Changes to CDCB Evaluation System (August 2022)

Disease resistance (health) traits for Brown Swiss animals

K. Gaddis, R. Mota and E.L. Nicolazzi

Beginning August 9, Brown Swiss animals will receive CDCB evaluations for disease resistance for six traits, including resistance to milk fever (MFEV), displaced abomasum (DA), ketosis (KETO), mastitis (MAST), metritis (METR) and retained placenta (RETP). These new traits will be incorporated into Net Merit $ (NM$) for Brown Swiss animals, through the sub-index Health $ with the total weight of the six health traits approximately 2%.

These CDCB health evaluations have been available for Holstein animals since April 2018 and Jersey animals since April 2020. Recent investigations indicated that expanding the evaluations to include Brown Swiss was feasible.

The same pipelines and process as those currently used for CDCB Holstein and Jersey health evaluations were expanded to include Brown Swiss data. Phenotypes are pre-adjusted for unequal variance prior to evaluation. Traditional Predicted Transmitting Abilities (PTAs) are estimated using a univariate BLUP repeatability animal model accounting for year-season, age-parity, herd-year, and permanent environmental effects, as well as a regression on both inbreeding and heterosis. Resulting PTAs are presented as percentage points above or below the breed’s average resistance with more positive values being favorable.

Specifics about the disease resistance PTAs for Brown Swiss:

• Total number of available Brown Swiss phenotypic records by trait ranged from 7,592 for ketosis to 17,391 for mastitis, as of April 2022.
• Overall incidence ranged from 0.7% for displaced abomasum up to 13.7% for mastitis, similar to incidences in both Holstein and Jersey.
• Heritabilities were assumed to be equivalent to those in Holstein, ranging from 0.6 to 3.1%.
• Average traditional reliabilities for bulls born since 2000 with ≥ 90% net merit (NM$) reliability ranged from 17 to 55%, depending on trait.
• Average genomic reliabilities for those bulls ranged from 29 to 57%.
• Maximum PTA reliability was 89% for mastitis.
• Among traits such as livability, productive life, and somatic cell score, PTA correlations in young bulls were favorable at 0.74, 0.53, and -0.13, respectively, with the sum of all health traits (Health $).

Genomic evaluations for Rear Leg Rear View (RLR) on Guernsey

R. Mota and E.L. Nicolazzi

Effective in August 2022 for Guernseys, the conformation trait Rear Leg Rear View (RLR), previously only receiving traditional PTAs, will receive genomic PTAs. RLR accounts for nearly one-third of Feet and Legs Composite (FLC), so variation in the FLC PTA and reliability are expected for Guernsey animals. FLC is also included in  Net Merit (NM$); however, minimal impact on NM$ is expected. The relative weight of FLC on NM$ is 5%, and typically a variation of $1 to $2 (at most) would be observed within NM$ due to changes in this trait.

Holstein Feet and Leg Composite (FLC) and Udder Composite (UDC) update

E.L. Nicolazzi and P. VanRaden

Feet and Legs Composite (FLC) and Udder Composite (UDC) have been updated to match HAUSA’s formula in https://www.holsteinusa.com/genetic_evaluations/ss_linear.html. FLC weights were slightly different from previously used values, and the standard deviation was updated. As for UDC only the centering of the composite was corrected to be 0. The impact of these changes on NM$ will be minimal and in most cases lower than $1 to $2 maximum variation.

Exclusion of 900 series IDs from female domestic percentile calculation

E.L. Nicolazzi and G. Fok

The procedure that calculates the female domestic percentile was modified to exclude IDs with manufacturer’s code 9XX (aka 900 series) from the group of “domestic” animals. This business rule change will impact the content and percentile values included in the format 105 distributed to the public (elite and top 5%) and the private 105 files distributed to breed associations and dairy record processing centers. It will also impact the female percentile tables published around release day.

Release day updates (information related to content of distributed files)

E.L. Nicolazzi

• A modification to the business rules applied to file format 40 (type evaluations for males) was requested by NAAB and agreed by the Jersey, Ayrshire, Guernsey and Brown Swiss associations. The change is related to the inclusion of all (publishable) genomic-only bulls for the NAAB format 40 file and the exclusion of genomic type evaluations for animals that do not meet the (genomic) publication requirements. All animals will still receive their traditional type evaluations, if available. Furthermore, body depth genomic evaluations will now be reported on publishable animals in both male and female files on Ayrshire, Brown Swiss and Guernsey (they had been previously receiving traditional values only).
• A recent change in an internal procedure was implemented to exclude foreign evaluations for animals with 100% of their daughters in USA. This (internal) change has no impact on evaluations. However, an unintended consequence was that Feed Saved daughters/herds for USA-only bulls will be blank in the August 38alloff file. CDCB will work on a solution to this unintended event to be implemented in the December run.