Genetic analysis and quantitative trait loci detection of udder traits in Jersey cattle

The udder is a crucial trait in dairy cattle breeding, influencing both milk production and quality. Understanding the genetic basis of udder traits is essential for improving breeding strategies. This study aims to estimate the genetic parameters of key udder traits in Jersey cattle, assess their impact on lactation performance, and identify quantitative trait loci associated with these traits.

The study was conducted on 1,631 first-lactation Jersey cows, evaluating eight udder traits: udder depth, central ligament, fore udder attachment, front teat position, teat length, rear udder height, rear udder width, and rear teat placement. Heritability estimates for these traits ranged from low to moderate, with udder depth showing the highest heritability at 0.291 ± 0.061, while fore udder attachment had the lowest at 0.080 ± 0.040. The udder traits significantly influenced lactation performance, including milk yield, milk fat percentage, milk protein percentage, somatic cell score, and milk urea nitrogen. All eight udder traits exhibited significant phenotypic correlations and certain genetic correlations. The highest positive genetic correlation was observed between rear teat position and front teat position, while the highest negative genetic correlation was found between teat length and rear teat position. Genome-wide association studies identified 39 significant single nucleotide polymorphisms, and transcriptome-wide association studies, along with gene ontology enrichment analysis, revealed candidate genes such as NFATC3, OSTF1, ENPP4, PRKCA, EFHB, TAS2R46, and SLC35G1, which may play a role in regulating udder traits.

This study provides valuable insights into the genetic architecture of udder traits in Jersey cattle. The identified genetic markers and candidate genes enhance our understanding of the factors influencing udder development and lactation performance. These findings lay the groundwork for future molecular research aimed at improving udder traits and breeding strategies in dairy cattle.