I am curious, when picking out a young horse, lets just say a weanling/yearling, how do you judge how it's conformation will turn out? I know there are probably obvious things, but it seems like they go through such drastic changes...
Does one just hope that they mature as lovely or awkward as the parents? Or are their any sure fire ways to see just how they will mature?
Sarah, how much like each of your parents are you in build?
That's how close you can know with horses, too. Even when there are measurements and tables of measurements -- as they have in Germany through the various verbands -- that's how close you can know. This is due to the reassortment of genes that occurs during reduction division for the formation of ova and sperm.
What I'm telling you is that the one and only way to get a good handle on what a foal is likely to look and move like, and what its temperament is likely to be, is to have as thorough a familiarity as possible with the sire and dam, and with any full siblings of the foal. After that, then a familiarity with all the uncles, aunts, grandsires and grand-dams, and the half-siblings.
This is what a good breeder will be well up on, and what a fly-by-night guy or a naive backyard enthusiast will not have a grasp of or care about, or be able to care about.
You will also need a thorough understanding of the content of the "Ranger Piece", i.e. the schedule of skeletal maturation in horses, because to some degree your question does also relate to this -- i.e., why they go through an awkward period at about 18 mos. of age, or why foals appear to be so long-legged. -- Dr. Deb