Genome-wide association analysis in Italian Simmental cows for lactation curve traits using a low-density (7K) SNP...

Area of Science:

• Animal Genetics
• Genomics
• Dairy Science

Background:

• High-throughput cow genotyping enables genome-wide association studies (GWAS).
• Utilizing directly recorded phenotypes and multiple records per animal enhances GWAS potential.
• Low-density genotyping offers a cost-effective approach for large-scale genetic studies.

Purpose of the Study:

• To conduct a genome-wide association study (GWAS) on lactation curve traits in Italian Simmental cows.
• To identify genetic markers associated with milk yield, fat, protein percentages, and somatic cell score.
• To explore candidate genes influencing dairy production traits using low-density genotyping data.

Main Methods:

• A GWAS was performed on 337 Italian Simmental cows genotyped with a 7K low-density BeadChip.
• Phenotypes were derived from principal component scores of test-day lactation curve records.
• Data were analyzed using a mixed linear model accounting for various fixed and random effects.

Main Results:

• Statistically significant markers were associated with the average lactation curve level for milk yield, fat, and protein percentages, and somatic cell score.
• No significant markers were found for the lactation curve shape component.
• Several suggestive candidate genes, including DGAT1, were identified, with roles in metabolism, immunity, and development.

Conclusions:

• Low-density genotyped females are valuable for GWAS, even for complex traits.
• The study identified genetic associations with the average lactation performance, offering insights for breeding programs.
• Further research can leverage these findings for novel trait discovery and genetic improvement in dairy cattle.