The August 2020 Hoard’s Dairyman Bull List is ready for download.

As readers recall, April’s bull list had a significantly different look due to the five-year base change that shifts all trait evaluation due to continued genetic progress. This August, Holsteins evaluations shifted a bit due to “A reset on calving ease.”

In preparation for this genetic evaluation, the Council on Dairy Cattle Breeding (CDCB) adjusted the phenotypic base to match the observed incidence rates for calving ease. As a result, the predicted transmitting abilities (PTAs) for those traits dropped as well.

That’s a sign of the improvement in the world of genetic evaluations.

Indexes slipped slightly

Due to the change in calving traits and the Net Merit (NM$) formula, values among Holsteins dropped slightly this August. Among the top genomic bulls that have calculations based solely on DNA tests, NM$ fell by $26. Among top proven bulls, NM$ dropped a little less . . . $21 NM$.

Holsteins TPI (Total Performance Index) remained steady.

“We factored the change in calving traits into our TPI formula, so the NM$ change does not impact the TPI values,” said Tom Lawlor, executive director of research and development at Holstein Association USA.

Brown Swiss is the only other dairy breed with calving ease evaluations. There was little impact in that breed.

Inbreeding considered, too

Overall, the Council on Dairy Cattle Breeding improved upon filling in the missing pedigree data on animals. As a result, the new inbreeding values will be slightly higher as more is known about the collective dairy cattle population.

In addition, CDCB is using a more current population of animals to estimate Expected Future Inbreeding (EFI). As a result, EFI values may be slightly higher.

These changes will result in a small reduction in PTAs.

For example, among top genomic bulls, protein and fat PTAs dropped about 3 pounds and Daughter Pregnancy Rate (DPR) by -0.25. That caused NM$ to slip by $19. Among top proven bulls, protein and fat PTAs fell about 2.5 pounds and Daughter Pregnancy Rate (DPR) receded by -0.31. That cause NM$ to slip by $15 among proven Holstein bulls.

When combined, both the inbreeding change and the NM$ formula change for calving traits will cause:

• The NM$ for top genomic bulls to drop by $45
• The NM$ for top proven bulls to drop by $36

This change in inbreeding also will caused a reduction in values for the respective breed indexes.

Again, click here to download the August 2020 Hoard’s Dairyman Bull List.