There are a few different registration entities in the US for Highland Cattle (and even more if you count all of the ones that claim to be). These are the main three and my experience with each.
1) AHCA - American Highland Cattle Association (https://highlandcattleusa.org/) AHCA will only register pure blood highlands. In order to prove they are pure, you have to provide records showing AHCA lineage. The standard height range for a pure blood highland is 48-60+ inches and while there are some that are smaller, they seem to be more of an unexplained anomaly than the result of intentional breeding. The AHCA community largely seems to frown on the mini-highland community, viewing the later as crossbred, poorly developed, or even sick and malnourished animals. My take away is that because of these views, there’s little hope of this community embracing the development of a pure blooded, consistently mini sized highland.
2) HHCA - Heartland Highland Cattle Association (https://www.heartlandhighlandcattleassociation.org/) HHCA will register an animal as being Highland by visual inspection and the honor system however, they do not recognize the term “mini”. As even crossbred highlands can visually appear to be pure blood highlands and well, the honor system isn’t exactly bullet proof, there are large numbers of HHCA registered “highland” cattle of varying sizes and genetically unknown backgrounds with HHCA registrations. The other problem I encountered is that a calf produced by HHCA registered parents, where there was no record of lineage prior to that, will receive a registration that claims the calf is the result of line breeding. Line breeding means that the father bred the daughter to produce the calf. This appears to be a software glitch but because the registry doesn’t own the software they are unable to correct it.
3) IMCBR - International Miniature Cattle Breeders Registry (https://minicattle.com/) IMCBR operated solely on the honor system until recently. They recognize the category “miniature cattle” and include height specific data in their database. They also recognize crossbred animals, allowing the breeder to identify both a primary and secondary breed.
Anyone can register any animal as “mini” and receive a temporary status registration, but at 3 yrs of age, in order to convert to a permanent registration, they require photo proof of height. This is a new requirement and likely to have negative consequences to temporary registrations that were about the convert that will now be delayed by 2.5 years, but there doesn’t appear to be any resolution to that.