Genetic correlation among linear type traits and productive traits in Girolando cattle

Area of Science:

• Animal Breeding and Genetics
• Dairy Science
• Quantitative Genetics

Background:

• Linear conformation traits are crucial for dairy cow soundness and function.
• Productive traits, particularly milk yield, are key to dairy profitability.
• Balancing productivity and longevity is essential for sustainable dairy breeding.

Purpose of the Study:

• To estimate genetic parameters among linear, productive, and longevity traits in dairy cows.
• To evaluate the effectiveness of pre-established and optimized selection indices.
• To identify optimal strategies for improving milk yield and functional longevity simultaneously.

Main Methods:

• Bivariate genetic models were used to estimate heritability and genetic correlations.
• Direct and correlated selection responses were assessed using two index approaches.
• Girolando breeding program data were analyzed for linear traits, milk yield, and longevity.

Main Results:

• Heritability estimates varied for linear (0.01-0.33) and productive traits (0.04-0.13).
• Strong genetic correlations were observed among linear traits (-0.73 to 0.97) and between linear and productive traits (-0.50 to 0.69).
• Udder traits, especially Fore Udder Attachment (FUA), showed strong positive associations with longevity; optimized indices outperformed pre-established ones.

Conclusions:

• Selection indices significantly improve dairy cow productivity and functional longevity compared to direct selection.
• Optimized, data-driven indices offer superior performance for balancing milk yield and longevity.
• Focusing on key traits within optimized indices provides efficient and parsimonious breeding strategies.