Transcriptomic and Meat Quality Differences in Longissimus Dorsi Muscle of Surgically Castrated Three-Year-Old Kazakh Horses.

Overview

• This study investigates how surgical castration affects the gene expression and meat quality of the longissimus dorsi muscle in three-year-old Kazakh horses, comparing stallions and geldings.

Objective and Background

• The Kazakh horse is valued for both milk and meat production.
• Understanding the biological effects of surgical castration on muscle tissue, especially gene expression related to muscle growth and meat quality, is important for optimizing production.
• Prior to this study, the impact of castration on muscle transcriptomics in Kazakh horses was not well understood.

Experimental Design

• Sample Collection:
  • Longissimus dorsi muscle (LDM) samples taken from 6 stallions (intact males, W group) and 6 geldings (castrated males, S group), all three years old.
• Comparative Analyses:
  • Meat quality parameters such as color, pH, cooking loss, and shear force were measured.
  • Histological (microscopic) examination of muscle tissue focused on muscle fiber cross-sectional area.
  • Transcriptomic profiling using gene expression analysis to identify differentially expressed genes (DEGs) linked to castration effects.

Key Findings: Meat Quality and Histology

• Meat Color and pH:
  • No significant differences were observed between stallions and geldings in meat color or pH parameters.
• Cooking Loss and Shear Force:
  • Both parameters were significantly reduced in the castrated horses (geldings), indicating potentially more tender meat with less moisture loss during cooking.
• Muscle Fiber Characteristics:
  • The cross-sectional area of muscle fibers was notably smaller in geldings than stallions, suggesting muscle fiber atrophy or reduced muscle growth following castration.

Transcriptomic Analysis and Biological Insights

• Gene Expression:
  • Identified 848 differentially expressed genes (DEGs) between stallions and geldings.
  • Of these, 415 genes were upregulated and 433 genes were downregulated in response to castration.
• Pathway Enrichment:
  • DEGs were primarily enriched in biological pathways related to actin cytoskeleton regulation, which plays a key role in muscle structure and function.
• Core Candidate Genes:
  • Eleven core genes were highlighted as important regulators potentially mediating muscle changes due to castration.
  • Examples include MYL2 and MYL3, which code for myosin light chain proteins involved in muscle contraction and growth, and TNNI1, a gene encoding a muscle protein involved in contraction regulation.

Implications and Conclusions

• Surgical castration induces significant changes at the molecular level in horse muscle, notably affecting gene networks related to muscle fiber structure and function.
• These molecular changes correspond to physical alterations such as smaller muscle fibers and improved meat tenderness without affecting meat color or pH.
• The identification of key genes and pathways provides potential targets for future efforts aimed at enhancing meat quality and understanding muscle development in horses.
• This study advances knowledge on how castration influences muscle biology in the Kazakh horse breed, with possible applications in animal husbandry and meat production optimization.