The April 2020 dairy sire summaries will include many updates and changes. Learn more about the coming changes below.
2020 genetic base change
In genetic evaluations, information on dairy cows born in a specific year is used to calculate a breed’s genetic averages. This genetic level is then used as a benchmark or reference point from which animals’ genetic merit is expressed. This April, the base population will be updated to cows born in 2015; these cows will serve as the new reference population (see image below). This update happens every five years and is adjusted across all breeds.
In this genomic era, genetic progress is happening faster than ever before, so the April 2020 base change will be even more significant than any of the past. This is a great reflection of the genetic progress made over the last five years.
Below are the estimated base change values for Holstein and Jersey cattle. With the April proofs, PTAs are expected to decrease by the amounts indicated in the table.
The complete list of traits and data on all breeds are available from the Council on Dairy Cattle Breeding (CDCB).
Base change big take-aways
- The relative rankings of animals will not change because of the base change. The same adjustment is applied to all animals in a breed.
- If a bull becomes negative for a trait, the negative PTA simply means the bull is lower for that trait than the cow population born in 2015. Keep in mind PTA/STA is often measured in tenths of a percentage point (or tenths of inches for type traits).
- The CDCB, Holstein Association USA and the American Jersey Cattle Association are updating and adjusting the models for some traits and indexes (see below). These adjustments could cause some changes in genetic ranking.
- To best achieve genetic selection progress use an index. Selection made with an index allows for balance among traits to get the whole.
CDCB Industry Updates
The CDCB has announced the release of disease resistance (health) genetic evaluations for the Jersey breed (mirroring what is already available for the Holstein breed). The six traits include resistance to milk fever, displaced abomasum, ketosis, mastitis, metritis and retained placenta.
CDCB is also adjusting calving trait evaluations. Daughter Calving Ease (DCE) and Daughter Stillbirth (DSB) as well as Sire Calving Ease (SCE) and Sire Stillbirth (SSB) could see some variation. Data edits and model adjustments have been made to increase accuracy, which could potentially re-rank bulls. For more information on CDCB Jersey health traits and CDCB calving trait adjustments, click here.
