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Genetic Evaluation of A ge at First Calving

Study evaluating the age at first calving data from January 1, 1997, to present, involving cows with calving ages between 540 and 1105 days. The analysis required the cow's sire to be at least 5 years old, with 8,193,513 first calvings examined using a complex model. The model equation includes fixed effects of herd-year-season of birth, random additive genetic effect, and random residual error. Summary statistics are provided for cows currently milking and active bulls, along with variance component estimates. Heritability values are HO = 0.027 and JE = 0.028. Genetic trends are identified for low and high active HO bulls, as well as low and high active JE bulls. Correlation analyses are conducted, and the study sheds light on genetic trends in age at first calving.

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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 and 1105 days • The cows sire had to be at least 5 years old • 8,193,513 first calvings

  3. Model y = hys + a + e y = age at first calving 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

  7. Correlations (Continued)

  8. Variance Component Estimates HO Heritability = 0.027 JE Heritability = 0.028

  9. Genetic Trend

  10. Genetic Trend

  11. Low Active HO Bulls

  12. High Active HO Bulls

  13. High and Low Active HO Bulls with > 90% rel

  14. Low Active JE Bulls

  15. High Active JE Bulls

  16. High and Low Active JE Bulls with > 90% rel

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