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Genetic Evaluation of A ge at First Calving

Genetic Evaluation of A ge at First Calving. Data. First calving from January 1, 1997 to present Calving ages between 540 d (18 mo) and 1095 d (36 mo) The cow’s sire had to be ≥ 5 years old 8,234,537 HO first calvings 521,806 JE first calvings. Model. y = hys + a + e

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Genetic Evaluation of A ge at First Calving

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  1. Genetic Evaluation of Age at First Calving

  2. Data • First calving from January 1, 1997 to present • Calving ages between 540 d (18 mo) and 1095 d (36 mo) • The cow’s sire had to be ≥ 5 years old • 8,234,537 HO first calvings • 521,806 JE first calvings

  3. Model y = hys + a + e y = age at first calving in days hys = fixed effect of herd-year-season of birth a = random additive genetic effect e = random residual error

  4. Summary Statistics ― Cows currently milking

  5. Summary Statistics ― Active Bulls

  6. Correlations Correlations among PTA for bulls with reliabilities of AFC ≥ 0.90.

  7. Correlations (continued) Correlations among PTA for bulls with reliabilities of AFC ≥ 0.90.

  8. Heritability of Fertility Traits

  9. Genetic Trend for Age at First Calving

  10. Active HO Bulls With Reliability ≥ 90%

  11. Active Jersey Bulls With Reliability ≥ 90%

  12. Conclusions • Genetic differences exist among bulls • Heritability higher than conception rate and lower than daughter pregnancy rate • Heifers that are older at AFC have lower yield, lower longevity, and lower lifetime profit

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