CDCB Health Traits Extend to Brown Swiss

The 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 six CDCB health traits have been available for Holsteins since April 2018 and Jerseys since April 2020. After a recent feasibility analysis, the same pipelines and processes used for Holstein and Jersey health traits were expanded to include Brown Swiss. The resulting PTAs are presented as percentage points above or below the breed’s average resistance with more positive values being favorable.

About the CDCB health traits for Brown Swiss:

• Total number of available Brown Swiss phenotypic records by trait ranged from 7,592 for ketosis to 17,391 for mastitis (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 $).

What’s New for August Evaluations?

CDCB announces three changes with the August evaluations, in addition to the Brown Swiss health traits.

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

• Genomic PTAs will be available for this conformation trait that previously received only traditional PTAs. RLR accounts for nearly one-third of Feet and Legs Composite (FLC) in Guernseys, so variation is expected in the FLC PTA and reliability. Minimal impact on NM$ is expected. The relative weight of FLC on NM$ is 5%, and typically a maximum variation of $1 to $2 would be observed within NM$ due to changes in this trait.

Holstein: Updates to Feet and Legs, Udder Composites

• Feet and Legs Composite (FLC) and Udder Composite (UDC) have been updated to precisely match HAUSA’s formula. FLC weights were slightly different from previously-used values, and the standard deviation was updated. In UDC, the centering of the composite was corrected to be 0. The impact of these changes on NM$ will be minimal (lower than $1 to $2 maximum variation in most cases).

Exclusion of 900 series IDs from female domestic percentile calculation

• 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 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.

Refer here for official explanation on the CDCB site.