Context It is believed that the X chromosome plays an important role in influencing quantitative traits. Despite this, until recently, X-linked genetic effects have not been considered in models to estimate genetic parameters for economically important traits of livestock. Aims A large dataset was analysed to quantify autosomal additive genetic, X-linked additive genetic and maternal effects on growth and efficiency-related traits in Baluchi sheep. Methods Traits included bodyweight at birth, weaning (WW), 6 months (W6), 9 months and yearling age, pre- and post-weaning average daily gain, pre- and post-weaning Kleiber ratio, pre- and post-weaning efficiency of growth (EFb), and pre- and post-weaning relative growth rate. Each trait was analysed using the REML procedure fitting a series of eight univariate animal models. For each trait, the most appropriate model was selected by the Akaike information criterion and Bayesian information criterion. Key results The X-linked genetic effect was significant only in models fitted to EFb, where the estimate of X-linked heritability was 0.02 ± 0.01 from the best model. Other traits were not affected significantly by X-linked genetic effects. Estimates of autosomal heritability () for growth traits were between 0.06 ± 0.02 (post-weaning average daily gain, pre-weaning relative growth rate) and 0.22 ± 0.04 (bodyweight at yearling age), and ranged between 0.02 ± 0.01 (EFb) and 0.08 ± 0.02 (pre-weaning Kleiber ratio) for efficiency-related traits. Maternal effects significantly contributed to phenotypic variation of most traits, with larger effects on traits measured early in life. For EFb, the Spearman’s correlation between breeding values including and excluding X-linked effects was 0.95. It was 1.00 for traits that were not affected by X-linked genetic effects. Conclusions Although the proportion of phenotypic variance attributed to X-linked loci for most traits was zero, the importance of X-linked genetic effects should be at least tested in models when estimating variance components for growth and efficiency traits of Baluchi sheep. Implications As estimates of genetic parameters are breed-specific, we recommend for growth and efficiency traits of sheep that the importance of X-linked genetic effects should be evaluated to assess if these effects should be included in models used in genetic evaluation.

For comparing reproductive performance of sexed versus conventional semen a total of 3573 heifer insemination records collected from five herds in four provinces of Iran were investigated. The studied provinces were classified into three regions: hot semiarid (Tehran and Alborz provinces), temperate semiarid (Khorasan Razavi province) and cold semiarid (Zanjan province). Various parameters including the conception rate, number of services per conception, calf sex ratio, calf birth weight, gestation length, calving ease score, abortion and stillbirth as well as twining rate were investigated. The logistic regression method was deployed for the analysis of categorical variables while the GLM procedure was applied for the analysis of continuous variables. The average conception rate of sex sorted and conventional semen was 48.3 and 63.8%, respectively. The utilisation of sex sorted semen resulted in 91.1% female calves. The conception rate, number of services per conception, gestation length, calf birth weight and the calf sex ratio were among the reproductive variables that were significantly influenced by the semen sexing. A greater number of services per conception and calving ease score were observed in hot and temperate semiarid areas. These climatic regions also provided a lower incidence of female calf births compared to the cold semiarid regions. Our results highly reaffirm the previous findings on the reproductive performance of sex sorted semen. Yet, climatic and management practices of a herd within a special climate have to be considered when deciding for utilisation of sex sorted semen in a dairy farm. ARTICLE HISTORY

The genealogical data of Cashmere goat breed of South Khorasan province of Iran was analysed in this study. Records from a total of 10,635 animals collected during 1988-2014 from 20 registered flocks were analysed for evaluating pedigree parameters. The reference population was defined as the living reproductive animals born from 2010 till 2014. The average inbreeding coefficient in the studied breed was about 0.07% (ranging from 0 to 25%). In addition, the average inbreeding coefficient for the reference population was about 0.85%. The main reason for the low inbreeding level obtained in Cashmere goat population was related to the extensive production system and lack of sire registration in a large number of animals (about 78% missing sire information). A total of 200 animals were inbred. The inbred animals were all related to the breeding station flock which was acting as a closed nucleus flock and was under the control of Animal Breeding and Milk Improvement Centre of Iran. The result of analysis for gene origin parameters indicated the lack of pedigree depth, which could leads to management problems for conservation of the studied breed.ARTICLE HISTORY

The objective of this study was to investigate genetic variation and genotype by environment (G × E) interactions for fertility (including age at first calving and calving interval), somatic cell score (SCS), and milk production traits for Iranian Holsteins. Different environments were defined based on the climatic zones (cold, semi-cold, and moderate) and considering the herd location. Data were collected between 2003 and 2018 by the National Animal Breeding Center of Iran (Karaj). Variance and covariance components and genetic correlations were estimated using 2 different models, which were analyzed using Bayesian methods. For both models, performance of traits in each climate were considered as different traits. Fertility traits were analyzed using a trivariate model. Furthermore, SCS and production traits were analyzed using trivariate random regression models (records in different climate zones considered as different traits). For the fertility traits, the largest estimates of heritability were observed in cold climate. Fertility performance was always better in cold environment. Genetic correlations between climatic zones ranged from 0.85 to 0.94. For daily measurements of SCS and production traits, heritability ranged from 0.031 to 0.037 and 0.069 to 0.209, respectively. Genetic variances were the highest in the semi-cold and moderate climates for the SCS and production traits, respectively. Furthermore, across the studied climates, 305-d genetic correlation ranged from 0.756 to 0.884 for SCS and from 0.925 to 0.957 for the production traits. The structure of genetic correlation within each climate indicated a negative correlation between early and late lactation for SCS, especially in the cold climate and for milk production in the moderate climate. For fat percentage, in all climatic zones, the lowest genetic correlations were observed between early and mid-lactation. In addition, for protein production in the cold climate, a negative correlation was observed between early and late lactation. Results indicated heterogeneous variance components for all the studied traits across various climatic zones. Estimated genetic correlations for SCS revealed that the genetic expression of animals may vary by climatic zone. Results indicated the existence of G × E interaction due to the climatic condition, only for SCS. Therefore, in Iranian Holsteins, the effect of G × E interactions should not be neglected, especially for SCS, as different sires might be optimal for use in different climatic zones.

No abstract