Dr Deb, referring to your article “TIMING AND RATE OF SKELETAL MATURATION IN HORSES, With Comments on Starting Colts and the State of the Industry” 2005 (Ranger), and in particular, focusing on these two points:
When is a Horse Skeletally Mature?
first para, last sentence...
"What people often don't realize is that there is a "growth plate" on either end of every bone behind the skull, and in the case of some bones (like the pelvis, which has many "corners") there are multiple growth plates."
The Schedule of Growth-Plate Conversion to Bone
final dot point (of 13 )
Pelvis - growth plates on the points of hip, peak of croup (tubera sacrale), and points of buttock (tuber ischii), between 3 and 4 years.
could these points, in any way (perhaps mis-read), suggest that the pelvis would be full size (ie full grown), if not totally fused, at the age of 2yrs? This question is particularly related to the purposes of breeding a filly with a suggestion of length in her body (ie back (thoracic vertebrae) and/or loin (lumbar vertebrae).
Diane, your question implies that you do not understand what "fusion" means. "Fusion" is the process whereby the remnant of embryologic cartilage, which is the growth plate, becomes resorbed, thus allowing the already-bony areas to either side to touch and then fuse.
Growth occurs in bones that have "growth plates" so long as the cartilage is still there. The cartilage is the mechanism by which skeletal bones grow in length. So long as the cartilage is still there, and "fusion" across the area where the cartilage had been has not occurred, the bone is still growing.
Many people do breed two year old fillies. They are far from fully developed. This tradition is especially strong in the Americas. It got started in Colonial times because horses were scarce and maximum production was necessary for economic reasons or even reasons of sheer survival. It is still common practice in poverty areas on all continents where horses are kept. Rich people do it too, out of ignorance or because they are involved in an industry that demands it (i.e. because they are involved with other people who are also ignorant).
You can breed a two year old filly and you may see no great signs of damage to her, but there will, nevertheless, be damage to her in ways that you cannot see. Some of these ways are: she will not achieve her own maximum potential size or development; the internal structure (calcium deposition) within teeth and bones will be compromised; her overall longterm soundness will be compromised.
This is why people who know something about horses and who are not on anybody else's schedule FIRST allow the horse to mature to at least four years, THEN race her or put her in whatever other performance category so that she can show that she is worthy of mothering a foal, and FINALLY breed her at six years or older.
So this is not a question about you having to decide whether the pelvis is full-sized. It is rather a question of you having to decide what is best for the livestock that you own; and so in similar manner for all horse owners. -- Dr. Deb
Thank you Dr Deb. The heart of the question was seeking an authorative answer to assist convincing novice breeder(s) that 2yo is way too early for breeding practices in terms of the horse (males included) especially in combination of being slightly longer.
Thanks muchly for your patience.
Personally, I have never bred a mare under 3yo and this was many years ago following the accepted mantra of the time as well as being a novice breeder. However, after the late 1990s I decided to leave breeding until a mare reached at least 5yo, birthing approx. 11 months later for the very reasons you have mentioned, along with breeding every second year, if a mare was to be bred at all. This decision was made after having exhumed my mare that had had six foals (the first 3 had two years between them, the final 3 were consecutive breedings) along with reading and watching your works. This mare was bred as a 4year old (late 1980s) and, apparently, showed skeletal wear possibly pertaining to her pregnancies ~ though not severely.
Accepted mantras are the bane to the horse in these more enlightened times!