (incomes of milk, fat, protein, calving, etc.) and inputs (costs of feed, labour, facilities, etc). Outputs have received considerable attention in breeding objectives for dairy cattle, whilst there has been less consideration of inputs. Feed is a major cost input for dairy producers. Hence, breeding for increasing main gross incomes (milk, fat and protein) and reducing main variable cost (feed) potentially can be of considerable importance. This study was conducted to estimation of genetic variation in income over feed cost (IOFC), as a single trait, and its association with some of other traits in Holstein dairy cows.

In Iran, sheep is a main domestic animal with population about 60 millions. So, evaluation of genetic variation in Iranian sheep is a critical necessity. This study is the first research on genetic variation within and between a small part of Iranian sheep using microsatellite markers.

The Breeding Center of Raeini (BCR) cashmere goats was established in 1965 in Kerman province, with a base population of 120, 8 and 42 does, bucks, and kids respectively. Some new animals have been introduced to the BCR population in some periods of time, and selected males have been sold out to the local breeders each year. Animals have been selected based on their phenotypic performance for fleece weight (FW) and fleece color (FC-white), and body weight (BW). Mating system has been planned based on non-relative mating, but some relative mating has been occurred. Inbreeding depression is one of the most important empact of having inbreeding in a population (Miglior and Burnside 1995). A decrease of 0.8% in fiber length and 6.3% in longevity per 10% increase of inbreeding coefficient in cashmere goats has been reported (Deb 1998). The objective of this study was to estimate the animals inbreeding coefficient and to explore the impact of inbreeding on some economic traits in Raeini cashmere goats.

Sheep growers in Iran who raise breeds with light body weight, most often are interested to use rams of the heavier breeds to inseminate their ewes in order to obtain heavier lambs at sale. However, this practice may or may not be supported with enough scientific evaluations, on which only the results of very few studies are available (Kiyanzad, 2001; Farid, 1991; Makarechian et al 1978). The objective of this work was to declare the growth and feedlot performances of crossbred lambs, resulted from Afshari, Moghani and Shal (three heavy breeds) rams and Varamini (a light breed) ewes. The perfrormance of pure Varamini lambs was also adopted as a comparison benchmark.

In this research we used stochastic method to simulate litter size data under assumption that the phenotype of the trait of interest is categorically distributed with a liability of normally distributed background effect. For the phenotypic categorical measurements, normal distribution of liability was assumed. Analysis was conducted by DFREML for phenotypic categorical data set. In the simulation process, we applied different true background heritabilities in combination with different threshold points. The points with the lowest heritability had the lowest variation in estimated heritability and those with the highest heritability had the highest variation. Results clearly show that by moving threshold points from the population mean towards the two tails of the distribution and also by increasing the true heritability, the differences between estimated heritability and true heritability increases. The linear model has always underestimated true heritabilities. It is possible to use our estimates to obtain a confidence range for true heritability when we have information about approximate location of threshold and estimates of heritability obtained by linear model.