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Abstract
BackgroundFertility is considered an important economic trait in dairy cattle. Most studies have investigated cow fertility while bull fertility has received much less consideration. The main objective of this study was to perform a comprehensive genomic analysis in order to unravel the genomic architecture underlying sire fertility in Holstein dairy cattle. The analysis included the application of alternative genome-wide association mapping approaches and the subsequent use of diverse gene set enrichment tools.ResultsThe association analyses identified at least eight genomic regions strongly associated with bull fertility. Most of these regions harbor genes, such as KAT8, CKB, TDRD9 and IGF1R, with functions related to sperm biology, including sperm development, motility and sperm-egg interaction. Moreover, the gene set analyses revealed many significant functional terms, including fertilization, sperm motility, calcium channel regulation, and SNARE proteins. Most of these terms are directly implicated in sperm physiology and male fertility.ConclusionsThis study contributes to the identification of genetic variants and biological processes underlying sire fertility. These findings can provide opportunities for improving bull fertility via marker-assisted selection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0454-6) contains supplementary material, which is available to authorized users.
Highlights
Fertility is considered an important economic trait in dairy cattle
Two complementary genome-wide association approaches, single-step genomic best linear unbiased prediction (ssGBLUP) and classical genome-wide association study (cGWAS), were performed in order to identify genomic regions and candidate genes associated with Sire Conception Rate (ĥ2 = 0.32)
It is worth noting that these two methods yielded very similar results. Both approaches have identified candidate genomic regions in BTA21 and BTA25 that may be underlying the genetic variation in dairy sire fertility
Summary
Fertility is considered an important economic trait in dairy cattle. The main objective of this study was to perform a comprehensive genomic analysis in order to unravel the genomic architecture underlying sire fertility in Holstein dairy cattle. Fertilization rate in highproducing dairy cows is about 75 %, and only 65 % of the fertilized eggs are considered viable at 5–6 days post-fertilization [5]. Many reasons may account for this decline in reproductive performance, including physiological, nutritional, environmental, and genetic factors. In this sense, several studies have recognized that there is substantial genetic variation underlying reproductive success in dairy cattle [6, 7]
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