نشریه اصلاح و به نژادی دام
سال دوم شماره 4 (پیاپی 6، زمستان 1401)

Over the past few years, an immune system has been discovered in bacteria that has led to the development of a powerful gene-editing technique called CRISPR/Cas9 (Clustered regularly interspaced short palindromic repeat). Because of its simplicity and flexibility, CRISPR technology has been widely used in many fields of research based on genome editing in animal, microbial, medical, pharmaceutical and plant sciences. This article discusses the history, basic mechanisms and applications of the CRISPR/Cas9 system and its potential for improving the performance of domestic animals. Given the widespread acceptance of this technology by all animal genome editing institutes in the world, as well as the advances that have been made in its evolution and enhancement of capabilities, it is obvious that the CRISPR/Cas9 system will soon undergo a dramatic transformation in the creation of lines and breeds with desired traits. In addition, extensive advances are being made to improve the capabilities and efficiencies of this technology for on-target genome editing as well as reducing the chances of editing off-target regions.

The aim was to estimate the inbreeding coefficient and its impact on important economic traits in Yazd native fowls breeding station by quantile regression. Therefore, 57400 data collected from 2001 to 2017 (15 generations) was used. Traits included body weight at hatch (BW1), the 8th (BW8) and 12th week (BW12), age and weight at sex maturity (ASM, WSM), the egg number (12 weeks of production) (EN), average egg weight (28th, 30th, 32th weeks of production) and the first egg weight (EW1). Data was edited by Foxpro and estimation of inbreeding coefficient was computed by CFC. The regression coefficient of inbreeding was fitted on generation by linear regression of Rsoftware. Impact of inbreeding on traits was investigated by quantile regression. The fixed effects in the models were sex, hatch number, generation and inbreeding depression was considered as covariate. Pedigree analysis showed that 79percent of population were inbred and average of individual inbreeding coefficient was %3. The slope trend of individual inbreeding was increased by 0.5 percent on generation. Exploring different trait quantile distributions, it was revealed that inbreeding depression had different impacts over range of its distribution in a way that a much pronounced effect was observed in extremes (25%, 75%).Quantile regression was not converged for BW1, ASM and EW1 and they were estimated by linear regression as 0.001, 0.053 and 0.063,respectively. According to quantile regression, the impact of inbreeding depression was not equal on different parts of traits' distribution, which give us a better insight of the effect of inbreeding.

Genomic selection can help in more accurate estimation of breeding values, genetic improvement resulting from a more precise and better selection of individuals, as well as control of inbreeding in animals. genomic simulation made it possible to make the necessary predictions before carrying out expensive genomic processes. The success of any breeding program depends significantly on how the base population is created. All the genetic diversity of the traits included in the breeding goal must be created in the base population. Therefore, it is essential to design a program to create a base population in linkage disequilibrium by simulating random mating between bee communities in breeding processes by considering bees' genetic characteristics and reproductive behavior. In this research, the genetic architecture of the honey bee was created by simulating various demographic and genomic factors using MATLAB software, and while investigating the effect of the effective population size with the NeEstimator software in four levels of minimum allelic frequency and in the generation with the maximum linkage disequilibrium, the impact of the number of queens and males in historical generations was studied and determined. Continuity disequilibrium occurs and increases, and conversely, as the mutation rate increases, the time to reach the maximum linkage disequilibrium decreases. Increasing the number of markers in populations with fewer individuals in historical generations decreased the time to reach maximum linkage disequilibrium. Linkage disequilibrium pattern in the genome is a powerful sign of the genetic processes of the population that construct it.

This study was carried out based on the records of 206107 Holstein cows which first calved during 1992 to 2013 in 496 herds of Iran. Three criteria for stayability, Survival up to 36, 48 and 54 months after first calving, were considered. Effect of production level, calving difficulty and season of first calving on stayability was quantified using a logistic regression model and a Probit function in JMP software. Five categories of milk yield was considered based on the average and variance of within herd-calving year of mature equivalent milk production for the production level to be taken into account. Average productive life was 1294.1 days and average survival to 36, 48 and 54 months after first calving were 0.55, 0.37 and 0.22, respectively. Dystocia decreased the probability of survival to 36 months of productive life between 4 to 14 percent (P < 0.01). Survival to 36 or 54 months after first calving was decreased by 28 percent in cows with sever calving difficulty. The chance of survival decreased between 24 to 36 percent in cows delivered by surgery. The probability of survival to 36 of productive life was increased up to 71 percent in high producing cows (P < 0.01). A similar pattern was observed between production level and other measures of stayability. There were no relationship between stayability and season of first calving.

In the livestock industry, the accurate genetic evaluation of economic traits pre-request the existence of homogeneity in residual variance, however; in practice, such different production levels and data recording at different times and environments are unlikely to result in the homogeneity of residual variance. The aim of this study was to investigate the genetic variance of the residual variance for Egg Weight and Age at Sexual Maturity of Azerbaijan native chickens. Data set consisted 8283 Egg Weight (EW) records and 6608 Age at Sexual Maturity (ASM) records related to 9 generations from the indigenous chicken breeding centers in the west Azerbaijan. To investigate the genetic variation of the residual variance was using the BLUPF90 software. Heritability of EW and ASM in a single trait model was estimated to be 0.288 (s.e. =0.022) and 0.355 (s.e =0.127), respectively. The heritability of residual variance of these traits was estimated 0.00484 (s.e. =0.004) and 0.00005 (s.e. =0.002), respectively, indicating the slight possibility of their genetic progression by direct genetic selection. The values of genetic correlations between traits and their residual variance were estimated to be -0.154 and -0.076, respectively, suggesting that genetic selection for EW enhancement would improve the genetic value for their uniformity, but about ASM, the expected results will not be very favorable if the trait is reduced. In conclusion, for accurate estimation of breeding value and ranking based on production traits in poultry, special attention to variance heterogeneity and necessary corrections is inevitable.

Basic color in horses, such as black and white, brown and chestnut ASIP and MC1R gene is affected. The relationship between color horse and purity the study of gene polymorphism Aguti put special attention. The purpose of this study was to evaluate the polymorphism in exon 2 gene Aguti population of Arabic horse in Khuzestan. In this study, PCR-RFLP method for the detection of different alleles of the Aguti gene in horses used. Bleed extension of the 45 head of horses in the city of Ahvaz, Dezful and Shush were collected. Polymerase chain reaction 101 bp fragment of exon 2 gene and gene-specific primers were used Aguti. 11 bp deletion in exon 2 gene ASIP (Aguti signaling protein) occurred because of the In / del (delete and Insertion) of the gene Aguti. Finally three band pattern AA, Aa, aa abundance 0.414, 0.457, 0.127, respectively. The allele frequencies of A and a 0.644 and 0.356 respectively.The results showed that this fragment of gene polymorphism and genotype AA, Aa, aa population was established. The results showed that there is Hardy-Weinberg dis equilibrium in the studied population.