Changes to evaluation system (December 2015)

Genetic variance for Jersey type traits

By Jan Wright

The genetic SD of several conformation traits will decrease by about 5% in Dec 2015 for Jerseys because an array overflow had affected the iterative herd variance adjustments for that breed only. The program bug had caused almost no change in PTA rankings, only the small changes in SD. Formulas for net merit will not be affected. New and previous SD for each trait are compared below.

Changes in Jersey genetic standard deviation for December 2015


New Genetic SD

Previous Genetic SD

Final score









Dairy Form



Foot angle



Rear leg (side view)



Rump angle



Rump width



Fore udder attachment



Rear udder height



Rear udder width



Udder depth



Udder cleft



Front teat placement



Teat length




Unknown parent group definitions

By Paul VanRaden, Jay Megonigal, Curt Van Tassell, and Mel Tooker

The automated system to assign unknown parent groups was revised to improve stability and convergence with data updates. The new group definitions are applied to yield traits, productive life (PL), somatic cell score (SCS), daughter pregnancy rate (DPR), heifer conception rate (HCR), and cow conception rate (CCR). Since Dec 2014 the animal model includes pedigrees for young animals, but too few cows with data were included in the most recent groups, so those groups will be combined. Genomic PTAs should change little because most parent averages were recomputed as needed, but parent averages for young, non-genotyped animals with missing sires or dams are the most affected.

Additional breeds from Interbull

By Paul VanRaden and Gary Fok

Bulls with breed codes MO (Montbeliard), NO (Normande), SM (Simmental), and Fleckvieh (FL) will be on the Simmental scale in the Interbull multitrait across-country evaluation (MACE) instead of the Holstein scale. As a result, about 7,000 foreign MO, NO, SM, and FL bulls will be converted by MACE onto the U.S. Holstein base. PTAs for bulls of those breeds will include the expected heterosis when mated to Holstein cows and be comparable to Holstein evaluations, as previously. The MACE system does not exchange fertility PTAs for those breeds, and conformation traits on U.S. scale are not available, so Holstein birth year averages are substituted for the missing traits. Reliability improves for the foreign bulls with U.S. daughters because of more pedigree information and additional ancestor PTAs from MACE for the additional breeds.

Editing changes for sire conception rate

By Duane Norman

An edit previously used in the calculation of sire conception rate (SCR) was if the expected calving date (last breeding date plus 280 days) was 21 or more days greater than the actual subsequent calving date, the breeding was deleted because it was assumed the date was recorded wrong or the service was to a cow already pregnant. However, the average heat cycle is 21 days but individual heats can vary by a few days.  According to Ray Nebel (personal communication), “the industry uses 18 to 24 as the normal estrous interval.” Therefore CDCB is changing this edit from 21 to 17 days to allow for the variation expected in the heat cycle.  The gestation period previously used in editing was 280 days; this is being modified to use the gestation period appropriate for the specific breed addressed, i.e., changed to the breed average in the literature (AY, 282; BS, 288; GU, 286; HO, 279; JE, 280; MS, 281; and WW, 280 days). These breed averages were obtained from national data from 1999 through 2006 (Norman et al., J. Dairy Sci. 92(5):2259–2269, 2009).

Another edit previously programmed in SCR was “A herd needed a conception rate between 10 and 90% over the entire 4 year period or the inseminations from the herd were not used” (Kuhn and Hutchison, J. Dairy Sci. 91(6):2481–2269, 2008 and Kuhn et al., J. Dairy Sci. 91(7):2823–2835, 2008). This range seems extreme so we are lowering this on the top to 75% to make it more in line with other procedures being used.

The number of age categories for SCR will be reduced in the Jersey breed to make them resemble more closely a smooth biological curve.