Inheritance of cow durability for linear type traits

Area of Science:

• Animal breeding and genetics
• Dairy cattle evaluation

Background:

• Cow durability is crucial for dairy herd profitability.
• Linear type traits are used by the Holstein Association for appraisal.
• Understanding the inheritance of durability traits is essential for genetic improvement.

Purpose of the Study:

• To assess the inheritance of cow durability using linear type traits.
• To evaluate the change in type scores from first to second parity as a measure of durability.
• To determine the genetic correlations between first parity scores, score changes, and fat-corrected milk (FCM).

Main Methods:

• A multiple-trait mixed model was used to analyze final scores and 14 linear type traits.
• Cow durability was defined as the change in type scores from first to second parity.
• Analyses were conducted with and without requiring second parity scores.

Main Results:

• Heritabilities for score changes ranged from 0% to 6% when second parity scores were required.
• When second parity scores were not required, heritabilities for score changes were under 8%, except for udder depth (17%).
• Genetic correlations between FCM and score changes varied, with some positive correlations between first lactation scores and score changes.

Conclusions:

• Appraising cows after the first parity provides limited new information for ranking sires based on linear type traits.
• Heritability estimates for cow durability traits (score changes) are generally low.
• Genetic correlations suggest some relationships between type traits and production, but their utility for predicting durability changes needs further investigation.