In the first proof run of the year in Canada, a base change is applied which essentially subtracts the average genetic improvement being made over the past year from the genetic numbers for every animal (both females and males). While an animal’s genetic makeup does not change, the amount of superiority over the population average will continue to decline as the population catches up. The base change for each breed and each trait within those breeds will differ. Here is a summary of the changes for key traits by breed as provided by the Canadian Dairy Network:

GENETIC BASE CHANGES FOR 2016
AY BC CN CU HO JE MS
LPI1  0 0 0 0 0 0 0
Milk (kg) 85 37 -13 -27 80 59 8
Fat (kg) 3.8 1.3 0.3 2.0 3.5 3.0 2.7
Protein (kg)  2.9 1.3 -0.1 -0.7 2.9 2.6 0.4
Conformation 0.71 0.65 0.52 0.23 0.90 0.27 0.18
Mammary System 0.66 0.54 0.70 0.11 0.91 0.25 0.14
Feet & Legs 0.67 0.61 0.24 0.35 0.59 .10 0.22
Dairy Strength 0.47 0.44 -0.07 0.25 0.47 0.22 0.11
Rump 0.26 0.28 0.34 -0.05 0.20 0.17 0.22
Herd Life2 0.43 0.37 0.09 0.05 0.62 0.08 -0.04
Somatic Cell Score3 -0.05 -0.03 -0.03 -0.05 -0.03 -0.01 -0.02
Daughter Fertility2 -0.10 0.22 -0.04 0.08 0.17 0.20 -0.08
1 – Base change for LPI is set to zero since it is already reflected by the change in the
“Constant” included in the LPI formula
2 – Traits expressed on scale of Relative Breeding Values (RBV)
3 – For Somatic Cell Score only. Negative base change values represent a desirable
trend in genetic progress.