We would like to call your attention to a policy change that will take effect over the course of the next 2 years changing one piece of the Genetic Expansion program:

Calves born beginning June 1, 2024 with an EXP sire and an EXP dam will be assigned to the GE herdbook level. Embryos created after August 31, 2023, from an EXP sire and an EXP dam will be assigned to the GE level atbirth. The embryo date corresponds approximately to the date that breedings would occur to create June 1, 2024offspring. Embryos created prior to that date fall under the old policy and maintain the EXP status.

This change does not impact show or award eligibility. Cows holding EXP or higher herdbook status will remain eligible. Additionally, the change does not impact any other herdbook level crosses (GE x full = EXP, EXP x full = full, etc.).

CHANGE

At the 2022 AMSS National Convention held in Champaign, Illinois the AMSS Board of Directors continued over ten years of discussions around breed improvement versus breed identity. All agree the Genetic Expansion program

has allowed the breed to improve dramatically and to thrive in today’s world. The program is vital to continuedimprovements and no discussion of closing the AMSS herdbook has been entertained. However, the drastic herdbookchanges that have taken place within our sister breeds (Dairy Shorthorns in UK and Illawarras in Australia) due to lowbreed percentages, led to deeper discussions regarding our status. The AMSS Board of Directors unanimously decided to reintroduce one of the original rules as a small step in maintaining the Milking Shorthorn breed identity. This step willhopefully prevent the need to take more drastic steps as our sister societies have had to do. We hope to not only maintainthe improvements made so far, but also protect the important Milking Shorthorn characteristics that make the Red, Whiteand Roan so great. These include reproductive traits, productive life, hardiness, calving ease, efficiency and overall versatility.

HISTORY

The AMSS Genetic Expansion program was designed by Dr. Clint Meadows of Michigan State University in the

1960’s using Mendelian genetics for percentage calculations. Within his design, any level crossed to the same level (EXP x EXP) was penalized and the offspring were dropped a level (EXP x EXP = GE). This was done to encourage breeders to work back towards higher breed purity. When the initial program was adopted by the AMSS Board of Directors in the early 1980’s any dairy breed outside of Holstein was penalized with an extra step involved in reaching full herdbook status (37000 registration numbers).

At the 2001 AMSS National Convention held in Cortland, New York the AMSS Board of Directors made some major changes to how the Genetic Expansion program worked (with major dissent from some influential breeders). First, the extra step (37000 registration number) requirement for non-Holstein dairy breeds was removed. All dairy breeds were welcomed into the AMSS herdbook at an equal level. Secondly, the penalty for crossing the same herdbook level (EXP x EXP) was removed.

NUMBERS

There are six levels within the current AMSS herdbook, initially linked to breed percentages (see below). Recent calculations of around 700 pedigrees are shown as a comparison.

Level	NATIVE	FULL HERDBOOK	EXPANDED HERDBOOK	GENETIC EXPANSION	GENETIC IDENTITY	GRADE /AOB
Description	N suffix, 100% Coates Herdbook		EXP suffix	GE prefix, 36000 registration number	GI prefix	Grade or any other breed
Meadow’s plan (estimated % MS)	100%	100%	≥75%	50-75%	<50%	0%
Current level(calculated % MS)	100%	59 – 99% Bulls: 86% Cows: 79%	42 – 76% Bulls: 65% Cows: 64%	33 – 73% Bulls: 49% Cows: 45%	10 – 35%	NA

These numbers include many older animals and genetic lines that have influenced the breed. Looking at the 2022 AMSS Sire Catalog for a smaller example, using currently available genetics, there are 36 full herdbook bulls who average 76.3% Milking Shorthorn and 21 EXP bulls which average 63.1%. These numbers are well under the purity levels that the original genetic expansion plan was aiming for and what Dr. Meadows laid out.

The breeding chart information below will go into effect June 1, 2024.