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Effect of herd by sire interaction variance on genetic evaluations

Effect of herd by sire interaction variance on genetic evaluations. Introduction. For almost 40 years, U.S. genetic evaluations have accounted for genotype-environment interaction. The animal model includes a term for interaction effects of sire and herd .

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Effect of herd by sire interaction variance on genetic evaluations

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  1. Effect of herd by sire interaction variance on genetic evaluations

  2. Introduction • For almost 40 years, U.S. genetic evaluations have accounted for genotype-environment interaction. • The animal model includes a term for interaction effects of sire and herd. • Multiple daughters of a bull in the same herd have reduced weight.

  3. History of Herd x Sire Effect • Magnitude of H x S variance (c2) estimated to be 14% in 1968 (Plowman and McDaniel JDS 51:306) • More recent research estimated c2 to be as low as 2% (Dimov et al, 1995 JDS 78:939) • As a result, c2 lowered to 10% in 1997.

  4. Methods – November 2004 • Official November 2004 predicted transmitting abilities (PTA) for Holstein protein yield with c2 = 10% were compared with PTA computed with reduced c2 of 5% and 1%. • Repeatability of protein yield was held constant at 0.55 by increasing permanent environmental variance (p2) as c2 was decreased.

  5. Herd × Sire Variance: Maximum Daughters / Herd

  6. Herd x Sire Variance: Daughters / Herd 1% H×S 5% H×S 10% H×S

  7. Mean PTA protein (kg)

  8. Mean reliability protein (%)

  9. Correlation with official PTA(c2 = 10%)

  10. Summary:top 100 active AI bulls • With c2 reduced from 10 to 5% • 98 bulls had no change in PTA protein • 2 bulls had PTA changes of 1 kg • With c2 reduced from 10 to 1% • 92 bulls had no change in PTA protein • 8 bulls had changes of 1 or 2 kg

  11. Summary:cows born since 1997 • Of 2.3 million recent cows, PTA protein changed >4 kg for: • 20 cows when c2 = 5% • 1256 cows when c2 = 1% • Cows changing the most were sired by non-AI bulls with many daughters in one or a few herds.

  12. Implementation – May 2005 • H x S variance for yield traits was reduced from 10% to 7% of total. • Repeatability for yield traits was held constant at 55% by increasing permanent environmental variance (p2) from 15% to 18% of total. • For DPR, c2 was 1%, now is 4%.

  13. May 2005 Herd × Sire Variances: Maximum Daughters / Herd

  14. Herd × Sire Variance:Daughters / Herd 5% H×S 7% H×S 10% H×S

  15. Changes from reducing c2 from 10% to 7% • 99 of the top 100 active AI bulls changed less than 1 kg PTA protein, only 1 bull changed 1 kg. • 597 cows changed >4 kg protein out of 2.3 million recent cows. • .999 correlation for both bulls and cows.

  16. Foreign experience • Great Britain had herd-by-sire interaction in lactation model but not in test day model research. • Several single herd bulls rose towards the top, so a H x S effect was added back into the new test day model in May.

  17. Conclusions • Reduction of c2 from 10% to 7% will facilitate AI companies obtaining more daughters per herd in large cooperating herds. • The H x S interaction protects against chance or fraud when sampling is limited to few herds.

  18. Further study ideas • Use of a relationship matrix among herd by sire or herd by animal interactions could be helpful but was not tested in the current studies. • Interactions of sire or animal with region, climate, or country could be useful in the future.

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