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

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

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

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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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