Genome-Wide Association Studies for Selected Reproductive traits in Iranian Holstein cattle

Document Type : Research Paper

Authors

• Mostafa Sdeghi
• Narges Maddahi
• Ardeshir Nejati-Javaremi
• Seyed Reza Miraei-Ashtiani
• Ali Jalil Sarghale

Department of Animal Science, Faculty of Agriculture and Natural Resources, University of Tehran , University of Tehran, Tehran, Iran

Abstract

Keywords

• Days open
• Day to first insemination
• interval from first to last insemination

Main Subjects

• Animal Breeding and Genetics

Extended Abstract

Introduction

The main goal in dairy industry is to achieve maximum profitability and the goal of animal breeding is to increase the economic efficiency of the system. Today, with vast advances in the field of molecular methods and the identification of a large number of genetic markers, including Single Nucleotide Polymorphic (SNP) markers, livestock breeders can investigate and find QTLs affecting these traits with higher accuracy. Genome-Wide Association Studies (GWAS) as a procedure might be used to find loci correlated with reproductive traits in Iranian Holstein cows.

Materials and methods

For this purpose, the hair samples of 150 cattle, born between 2012-2014 in one of the cattle farms of Ferdous Pars company, were used for genotyping based on 30.108 SNPs chip. The data were analyzed using the least square variance analysis method using the GLM. GWAS analysis was performed after controlling the quality of the data.

Results and Discussion

The results showed that 2 SNPs associated with the Days to first services and 12 SNPs associated with Interval from First to Last Insemination (p<0.04). 11 SNPs in the Days Open and 5 SNPs for the Number of Services per Conception showed significant correlation (p<0.04) with these traits. In the Post-GWAS stage, some Quantitative Trait Loci and various genes were identified that affected or controlled the traits. QTLs, were observed near the SNPs related to IFL, DO and NSPC traits, they are related to body weight traits. So the heifer must have reached optimal weight at insemination time. In BTA20, near the SNP association on day to the first insemination, 1 QTL was associated with the stillbirth trait and 1 QTL with high correlation Rump angle trait was observed. Stillbirth and suitable Rump angle can be effective in returning the uterus to normal conditions and improving reproductive traits. Several QTLs affected on mamma structure traits (Udder width, Udder attachment, Udder height), milk production (Milk yield, Milk fat percentage) were observed in BTA20 and BTA27 in the vicinity of SNPs related to DFS traits. So in the near the SNPs identified, there are most QTLs that are correlated with milk production, reproduction, physical index and health traits. Out of the related genes, RHO gene on chromosome 28 is effected on ovulation, the length of the reproductive cycle and fertility. CAMK2D gene in chromosome 6 was related to the number of insemination per conception and fertility techniques. In BTA21, GABRB3 gene was related to the beginning and end of lactation in cows, and lactation is one of the effective traits for the number of inseminations per conception. NUF2 gene on chromosome 3 that affects the development of the oocyte, ANAPC1 gene on chromosome 11, which affects sperm motility, PITX2 gene in chromosome 6, affected on milk production, ELOVL6 gene in chromosome 6 affects increases body weight, CAMK2D gene in chromosome 6 is effective artificial insemination number trait and fertility techniques.

Conclusion

it can be concluded that chromosomes 3, 6 and 11 have SNPs that are more strongly related to reproductive traits.