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Enhancing Productive Life in Dairy Cows: Genetic Trends and Lactation Curves

This study examines factors predicting Productive Life (PL) in dairy cows, focusing on updating PL for censored cows and refining trait definitions using lactation curves. The research includes data from over 1 million Holsteins born from 1994 to 1997, exploring PL heritabilities, correlations, and calf value goals. Results indicate changing PL parameters over time and suggest extending lactation length limits or utilizing lactation curve credits.

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Enhancing Productive Life in Dairy Cows: Genetic Trends and Lactation Curves

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  1. Productive Life Including All Lactations, Longer Lactations, and Calf Value

  2. Goals • Allow credit for longer lactations in productive life (PL) Tsuruta et al, 2005, JDS 88:1156 • Update factors that predict PL for cows still alive (censored cows) • Improve the PL trait definition by considering lactation curves

  3. Data Sets • Variance estimation from AIPL data • 1,098,329 Holsteins born 199497 • 5109 sires with relationship matrix • 10 mo, 12 mo, or unlimited length • 2-mo calf value also considered • Data censored at 36 to 84 mo of age • Herds with complete lactations from DRMS history file

  4. PL Heritabilities and Correlations

  5. Correlation of PL with Protein Phenotypic = .33 1993, Genetic = .46 JDS 76:2758

  6. Early Measures of PL10-mo limit

  7. Distribution of Months Until Culling1st-parity cows

  8. 35 30 25 20 15 10 5 0 Lactation Curveyield = 5.9 + 9.5e[.059(1  e.047*t)/.047  .0018*t]

  9. First- and Later-Parity Shapes

  10. Current PL Credits 140 120 100 80 Credit (%) 60 40 1 2 3 20 0 0 1 2 3 4 5 Years

  11. Possible PL Credits 140 120 100 80 Credit (%) 60 40 1 2 3 20 0 0 1 2 3 4 5 Years

  12. Proposed PL Credits

  13. Conclusions • PL parameters are changing across time • Phenotypic correlations are fairly stable • Genetic correlations have declined rapidly • PL at 36-mo censoring has less info • Heritability is lower than 1993 estimate • Genetic correlation with final PL = .87 (vs .92) • Can increase lactation length limit in PL to 12 mo or use lactation curve credits

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