Meta-analysis: Finding Markers Associated With Reproductive Performance Across Cattle Breeds

Single nucleotide polymorphisms (SNP) associated with reproductive performance have two applications: 1) selection tools can be developed to drive genetic gain and 2) gene discovery can be used to better understand reproductive physiology. The difficulty and cost of measuring reproductive traits results in a paucity of data, limiting the ability to validate SNP associations. To overcome this issue, we pooled data from 4 genome-wide association studies (50K SNP array) involving 3 heifer populations (i.e. Brahman, Tropical Composite and Brangus) and one population of Brahman bulls. Measurements included 20 growth and reproduction traits. We found 361 SNP associated (P < 0.001) with 2 or more traits and > 50% of these mapped to chromosomes 14 and X. SNP between 24.7 and 28.3 Mb of BTA 14 were associated with IGF1 serum levels across gender and breeds. This region was also associated with heifer age at puberty, post-partum anoestrus interval in cows and scrotal circumference (SC) in bulls. On chromosome X, SNP between 0.9 and 5.8 Mb were associated with percentage of normal sperm, SC, Brahman age at puberty and IGF1 in Tropical Composite heifers; and SNP between 80 and 92 Mb were associated with SC in Brahman, post-partum anoestrus interval in Tropical Composite and heifer pregnancy rate in Brangus. Other regions associated with reproduction were at BTA 3, 5 and 8. Collectively these regions harbor 11% of the SNP associated to 2 or more reproductive traits. SNP associated across populations signal regions of interest for building genomic selection tools that could work across breeds. Targeting these regions should bring new insight regarding genes regulating reproductive performance.