![]() Results from the breeding soundness examination and repeated observations of semen quality complement the fertility evaluation for each bull. Semen from individual bulls is used for thousands of artificial inseminations for which the fertilization success is monitored. These results could aid in the development of novel genomic tools that allow early detection and culling of subfertile bull calves.Ĭattle are ideally suited to investigate the genetics of male fertility. Genes affected by these candidate causal variants include AK9, TTLL9, TCHP, and FOXN4. Notably, some of these variants were classified as strong candidate causal variants, i.e., mutations with deleterious effects located on genes exclusively/highly expressed in testis. We identified a set of nonsense mutations, missense mutations, and frameshift variants carried by low-fertility bulls. The sequencing depth per pool varied from 39× to 51×. The DNA-sequencing analysis included reads quality control (using FastQC), genome alignment (using BWA and ARS-UCD1.2), variant calling (using GATK) and variant annotation (using Ensembl). ![]() For each genomic region, two DNA pools were constructed from Here, we aimed to identify candidate causal variants responsible for this variation using targeted sequencing (10 Mb per region). Each of these regions explained about 5-8% of the observed differences in sire conception rate between Holstein bulls. We have previously identified five genomic regions, located on BTA8 (72.2 Mb), BTA9 (43.7 Mb), BTA13 (60.2 Mb), BTA17 (63.3 Mb), and BTA27 (34.7 Mb), that show large dominance effects on bull fertility. Since the semen from a single bull can be used to inseminate hundreds of cows, one subfertile bull could have a major impact on herd reproductive efficiency. This study represents the foundation for the development of novel tools that will allow dairy producers, breeders, and artificial insemination companies to make enhanced management and selection decisions on Brown Swiss male fertility.īull fertility is a key factor for successful reproductive performance in dairy cattle. Improving reproduction performance is one of the major challenges of the dairy industry worldwide, and for this, it is essential to have accurate predictions of service sire fertility. We also showed that the prediction of bull fertility is feasible as our cross-validation analyses achieved predictive correlations equal to 0.30 for sire conception rate. Interestingly, our analyses revealed that there is a substantial variation in conception rate among Brown Swiss bulls, with more than 20% conception rate difference between high-fertility and low-fertility bulls. Model predictive ability was evaluated using 10-fold cross-validation with 10 replicates. We then estimated sire conception rate using only factors related to the bull. We first evaluated cow pregnancy success, including factors related to the bull under evaluation, such as bull age, bull inbreeding, and AI organization, and factors associated with the cow that receives the dose of semen, including herd-year-season, cow age, parity, and milk yield. The data set included a total of 397,926 breeding records from 1,228 bulls and 129,858 lactating cows between first and fifth lactation from 2000 to 2019. The main objective of this study was to investigate bull fertility in the Italian Brown Swiss dairy cattle population using confirmed pregnancy records. Alternatively, bull fertility can be directly evaluated using cow field data. Another group with apparent large importance was the various traits related to health and resistance to parasites, which is well in line with the sturdy nature of this breed.ĭairy bull fertility is traditionally evaluated using semen production and quality traits however, these attributes explain only part of the differences observed in fertility among bulls. Overall, we have identified selection signatures with quantitative trait loci (QTL) and genes pointing towards all three production purposes of the Valachian sheep, milk, meat, and wool, including their quality characteristics. ![]() The selection signatures between breeds were assessed based on variance in linkage disequilibrium. The selection signatures within breeds were identified based on the top 1% of most homozygous regions within the breed, the so-called ROH islands. The inbreeding levels were assessed with runs of homozygosity (ROH). A total of 97 sheep (18 male and 79 female) from the Original Valachian, and 69 sheep (25 male and 44 female) from the Improved Valachian populations were genotyped using the GeneSeek GGP Ovine 50 K chip. As they are an important animal genetic resource within the country, but with decreasing population size, our aim is to identify potentially valuable genomic regions. This study explored the genomic diversity and selection signatures in two Slovakian national breeds, the Original Valachian and the Improved Valachian sheep.
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