Genome-wide association study associated with first lambing age and lambing interval traits in Zandi sheep

First lambing age and lambing interval are among the most important reproductive traits affecting profitability of sheep breeding systems. The present study aimed to conduct a genome wide association studies (GWAS) for identifying the loci associated with first lambing age and lambing interval in Zandi native sheep using the 50K arrays.

For this purpose, phenotypes records and genotypic data related to first lambing age and lambing interval were obtained from 96 Zandi sheep. Different steps of quality control and identification of independent SNP markers were performed by PLINK software. After quality control, 94 animals and 36070 markers were identified for further analysis. Genome wide association study was performed with reproductive traits using GEMMA software. Using the Genome Data Viewer software from NCBI database based on last assembly (ARS-UI_Ramb_v2.0) the SNP were assigned to genes if they were within the genomic sequence of the gene or within a flanking region of 300 kb up- and downstream of the gene. Finally, from online bioinformatics databases for the assignment of the genes to functional categories, DAVID and PANTHER databases were used.

In this research, seven SNP markers on chromosomes 1, 2, 3, 6, 11 and 23 were identified. Also, we identified different sets of candidate genes related to reproductive traits: UMPS, ITGB, SMARCAL1, APAF1, UGT8 and ST8SIA5 in Zandi sheep. Some of the found genes, are consistent with some of the previous studies related to reproductive traits. Some of the genes were found are consistent with some previous studies and to be involved biological pathways related to fertilization, ovulation rate, estrogen biosynthesis, conception rate, skeletal muscle development, early development of the fetus and puberty.

The results of our research can be used to understand the genetic mechanism controlling reproductive traits and considering, this study supported previous results from GWAS of reproductive traits, also revealed additional regions, using these findings could potentially be useful for genetic selection in sheep for age at first lambing.